Enhancing Dynamic Fracture Behavior of Laminated Composite by Short Fiber Reinforcement

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AbstractContinuous fiber reinforced laminated composites are mostly preferred in engineering applications where in-plane strength and modulus are key requirements. Although the composites’ in-plane mechanical and failure behavior can be tailored to meet the end user requirements, their weaker out-of-plane characteristics often remain a cause of concern. Failure in such materials initiates either at fiber/matrix interfaces or from matrix-rich regions within the laminae or at the interlaminar regions. Stiffening matrix-rich zones by using reinforcements is one of the methods which is employed to reduce the probability of failure. In this investigation, a short fiber reinforced matrix is used to enhance the failure characteristics of laminated composites under impact loading conditions. Sixteen layers of plain weave bidirectional Glass Fiber Reinforced Polymer (GFRP) composites are fabricated by hand layup technique. Neat epoxy and chopped fiber reinforced epoxy systems are used as matrix materials to prepare unreinforced and reinforced laminates. Impact tests are conducted at 5 and 20 J energy levels by following ASTM D7136M standards. At lower impact energy, nearly 50% reduction in visible damage area is observed in the case of reinforced laminates, whereas at higher impact, the damage areas differ only by 6.5%. While the force associated to failure initiation remains unaffected by short fiber reinforcement, it improves the laminate's response by inducing higher resistance to deformation. The laminate stiffness in general is observed to increase with increasing impact energy as well with the short fiber reinforcements. The data exhibits higher energy dissipation at higher impact energy with only a marginal influence of reinforcement. SEM images reveal transverse matrix cracking at lower impact energy in both unreinforced and short fiber reinforced cases with a few interlaminar failures in the prior. On the contrary, when the laminates are subjected to higher impact energy, significant matrix cracking along with the delamination at several interfaces is observed.KeywordsGFRPImpact energyFracture mechanisms