| 1. |
- Adekunle, Kayode, et al.
(författare)
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Impact and flexural properties of flax fabrics and Lyocell fiber-reinforced bio-based thermoset
- 2011
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Ingår i: Journal of reinforced plastics and composites (Print). - : SAGE Publications. - 0731-6844 .- 1530-7964. ; 30:8, s. 685-697
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Tidskriftsartikel (refereegranskat)abstract
- A bio-based thermoset resin was reinforced with flax fabrics and Lyocell fiber. The effect of different weave architectures was studied with four flax fabrics with different architectures: plain, twill (two different types), and dobby. The effect of the outer ply thickness was studied and characterized with flexural and impact testing. Composites manufactured with plain weave reinforcement had the best mechanical properties. The tensile strength, tensile modulus, flexural strength, flexural modulus, and impact strength were 280MPa, 32GPa, 250MPa, 25GPa, and 75 kJ/m (2), respectively. Reinforcements with twill-weave architecture did not impart appreciable flexural strength or flexural modulus even when the outer thickness was increased. Plain- and dobby (basket woven style)-weave architectures gave better reinforcing effects and the flexural properties increased with an increase in outer thickness. Water absorption properties of the composites were studied and it was observed that the hybridization with Lyocell fiber reduced the water uptake. Field-emission scanning electron microscopy was used to study the micro-structural properties of the composites.
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| 2. |
- Almgren, Karin M., et al.
(författare)
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Effects of Moisture on Dynamic Mechanical Properties of Wood Fiber Composites Studied by Dynamic FT-IR Spectroscopy
- 2008
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Ingår i: Journal of reinforced plastics and composites (Print). - : SAGE Publications. - 0731-6844 .- 1530-7964. ; 27:16-17, s. 1709-1721
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Tidskriftsartikel (refereegranskat)abstract
- Wood fiber reinforced polylactide is a biodegradable composite where both fibers and matrix are from renewable resources. In the development of such new materials, information on mechanical behavior on the macroscopic and the molecular level is useful. In this study, dynamic Fourier transform infrared (FT-IR) spectroscopy is used to measure losses at the molecular level during cyclic tensile loading for bonds that are characteristic of the cellulosic fibers and the polylactid matrix. This molecular behavior is compared with measured macroscopic hysteresis losses for different moisture levels. The results show that moisture ingress will transfer the load from the fibers to the matrix, and that a more efficient fiber-matrix interface would diminish mechanical losses. Although the dynamic FT-IR spectroscopy method is still qualitative, this investigation shows that it can provide information on the stress transfer of the constituents in wood fiber reinforced plastics.
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| 3. |
- Andersons, J., et al.
(författare)
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Scale effect of the tensile strength of flax-fabric-reinforced polymer composites
- 2011
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Ingår i: Journal of reinforced plastics and composites (Print). - : SAGE Publications. - 0731-6844 .- 1530-7964. ; 30:23, s. 1969-1974
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Tidskriftsartikel (refereegranskat)abstract
- The development of UD natural fiber composites, considered for application as structural materials, necessitates evaluation of the scale effect of their strength. Alignment of the fibers in flax bast fiber composites can be achieved by employing textile reinforcement, such as yarns and fabrics. Cutting specimens for mechanical tests out of such textile-reinforced composite plates results in a complex non-uniform reinforcement structure at their edges, which may affect the strength of specimens. Scale effect of the tensile strength in the fiber direction of flax-fabric-reinforced composites is studied in the current work. A model accounting for both volume and edge effect of the specimens on their tensile strength is proposed. © The Author(s) 2011.
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| 4. |
- Berglund, Lars A., et al.
