| 1. |
- Andersons, J., et al.
(author)
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Fibre fragment distribution in a single-fibre composite tension test
- 2001
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In: Composites Part B. - 1359-8368 .- 1879-1069. ; 32:4, s. 323-332
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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
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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
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In: Composites Part B. - 1359-8368 .- 1879-1069. ; 34:7, s. 587-592
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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)
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Some computational aspects of iterated structures
- 2001
-
In: Composites Part B. - 1359-8368 .- 1879-1069. ; 32:6, s. 485-490
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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)
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On the effect of stacked fabric layers on the stiffness of a woven composite
- 2002
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In: Composites Part B. - 1359-8368 .- 1879-1069. ; 33:8, s. 619-629
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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)
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Strengthening concrete beams for shear using CFRP-materials : evaluation of different application methods
- 2000
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In: Composites Part B. - 1359-8368 .- 1879-1069. ; 31:2, s. 87-96
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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)
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A review of dental composites : Challenges, chemistry aspects, filler influences, and future insights
- 2021
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In: Composites Part B. - : Elsevier. - 1359-8368 .- 1879-1069. ; 216
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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)
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Fibre orientation distribution function mapping for short fibre polymer composite components from low resolution/large volume X-ray computed tomography
- 2024
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In: Composites Part B: Engineering. - 1359-8368. ; 275
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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)
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Electrocoating of carbon fibres at ambient conditions
- 2016
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In: Composites Part B. - : Elsevier Ltd. - 1359-8368 .- 1879-1069. ; 91, s. 94-102
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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)
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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
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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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