Experimental Investigation of Energy Release Rate for In-plane Shear Mode in GFRP Composites

Abstract

ABSTRACT:The main drawback of fiber reinforced composites is inter-laminar fracture, especially delamination. Due to the nature of composite fabrication delamination is being a common failure. Composites are made in a variety of manufacturing techniques that are available. Commonly, a layered stacking of fibers in a primary plane is observed in each of these techniques. The interfacing part between the layers of the composites is not obviously reinforced with fibers which in turn lead to the inter-laminar fracture or delamination. The strain energy release rate (G C ) is the best material property that can represent the resistance to delamination which can be both experimentally and numerically obtained. The principal attention of the present study is to obtain the inter-laminar fracture toughness in composites caused because of the pure sliding mode. An inter-laminar fracture for mode II (G IIC ) crack propagation is studied for GFRP materials having unidirectional 00 orientation of fiber. Compliance calibration method is used to study on the experimental investigation of toughness G IIC for fiber volume of 40%, 50% and 60%. Investigation was directed according to ASTM D7905 using End Notched Flexure specimen which is fabricated using E-glass fiber and epoxy matrix in hand layup method. Results obtained are again correlated with numerical analysis using virtual crack closure technique (VCCT) method. Keywords: Energy Release rate, Fracture Toughness, Virtual Crack Closure technique, Edge Notch Flexure specimen. I. INTRODUCTIONThe composite materials undergo failure due to many aspects like impact or static overloading, fatigue, overheating, hygrothermal effect, creep etc. One of the most regularly used manufacturing technique used of set up a composite structure is laminating of composite materials. Delamination is being the major limiting factor for the composite structures that are laminated. Delamination being a mainly significant mode of failure observed particularly in reinforced fiber laminate composites structures. Delamination is the separation of the laminated fiber reinforced layers that are bonded together to form laminated composite. These de-laminations are the results of the impact by any foreign object or manufacturing defects and this can cause a significant reduction in strength and stiffness of the component or the structure. Linear fracture mechanics depending on energy have been extensively used in de-lamination model of composite and their study. The strain energy release rate 'G' to be verified for resolving loads that cause delamination expansion by using this fracture mechanics approach. In some of the conditions that involve the inter-laminar fracture-toughness or critical strain-energy-release rate, 'G C ' in composites. The energy that is released for the crack to grow for unit area in the test specimen undergoing constant displacement is called as the strain-energy-release rate. The capacity of a material having a crack to resist the growth of fracture on that material is called as cr...