| 1. |
- Andersons, J., et al.
(author)
-
Fibre fragment distribution in a single-fibre composite tension test
- 2001
-
In: Composites Part B. - 1359-8368 .- 1879-1069. ; 32:4, s. 323-332
-
Journal article (peer-reviewed)abstract
- Single fibre fragmentation tests are performed for brittle fibres with Weibull strength distribution and different surface treatments. The fragmentation process is modelled and closed-form expressions for break spacing distribution are obtained. The model accounts for the effect of finite fibre length on the initial fragmentation as well as for break interaction on the advanced fragmentation stage. It is assumed that the exclusion zone due to fibre-matrix interface failure and stress recovery in the fibre is linearly dependent on the applied load. This assumption is validated experimentally. The derived theoretical average fragment length dependence on applied load is used to determine the fibre strength distribution parameters and the effective interfacial shear stress for carbon/epoxy single fibre composites with different fibre surface treatment and for glass/vinylester single fibre composite. Fragment length distribution is predicted for several load levels. Predictions are in good agreement with experimental data
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| 2. |
- Byström, Johan, et al.
(author)
-
An evaluation of different models for prediction of elastic properties of woven composites
- 2000
-
In: Composites Part B. - 1359-8368 .- 1879-1069. ; 31:1, s. 7-20
-
Journal article (peer-reviewed)abstract
- A critical analysis of two simple and convenient analytical models for calculation of elastic properties of woven fabric composites is performed. Predictions of these models are compared with results obtained using the method of reiterated homogenization and with experimental data for plain weave glass fiber and carbon fiber polyester composites. Three different scales are identified in the analysis. The first scale predictions, which are the tow properties (obtained by applying Hashin's concentric cylinder model, the Halpin-Tsai expressions or mathematical homogenization technique), are the most critical because they form the input information for woven composite modeling. It appears that the uncertainty in this information causes larger differences in predictions than the deviations between models of different degree of accuracy. This fact sets limits on the required accuracy of the models. Model comparisons reveal that the woven compoiste model based on isostrain assumption in the compoiste plane and isostress assumption for out-of-plane components is in very good agreement with both experimental data and the reiterated homogenization method, whereas the modified mosaic parallel model fails to describe composites with large interlaced regions.
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| 3. |
- Byström, Johan
(author)
-
Influence of the inclusions distribution on the effective properties of heterogeneous media
- 2003
-
In: Composites Part B. - 1359-8368 .- 1879-1069. ; 34:7, s. 587-592
-
Journal article (peer-reviewed)abstract
- In this paper we investigate the effective conductivity of composite materials by means of the homogenization method. We concentrate on composites with circular or elliptic cylindrical inclusions. In particular, we are interested in the effect of the distribution of the cylinders in the continuous material on the effective properties. We compare rectangular and hexagonal distributions with random distributions for different volume fractions of the inclusions. We also study the effect of the number of inclusions in each periodic cell for the random structure as well as shape influence of the elliptical inclusions.
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| 4. |
- Byström, Johan, et al.
(author)
-
Some computational aspects of iterated structures
- 2001
-
In: Composites Part B. - 1359-8368 .- 1879-1069. ; 32:6, s. 485-490
-
Journal article (peer-reviewed)abstract
- We consider some computational aspects of effective properties for some multi-scale structures. In particular, we discuss iterated square honeycombs and another type of square honeycombs containing up to 4000 small discs randomly distributed inside each square. We present some numerical methods for estimating the effective conductivity with good control of the accuracy.
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| 5. |
- Jēkabsons, Normunds, et al.
(author)
-
On the effect of stacked fabric layers on the stiffness of a woven composite
- 2002
-
In: Composites Part B. - 1359-8368 .- 1879-1069. ; 33:8, s. 619-629
-
Journal article (peer-reviewed)abstract
- Most micromechanical models for stiffness prediction of woven composites assume independence of the Q-matrix on the number of fabric layers in the composite. For example, the moduli of single and 10 layer composites are assumed to be equal in the case when all layers have the same in-plane orientation. Although this statement is likely to be true for isotropic materials or even for unidirectional laminated composites, it may not be valid in some cases of woven composites. This paper contains experimental and theoretical investigations of plain weave carbon fiber/polyester composites. Specimens with one single and eight layers of fabrics are tested and observable differences of mechanical properties are obtained. The theoretical part of this article consists of derivation and application of several micromechanical models on these particular composites. The use of those simplified models finally allows us to find the main mechanisms which cause the observed effects.
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| 6. |
- Täljsten, Björn, et al.
(author)
-
Strengthening concrete beams for shear using CFRP-materials : evaluation of different application methods
- 2000
-
In: Composites Part B. - 1359-8368 .- 1879-1069. ; 31:2, s. 87-96
-
Journal article (peer-reviewed)abstract
- This paper presents different methods and tests for the application of carbon fibre reinforced plastic (CFRP) fabrics and tapes to concrete beams. The purpose of the tests were twofold; first to study the shear force capacity of the beams both before and after strengthening; and second, to examine three different ways of applying the fabrics. These were: two hand lay-up systems, one vacuum injection system and one pre-preg system. The total number of beams tested was eight. The test results proved that a very good strengthening effect in shear could be achieved by bonding fabrics to the face of concrete beams. However, a lot of energy was released at failure, which led to brittle failures. The tests also showed that the techniques which used hand lay-up were preferable as compared to other systems, even though the fibre weight fraction was considerably less. However, the vacuum injection system was the most environmentally friendly method.
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| 7. |
- Aminoroaya, Alireza, et al.
(author)
-
A review of dental composites : Challenges, chemistry aspects, filler influences, and future insights
- 2021
-
In: Composites Part B. - : Elsevier. - 1359-8368 .- 1879-1069. ; 216
-
Research review (peer-reviewed)abstract
- Resin-based dental composites are promising tooth-resembling materials in restorative dentistry. The limited longevity of dental composite restorations due to the bulk/marginal fracture and secondary caries as well as possible health risks are the critical challenges faced by such materials. Therefore, developments of resin-based dental composites received considerable attention in academic researches for clinical applications. A comprehensive review of the recent developments in the scientific literature on resin-based dental composites is presented in this article. Firstly, in the article, the challenges in dental composites are introduced and then the chemical aspects of the systems are classified through a review of employed resins. Subsequently, the different characteristics related to the fillers employed for the development of the resin-based dental composites are described. Finally, conclusions are drawn and future insights are proposed. This article provides an insight that paves the way for tailoring and designing resin-based dental composites for clinical applications.
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| 8. |
- Auenhammer, Robert, 1991, et al.
(author)
-
Fibre orientation distribution function mapping for short fibre polymer composite components from low resolution/large volume X-ray computed tomography
- 2024
-
In: Composites Part B: Engineering. - 1359-8368. ; 275
-
Journal article (peer-reviewed)abstract
- Short glass fibre injection moulded composites, used in interior and exterior automotive parts, are exposed to complex stress states, for example during a crash. As the fibre scale dominates the composite’s material properties, numerical models need to account for the local fibre orientation. In recent years, mould flow simulation results have been exploited to predict the fibre orientations for finite element models, albeit with limited accuracy. Alternatively, X-ray computed tomography can be used to directly image and analyse fibre orientations. Traditionally, achieving the necessary resolution to image individual fibres restricts the imaging to small regions of the component. However, this study takes advantage of recent advancements in imaging and image analysis to overcome this limitation. As a result, it introduces, for the first time, a reliable, fast, and automated fibre orientation mapping for a full component based on image analysis at the individual fibre level; even for cases where the pixel size is significantly larger than the fibre diameter. By scanning at lower resolutions, a drastically larger volume of interest can be achieved. The resulting fibre orientation analysis and mapping algorithm, based on X-ray computed tomography, is well matched to the level of information required for automotive crash modelling with a standard element-size of a few millimetres. The entire process, encompassing image acquisition, image analysis and fibre orientation mapping, can be directly integrated into an industrial full component application in a matter of hours.
