Compressive response and failure mode of glass fiber reinforced polyimide composite honeycomb with cell wall defects

Obtaining some functions for honeycombs can be normally realized by perforating holes on the cell walls. However, excessive perforations, which are always identified as defects, have been shown to reduce the mechanical properties of the honeycomb. Continuous glass fiber reinforced polyimide composite(GF/PI) honeycombs are prepared in this work to investigate their compression processes by finite element analysis and 3D-DIC assisted quasi-static compression tests in order to further reveal the influence mechanism of perforation-induced cell wall defects on their out-of-plane compressive responses and failure modes. The results show that the failure mode of defect-free GF/PI honeycomb is progressive crushing mode, while the GF/PI honeycombs with certain configurations of cell wall defects fail in a fracture mode and fracture/progressive crushing mixed mode. These failure modes ultimately lead to the degradation of the energy absorption performance of the GF/PI honeycombs with cell wall defects. Subsequently, by increasing the matrix content, the failure modes of GF/PI honeycombs with cell wall defects are altered to progressive crushing owing to the reduction of the average maximum damage strain of the cell wall. In addition, the energy absorption performance of GF/PI honeycomb with the same defects configuration is effectively enhanced by 14.24%. This method significantly improves the compressive response and provides theoretical guidance for the structural-functional integrated design of honeycomb sandwich structures in high-performance radomes.