(författare)
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Transverse Cracking and Local Delamination in [04/90n]s and [90n/04]s Carbon Fiber/Toughened Epoxy Laminates
- 1992
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Ingår i: Journal of reinforced plastics and composites (Print). - : SAGE Publications. - 0731-6844 .- 1530-7964. ; 11:6, s. 643-660
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Tidskriftsartikel (refereegranskat)abstract
- [04/90n]s and [90n/04 ]s laminates were used to study 90°-layer failure mechanisms in HTA/6376 carbon fiber/toughened epoxy. The different stacking sequences were chosen to vary the stress states, since experimental results show differences in failure strains as well as in the local delamination behavior at the crack tip. Differences in the onset of transverse cracking and local delamination behavior between [04/90m]s and [90 n/04]s laminates was discussed using a model based on linear elastic fracture mechanics (LEFM). Although quantitative LEFM-predictions do not agree with data for the carbon fiber/toughened epoxy investigated, the general predictions for differences in and causes of local delamination behavior were confirmed by experimental data. The fact that the main features were correctly predicted, encourages the development of some modified LEFM-approach to describe toughened matrix composites.
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| 5. |
- Fernberg, Patrik, et al.
(författare)
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Mechanisms controlling particle distribution in infusion molded composites
- 2006
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Ingår i: Journal of reinforced plastics and composites (Print). - : SAGE Publications. - 0731-6844 .- 1530-7964. ; 25:1, s. 59-70
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Tidskriftsartikel (refereegranskat)abstract
- This article presents results from an experimental investigation in which two grades of aluminatrihydroxide (ATH) particles are added to liquid resin and used in infusion molding experiments. Based on the results, potential key mechanisms controlling resin flow and hence also the final particle distribution are proposed. A pore doublet model is proposed to explain the seemingly random spatial distribution of particle-dense regions within the final material. These dense regions are found within flow channels, at locations where local shear strain rates are low. This suggests that they are formed as a consequence of a Bingham type of viscosity behavior observed for the suspension and/or due to filtering of particles during fiber bundle impregnation. © 2006 SAGE Publications.
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| 6. |
- Frishfelds, Vilnis, et al.
(författare)
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Automatic recognition and analysis of scanned non-crimp fabrics for calculation of their fluid flow permeability
- 2007
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Ingår i: Journal of reinforced plastics and composites (Print). - : SAGE Publications. - 0731-6844 .- 1530-7964. ; 26:3, s. 285-296
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Tidskriftsartikel (refereegranskat)abstract
- Automatic recognition of scanned images of distorted bi-axial fiber bundle arrangements is considered in order to obtain the overall permeability of the formed fiber network. Scanned images are pre-processed with color normalization followed by usage of a threshold to find the pixels belonging to the bundles, the threads keeping the bundles together, and the distinct gaps formed between the bundles. Since the scanned images virtually have a perfect grayscale, the intensity can be treated as a corresponding signal of the image. Next the regular character of the fiber network is investigated using Fourier analysis on the fiber bundles as well as on the threads. The direction, position, and spatial separation of the fiber bundle and the threads are obtained in this way. In order to recognize the bottom fiber bundle layer a fine structure technique is used. Small clusters falsely identified as belonging to the bottom bundle layer are removed by application of a threshold to the perimeter of the cluster. The gaps in the top bundle layer are identified more clearly in this way. Next, a local Fourier analysis is applied to obtain the local distortion of the bundle and the thread structure yielding the characteristic distribution of the gaps between the bundles. Finally the distribution of the width of the threads is obtained by simply identifying the minimal distance between the sides of the threads.
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| 7. |
- Giannadakis, Konstantinos, et al.
(författare)
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The sources of inelastic behavior of Glass Fibre/Vinylester non-crimp fabric [±45]s laminates
- 2011
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Ingår i: Journal of reinforced plastics and composites (Print). - : SAGE Publications. - 0731-6844 .- 1530-7964. ; 30:12, s. 1015-1028
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Tidskriftsartikel (refereegranskat)abstract
- The non-linear and time-dependent stress-strain response of NCF [±45]s laminates in tension is studied. Testing methodology is suggested to separate and quantify the effect of damage development, non-linear viscoelastic effects, and viscoplasticity on the inelastic response. This is achieved by decomposition of viscoelastic and viscoplastic response, both of them being affected by microdamage accumulated during the service life. Material model based on Schapery's work on viscoelasticity and Zapas viscoplastic function with added damage terms is presented and used. Simulation is performed and validated with constant stress rate tensile tests, identifying the non-linear viscoelasticity and viscoplasticity as the major sources of the non-linear response.
