Implementation of a new approach based on the functionally graded materials concept to improve the strength of laminated composites containing open‐hole

The main objective of the present study is to implement a functionally graded materials (FGM) technique to reduce the hole effect in fiber reinforcement polymers. The tensile and fracture behaviors of conventional and FGM composites containing open holes have been investigated. Open‐hole specimens having different hole sizes have been fabricated using a hand lay‐up technique with different cross‐ply stacking sequences and various numbers of layers to study the open‐hole effect on their tensile strength. On the other hand, a three‐dimensional finite element analysis with the Hashin model was implemented to observe the failure modes along each layer. Experimental and numerical data revealed that the FGM technique enhanced the performance of specimens in the presence of a hole by increasing the fibers around the hole area. Furthermore, the [0°/90°/0°] sequence has more tensile strength than [0°/90°]s and [0°/90°/0°/90°/0°] sequences. It can be concluded that the bearing capacity of cross‐ply laminates is proportionally dependent on the ratio of the number of 0° layers to the number of 90° layers and inversely dependent on the specimen thickness. Highlights Dense fibers around the open hole improve its strength in laminated composite. The FGM concept has been successfully employed to improve open‐hole strength. The stacking sequence [0°/90°/0°] has better tensile strength than [0°/90°]s. FEA has successfully simulated the FGM concept around the open hole. The open‐hole failure occurred in the same direction as fiber orientation. Effect of the cross‐stacking sequence and the number of layers on the failure stages of open‐holed plates made of FGM composite laminates.