Delamination Behavior of CFRP Laminated Plates under the Combination of Tensile Preloading and Impact Loading.

When subjected to impact loading, aircraft composite structures are usually in a specific preloading condition (such as tension and compression). In this study, ballistic tests were conducted using a high-speed gas gun system to investigate the effect of biaxial in-plane tensile preload on the delamination of CFRP laminates during high-speed impact. These tests covered central and near-edge locations for both unloaded and preloaded targets, with the test speeds including 50 m/s, 70 m/s, and 90 m/s. The delamination areas, when impacting the center location under 1000 µÎµ, show a 14.2~36.7% decrease. However, the cases when impacting the near-edge location show no more than a 19.3% decrease, and even more delamination areas were observed. In addition, in order to enhance the understanding of experimental phenomena, numerical simulations were conducted using the ABAQUS/Explicit solver, combined with the user subroutine VUMAT with modified Hou criteria. The experimental and simulation results were in good agreement, and the maximum error was approximately 12.9%. The results showed that not only the preloading value but also the impact velocity have significant influences on the delamination behavior of preloaded CFRP laminated plates. Combining detailed discussions, the biaxial tensile preload enhanced the resistance to out-of-plane displacement and caused laminate interface stiffness degradation. By analyzing the influence of the preloading value and impact velocity on competing mechanisms between the stress-stiffening effect and interface stiffness degradation effect, the complex delamination behaviors of laminates under various preloading degrees and impact velocities at different impact locations were reasonably explained.

A revised Ladevèze criteria for carbon fiber reinforced laminated plates.

All parameters of revised Ladevèze failure criterion in Table 1 were determined based on mechanical tests which mainly include quasi-static tensile experiments, quasi-static compressive experiments, quasi-static tensile cyclic loading experiments, the dynamic tensile experiments, dynamic compressive experiments, quasi-static and dynamic inter-laminar shear experiments. The quasi-static experiments were performed using an electronic universal testing machine with a maximum load capacity of 10KN, and the split Hopkinson pressure bar (SHPB) and split Hopkinson tension bar (SHTB) were employed in dynamic experiments. In addition, the parameters of traditional orthogonal anisotropic model and cohesive layer for the laminated plates are listed in Table 2.