Layer-wise damage prediction in carbon/Kevlar/S-glass/E-glass fibre reinforced epoxy hybrid composites under low-velocity impact loading using advanced 3D computed tomography

Abstract

Examination of stacking sequence effect is essential in optimising the properties of synthetic fibre reinforced hybrid polymer composites for protecting the aircraft structure from the barely visible impact damage during low-velocity impact (LVI) events. It is important to know the quasi-static mechanical properties of polymer composites before analysing the LVI damage. Therefore, in this study, both quasi-static mechanical (tensile, flexural and punch-shear) and LVI properties of epoxy reinforced woven roving, E-glass and three different interply hybrid fabric (S-glass-E-glass, Carbon-E-glass and Kevlar-E-glass) composites are investigated. In all these hybrid composites, E-glass fabric layers are placed in the interior. Analysis of LVI properties indicated a 7.5% increase in the maximum energy absorption for laminates having Kevlar fibre as surface layers as against 3.4% decrease in energy absorption and 13.5% for laminates with carbon fibre and S-glass fibre as surface layers, respectively, compared to the E-glass/epoxy composite. An X-ray computed tomography is used for observing the layer-wise damage mechanisms of the LVI tested specimens from damage initiation to final perforation, which predicts that the bottommost layers of the plate are subjected to more damage. The damage area for each layer of the composite plates are measured using Image J software. Carbon-E-glass/epoxy composites are found to have more damage area than the other laminates. The delamination and damage zone of the plates are detected using the ultrasonic C-scan. The scanning electron microscopy is used to examine the fractured surfaces of tensile, flexural and punch-shear tested specimens.