A comparative study on failure mechanisms of open-hole and filled-hole composite laminates: Experiment and numerical simulation

The strength of composites with open holes (OH) and filled holes (FH) is a critical factor in determining mechanical allowances for engineering design. This study employs both experimental and numerical analyses to investigate the mechanical behaviour of composite laminates subjected to open-hole tension (OHT) and open-hole compression (OHC), filled-hole tension (FHT) and filled-hole compression (FHC). A progressive damage model (PDM) has been developed to predict the load-carrying capacity of both OH and FH laminates, with deviations lower than 6 % in comparison to the corresponding experimental results. Results indicate that OHC/FHC laminates experience more pronounced damage compared to OHT/FHT laminates prior to the maximum load. Additionally, delamination in FHC laminates is significantly reduced compared to OHC laminates. In comparison to OHT/OHC laminates, the presence of a filled bolt increases the maximum load of FHT/FHC laminates by 10.8 % and 36.0 %, respectively, due to relieving the stress concentration near the hole. Moreover, a higher contact friction coefficient between the bolt and laminate leads to a higher maximum load, particularly for FHC laminates, as the increased friction effectively hinders the matrix crack propagation. These findings provide valuable insights for assisting the design of composite structures.