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| 8. |
- Haghani Dogaheh, Reza, 1979, et al.
(författare)
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Effect of Laminate Tapering on Strain Distribution in Adhesive Joints: Experimental Investigation
- 2010
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Ingår i: Journal of Reinforced Plastics and Composites. - : SAGE Publications. - 0731-6844 .- 1530-7964. ; 29:7, s. 972-985
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Tidskriftsartikel (refereegranskat)abstract
- Strain distribution in adhesive joints with untapered and normal-tapered laminates has been investigated using an experimental method. An optic measurement system, ARAMIS, was used to monitor the strain field in the adhesive layer. The results indicated that normal tapering of the laminate did not affect the shear and principal strain components, but it increased the maximum peeling strain in the joint for the tapering length examined in this study. The strength and failure mode of joints were also studied. It was found that normal tapering of the laminate did not improve the strength of the joint in comparison to joints with untapered laminates. Failure took place at the steel-adhesive interface in both configurations.
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| 9. |
- Hassan, Mohammad L., et al.
(författare)
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Improving cellulose/polypropylene nanocomposites properties with chemical modified bagasse nanofibers and maleated polypropylene
- 2014
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Ingår i: Journal of reinforced plastics and composites (Print). - : SAGE Publications. - 0731-6844 .- 1530-7964. ; 33:1, s. 26-36
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Tidskriftsartikel (refereegranskat)abstract
- The properties of cellulose/polypropylene (PP) nanocomposites with n-octadecyl-modified bagasse nanofibers (MBNF) were compared to those with maleated polypropylene (MAPP) coupling agent. The nanocomposites were prepared by twin-screw extrusion with bagasse nanofiber (BNF) content varying from 2.5 to 10 wt%. The compression molded nanocomposites sheets were characterized regarding their tensile strength properties, dynamic mechanical thermal properties, crystallinity, water absorption, transparency and loss of strength due to composting in soil. As a compatibilizer to improve the tensile strength properties and transparency of PP/cellulose nanofibers nanocomposites, MAPP was more effective than n-octadecyl-modified cellulose nanofibers. The crystallinity of the nanocomposites was lower than that of neat PP except for those prepared using high loading of MBNF. Dynamic mechanical thermal analysis (DMTA) of the prepared materials showed that adding the different nanofibers (treated or untreated) resulted in better mechanical thermal properties above glass transition temperature (Tg) of PP. Water absorption capability in all nanocomposites was weakened while that in PP/MBNF was the lowest. No significant differences were found between the nanocomposites with different kinds of nanofibers regarding the loss of their tensile strength after compositing in soil up to six months.
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| 10. |
- Heidari-Rarani, M, et al.
(författare)
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Micromechanical modeling of the mechanical behavior of unidirectional composites – A comparative study
- 2018
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Ingår i: Journal of Reinforced Plastics and Composites. - : SAGE Publications. - 0731-6844 .- 1530-7964. ; 37:16, s. 1051-1071
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Tidskriftsartikel (refereegranskat)abstract
- Laminated fiber reinforced composites are increasingly being used in various load-bearing applications including for instance aerospace and wind energy power industries. Understanding the mechanical behavior of a unidirectional lamina as the basic part of a laminated composite is of great interest from a design perspective and also for the analysis of composite structures. At the micro-level, mechanical behavior of a lamina including stiffness and strength is studied based on the mechanical properties of individual constituents. This study focuses on micromechanical approaches such as strength of materials, elasticity, semi-empirical, and numerical methods for the prediction of the stiffness and strength of a unidirectional lamina. To assess the accuracy of these models, results of each model are compared against experimental results available in the literature for unidirectional composites with different fiber volume fractions. Moreover, recent studies on micromechanical modeling of unidirectional composites are reviewed.
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