Experimental and Numerical Investigations on Flexural Behaviour of Delaminated Carbon Fibre Reinforced Polymer Composites

Abstract

Fiber reinforced polymer (FRP) composite laminates are widely used in the fields of aerospace, automobile and marine engineering because of their advantageous properties such as high specific strength, high damage tolerance, high specific stiffness, good corrosion and high fatigue resistance. In composites, defects are induced during their fabrication or low velocity impact due to tool hit, bird strike, ground handling, lightning strike and deterioration of environmental conditions during service life. The existence of defects leads to initiate various damage forms such as matrix cracking, interfacial debonding, fiber breakage and delamination. Of these damage modes, delamination is a crucial deformation of fiber layers that degrades the structural performance of FRP composites. Hence, investigation of induced delamination on the structural performance has great importance. newlineIn the present study, unidirectional carbon fibers were reinforced with a mixture of epoxy (Araldite CY230) and hardener (Aradur HY951) to fabricate carbon fiber reinforced polymer (CFRP) laminates with a stacking sequence of [0/0/45/ newline-45/90/45/-45/90/90/-45/45/90/-45/45/0/0] using hand lay-up method and vacuum bagging technique. The laminates consisted of 16 layers. The thickness of each laminate was 3.2 mm. Three types of CFRP laminates were used with same stacking sequence. The first type (i.e. type A) is an intact laminate (i.e, without induced delamination). The second and third type laminates consist of single and multiple induced delaminations respectively. A polytetrafluoroethylene (PTFE) film was used in the second and third types of laminates to create artificial delamination. The second type (i.e. type B) consisted of a circular PTFE (dia 14 mm) which was embedded between second and third plies. Third type (i.e. type C) consisted of five PTFEs with different sizes (14 mm, 16 mm, 18 mm, 20 mm and 22 mm). They were positioned in triangular pattern at the interfaces of adjacent plies (second ply to seventh ply).