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| 9. |
- Bachinger, Angelika, et al.
(author)
-
Electrocoating of carbon fibres at ambient conditions
- 2016
-
In: Composites Part B. - : Elsevier Ltd. - 1359-8368 .- 1879-1069. ; 91, s. 94-102
-
Journal article (peer-reviewed)abstract
- Electrocoating at constant current is less sensitive to moisture and oxygen than electrocoating at controlled potential, which makes it more interesting for industrial implementation. The galvanostatic electrocoating of carbon fibres with Poly(methylmethacrylate) (PMMA) was therefore studied and compared to the well researched potentiostatic electrocoating procedure. The influence of different experimental parameters on the coating efficiency was investigated in order to identify the mechanisms that are involved in the cathodic electrocoating at constant current. It could be confirmed that the involved mechanisms differ from potentiostatic electrocoating and it was found that galvanostatic electrocoating is more efficient at ambient conditions compared to potentiostatic electrocoating. Polymer layers that cover the entire carbon fibre surface could be achieved in a continuous process by galvanostatic electrocoating under ambient conditions.
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| 10. |
- Bader, Thomas K., 1980-, et al.
(author)
-
Combined ultrasonic-mechanical characterization of orthotropic elastic properties of an unrefined bagasse fiber-polypropylene composite
- 2016
-
In: Composites Part B. - : Elsevier BV. - 1359-8368 .- 1879-1069. ; 95, s. 96-104
-
Journal article (peer-reviewed)abstract
- Use of wood-fiber plastics for construction purposes calls for comprehensive understanding of their anisotropic mechanical properties. As a respective contribution, we here report the first-ever complete elasticity characterization of an orthotropic bagasse fiber polypropylene composite, requiring identification of nine independent constants. For this purpose, we carry out characterization in principal material directions. Six diagonal stiffness tensor components are quantified based on ultrasonic longitudinal and shear wave velocity measurements; and three diagonal compliance tensor components are identified as the inverses of three Young’s moduli derived from unloading regimes of quasi-static uniaxial compression tests. Combination of all measurement data in the framework of orthotropic linear elasticity provides access to all off-diagonal stiffness and compliance tensor components, opening the door to quantifying six Poisson’s ratios.
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| 11. |
- Basso, Margherita, et al.
(author)
-
Effect of food chemicals and temperature on mechanical reliability of bio-based glass fibers reinforced polyamide
- 2019
-
In: Composites Part B. - : Elsevier. - 1359-8368 .- 1879-1069. ; 157, s. 140-149
-
Journal article (peer-reviewed)abstract
- This paper presents an experimental study to assess the effects of food chemicals and temperature on the mechanical performance of glass fiber reinforced bio-based polyamide. The diffusion of food chemicals was mainly driven by thermal energy, following Arrhenius law in all tested environments. Degradation of mechanical properties and decrease in reliability were assessed, due to the plasticization of polymer matrix. Secondary but not negligible effect on flexural strength degradation is given by the different chemical interaction between polymeric chains and molecules of food chemicals. Colour change was measured and resulted to be positively correlated to diffusion.
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| 12. |
- Basso, Margherita, et al.
(author)
-
Nonlinear creep behaviour of glass fiber reinforced polypropylene : Impact of aging on stiffness degradation
- 2019
-
In: Composites Part B. - : Elsevier. - 1359-8368 .- 1879-1069. ; 163, s. 702-709
-
Journal article (peer-reviewed)abstract
- Nonlinear creep behavior of one commercial short glass fiber reinforced polypropylene was investigated using tensile creep tests and stiffness degradation measurements. The impact of thermal aging and following quenching was evaluated on the latter mechanical property. Experimental results were modeled applying nonlinear viscoelastic model used by Pupure et al. (2013) and developed by Lou and Schapery [1,2]. Results showed that this model can describe nonlinear behavior of short glass fiber reinforced polymer composites, where microdamage is given by debonding of fiber-matrix interfaces already at low strains, where cracks propagate and lead to tensile creep fracture.
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| 13. |
- Berrocal, Carlos Gil, 1986, et al.
(author)
-
Corrosion-induced cracking and bond behaviour of corroded reinforcement bars in SFRC
- 2017
-
In: Composites Part B: Engineering. - : Elsevier BV. - 1359-8368. ; 113, s. 123-137
-
Journal article (peer-reviewed)abstract
- This paper investigates, experimentally and numerically, the effect of fibre reinforcement on the initiation of corrosion-induced cracks in concrete and the bond behaviour of corroded reinforcement bars in fibre reinforced concrete. The fibres, due to their confining effect, contributed to delay crack initiation, improve the post-peak bond behaviour and retain the initial splitting strength for corrosion levels of up to 8%. The mechanisms for delayed crack initiation were explained through 3D finite element analyses of the experiments whereas a 1D model, using experimental bond-slip curves as an input, was employed to quantify the beneficial effect of fibres on the reinforcement anchorage length.
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| 14. |
- Bull, Peter Hoaas, et al.
(author)
-
Compressive strength after impact of CFRP-foam core sandwich panels in marine applications
- 2004
-
In: Composites Part B. - : Elsevier BV. - 1359-8368 .- 1879-1069. ; 35:6-8, s. 535-541
-
Journal article (peer-reviewed)abstract
- A plastic micro buckling approach is investigated in order to see whether it can be used to analytically predict the residual strength of carbon fiber sandwich structures. A parametric study on impact damage resistance and residual strength of sandwich panels with carbon fiber-vinylester faces and PVC foam core is conducted. Two sandwich configurations are studied. The first configuration consists of thin faces and an intermediate density core, representative of a panel from a superstructure. The second configuration consists of thick faces and a high density core, representative of a panel from a hull. Two different impactor geometries are used. One spherical impactor and one pyramid shaped impactor are used in a drop weight rig to inflict low velocity impact damage of different energy levels in the face of the sandwich. The damages achieved ranges from barely visible damages to penetration of one face. Residual strength is tested using in-plane compression of the sandwich plates either instrumented with strain gauges or monitored with digital speckle photography.
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| 15. |
- Carlson, Tony, et al.
(author)
-
Structural carbon fibre composite/PET capacitors-Effects of dielectric separator thickness
- 2013
-
In: Composites Part B. - : Elsevier BV. - 1359-8368 .- 1879-1069. ; 49, s. 16-21
-
Journal article (peer-reviewed)abstract
- This paper presents an approach towards realising novel multifunctional polymer composites with combined structural and electric energy storing ability. A series of structural capacitors were made using three thicknesses of DuPont Mylar A thermoplastic PET as a dielectric separator employing carbon fibre/epoxy pre-pregs as structural electrodes. Plasma treatment was used as a route for improved epoxy/PET adhesion. The manufactured materials were mechanically and electrically tested to evaluate their multifunctional efficiency. The multifunctional materials developed show good potential for replacing steel, aluminium and other materials with lower specific mechanical properties but do not match the high specific mechanical and electrical performance of monofunctional composites and capacitors.
