Synergistic effects on damage behavior and failure mechanisms of pre-tensioned hybrid laminates subjected to ballistic impacts

Understanding the synergistic effects of preload and impact on damage behavior is critical for composite structures under service conditions, yet it remains inadequate characterization. This study systematically investigates mechanical responses and failure mechanisms of pre-tensioned hybrid carbon/glass fabric laminates subjected to ballistic impacts with varying velocities and angles. A preload-impact coupled testing platform is developed to perform ballistic impact tests. A rate-dependent numerical model is also proposed to capture detailed damage evolution along with comparative analysis of experimental data. Results show that fiber shearing and interlaminar delamination dominate the failure of laminates. Pretension fundamentally reconfigures damage mechanisms where thresholds exist. Pretension below 10% of the ultimate tensile strength (UTS) enhance energy absorption via stable damage propagation, whereas one exceeding 30% UTS triggers unstable failure. Compared to normal impacts, oblique impacts induce substantially greater delamination, generating distinctive asymmetric damage morphologies through amplified interlaminar shear. Increasing impact velocity reduces delamination, shifting the dominant energy dissipation mechanism from interlaminar fracture to fiber failure. Variations of in-plane impact angles, on the other hand, show infinitesimal influence on failure characteristics. Conclusively, these findings can guide further investigation into specific design guidelines under preload to enhance structural survivability