Investigation of Damaged Glass Fiber Reinforced Polymer Composites in 3 Point Bending

Abstract

Composites materials are used in almost all aspects of the industrial and commercial fields in aircraft, ships, common vehicles, etc. Their most attractive properties are the high strength-to-weight ratio and high stiffness-to-weight ratio. However, these materials also have some problems such as fiber breakage, matrix cracking and delamination. Matrix cracks and fiber breakages play an important role in laminates under tensile load. However, delamination is the critical parameter for laminates under compression and one of the most common failure modes in composite laminates. Delamination may be formed due to a wide variety of foreign object impact damage, poor fabrication process, and fatigue from environment cycle. In the present study, an experimental work was carried out to determine the ultimate breaking load using flexure tests of damaged, 90-degree glass fiber-reinforced, laminated composites loaded in 3-point bending. E-glass/epoxy composites were manufactured to fabricate the specimens, using Hand lay-up technique. The laminated composites were prepared, with lateral and longitudinal multiple delaminations and broken fiber strands. The delamination length of the manufactured specimen was fixed to 15.5% of the global beam length. Te sts were carried out on laminated beams with [90° 20] and [90° 32] stacking sequence. The influence of various defects on the residual strength of the defected laminated composites was examined using the load verses displacement graphs. The results show that, the increase in the number of lateral multiple delaminations and broken fiber strands significantly reduces the residual ultimate strength of the laminated composites.