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| 16. |
- Carlstedt, David, 1984, et al.
(author)
-
Performance analysis framework for structural battery composites in electric vehicles
- 2020
-
In: Composites Part B: Engineering. - : Elsevier BV. - 1359-8368. ; 186
-
Journal article (peer-reviewed)abstract
- In this paper, a novel modelling framework to estimate system level performance of electric vehicles utilizing a structural battery composite material is presented. Electrical and mechanical properties are derived from material data of the constituents, device design and connection/layup schemes. Knowledge of the multifunctional, i. e. electrical and mechanical, performance of the structural battery composite allows for estimation of the electric vehicle drive range for any known drive cycle. The framework is used to evaluate effect on drive range from the introduction of structural batteries into existing electric vehicles (EVs). Comparative studies performed for Tesla model S and BMW i3 demonstrate a compelling vehicle weight saving potential with maintained drive range performance. Alternatively, if vehicle weight is to be maintained from the introduction of structural batteries the resulting drive range for lightweight EVs will be increased by 70%.
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| 17. |
- Carmeli, Enrico, et al.
(author)
-
Crystallization kinetics of melt-mixed 3D hierarchical graphene/polypropylene nanocomposites at processing-relevant cooling rates
- 2022
-
In: Composites Part B: Engineering. - : Elsevier BV. - 1359-8368. ; 247
-
Journal article (peer-reviewed)abstract
- Knowledge of the solidification behaviour of isotactic polypropylene (iPP) composites with reduced graphene oxide nanoplatelets is key to open the possibility to widespread use of these high performing nanocomposites. The crystallization behaviour of these systems, with filler content in the range of 0.2–3.5 wt% has been investigated by differential scanning calorimetry (up to 100 °C/min) and ex-situ structural and morphological characterization of samples prepared at processing-relevant cooling conditions (up to 2000 °C/s). Compared to the self-nucleated neat iPP, the nucleation efficiency was estimated to vary from 44 to 93% when increasing the filler content. Such a high nucleating efficiency has not been reported yet for a nanocomposite with iPP matrix. This result is due to the very good dispersion of the filler in these melt-mixed graphene-based polypropylene systems. The nucleation ability of the graphene filler does not reach a saturation in the concentration range studied. The gap between laboratory and industrial cooling rate scale is here reduced thanks to the information achieved from the fast-cooling experiments. By varying the filler amount in the investigated range, a significant shift of the cooling rate window in which the transition from α-to mesophase dominated crystallization takes place was detected. Notably, with 3.5 wt% graphene platelets, α-phase crystals are predominantly present in the material even after quenching at 1000 °C/s, similar to highly nucleated commercial iPP grades.
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| 18. |
- Ebead, Usama, et al.
(author)
-
Pull-off characterization of FRCM/Concrete interface
- 2019
-
In: Composites Part B. - : Elsevier. - 1359-8368 .- 1879-1069. ; 165, s. 545-553
-
Journal article (peer-reviewed)abstract
- Fabric-reinforced cementitious matrix (FRCM) composites are usually surface-applied for strengthening reinforced concrete (RC) structures. The efficacy of the FRCM strengthening systems is dependent on the FRCM/concrete bond performance. This paper reports on the experimental results of FRCM/concrete bond characterization through pull-off tests. Six FRCM-strengthened RC slabs (500mm×500mm×100 mm) were prepared and enabled conducting 72 FRCM/concrete pull-off tests. The parameters investigated included: (a) FRCM material (carbon or polyparaphenylene benzobisoxazole (PBO)); (b) level of substrate roughness (no/low/high roughening); and (c) specimen’s test age (7, 28, 56, and 84 days). All FRCM systems were single-plied. The study revealed a significance of the surface preparation and test age of specimens on the FRCM/concrete pull-off strength. High-roughness specimens showed an average of 74% pull-off strength increase compared to those without roughening. Also, specimens tested at Day 84 showed 54% strength increase compared to those tested at Day 7, on average. PBO-FRCM system showed slightly higher pull-off strength than that of the carbon counterpart. The specimens showed two distinctive failure types at the (i) fabric/mortar interface and (ii) concrete/matrix interface: the latter was more prominent in carbon-FRCM. Nonetheless, the failure mode was most dependent on the fabric geometry and the substrate roughness. Based on a statistical analysis of the tested specimens, prediction models were proposed for the FRCM/concrete pull-off strength and failure mode.
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| 19. |
- Ekh, Johan, et al.
(author)
-
Secondary Bending in Multi Fastener, Composite-to-Aluminium Single Shear Lap Joints
- 2005
-
In: Composites Part B. - : Elsevier BV. - 1359-8368 .- 1879-1069. ; 36, s. 195-208
-
Journal article (peer-reviewed)abstract
- A novel technique to study secondary bending due to the eccentric load path in single shear, composite-to-aluminium lap joints has been developed and used in a parametric study. The method is based on the specimen curvature, which is derived from lateral displacements of the surface. The lateral displacements are measured with an optical measurement system or calculated with the finite element method. It was found that the specimen curvature is equivalent to the secondary bending which is usually measured with strain gauges in the vicinity of the bolt holes. The two most important parameters affecting specimen curvature is the overlap length and the thickness of the aluminium plate in the joints.
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| 20. |
- Eliasson, Sara, et al.
(author)
-
Numerical fatigue assessment of a cross-ply carbon fiber laminate using a probabilistic framework
- 2024
-
In: Composites Part B. - : Elsevier Ltd. - 1359-8368 .- 1879-1069. ; 281
-
Journal article (peer-reviewed)abstract
- A probabilistic framework is developed utilizing a two-scale modeling approach to efficiently consider the material variability that is typical for composite materials. The modeling integrates a macro-scale model with effective elastic properties extracted from micro-mechanical simulations. Using a weakest link modeling approach for fatigue assessment the combined effects of defects on fatigue strength in a Carbon Fiber Reinforced Polymer (CFRP) material can be investigated. A full fatigue test program is presented and is used to calibrate the probabilistic fatigue model. By including material variability in the numerical model, the calibrated probabilistic model improves the fatigue life prediction.
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| 21. |
- Esmaily, Mohsen, 1987, et al.
(author)
-
A new semi-solid casting technique for fabricating SiC-reinforced Mg alloys matrix composites
- 2016
-
In: Composites Part B: Engineering. - : Elsevier BV. - 1359-8368 .- 1879-1069. ; 94, s. 176-189
-
Journal article (peer-reviewed)abstract
- The capability of the newly developed rheocasting (RC) technique in combination with the RheoMetal process for producing SiC particulate-reinforced AM50 and AZ91D matrix composites (Mg-based MMCs) was investigated. The quality of the MMCs was studied by analyzing the fraction of casting pores, number density of SiC clusters and the uniformity of SiC particles. Solid fraction, particle size and oxidation of SiC particles had strong impacts on the overall quality of the MMCs. The MMCs produced by 40% solid fraction and oxidized micron-sized SiC particles exhibited an excellent casting quality. A low-quality MMC was obtained when non-oxidized sub-micron sized SiC particles were employed. The results showed the formation of various types intermetallic particles and carbides such as MgO, Mg2Si, Al2MgC2, Mg2C3, Al4C3 as the interfacial reaction products of SiC/Mg alloy's melts. Mg hydride (alpha-MgH2) was also identified in inter-dendritic regions of the MMCs for the first time.
