Abstract
A new, partially discontinuous architecture is proposed to improve the mechanical performance of pseudo-ductile, unidirectional (UD) interlayer carbon/glass hybrid composites. The concept was successfully demonstrated in different laminates with high strength and high modulus carbon and S-glass epoxy UD prepregs. The novel hybrid architecture provided pseudo-ductile tensile stress–strain responses with a linear initial part followed by a wide plateau and a second linear part, all connected by smooth transitions. The best hybrid configuration showed 60% improvement in modulus compared to pure glass, 860MPa plateau stress and 2% pseudo-ductile strain. The initial modulus, the plateau stress and the overall tensile stress–strain response of each specimen configuration were predicted accurately.
Highlights
High performance composites provide excellent specific strength and stiffness properties especially in comparison with higher density metallic materials but fail to deliver a safe failure mode similar to metals’ progressive yielding and strain hardening with detectable warning and a wide margin before final failure
The mode II energy release rate at the carbon layer failure strain should always be lower than the fracture toughness (GIIc) in a continuous carbon/glass hybrid composite to avoid sudden delamination and load drops
Variable carbon/epoxy platelet thickness will result in different hybrid moduli due to the change in carbon/glass ratio and attention must be paid to ensure the continuous glass layers have enough strength to take the load shed by the pulled-out platelets
Summary
High performance composites provide excellent specific strength and stiffness properties especially in comparison with higher density metallic materials but fail to deliver a safe failure mode similar to metals’ progressive yielding and strain hardening with detectable warning and a wide margin before final failure. Strong potential for demonstrating pseudo-ductility while maintaining high performance in UD composites was shown earlier by the authors [13,14,15] using emerging thin ply prepregs to suppress delamination in interlayer hybrid configurations. The discontinuous prepreg layers in the experimental part of this study are integral elements of a hybrid laminate architecture carefully designed to exhibit controlled interlaminar damage initiation and stable mode II crack propagation which results in the stable pull-out of the carbon/epoxy platelets. The key challenge of this study is to improve the tensile performance and extend the design envelope of previously developed UD pseudo-ductile thin-ply continuous carbon/glass interlayer hybrid composites [13] by increasing the carbon/glass ratio and the initial modulus of the hybrid laminates. Emphasis was put on accurate prediction of the stress–strain response of the novel hybrid material architecture
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