A novel integrated forming strategy based on chemical vapor infiltration for C/C honeycomb with variable stiffness

Variable stiffness Carbon/Carbon (C/C) honeycomb can be designed to exhibit varying stiffness based on the structural load gradient, facilitating a high degree of alignment between structural performance and function. The elimination of mass redundancy and achievement of extreme light-weighting confer promising applications in the aerospace sector. However, the universal preparation approach for variable stiffness honeycomb faces challenges related to material mass redundancy and susceptibility to cracking at the bonds. Consequently, addressing the integrated forming issues associated with variable stiffness honeycomb becomes urgent. In this study, firstly, the conventional honeycomb densification method and the CVI domain-limited reactor design approach for integrated forming of variable-stiffness honeycombs are discussed. Subsequently, a multi-physics field coupling model for C/C honeycomb forming is developed, and its accuracy is validated through honeycomb forming experiments. The influence of three key process parameters, gas residence time, temperature, and pressure, on the quality of honeycomb forming were explored. Following the influence laws, the study applies specific process parameters to the three distinct regions of the reactor. Through this meticulously regulated process, the final variable stiffness honeycomb attains a 17.6 % reduction in weight compared to a constant density honeycomb of the same volume.