Fatigue behavior and nonlinear life prediction of open-hole thermoplastic composite laminates with drilling-induced delamination

Abstract

This research explores the fatigue behavior of thermoplastic composite laminates by focusing on the effects of drilling-induced delamination on fatigue performance. Fatigue tests were conducted on specimens with varying delamination factors and compared with unnotched specimens. Under static loading condition, the presence of open holes reduced the maximum strength by 45%, highlighting the detrimental impact of stress concentrations. Fatigue test results revealed distinct low cycle fatigue (LCF) and high cycle fatigue (HCF) regimes, with a transition from fiber-dominated failure to matrix-dominated failure as the number of cycles increased. The transition region varied with the delamination factor that occurring earlier for specimens with lower delamination. Nonlinear fatigue life prediction model was developed to integrate LCF and HCF behaviors into a single equation. The validated model that against experimental data achieved an error of less than 1.5%, demonstrating its robustness and accuracy in predicting fatigue performance. The use of thermoplastic composites, known for their recyclability and superior damage tolerance, underscores their potential for aerospace applications where lightweight and durable materials are critical. The findings of this study emphasize the importance of optimizing drilling parameters to minimize delamination and enhance fatigue performance of thermoplastic composites.