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| 22. |
- Faroughi, S., et al.
(author)
-
NURBS-based modeling of laminated composite beams with isogeometric displacement-only theory
- 2019
-
In: Composites Part B. - : Elsevier. - 1359-8368 .- 1879-1069. ; 162, s. 89-102
-
Journal article (peer-reviewed)abstract
- This paper develops a formulation for displacement-only beam elements based on isogeometric analysis, with intended application to laminated composite members. The main purpose of the current study was to overcome some deficiencies of commonly used beam theories, such as shear-locking, the lacking relevance of isotropic materials for multi-layer composites, the incompatibility with other continuum elements, and the limited continuity in interpolation. A bi-variable non-uniform rational B-spline (NURBS) beam element with complete plane-stress elasticity terms and geometrical expressions was developed. Shear-locking, interlaminar stresses, the deep-beam situation, and vibration features were evaluated for several aspect ratios, ply orientations, and NURBS degrees, in order to verify the efficiency and accuracy. h-, p- and k-refinements were used to improve the displacement field. The validity of the solutions was measured based on results from plane-stress finite element analysis, and compared to the alternative Carrera unified formulation. Results show that the isogeometric displacement-only beam theory can provide the interlaminar stress distribution, gives high accuracy for mid and high-range eigen-frequencies, and avoids the shear-locking phenomenon.
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| 23. |
- Floruț, Sorin-Codruț, et al.
(author)
-
Tests on reinforced concrete slabs with cut-out openings strengthened with fibre-reinforced polymers
- 2014
-
In: Composites Part B. - : Elsevier BV. - 1359-8368 .- 1879-1069. ; 66, s. 484-493
-
Journal article (peer-reviewed)abstract
- This paper presents the results of experimental investigations on reinforced concrete slabs strengthened using fibre-reinforced polymers (FRP). Eight tests were carried out on four two-way slabs, with and without cut-out openings. Investigations on slabs with cut-outs revealed that the FRP can be placed only around the edges of the cut-out when retrofitting the slabs whereas, in the situation of inserting cut-outs combined with increased demands of capacity, it is necessary to apply FRP components on most of the soffit of the slab. The proposed strengthening system enabled the load and deflection capacities of the FRP-strengthened slabs, in relation to their un-strengthened reference slabs, to be enhanced by up to 121% and 57% for slabs with and without cut-outs respectively.
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| 24. |
- Forsgren, Lilian, 1990, et al.
(author)
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Water-assisted extrusion and injection moulding of composites with surface-grafted cellulose nanocrystals – An upscaling study
- 2021
-
In: Composites Part B: Engineering. - : Elsevier BV. - 1359-8368. ; 208
-
Journal article (peer-reviewed)abstract
- The large-scale surface modification of cellulose nanocrystals (CNC) was carried out to produce CNC-containing composites, in a scale of 3 kg, using industrial-scale melt processing techniques such as twin-screw extrusion and injection moulding. Two different polymer matrices, ethylene-acrylic acid copolymer (EAA) and low-density polyethylene (LDPE), were reinforced with 10 wt% unmodified cellulose nanocrystals (CNC) or surface-treated CNC, where a 2-hydroxyproyl-N-diallyl group had been grafted onto the sulphate half-ester groups on the CNC surfaces. This was achieved by mixing an aqueous CNC dispersion and the polymer pellets directly in the twin-screw extruder followed by a second dry compounding step prior to shaping by injection moulding. The injection-moulded materials were characterized with respect to their mechanical properties and thermal stability. The addition of 10 wt % CNC resulted in all cases in an increase in the yield strength and stiffness by 50–100%, most significantly for the EAA based composites. There were indications of the presence of a stable interphase and a percolating network in the EAA-based materials, according to dynamic-mechanical measurements. A reduction in thermal stability was observed for the melt-processed samples containing diallyl-modified CNC and discoloration in the EAA based samples.
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| 25. |
- Gaff, Milan, 1978-, et al.
(author)
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Plasticity properties of thermally modified timber in bending : the effect of chemical changes during modification of European oak and Norway spruce.
- 2019
-
In: Composites Part B. - : Elsevier. - 1359-8368 .- 1879-1069. ; 165, s. 613-625
-
Journal article (peer-reviewed)abstract
- The plasticity of thermally modified European oak (Quercus robur L.) and f thermally modified Norway spruce (Picea abies Karst. (L.)) timber was evaluated in bending, and the plastic properties were related to the changes in chemical composition of the wood after modification. The objective was to gain new knowledge about the properties of materials in the plastic region of the force-deformation diagram in bending. A new software was developed (MATESS) and used to identify important characteristics of the material. This software eliminates shortcomings in current standards, such as simplifications in the evaluation of data when sufficiently sensitive measuring equipment is not available. The characteristics studied were: modulus of rupture (MOR), plastic potential (PP) chord modulus (CHM), the moduli of plasticity (EE), and the moduli of plasticity (EMV, EP). Extractives, lignin, cellulose, holocellulose, and hemicelluloses were analysed chemically to reveal the patterns that occur during the loading of the specimens. Thermal modification has different effects on the mechanical properties of oak and spruce, especially on CHM, EMV and EP, due to their different contents and structures of their chemical components. A strong correlation (r > 0.90) between hemicellulose content and MOR and Pp values was found for both species. The coefficients of determination indicated a very low dependence (r2 < 0.1) of MOR, PP, CHM, EE, EMV and EP, on the average density.
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| 26. |
- Gulfo Hernandez, Luis Fernando, 1989, et al.
(author)
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A 3D voxel-based mesostructure generator for finite element modelling of tow-based discontinuous composites
- 2024
-
In: Composites Part B: Engineering. - 1359-8368. ; 278
-
Journal article (peer-reviewed)abstract
- Tow-based discontinuous composites manufactured with ultra-thin tapes display high stiffness, strength, and in-plane isotropy, thus competing with composite laminates. Their complex 3D microstructure affects the mechanical response, in turn demanding 3D generators that capture the tape waviness, resin pockets, and thickness and fibre content variations. The present work proposes an automated numerical framework combining a 3D voxel-based mesostructure generator with finite element models. A modified 3D random sequential absorption technique is developed with bin-guided allocation, draping, and thickness control. A statistical study is used to size the statistical volume elements and predict the elastic properties of thick, thin, and ultra-thin tow-based discontinuous composites. The results are compared with the experimental values from the literature. Despite uncertainties in physical tape properties, the resulting stiffnesses are predicted with good accuracy.
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| 27. |
- Hejll, Arvid, et al.
