Finite element analysis of drilling-induced damage responses on FRP hybrid bio/composite laminates

Machining/drilling is crucial in the joining process of composites. However, drilling composite
materials often leads to hole dimensional inaccuracy, surface roughness and delamination, among others. These drilling-induced damage (DID) responses are associated with torque and thrust (principal drilling forces), and rampant in fibre-reinforced polymeric (FRP) hybrid bio/composite laminates. Therefore, a three-dimensional (3D) numerical approach, using finite element method (FEM) was undertaken to analyse the DID responses of FRP hybrid bio/composite laminates. Drilling simulation was performed at spindle velocity and feed rate of 3000 rpm and 5 mm/s, respectively. Both thrust force and torque were produced, computed and interpreted. From the results obtained, it was evident that drilling of synthetic (glass, G and carbon, C) FRP hybrid composites demanded higher or substantial torque and thrust forces, due to their superior strengths, exemplified by the (2G+2F)13 samples, when compared with the weaker natural/plant (flax, F; jute, J and hemp, H) FRP hybrid bio/composites, especially (J+F)27 samples. In addition, the investigation established the advantages of dual layup methods over single arrangements. Carbon and glass FRP hybrid composites exhibited excellent hybridisation properties, but their brittleness necessitated careful management of torque and thrust forces to prevent high DID responses. Summarily, this investigation provided a guide for FRP hybrid bio/composites design and drilling, in addition to opportunities for additional research on other process parameters towards further study.