Effect of delamination depth on compressive properties of aircraft composite laminates

Aircraft composite laminates are susceptible to delamination damage throughout their lifecycle, from manufacturing to in-service operation. The existence of delamination damage results in a significant degradation in structural strength, stiffness, and stability, which can induce early instability and precipitate global failure. Therefore, it is necessary to explore the influence of delamination damage on the mechanical properties of composite laminates. Addressing the material selection for delamination-critical regions in aircraft structures is an imperative research objective. Further analysis is warranted to understand how delamination depth affects the mechanical behavior of composite structures. Therefore, four kinds of carbon fiber reinforced epoxy resin matrix composites were selected for single delamination damage and impact damage (gradient delamination damage). Quasi-static compression, low-velocity impact and compression after impact tests were carried out to compare the compressive residual strength of four composite laminates with delamination damage. Combined with finite element simulation, the influence trend of delamination depth on the compression performance of composite laminates is explored, and the reason for this trend is analyzed. The results show that compared with the unidirectional prepreg, the selection of high strength fabric prepreg in delamination-critical regions of the aircraft structure will bring better results, and the maximum compressive residual strength can be increased by 118.31%. Additionally, different delamination depths will lead to the bearing capacity of composite laminates determined by different sub-plates. The influence of delamination damage on the compressive properties of aircraft composite laminates has been discussed in depth, which provides a research basis for the damage tolerance design of aircraft composite structures.