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Larissa Gorbatikh - One of the best experts on this subject based on the ideXlab platform.
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Maximising the hybrid effect in unidirectional hybrid composites
Materials & Design, 2016Co-Authors: Yentl Swolfs, Ignaas Verpoest, Larissa GorbatikhAbstract:The Failure Strain of fibre-reinforced composites can be increased by fibre hybridisation. A recently developed model for unidirectional composites was extended to hybrid composites to analyse this synergetic effect, called the hybrid effect. The model predicts individual fibre breaks and interactions among clusters of fibre breaks. Three key parameters were studied to understand how they can maximise the hybrid effect, namely low elongation fibre strength scatter and hybridisation fibre stiffness and Failure Strain. Larger strength scatter of the low elongation fibres leads to larger hybrid effects, as the scatter spreads out the cluster development over a larger Strain interval. The Failure Strain ratio of the two fibre types should be above 2 for the properties used here, but a higher ratio did not yield any additional benefits. Increasing the stiffness of the hybridisation fibre reduces the stress concentrations on the low elongation fibre and may also enlarge the hybrid effect. These conclusions provide guidelines for designing optimal hybrid composites.
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global load sharing model for unidirectional hybrid fibre reinforced composites
Journal of The Mechanics and Physics of Solids, 2015Co-Authors: Yentl Swolfs, Varun P. Rajan, Larissa GorbatikhAbstract:© 2015 Elsevier Ltd. All rights reserved. A promising strategy to increase the tensile Failure Strain of carbon fibre-reinforced composites is to hybridise carbon fibres with other, higher-elongation fibres. The resulting increase in Failure Strain is known as the hybrid effect. In the present article, a global load-sharing model for hybrid composites is developed and used to carry out a parametric study for carbon/glass hybrids. Hybrid effects of up to 15% increase in Failure Strain are predicted, corresponding reasonably well to literature data. Scatter in the carbon fibre strength is shown to be crucial for the hybrid effect, while the scatter in glass fibre strength is much less important. In contrast to reports in earlier literature, the ratio of Failure Strains of the two fibres has only a small influence on the hybrid effect. The results provide guidelines for designing optimal hybrid composites.
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Intralayer hybridisation to combine the ductility of self-reinforced polypropylene with the stiffness of carbon fibre
2015Co-Authors: Yentl Swolfs, J Shi, Yannick Meerten, Peter Hine, Ian Macmillan Ward, Ignace Verpoest, Larissa GorbatikhAbstract:Combining a reasonable stiffness and a high ultimate Failure Strain in a single material is challenging task. Intralayer hybridisation of self-reinforced polypropylene (SRPP) with carbon fibre is proposed as a new strategy to increase stiffness while maintaining a high Strain to Failure. The bonding between SRPP and the carbon fibre prepregs was found to be a crucial parameter in these hybrids. It can be altered either directly by replacing the homopolymer polypropylene (PP) matrix in the prepregs by a maleic anhydride PP, or indirectly by changing the carbon fibre volume fraction. Weak bonding was key to preserving a high ultimate Failure Strain and impact resistance. Strong bonding reduced the ultimate Failure Strain and impact resistance, but improved flexural properties. These results reveal a delicate balance in optimising the bonding in hybrid composites to achieve optimum performance.
