INVESTIGATION OF BENDING AFTER IMPACT FAILURE BEHAVIOR IN FOAM-CORE HYBRID SANDWICH COMPOSITES AT EXTREME LOW TEMPERATURE

Abstract

In this study, we investigate the behaviour of foam-core sandwich composites, specifically with regards to bending after impact (BAI), in the presence of carbon fiber reinforced polymer (CFRP) and/or glass fiber reinforced polymer (GFRP) facesheets. To accomplish this, we utilize an Instron 5582 universal testing machine to conduct 3- point bend test on specimens that have previously undergone impact testing. The 3-point bend tests are conducted at both room temperature (23°C) and low temperature (-70°C) to evaluate the effect of low temperature (LT) on the BAI behaviour of the composite materials. Moreover, we explore the effect of different stacking sequence and layup configuration of GFRP and CFRP layers on sandwich composites under flexural loading. We analyse the force-displacement curves and compare peak stress values to gain insight into the influence of the CFRP and GFRP hybrid facesheets. Results suggest that altering the arrangement of CFRP and GFRP layers has a significant impact on the flexural strength of the hybrid composite. At LT, the specimens experience more flexural damage due to increase in brittleness. However, the peak stress at LT increases due to the increase in the compressive strength of the CFRP layers. Specimens featuring a GFRP layer on the outside (referred to as ‘glass first’ specimens) and specimens with alternating CFRP/GFRP layers, with CFRP positioned on the outermost layers (referred to as ‘CGCG’), when impacted at 15J, experience core shear and core debonding at LT flexural test. Overall, GC is found to be the optimal configuration. This configuration provides excellent strength from the inner CFRP layer and while the outer GFRP layer offers damage resistance during impact test.