Influence of Complex Geometries on Damage Tolerance of Porous Carbon Fiber Network

Abstract

Porous materials exhibit a variety of attractive functional properties for aerospace applications, such as low density and low thermal conductivity. However, they must also be mechanically robust and damage tolerant to fully realize their potential. Currently, it is costly and time-consuming for testing under service conditions, therefore, computational models are a good path forward. Due to the inherent microstructural stochasticity of these structures, however, their behavior is difficult to effectively model without detailed experimental studies for validation and benchmarking. To that end this study investigates the mechanical properties of a porous carbon fiber network and ties together the global macroscopic observations to the local mesoscale behaviors dictated by individual fibers and fiber junctions. Strain localization was observed using digital image correlation (DIC) and tied to features within the macroscopic stress–strain plots. Work to quantify the impact of the addition of complex geometries (e.g., cracks and through-holes) on mechanical reliability was conducted. The defects resulted in distinct macroscale mechanical characteristics and mesoscale deformation behaviors, depending on defect type and loading orientation. These results provide broad experimental data to inform and validate modeling approaches to accurately predict and tailor the reliability of porous parts under service conditions.