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Model validation of the hybrid effect in carbon/glass hybrid composites
2015Co-Authors: Yentl Swolfs, Gergely Czel, Michael R Wisnom, Ignace Verpoest, Meisam Jalalvand, Larissa GorbatikhAbstract:Carbon fibre-reinforced composites typically have a Failure Strain of about 2%. One way to delay the Failure of the carbon fibres and increase the Failure Strain is through fibre hybridisation [1]. By adding glass fibres for example, the apparent Failure Strain of carbon fibre can be increased. This synergetic effect is called the “hybrid effect” in the literature. The hybrid effect has caused confusion in the literature as soon as it was discovered by Hayashi in 1972 [2]. Initially, the synergism was attributed to differences in thermal contractions of both fibre types. Soon, it became clear that this was insufficient to explain the hybrid effect. The focus then shifted to changes in the Failure development. This approach was more successful in predicting the hybrid effect, although the predictions remained qualitative [3]. Model validations of the hybrid effect are hampered by two types of experimental difficulties. Firstly, tensile tests on unidirectional carbon fibre composites are often affected by stress concentrations at the grips. This strongly reduces the measured Failure Strains. Hybrid composites are less prone to these stress concentrations, as the glass fibres shield the stress concentrations from the carbon fibres. This often leads to a larger measured Failure Strain, which could falsely lead to the conclusion of a large, positive hybrid effect. Secondly, carbon and glass fibres should be well dispersed to achieve a measurable hybrid effect, but the required preforms are difficult to obtain commercially. This abstract proposes a new methodology for experimentally validating models for the hybrid effect. This consists of sandwiching a 30 µm thin carbon fibre ply in between glass plies (see Fig. 1). Such thin layers are required to achieve a large hybrid effect. The reference Failure Strain for the carbon fibre ply is also measured in a hybrid composite to avoid stress concentrations in the grips. In this case however, the carbon fibre ply is much thicker. A strength model is required to determine the minimum layer thickness to avoid a significant hybrid effect.
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the effect of fibre dispersion on initial Failure Strain and cluster development in unidirectional carbon glass hybrid composites
Composites Part A-applied Science and Manufacturing, 2015Co-Authors: Yentl Swolfs, Robert M Mcmeeking, Ignaas Verpoest, Larissa GorbatikhAbstract:Abstract By adding glass fibres to carbon fibre composites, the apparent Failure Strain of the carbon fibres can be increased. A strength model for unidirectional hybrid composites was developed under very local load sharing assumptions to study this hybrid effect. Firstly, it was shown that adding more glass fibres leads to higher hybrid effects. The hybrid effect was up to 32% for a hybrid composite with a 10/90 ratio of carbon/glass fibres. The development of clusters of broken fibres helped to explain differences in the performance of these hybrid composites. For 50/50 carbon/glass hybrids, a fine bundle-by-bundle dispersion led to a slightly smaller hybrid effect than for randomly dispersed hybrids. The highest hybrid effect for a 50/50 ratio, however, was 16% and was achieved in a composite with alternating single fibre layers. The results demonstrate that thin ply hybrids may have more potential for improved mechanical properties than comingled hybrids.
Yentl Swolfs - One of the best experts on this subject based on the ideXlab platform.
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Maximising the hybrid effect in unidirectional hybrid composites
Materials & Design, 2016Co-Authors: Yentl Swolfs, Ignaas Verpoest, Larissa GorbatikhAbstract:The Failure Strain of fibre-reinforced composites can be increased by fibre hybridisation. A recently developed model for unidirectional composites was extended to hybrid composites to analyse this synergetic effect, called the hybrid effect. The model predicts individual fibre breaks and interactions among clusters of fibre breaks. Three key parameters were studied to understand how they can maximise the hybrid effect, namely low elongation fibre strength scatter and hybridisation fibre stiffness and Failure Strain. Larger strength scatter of the low elongation fibres leads to larger hybrid effects, as the scatter spreads out the cluster development over a larger Strain interval. The Failure Strain ratio of the two fibre types should be above 2 for the properties used here, but a higher ratio did not yield any additional benefits. Increasing the stiffness of the hybridisation fibre reduces the stress concentrations on the low elongation fibre and may also enlarge the hybrid effect. These conclusions provide guidelines for designing optimal hybrid composites.
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global load sharing model for unidirectional hybrid fibre reinforced composites
Journal of The Mechanics and Physics of Solids, 2015Co-Authors: Yentl Swolfs, Varun P. Rajan, Larissa GorbatikhAbstract:© 2015 Elsevier Ltd. All rights reserved. A promising strategy to increase the tensile Failure Strain of carbon fibre-reinforced composites is to hybridise carbon fibres with other, higher-elongation fibres. The resulting increase in Failure Strain is known as the hybrid effect. In the present article, a global load-sharing model for hybrid composites is developed and used to carry out a parametric study for carbon/glass hybrids. Hybrid effects of up to 15% increase in Failure Strain are predicted, corresponding reasonably well to literature data. Scatter in the carbon fibre strength is shown to be crucial for the hybrid effect, while the scatter in glass fibre strength is much less important. In contrast to reports in earlier literature, the ratio of Failure Strains of the two fibres has only a small influence on the hybrid effect. The results provide guidelines for designing optimal hybrid composites.