(author)
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Large scale hybrid FRP composite girders for use in bridge structures : theory, test and field application
- 2005
-
In: Composites Part B. - : Elsevier BV. - 1359-8368 .- 1879-1069. ; 36:8, s. 573-585
-
Journal article (peer-reviewed)abstract
- This paper presents the manufacturing process and testing of large scale hybrid composite girders. The evaluation of the girders was a part of the European funded ASSET project. The bridge project, started in 1998 and finished in the autumn of 2002. The ASSET project has in brief covered the design, manufacture and construction of a fully polymer composite traffic bridge. The longitudinal girders are the most important part for the load carrying system of the bridge. Different types of girders were discussed, i.e. steel, concrete or FRP girders. Due to the advantages of FRP girders, for example; light weight, easy installation, superb durability and less maintenance compared to traditional materials it was decided to use FRP in the girders. However, before this could be carried out, tests were needed to verify theoretical calculations. Also a FE-analysis has been carried out, and this analysis is compared with an engineering analytical solution and tests. Both the numerical and the analytical theory correspond quite well with obtained test results.
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| 28. |
- Heshmati, Mohsen, 1987, et al.
(author)
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Durability of bonded FRP-to-steel jointsEffects of moisture, de-icing salt solution, temperature and FRP type
- 2017
-
In: Composites Part B: Engineering. - : Elsevier BV. - 1359-8368. ; 119, s. 153-167
-
Journal article (peer-reviewed)abstract
- This paper investigates the effects of environmental ageing on the mechanical response of adhesively bonded double-lap shear joints made of steel and CFRP or GFRP adherents. One hundred and ninety-two specimens, 84 joints and 108 material coupons, were aged for up to three years in various environments including (i) immersion in distilled water at 20 °C and 45 °C, (ii) immersion in de-icing salt solution at 20 °C and 45 °C and (iii) exposure to 95% relative humidity at 45 °C. In general, immersion at 45 °C resulted in noticeably greater strength reductions at both material and joint level. While the strength and stiffness of the joints made of GFRP material underwent significant reductions, the CFRP/steel joints were affected to a considerably smaller degree. FE simulations showed the impact of the permeability of FRP adherents and moisture distribution at the FRP/adhesive interface on the integrity and strength of the joints. The joint-level results are compared with the most relevant durability data in the literature.
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| 29. |
- Heshmati, Mohsen, 1987, et al.
(author)
-
Durability of CFRP/steel joints under cyclic wet-dry and freeze-thaw conditions
- 2017
-
In: Composites Part B: Engineering. - : Elsevier BV. - 1359-8368. ; 126, s. 211-226
-
Journal article (peer-reviewed)abstract
- Strengthening of steel structures with adhesively bonded carbon fibre reinforced polymer (CFRP) materials have become increasingly popular in the last decade. However, uncertainties regarding the durability and long-term performance of CFRP/steel joints is a major obstacle for their growing application. Previous research indicates the deleterious effects of moisture and thermal cycles on the mechanical performance of these joints. To the authors' knowledge, the combined effects of moisture and thermal cycles have been scarcely investigated. This paper presents the results of extensive experimental investigations at material- and joint-level subjected to various cyclic environmental scenarios. Special consideration is given to the role of moisture, i.e. distilled- or salt-water, when combined with freeze thaw cycles. Moreover, the possibility of providing a predictive modelling platform for residual strength prediction of environmentally aged joints using sequentially coupled moisture diffusion fracture analysis is explored. The results show 11% and 47% strength reductions for the CFRP/steel joints after a complete wet-dry cycle in distilled- and salt-water, respectively, which are significantly larger than those observed after only the wet exposure. In addition, 125 and 250 freeze-thaw cycles were found to have no unfavourable effects on the strength of dry or preconditioned joints. (C) 2017 Elsevier Ltd. All rights reserved.
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| 30. |
- Heshmati, Mohsen, 1987, et al.
(author)
-
Effects of moisture on the long-term performance of adhesively bonded FRP/steel joints used in bridges
- 2016
-
In: Composites Part B: Engineering. - : Elsevier BV. - 1359-8368. ; 92, s. 447-462
-
Journal article (peer-reviewed)abstract
- Concerns regarding the durability of adhesively-bonded fibre-reinforced-polymer (FRP)/steel joints in bridges have been a major obstacle to their growing application. On the one hand, the available long-term data of FRPs used in bridges is rare and, on the other hand, the existing assessment approaches have mainly been developed to address the needs of industries, such as the aviation sector, with distinct differences. This paper uses both experimental and numerical approaches to investigate the effects of moisture, as one of the most influential factors, on the long-term performance of FRP/steel joints used in bridges. Gravimetric measurements are used to characterise the 3D moisture-diffusion properties for different FRPs and an adhesive material in various ageing conditions. Fast curing of the adhesive was found to have no significant effect on the diffusion properties of fully cured epoxy specimens. Salt water was found to degrade the mechanical properties of adhesive to a lesser degree than distilled water. The tested double-lap-shear joints of FRP/steel showed ca. 5% strength gain after eight months and ca. 9% reduction in the failure load after 12 months of ageing. While the elastic modulus of adhesive was found to decrease significantly with increasing moisture content, the stiffness reduction was found to be trivial in the joint-level. The results of coupled diffusion-mechanical finite element analyses indicate the importance of adherend permeability on moisture ingression into the joints. Moreover, the presence of small amounts of moisture at the steel/adhesive interface for less than a critical period is found to increase the joint strength. However, prolonged exposure to the same moisture content degrades the strength of the joint, and is, thus, time dependent.
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| 31. |
- Heshmati, Mohsen, 1987, et al.
(author)
-
Environmental durability of adhesively bonded FRP/steel joints in civil engineering applications: State of the art
- 2015
-
In: Composites Part B: Engineering. - : Elsevier BV. - 1359-8368. ; 81, s. 259-275
-
Journal article (peer-reviewed)abstract
- Over the past three decades, the strengthening and repair of existing civil engineering structures using FRP laminates has attracted a great deal of attention. With the advances in polymer science, adhesive bonding has become a common joining technology in these applications. Despite numerous studies that address the short-term behaviour of adhesively bonded FRP/steel joints, uncertainty with respect to long-term performance still remains. This knowledge gap is regarded as a critical barrier, hindering the widespread application of FRPs to strengthen and retrofit steel structures. This paper presents the state of the art in terms of the durability of FRP/steel joints used in civil engineering applications. Important influential factors relating to the durability of adhesively bonded joints are reviewed and different damage mechanisms are discussed. Moreover, related investigations of the combined environmental durability of these joints are critically reviewed and the findings are presented. The paper concludes with a discussion to motivate future research topics, while it is emphasised that the generalisation of the available results is questionable.
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| 32. |
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| 33. |
- Hosseini-Hashemi, S., et al.
(author)
-
On the exact in-plane and out-of-plane free vibration analysis of thick functionally graded rectangular plates: Explicit 3-D elasticity solutions
- 2013
-
In: Composites Part B: Engineering. - : Elsevier BV. - 1359-8368 .- 1879-1069. ; 46, s. 108-115
-
Journal article (peer-reviewed)abstract
- In this paper exact closed-form solutions of 3-D elasticity theory are presented to study both in-plane and out-of-plane free vibrations for thick functionally graded simply supported rectangular plates. The solution procedure of the transverse vibration utilizes Levinson's representation form to describe the displacement; in this way, the 3-D elasto-dynamic equations are written in terms of some suitable independent functions satisfying ordinary differential equations. A similar procedure is presented for in-plane vibration by introducing an appropriate displacement field. In each case, the obtained ordinary differential equations are analytically solved and boundary conditions are satisfied. The proposed solutions are validated by comparing some of the present results with corresponding results known in the literature as well as with 3-D Finite Element Method. Finally, the influence of inhomogeneity on the natural frequencies for a thick functionally graded rectangular plate is discussed.
