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As the use of composite laminates are unceasingly increasing more and more in many applications, the in-depth understanding about the impact response of composite laminates in certain areas like sport, aerospace and automotive has gained more attention of the designers and scientists over the last two decades. The authors have focused to review the impact properties of fibre reinforced composites particularly impact damage tolerance. Impact resistance, damage tolerance, composite failure and methods of assessing damage tolerance are presented. Furthermore, the approaches for improving damage tolerance such as fibre architectures resin system, and hybridisation using either yarn hybridisation or hybrid layers are discussed. In the end, a survey of modelling the impact damage of laminated composites is made by considering the inter-laminar and intra-laminar failures as key point for evaluating the response of laminates under impact loading. Graphical Abstract [ABSTRACT FROM AUTHOR]

This study examines empirically and theoretically the open-hole tension and compression characteristics of thermoset composites using hybrid glass/polypropylene and glass/innegra yarns. The Abaqus software, finite element analysis (FEA) has been adopted to predict the tensile and compressive failure loads and damage failure modes for un- and notched samples under tensile and compressive strength tests. The commingling technique was used to create hybrid yarns, which were then transformed into non-crimp preforms before the infusion procedure. It was noticed that the inclusion of thermoplastic polypropylene (PP) and innegra fibres increased the ductility of yarns and composites. Densities of hybrid composites were also reduced by up to 20% when compared to pure glass/epoxy composites. Tensile and open-hole tensile (OHT) test results revealed that hybrid composites are less notch sensitive than glass/epoxy composites due to enhanced composite ductility. For glass composites, having holes resulted in a 41% decrease in tensile strength, compared to reductions of only 25% and 26% for PP and innegra fibre composites, respectively. Further, compression and open-hole compression (OHC) tests presented similar results with OHT tests whilst compressive strength reduction was lower for hybrid composites (10% and 11%) compared to glass/epoxy (28%) ones. The results of the numerical simulation for damage failure modes and tensile and compressive failure loads for un-notch and notched composite laminates are consistent with the experimental findings both qualitatively and quantitatively. [ABSTRACT FROM AUTHOR]

Advanced composite materials are widely used in civil and military applications due to their superior specific strength and stiffness. However, they are susceptible to damage during impact loading. In order to improve the impact performance, yarn hybridisation and fibre architecture have been investigated in this study in order to evaluate their influence on the damage tolerance (i.e. post- impact flexural strength) of glass composite laminates. Two types of yarn have been used here, namely, pure glass yarns as a bench-mark and hybrid yarns (glass-polypropylene) to manufacture non-crimp and woven (twill and satin) fabric composites. The composite laminates were then subjected to low-velocity impact tests at various impact energies. Afterwards, post- impact flexural strength has been evaluated with a four-point bending test. It has been observed that the non-crimp and woven hybrid composites laminates displayed smaller damage areas compared to the non-crimp glass composites laminates. In addition, although the hybrid laminates have exhibited lower flexural strength properties than the non-crimp glass laminates, the former has shown higher post-impact flexural strength. Fractography analysis has suggested here that the damage failure modes such as intra-yarn cracks have been produced in the hybrid yarns laminates and intra-yarn and inter-yarn cracks have been produced in hybrid fabric laminates. These damage failures have contributed for absorbing impact energy leading to an enhancement of the damage tolerance of the hybrid laminates. [ABSTRACT FROM AUTHOR]