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Intralayer hybridisation to combine the ductility of self-reinforced polypropylene with the stiffness of carbon fibre
2015Co-Authors: Yentl Swolfs, J Shi, Yannick Meerten, Peter Hine, Ian Macmillan Ward, Ignace Verpoest, Larissa GorbatikhAbstract:Combining a reasonable stiffness and a high ultimate Failure Strain in a single material is challenging task. Intralayer hybridisation of self-reinforced polypropylene (SRPP) with carbon fibre is proposed as a new strategy to increase stiffness while maintaining a high Strain to Failure. The bonding between SRPP and the carbon fibre prepregs was found to be a crucial parameter in these hybrids. It can be altered either directly by replacing the homopolymer polypropylene (PP) matrix in the prepregs by a maleic anhydride PP, or indirectly by changing the carbon fibre volume fraction. Weak bonding was key to preserving a high ultimate Failure Strain and impact resistance. Strong bonding reduced the ultimate Failure Strain and impact resistance, but improved flexural properties. These results reveal a delicate balance in optimising the bonding in hybrid composites to achieve optimum performance.
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Model validation of the hybrid effect in carbon/glass hybrid composites
2015Co-Authors: Yentl Swolfs, Gergely Czel, Michael R Wisnom, Ignace Verpoest, Meisam Jalalvand, Larissa GorbatikhAbstract:Carbon fibre-reinforced composites typically have a Failure Strain of about 2%. One way to delay the Failure of the carbon fibres and increase the Failure Strain is through fibre hybridisation [1]. By adding glass fibres for example, the apparent Failure Strain of carbon fibre can be increased. This synergetic effect is called the “hybrid effect” in the literature. The hybrid effect has caused confusion in the literature as soon as it was discovered by Hayashi in 1972 [2]. Initially, the synergism was attributed to differences in thermal contractions of both fibre types. Soon, it became clear that this was insufficient to explain the hybrid effect. The focus then shifted to changes in the Failure development. This approach was more successful in predicting the hybrid effect, although the predictions remained qualitative [3]. Model validations of the hybrid effect are hampered by two types of experimental difficulties. Firstly, tensile tests on unidirectional carbon fibre composites are often affected by stress concentrations at the grips. This strongly reduces the measured Failure Strains. Hybrid composites are less prone to these stress concentrations, as the glass fibres shield the stress concentrations from the carbon fibres. This often leads to a larger measured Failure Strain, which could falsely lead to the conclusion of a large, positive hybrid effect. Secondly, carbon and glass fibres should be well dispersed to achieve a measurable hybrid effect, but the required preforms are difficult to obtain commercially. This abstract proposes a new methodology for experimentally validating models for the hybrid effect. This consists of sandwiching a 30 µm thin carbon fibre ply in between glass plies (see Fig. 1). Such thin layers are required to achieve a large hybrid effect. The reference Failure Strain for the carbon fibre ply is also measured in a hybrid composite to avoid stress concentrations in the grips. In this case however, the carbon fibre ply is much thicker. A strength model is required to determine the minimum layer thickness to avoid a significant hybrid effect.
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the effect of fibre dispersion on initial Failure Strain and cluster development in unidirectional carbon glass hybrid composites
Composites Part A-applied Science and Manufacturing, 2015Co-Authors: Yentl Swolfs, Robert M Mcmeeking, Ignaas Verpoest, Larissa GorbatikhAbstract:Abstract By adding glass fibres to carbon fibre composites, the apparent Failure Strain of the carbon fibres can be increased. A strength model for unidirectional hybrid composites was developed under very local load sharing assumptions to study this hybrid effect. Firstly, it was shown that adding more glass fibres leads to higher hybrid effects. The hybrid effect was up to 32% for a hybrid composite with a 10/90 ratio of carbon/glass fibres. The development of clusters of broken fibres helped to explain differences in the performance of these hybrid composites. For 50/50 carbon/glass hybrids, a fine bundle-by-bundle dispersion led to a slightly smaller hybrid effect than for randomly dispersed hybrids. The highest hybrid effect for a 50/50 ratio, however, was 16% and was achieved in a composite with alternating single fibre layers. The results demonstrate that thin ply hybrids may have more potential for improved mechanical properties than comingled hybrids.