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| 34. |
- Huang, Yongxin, et al.
(author)
-
Statistical analysis of oblique crack evolution in composite laminates
- 2014
-
In: Composites Part B. - : Elsevier BV. - 1359-8368 .- 1879-1069. ; 65, s. 34-39
-
Journal article (peer-reviewed)abstract
- A previously developed statistical model for transverse cracking in cross ply laminates is extended to oblique cracking in multidirectional laminates. The oblique cracks are assumed to form in a ply when the local in-plane tensile stress normal to fibers exceeds the transverse strength of the ply. This strength is assumed to have a statistical distribution given by a two-parameter Weibull function. The model is applied to a glass-epoxy [0/602/0/-602]s laminate in which cracking evolution of the four -600 plies in the middle of the laminate is examined. The local stress field in the cracked -600 plies is calculated by a three-dimensional finite element method based on a unit cell construction developed by Li et al. [1]. The measured crack density is found to agree well with that calculated by the statistical model
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| 35. |
- Iyer, Kaushik, et al.
(author)
-
The multi-objective optimization framework: A step towards minimizing life-cycle costs and energy consumption of carbon fibre automotive structures
- 2024
-
In: Composites Part B. - : Elsevier BV. - 1359-8368 .- 1879-1069. ; 271
-
Journal article (peer-reviewed)abstract
- Design of a sustainable and economical composite structure is challenging due to the often contradicting design drivers such as energy consumption and cost. Therefore, predicting the environmental and economic impact in the early stages of product design results in the significant reduction of energy consumption and cost. Consequently, the impact of contrasting objectives on an optimized carbon fibre reinforced polymer (CFRP) demonstrator is evaluated in this study. This evaluation is performed by integrating a predictive life-cycle assessment and costing framework in a multi-objective optimization methodology. The varying design configurations include designs with and without stiffeners. Furthermore, the impact of end-of-life allocation on the optimized design is also evaluated in this study. The results show a marked difference between the energy consumption of the various optimized designs with energy optimization producing the most efficient solution. However, the mass of the demonstrator increases by 7–9 kg across the different design configurations when the closed loop allocation model is implemented. Consequently, the results show the importance of selecting an appropriate EOL allocation methodology in evaluating the energy consumption of a product. The results also show that the parameters driving the energy consumption (mass and material configuration) and cost (complexity and manufacturability) are varied and often contrasting. The differences in mass, cost, and energy optimized designs further reinforces the importance of coupling cost and energy evaluation in design of sustainable products. Finally, the study demonstrates the need for a holistic life-cycle based assessment in early stage sustainable product design.
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| 36. |
- Karlsson Hagnell, Mathilda, et al.
(author)
-
A composite cost model for the aeronautical industry : Methodology and case study
- 2015
-
In: Composites Part B. - : Elsevier BV. - 1359-8368 .- 1879-1069. ; 79, s. 254-261
-
Journal article (peer-reviewed)abstract
- This paper presents a novel composite production cost estimation model. The strength of the model is its modular construction, allowing for easy implementation of different production methods and case studies. The cost model is exemplified by evaluating the costs of a generic aeronautical wing, consisting of skin, stiffeners and rib feet. Several common aeronautical manufacturing methods are studied. For studied structure, hand layup is the most cost-effective method for annual volumes of less than 150 structures per year. For higher production volumes automatic tape layup (All) followed by hot drape forming (HDF) is the most cost-effective choice.
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| 37. |
- Karlsson, Tobias, et al.
(author)
-
Sensing abilities of embedded vertically aligned carbon nanotube forests in structural composites: From nanoscale properties to mesoscale functionalities
- 2023
-
In: Composites Part B: Engineering. - : Elsevier BV. - 1359-8368 .- 1879-1069. ; 255
-
Journal article (peer-reviewed)abstract
- In this paper, Vertically Aligned Carbon Nanotube (VACNT) forests are embedded into two different glass fibre/epoxy composite systems to study their sensing abilities to strain and temperature. Through a bottom-up approach, performing studies of the VACNT forest and its individual carbon nanotubes on the nano-, micro-, and mesoscale, the observed thermoresistive effect is determined to be due to fluctuation-assisted tunnelling, and the linear piezoresistive effect due to the intrinsic piezoresistivity of individual carbon nanotubes. The VACNT forests offer great freedom of placement into the structure and reproducibility of sensing sensitivity in both composite systems, independent of conductivity and volume fraction, producing a robust sensor to strain and temperature.
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| 38. |
- Katsivalis, Ioannis, 1986, et al.
(author)
-
Fatigue performance and damage characterisation of ultra-thin tow-based discontinuous tape composites
- 2024
-
In: Composites Part B: Engineering. - : Elsevier BV. - 1359-8368 .- 1879-1069. ; 281
-
Journal article (peer-reviewed)abstract
- Tow-based discontinuous composites are an attractive alternative material to conventional continuous composites as they offer in-plane isotropy, enhanced manufacturability allowing to achieve complex 3D shapes with high curvatures and local reinforcement in critical areas, while also maintaining high strength and stiffness, therefore expanding the design space significantly. In addition, the use of ultra-thin tapes and optimised manufacturing methods can increase the mechanical properties even further and change the damage mechanisms. Fatigue, however, could be a limiting design factor, as the fatigue behaviour of these materials has not been fully characterised. This work presents a complete study on the fatigue response of ultra-thin tow-based discontinuous composites: fatigue S–N curves are measured, and the damage and failure mechanisms are characterised utilising optical and scanning electron microscopy. Finally, a critical interpretation of the results is also presented by comparing the performance of ultra-thin tow-based discontinuous composites against other similar fibre reinforced composites and metals. It is shown that the optimised manufacturing methods combined with low tape thickness leads to enhanced quasi-isotropic fatigue performance. In addition, the fatigue limit was raised significantly compared to other discontinuous composites, and the tow-based discontinuous composites outperformed their metal counterparts when the results were normalised with density.
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| 39. |
- Kelly, Gordon, et al.
(author)
-
Bearing strength of carbon fibre/epoxy laminates : effects of bolt-hole clearance
- 2004
-
In: Composites Part B. - : Elsevier BV. - 1359-8368 .- 1879-1069. ; 35:4, s. 331-343
-
Journal article (peer-reviewed)abstract
- The bearing strength of carbon fibre epoxy laminates manufactured from non-crimp fabric from heavy tow yarn has been investigated. The effects of laminate stacking sequence and geometry on the bearing strength have been determined experimentally together with the effect of initial bolt-hole clearance on the bearing strength at 4% hole deformation and at ultimate load. Significant reduction in bearing strength at 4% hole deformation was found for both pin-loaded and clamped laminates as a result of bolt-hole clearance. It was concluded that the effect of bolt-hole clearance is significant with regard to the design bearing strength of mechanically fastened joints. A three-dimensional non-linear finite element model was developed to investigate the effects of bolt-hole clearance on the stress field in the laminate adjacent to the hole. The magnitude and distribution of stress at the hole was found to be significantly dependent on the level of clearance.
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| 40. |
- Kong, Xueying, et al.
