Heterogenous microstructure materials are utilized in a variety of applications due to their attractive functional properties. One such material is Phenolic Impregnated Carbon Ablator (PICA), which is a composite made of porous carbon preform and phenolic resin that is used as a material in some state-of-the-art aerospace thermal protection systems. Much of the research surrounding PICA and other similar porous carbon materials has focused on functional properties alone but understanding mechanical properties and damage tolerance is also necessary to ensure optimal functional performance in service. A mechanism-informed understanding of the mechanical properties of these materials, however, is complicated by their stochastic microstructure which leads to structure-properties relationships that are contingent on features spanning several orders of magnitude in length scale. In this study, micromechanical compression testing of FiberForm, a porous carbon fiber material that is a substrate for PICA, has been conducted. The results of the compression tests were then coupled with digital image correlation (DIC) to tie mesoscale deformation behavior to macroscale mechanical properties. It was observed that in simple uniaxial stress states, the operative deformation mechanism was dependent on the orientation between the loading axis and general fiber direction. Complex stress states that more closely match those experienced in service, imposed using through-holes and notches, resulted in damage accumulation mechanisms significantly differing from those observed in uniaxial testing. Due to its use as an integral part of the fabrication of PICA, it is believed that understanding the deformation behavior of FiberForm can give insight into the expected performance of PICA. Furthermore, these results will provide broad experimental data to inform and validate modeling approaches to accurately predict and tailor the reliability of porous parts under service conditions.
2025-04-09 09:00:00
