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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]

Advanced composites are widely used in primary and secondary structural applications, for example, aerospace, automotive, marine, and renewable energy sectors. But it is well recognized that the impact resistance and damage tolerance of composite laminates are in general poor, which is a major challenge for optimizing structural designs. In this regard, an experimental study is conducted for enhancing the damage tolerance of 2D woven composite laminates by exploring yarn‐level fiber hybridization. Hybrid yarns are produced by combing high‐strength fibers, that is, S‐glass, and high‐toughness fibers, that is, polypropylene [PP], and using commingling and core‐wrapping processes. Using the hybrid yarns, 2D fabrics, that is, with 5H satin, 2/2 twill, and 2/2 basket architectures, are weaved, and subsequently hybrid S‐glass/PP/epoxy laminates are manufactured via vacuum assisted resin infusion. The low velocity impact response and energy absorption of the hybrid laminates are investigated by drop‐weight impact tests at different energy levels, that is, 15 J, 25 J, 35 J, and 50 J. The damage tolerance is studied by compression‐after‐impact (CAI) tests, measuring the residual compressive strength of the damaged laminates. Furthermore, the failure modes are investigated using scanning electron microscopy for identifying damage mechanisms in the hybrid laminates after the impact and CAI tests. The impact response and damage tolerance of the 5H satin, 2/2 twill, and 2/2 basket fabric laminates are compared with that of noncrimp‐fabric laminates produced with (ie, S‐glass/PP yarns) and without (ie, S‐glass yarns) yarn‐level hybridization. It is shown that yarn‐level hybridization and fiber architecture significantly affect the impact behavior and damage tolerance of the 2D woven S‐glass/PP/epoxy hybrid laminates investigated. The microscopy studies show that intra‐yarn, inter‐yarn, inter‐lamina failure mechanisms can in general be introduced by combining yarn‐level fiber hybridization and fiber architecture for modifying failure and energy dissipation mechanisms under low velocity impact and hence the damage tolerance of composite laminates. [ABSTRACT FROM AUTHOR]