(author)
-
All-cellulose-based freestanding porous carbon nanocomposites and their versatile applications
- 2022
-
In: Composites Part B. - : Elsevier. - 1359-8368 .- 1879-1069. ; 232
-
Journal article (peer-reviewed)abstract
- Porous carbons are key functional materials in a range of industrial processes such as gas adsorption and separation, water treatment, and energy conversion and storage. It is, however, important from a sustainability perspective for porous carbons to be synthesized from naturally abundant biopolymers. Nanoengineering of porous carbons using facile binder-free techniques presents significant challenges, but is deemed beneficial for broadening their field of use and improving their application performance. This paper discusses the processing of cellulose-based porous carbons interwoven with cellulose nanofibers to fabricate freestanding nanopapers and aerogels, aiming at developing processable, fully sustainable, and all-cellulose-based carbon nanocomposites. The aerogels, which have cellular networks, low density and high mechanical strength, were investigated as sorbents for CO2 capture and removal of various organics. The presence of rich ultramicropores allows the aerogels to adsorb relatively high amounts of CO2, with high selectivity of CO2-over-N-2 (up to 111). More importantly, the sorbents have high CO2 working capacities and excellent recyclability under temperature swing adsorption conditions. In addition, the aerogels can adsorb various organic solvents remarkably well, corresponding to 100-217 times their own weight. The nanopapers are active photothermal materials that can be applied as solar absorbers for interfacial solar vapor generation, providing a high evaporation rate (1.74 kg m(-2) h(-1) under one sun illumination). The nanopapers were also employed as electrodes in flexible, foldable super capacitors with high areal capacitances. This study may provide a basis for further development of and new application areas for all-cellulose-based nanocomposites.
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| 41. |
- Kumar, Anuj, et al.
(author)
-
Hydrophobic treatment of wood fibrous thermal insulator by octadecyltrichlorosilane and its influence on hygric properties and resistance against moulds
- 2016
-
In: Composites Part B. - : Elsevier. - 1359-8368 .- 1879-1069. ; 106, s. 285-293
-
Journal article (peer-reviewed)abstract
- The natural fibrous materials are widely used as thermal insulator for building application. The thermal insulating performance of natural fibrous material are affecting by the high humidity and temperature. Due to high moisture in natural fibrous insulators, they are very susceptible for microorganisms attack as well as the reduction in the thermal insulating properties. In this work, hydrophobic surface treatment was given to the wood fibrous insulator using octadecyltrichlorosilane (OTS). The deposition of OTS monolayers on wood fibers surface was confirmed by X-ray photoelectron microscopy (XPS), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and water contact angle of wood fibers measured by sessile drop method. The influence of hydrophobic treatment on hygric properties of wood fibrous insulator was characterized using especially designed double-climatic set-up. The effectiveness of hydrophobic treated wood fibers towards mould fungi growth was also examined. The hydrophobic treatment improved the hygric properties and effectiveness towards mould significantly.
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| 42. |
- Lay, Makara, et al.
(author)
-
Comparison of physical and mechanical properties of PLA, ABS and nylon 6 fabricated using fused deposition modeling and injection molding
- 2019
-
In: Composites Part B. - : ELSEVIER SCI LTD. - 1359-8368 .- 1879-1069. ; 176
-
Journal article (peer-reviewed)abstract
- The objective of this study was to compare the physical and mechanical performance of poly(lactic acid) (PLA), acrylonitrile butadiene styrene (ABS), and nylon 6 fabricated using fused deposition modeling (FDM) and conventional injection molding. It is found that different processing methods did not affect the viscosity of the samples, and the percentage difference for the density measurement is less than 4%. Water absorption of FDM samples is approximately 108% higher compared to those fabricated using the injection molding. The results also revealed that the FDM method did not strongly affect the degree of crystallinity of ABS, but it increased the degree of crystallinity of PLA and nylon 6. The tensile strength, Youngs modulus, elongation at break, and impact strength of FDM samples were approximately 48%, 50%, 48%, and 78%, lower compared with the injection molded samples. The results presented can provide a guide to manufacturing the final products using FDM with the desired performance.
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| 43. |
- Lay, Makara, et al.
(author)
-
Converting dead leaf biomass into activated carbon as a potential replacement for carbon black filler in rubber composites
- 2020
-
In: Composites Part B. - : Elsevier. - 1359-8368 .- 1879-1069. ; 201
-
Journal article (peer-reviewed)abstract
- In this work, the feasibility of converting dead leaf biomass into green activated carbon for use as a reinforcement filler in natural rubber composites was assessed. The dead leaf activated carbon (DLAC) was prepared by pyrolysis at 550, 700, 900, and 1000 degrees C at a heating rate of 10 degrees C min(-1) under nitrogen gas flow of 100 cm(3) min(-1) and was activated by CO2 gas at the same flow rate when the pyrolysis temperature was reached. The properties of DLACs were characterized by particle size analysis, density, scanning electron microscopy, elemental energydispersive X-ray spectroscopy and Raman spectroscopy. The results revealed that the DLAC obtained by pyrolysis at 1000 degrees C had a small particle size of 28.86 tint; a highly porous structure; high carbon purity, at 82.58%; and a low density, at 1.588 g cm(-3). The effect of different DLAC contents (5, 10, and 15 phr) on the curing properties and the physical and mechanical performance of the rubber composites was investigated and compared with rubber composites containing carbon black (CB). The results showed that the addition of DLAC increased the maximum torque and reduced the scorch and cure times. The tensile strength for rubber composites containing 15 phr of DLAC increased by 8%, the M100 and M300 improved 40%, and the elongation at break and crosslink density decreased by approximately 5% and 24%, respectively. The studied DLAC is a promising, cost-effective alternative to commercial carbon black for improving the performance of rubber composites.
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| 44. |
- Li, J., et al.
(author)
-
Multifunctional metal matrix composites with embedded printed electrical materials fabricated by Ultrasonic Additive Manufacturing
- 2017
-
In: Composites Part B. - Kidlington : Pergamon Press. - 1359-8368 .- 1879-1069. ; 113, s. 342-354
-
Journal article (peer-reviewed)abstract
- This work proposes a new method for the fabrication of multifunctional Metal Matrix Composite (MMC) structures featuring embedded printed electrical materials through Ultrasonic Additive Manufacturing (UAM). Printed electrical circuitries combining conductive and insulating materials were directly embedded within the interlaminar region of UAM aluminium matrices to realise previously unachievable multifunctional composites. A specific surface flattening process was developed to eliminate the risk of short circuiting between the metal matrices and printed conductors, and simultaneously reduce the total thickness of the printed circuitry. This acted to improve the integrity of the UAM MMC's and their resultant mechanical strength. The functionality of embedded printed circuitries was examined via four-point probe measurement. DualBeam Scanning Electron Microscopy (SEM) and Focused Ion Beam (FIB) milling were used to investigate the microstructures of conductive materials to characterize the effect of UAM embedding energy whilst peel testing was used to quantify mechanical strength of MMC structures in combination with optical microscopy. Through this process, fully functioning MMC structures featuring embedded insulating and conductive materials were realised whilst still maintaining high peel resistances of ca. 70 N and linear weld densities of ca. 90%. © 2017 Elsevier Ltd
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| 45. |
- Li, Yongqiang, et al.
