Implementing functionally graded fibers technique to enhance pinned-joint performance in cross-ply laminate polymeric composites

There are several techniques for improving the bearing performance of laminated composites, such as metal-bonded inserts, steered fiber, nano-reinforcements of the matrix, and molded holes. Although functionally graded materials (FGM) were successfully implemented in adhesive joints, it is still not used in bolted joints. The novelty of this work and its objective are implementing the FGM concept to improve the bearing performance of pinned joints in cross-ply glass fiber-reinforced epoxy laminated composites. The effect of the joint geometries and stacking sequences on pinned joints bearing strength and failure modes were investigated. A 3-D finite element model based on Hashin's failure criteria was performed to predict joint strength and progressive failure. It was found that the FGM pinned joint (FG-CM) had higher bearing strength than the conventional pinned joints technique (C-CM). The bearing strength of composite with stacking sequence [90°/0°/90°]s was higher than that of [0°/90°/0°]s for both FG-CM and C-CM.