Manoj Gupta - One of the best experts on this subject based on the ideXlab platform.
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Improving significantly the Failure Strain and work hardening response of LPSO-strengthened Mg-Y-Zn-Al alloy via hot extrusion speed control
Metals and Materials International, 2017Co-Authors: Winston Chee, Jimmy Chan, Richard Kwok, Manoj GuptaAbstract:The effect of hot extrusion speed on the microstructure and mechanical properties of MgY_1.06Zn_0.76Al_0.42 (at%) alloy strengthened by the novel long-period stacking ordered (LPSO) phase was systematically investigated. Increase in the speed of extrusion accelerated dynamic recrystallization of α-Mg via particle-stimulated nucleation and grain growth in the alloy. The intensive recrystallization and grain growth events weakened the conventional basal texture and Hall-Petch strengthening in the alloy which led to significant improvement in its Failure Strain from 4.9% to 19.6%. The critical strengthening contribution from LPSO phase known for attributing high strength to the alloy was observed to be greatly undermined by the parallel competition from texture weakening and the adverse Hall-Petch effect when the alloy was extruded at higher speed. Absence of work hardening interestingly observed in the alloy extruded at lower speed was discussed in terms of its ultra-fine grained microstructure which promoted the condition of steady-state defect density in the alloy; where dislocation annihilation balances out the generation of new dislocations during plastic deformation. One approach to improve work hardening response of the alloy to prevent unstable deformation and abrupt Failure in service is to increase the grain diameter in the alloy by judiciously increasing the extrusion speed.
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Effect of homogenization on enhancing the Failure Strain of high strength quaternary LPSO Mg–Y–Zn–Al alloy
Materials Science and Engineering: A, 2015Co-Authors: Xinghe Tan, Keat How Winston Chee, Kwok Weng Jimmy Chan, Wai Onn Richard Kwok, Manoj GuptaAbstract:Abstract The current work investigates the effect of homogenization on enhancing the Failure Strain of a high strength MgY 1.06 Zn 0.76 Al 0.42 (at.%) alloy. Bulk 14H long-period stacking ordered (LPSO) phases (≥10 µm) were progressively broken down into acicular fine platelets (≤2 µm) with increase in homogenization time (1, 2, 4 and 6 hours) at 450 °C. The high density of fine LPSO platelets (≤2 µm inter-particle spacing) were experimentally observed to be more effective than the bulk LPSO phases (≥10 µm inter-phase spacing) in promoting dynamic recyrstallization (DRX) via particle simulated nucleation (PSN) during extrusion which was critical for basal texture weakening to enhance the Failure Strain of the as-extruded alloy. The alloy homogenized for 2 hours prior to hot extrusion (as-extruded alloy B) displayed the highest tensile yield (376 MPa) and ultimate tensile strength (416 MPa) with significant improvement in Failure Strain (+80%) compared to as-extruded alloy A (homogenized for 1 hour prior to hot extrusion).
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Enhancement of compressive strength and Failure Strain in AZ31 magnesium alloy
Journal of Alloys and Compounds, 2009Co-Authors: Muralidharan Paramsothy, Narasimalu Srikanth, S F Hassan, Manoj GuptaAbstract:Abstract New bimetal AZ31/AA5052 macrocomposite containing millimeter-scale aluminium alloy core reinforcement was fabricated using solidification processing followed by hot coextrusion. Microstructural characterization revealed decreased intermetallic particle spacing, Mg texture change and significant interfacial interdiffusion of Mg and Al into each other. Compressive testing revealed that presence of AA5052 core increased compressive yield strength (0.2% CYS) (+51%), ultimate compressive strength (UCS) (+4%), average Failure Strain (+18%) and work of fracture (WOF) (+50%) of AZ31. The effect of presence of mm-scale AA5052 core on the compressive properties of the bimetal macrocomposite is investigated in this paper.