(author)
-
Chemical and mineralogical characteristics of carbonated and uncarbonated cement pastes subjected to high temperatures
- 2021
-
In: Composites Part B: Engineering. - : Elsevier BV. - 1359-8368. ; 216
-
Journal article (peer-reviewed)abstract
- The fire-resistance of carbonated concrete under high temperatures is significant due to its direct exposure during an accidental fire. To evaluate the carbonation effect on fire-resistance of concrete, the chemical and mineralogical changes of uncarbonated and carbonated cement pastes subjected to high temperatures were thoroughly investigated in this research by employing micro-measurement methods including thermal-gravimetric analysis (TGA), X-ray diffraction (XRD) and Si nuclear magnetic resonance ( Si NMR). Uncarbonated cement paste results showed the decomposition of portlandite at 400 °C with the formation of lime, whilst the depolymerization of C–S–H happened simultaneously to generate monomeric silicon tetrahedron. Above 720 °C, all the C–S–H depolymerized to crystalline C S. Carbonated cement pastes on the other hand showed that amorphous calcium carbonate and part of vaterite decomposed between the range of 400–600 °C, while the rest of the vaterite and calcite were decomposed at 600–720 °C. The individual content of calcium carbonate polymorph could not be obtained using a TGA curve. Besides, the calcium-modified silicate gel was significantly decomposed at 500 °C and completely depolymerized to crystalline C S at 950 °C. In summary, carbonated pastes show better resistance to high temperatures with its heat absorption capacity 3.3 times as high as the uncarbonated sample, which delays the temperature development in the inner layer. Therefore, a reasonable carbonation process could help to improve the fire resistance of concrete to some extent.
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| 46. |
- Linghoff, Dag, 1970, et al.
(author)
-
Performance of steel beams strengthened with CFRP laminate - Part 1: Laboratory tests
- 2010
-
In: Composites Part B: Engineering. - : Elsevier BV. - 1359-8368. ; 41:7, s. 509-515
-
Journal article (peer-reviewed)abstract
- Research on the behaviour of beams strengthened with different configurations of carbon-fibre-rein-forced-polymer (CFRP) laminates, in both the serviceability and ultimate limit state, has been conducted at Chalmers University of Technology. Additionally, the failure modes and the interfacial shear stresses in the bond line have been studied. The methods used in the research work were laboratory tests and simplified analytical solutions and the work took the form of parametric studies on the strengthened steel beams. CFRP laminates and epoxies with different material properties were attached to the tension flange of steel beams with I cross-sections. The strengthened beams were tested in four-point bending where the deflection of the beams and the strains, in both the steel beams and the laminates, were measured. The results show that it is possible to increase the moment capacity of a steel beam with CFRP bonded to its tension flange. Additionally, it is possible to predict the degree of increase in capacity by using simplified analytical solutions. (C) 2010 Elsevier Ltd. All rights reserved.
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| 47. |
- Linghoff, Dag, 1970, et al.
(author)
-
Performance of steel beams strengthened with CFRP laminate - Part 2: FE analyses
- 2010
-
In: Composites Part B: Engineering. - : Elsevier BV. - 1359-8368. ; 41:7, s. 516-522
-
Journal article (peer-reviewed)abstract
- A new method for repairing and strengthening steel is under development and consists of using CFRP (carbon-fibre-reinforced-polymer) laminates bonded to the steel substrate. Research on this method has been conducted by a few research groups in recent years. The idea is to let the CFRP laminate carry a large part of the stresses and thereby reduce the load on the steel, which may have had its capacity lowered due to deterioration or fatigue. The present paper presents the results of FE analyses of steel beams strengthened with bonded CFRP laminates. The interfacial shear and peeling stresses that appear in the bond line between the steel and CFRP laminate are studied in both the elastic and plastic phase of the steel beam. Comparisons with the results obtained from laboratory tests conducted on steel beams strengthened with bonded CFRP laminates show that the behaviour of the strengthened beams can be captured using FE analyses. The distribution of the shear and peeling stresses near the end of the bond line were obtained from the FE analyses, together with the interfacial stresses that develop near beam mid-span due to the yielding of the steel. These stresses may exceed the capacity of the adhesive and cause debonding in this region. (C) 2010 Elsevier Ltd. All rights reserved.
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| 48. |
- Lundström, Fredrik, et al.
(author)
-
A method for inductive measurement of equivalent electrical conductivity in thin non-consolidated multilayer carbon fibre fabrics
- 2018
-
In: Composites Part B: Engineering. - : Elsevier BV. - 1359-8368. ; 140, s. 204-213
-
Journal article (peer-reviewed)abstract
- Carbon fibre fabrics are electrically conductive and therefore possess the prerequisites for being inductively heated. In-situ heating by induction could significantly reduce processing time and energy consumption during consolidation of carbon fibre composites, but to control the induction heating process properly the electrical conductivity of the fabric must be known. The work presented in this article puts forward and validates a method for inductively measuring the equivalent electrical conductivity in thin dry multilayer carbon fibre fabrics as a function of the fibre volume fraction by varying the applied pressure on the fabric. The method has been tested on twill weave fabric based on the PAN (polyacrylonitrile) fibre T700S from Toray and the results show good agreement with a simplified model for electrical conductivity in carbon fibre fabrics and existing models for the relation between fibre volume fraction and pressure.
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| 49. |
- Lundström, Fredrik, et al.
(author)
-
A numerical model to analyse the temperature distribution in cross-ply CFRP during induction heating
- 2020
-
In: Composites Part B: Engineering. - : Elsevier BV. - 1359-8368. ; 202
-
Journal article (peer-reviewed)abstract
- Heat generation in CFRP (carbon fibre reinforced plastic) with electromagnetic induction can result in several benefits to manufacturing and production. However, during induction heating of anisotropic materials such as CFRP, the temperature distribution depends on electrical and thermal conductivity in different directions. This article presents a numerical model for computing the temperature distribution and heating power distribution in cross-ply CFRP plates, based on unidirectional plies, during induction heating. The unidirectional layers are represented as homogeneous and anisotropic domains in which electrical and thermal conductivity are represented with tensors. The electrical and thermal properties were measured and used in the numerical model to compute the temperature distribution in a number of CFRP-plates with different fibre volume fractions and layer thicknesses, and then the numerical model was validated by recording the temperature distribution with a thermographic camera during induction heating of the CFRP-plates. The experiments showed good agreement with the results from the numerical model.
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| 50. |
- Lundström, Fredrik, et al.
(author)
-
Analysis of the temperature distribution in weave-based CFRP during induction heating using a simplified numerical model with a cross-ply representation
- 2021
-
In: Composites Part B: Engineering. - : Elsevier BV. - 1359-8368. ; 223
-
Journal article (peer-reviewed)abstract
- Induction heating of carbon fibre reinforced plastics, CFRP, has a great potential within different application areas, such as induction welding and curing of thermosets, due to fast and energy efficient heating. Simulation models can obviously be valuable for example during optimization. This article shows how temperature distribution during induction heating of CFRP based on woven fabric can be simulated using a finite element model with a unidirectional layer representation, thus simplifying the geometry significantly. Electrical and thermal properties were measured and used in the numerical model. The simulated and measured temperature distributions show good agreement, where the prediction of peak temperature is within just a few percent for the plates with a fibre volume fraction above 50% while the same difference is just above 10% percent for the plate with a fibre volume fraction below 40%.
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