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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]

Owing to the importance of fibre architectures in the design of textile composite materials, understanding their effect on the failure mechanisms of these composites have taken more considerations. In this regards, non-crimp preform and 2/2 twill fabric have been manufactured from glass fibre by using pin-board and power loom machines respectively, and subsequently composites laminates from both preforms are manufactured via vacuum assisted resin infusion method. In addition, quasi-static tensile and compressive strength tests have been conducted for the composite laminates that have same volume fraction. Damage failure mechanisms that occurred in compressive strength in both composites have been examined by using scanning electronic machine (SEM). Findings show that the mechanical properties are primly determined by fibre architectures and the presence of fibre crimp can further weaken tensile and compressive strength values. It was noticed that the tensile strength of non-crimp composite was 610 MPa whereas that of twill fabrics composite laminates it was found to be 350 MPa and 440 MPa in warp and weft directions respectively. Moreover, in case of twill fabric composites, fibre crimp has a considerable effect on the mode and characteristics of damage in the compressive loading; this leads to fibre fracture and kinks that primarily happened in the intersection point of warp and weft yarns. Results also showed improved ductility, strain to failure and absorbing energy in the twill fabric composites compared to non-crimp composites under in-plane shear strength test. [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]

Fabric preforms undergo transverse compaction during composite manufacturing. This compaction changes the preform thickness, fibre volume fraction (FVF), tow geometry and voids for resin flow. In this paper, influence of yarn hybridisation and fibre architecture on the compaction response of woven fabric preforms has been studied. A series of cyclic compression tests have been carried out on both dry and wet preforms. The effect of hybridisation on compressibility has been investigated for single as well as multilayer fabrics. The influence of interlacement pattern (twill and satin fabrics) with hybrid yarns has also been investigated. Nesting efficiencies of multilayer stacks have been studied by utilising mechanical test results. Additionally, the meso-structure of single and multilayer fabrics under 1 bar pressure has been analysed using SEM images. It is observed that the thickness reduction for single layer twill hybrid fabric is 38% while thickness reduction for twill S-glass fabric is 67% at 100 kPa. Moreover, single layer hybrid twill fabrics have shown higher compressibility resistance (60% thickness reduction at 100 kPa) compared to single layer hybrid satin fabrics (which showed 67% thickness reduction at 100 kPa). Whereas opposite trend is observed for multilayer hybrid fabrics due to nesting effect. [ABSTRACT FROM AUTHOR]

High modulus/high strength continuous fibres are used extensively for manufacturing textile preforms, as a reinforcement, for composites due to their excellent specific properties. However, their brittle behaviour and tendency to separate easily into individual filaments or bundles can lead to damages during manufacturing processes such as weaving and braiding. Thus, the critical step in the development of an optimal yarn for textile-reinforced composites is to find an optimum twist, which results in a minimum loss of properties of the composite laminates, while maintaining good processability and sufficient strength for textile and/or composite manufacturing. In this study, twist level has been varied to improve the handling and tensile properties of S-glass yarns (i.e. tensile strength). Varying levels of yarn twist (15–40 twists metre−1) were employed to study its impact on the tensile properties (i.e. tensile strength, modulus, elongation at break etc.). Furthermore, the effect of twist on the tensile properties of non-crimp cross-ply composites produced via vacuum infusion process was studied. It was observed that mechanical performance (i.e. tensile strength properties) of twisted yarns is improved up to 30 twists metre−1 while it is deteriorated at 40 twists metre−1. At yarn level, the experimental results were compared with theoretical estimations utilizing existing models for twisted yarns properties. Discrepancies were observed between experimental and theoretical results especially for high level of twist. The tensile strength and elongation of S-glass cross-ply composites at all levels of twist were higher compared to the composite laminates manufactured by using non-twisted yarns. At composite level, the experimental results were also computed employing rule of mixture and good agreement was observed between experimental and predicted results. [ABSTRACT FROM AUTHOR]