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Adding carbon nanotubes and integrating with AA5052 aluminium alloy core to simultaneously enhance stiffness, strength and Failure Strain of AZ31 magnesium alloy
Composites Part A: Applied Science and Manufacturing, 2009Co-Authors: Muralidharan Paramsothy, Narasimalu Srikanth, S F Hassan, Manoj GuptaAbstract:Abstract New bimetal AZ31-CNT/AA5052 macrocomposite comprising: (a) carbon nanotube (CNT) reinforced magnesium alloy AZ31 shell and (b) aluminium alloy AA5052 millimeter-scale core reinforcement was fabricated using solidification processing followed by hot coextrusion. Microstructural characterisation revealed more rounded intermetallic particle of decreased size, reasonable CNT distribution, and dominant (1 0 −1 1) texture in the longitudinal and transverse directions in the AZ31-CNT nanocomposite shell. Interdiffusion of Mg and Al across the core-shell macrointerface into each other was also significant. Compared to monolithic AZ31, the AZ31-CNT shell had significantly higher hardness (+30%). In tension, the presence of CNT (in the AZ31 shell) and AA5052 core significantly increased stiffness (+39%), ultimate strength (+13%), Failure Strain (+17%) and work of fracture (+27%) of AZ31, while yield strength (−2%) was marginally decreased. In compression, the presence of CNT (in the AZ31 shell) and AA5052 core significantly increased yield strength (+35%), Failure Strain (+42%) and work of fracture (+70%) of AZ31, while ultimate strength (+1%) was marginally increased. The effect of joint presence of: (a) CNT (in the AZ31 shell) and (b) AA5052 millimeter-scale core on tensile and compressive properties of AZ31 is investigated in this paper.
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heat treating below recrystallization temperature to enhance compressive Failure Strain and work of fracture of magnesium
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: Muralidharan Paramsothy, Narasimalu Srikanth, S F Hassan, Manoj GuptaAbstract:Abstract New bimetal magnesium/aluminium macrocomposite containing millimeter-scale Al core reinforcement was fabricated using solidification processing followed by hot coextrusion. Microstructural characterisation revealed increased grain size, Mg texture change and unbalanced interfacial interdiffusion of Mg and Al into each other. Stress at the bimetal interface was attributed to solid solution formation, thermal expansion mismatch, unbalanced Kirkendall Strain, lattice misfit Strain, and Strain localization effects, these being interface localized strengthening phenomena. Compressive testing revealed that presence of Al core decreased 0.2% YS (−23%) and ultimate compressive strength (UCS) (−11%), but significantly increased Failure Strain (+134%) and work of fracture (+60%) of Mg in the as-extruded macrocomposite. Also, interfacial relaxation during heat treating significantly increased Failure Strain (+17%) and work of fracture (+17%) of Mg/Al macrocomposite without compromising 0.2% YS and UCS. The effects of presence of millimeter-scale Al core as well as interfacial relaxation on the compressive properties of the bimetal macrocomposite are investigated in this paper.
Ignaas Verpoest - One of the best experts on this subject based on the ideXlab platform.
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Maximising the hybrid effect in unidirectional hybrid composites
Materials & Design, 2016Co-Authors: Yentl Swolfs, Ignaas Verpoest, Larissa GorbatikhAbstract:The Failure Strain of fibre-reinforced composites can be increased by fibre hybridisation. A recently developed model for unidirectional composites was extended to hybrid composites to analyse this synergetic effect, called the hybrid effect. The model predicts individual fibre breaks and interactions among clusters of fibre breaks. Three key parameters were studied to understand how they can maximise the hybrid effect, namely low elongation fibre strength scatter and hybridisation fibre stiffness and Failure Strain. Larger strength scatter of the low elongation fibres leads to larger hybrid effects, as the scatter spreads out the cluster development over a larger Strain interval. The Failure Strain ratio of the two fibre types should be above 2 for the properties used here, but a higher ratio did not yield any additional benefits. Increasing the stiffness of the hybridisation fibre reduces the stress concentrations on the low elongation fibre and may also enlarge the hybrid effect. These conclusions provide guidelines for designing optimal hybrid composites.
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the effect of fibre dispersion on initial Failure Strain and cluster development in unidirectional carbon glass hybrid composites
Composites Part A-applied Science and Manufacturing, 2015Co-Authors: Yentl Swolfs, Robert M Mcmeeking, Ignaas Verpoest, Larissa GorbatikhAbstract:Abstract By adding glass fibres to carbon fibre composites, the apparent Failure Strain of the carbon fibres can be increased. A strength model for unidirectional hybrid composites was developed under very local load sharing assumptions to study this hybrid effect. Firstly, it was shown that adding more glass fibres leads to higher hybrid effects. The hybrid effect was up to 32% for a hybrid composite with a 10/90 ratio of carbon/glass fibres. The development of clusters of broken fibres helped to explain differences in the performance of these hybrid composites. For 50/50 carbon/glass hybrids, a fine bundle-by-bundle dispersion led to a slightly smaller hybrid effect than for randomly dispersed hybrids. The highest hybrid effect for a 50/50 ratio, however, was 16% and was achieved in a composite with alternating single fibre layers. The results demonstrate that thin ply hybrids may have more potential for improved mechanical properties than comingled hybrids.
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The effect of fibre dispersion on initial Failure Strain and cluster development in unidirectional carbon/glass hybrid composites
Composites Part A: Applied Science and Manufacturing, 2015Co-Authors: Yentl Swolfs, Robert M Mcmeeking, Ignaas Verpoest, Larissa GorbatikhAbstract:Abstract By adding glass fibres to carbon fibre composites, the apparent Failure Strain of the carbon fibres can be increased. A strength model for unidirectional hybrid composites was developed under very local load sharing assumptions to study this hybrid effect. Firstly, it was shown that adding more glass fibres leads to higher hybrid effects. The hybrid effect was up to 32% for a hybrid composite with a 10/90 ratio of carbon/glass fibres. The development of clusters of broken fibres helped to explain differences in the performance of these hybrid composites. For 50/50 carbon/glass hybrids, a fine bundle-by-bundle dispersion led to a slightly smaller hybrid effect than for randomly dispersed hybrids. The highest hybrid effect for a 50/50 ratio, however, was 16% and was achieved in a composite with alternating single fibre layers. The results demonstrate that thin ply hybrids may have more potential for improved mechanical properties than comingled hybrids.
Robert M Mcmeeking - One of the best experts on this subject based on the ideXlab platform.
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the effect of fibre dispersion on initial Failure Strain and cluster development in unidirectional carbon glass hybrid composites
Composites Part A-applied Science and Manufacturing, 2015Co-Authors: Yentl Swolfs, Robert M Mcmeeking, Ignaas Verpoest, Larissa GorbatikhAbstract:Abstract By adding glass fibres to carbon fibre composites, the apparent Failure Strain of the carbon fibres can be increased. A strength model for unidirectional hybrid composites was developed under very local load sharing assumptions to study this hybrid effect. Firstly, it was shown that adding more glass fibres leads to higher hybrid effects. The hybrid effect was up to 32% for a hybrid composite with a 10/90 ratio of carbon/glass fibres. The development of clusters of broken fibres helped to explain differences in the performance of these hybrid composites. For 50/50 carbon/glass hybrids, a fine bundle-by-bundle dispersion led to a slightly smaller hybrid effect than for randomly dispersed hybrids. The highest hybrid effect for a 50/50 ratio, however, was 16% and was achieved in a composite with alternating single fibre layers. The results demonstrate that thin ply hybrids may have more potential for improved mechanical properties than comingled hybrids.
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The effect of fibre dispersion on initial Failure Strain and cluster development in unidirectional carbon/glass hybrid composites
Composites Part A: Applied Science and Manufacturing, 2015Co-Authors: Yentl Swolfs, Robert M Mcmeeking, Ignaas Verpoest, Larissa GorbatikhAbstract:Abstract By adding glass fibres to carbon fibre composites, the apparent Failure Strain of the carbon fibres can be increased. A strength model for unidirectional hybrid composites was developed under very local load sharing assumptions to study this hybrid effect. Firstly, it was shown that adding more glass fibres leads to higher hybrid effects. The hybrid effect was up to 32% for a hybrid composite with a 10/90 ratio of carbon/glass fibres. The development of clusters of broken fibres helped to explain differences in the performance of these hybrid composites. For 50/50 carbon/glass hybrids, a fine bundle-by-bundle dispersion led to a slightly smaller hybrid effect than for randomly dispersed hybrids. The highest hybrid effect for a 50/50 ratio, however, was 16% and was achieved in a composite with alternating single fibre layers. The results demonstrate that thin ply hybrids may have more potential for improved mechanical properties than comingled hybrids.
