Analysis of Performance of Additively Manufactured Reinforced Ablatives

This study investigates reentry conditions for Mars missions, focusing on extreme anaerobic heating. This work studies poly(ether ketone ketone) (PEKK), a high-performance thermoplastics polymer, in both small-scale laboratory and simulated oxyacetylene test bed conditions to eliminate low-performing polymeric materials. Previous research demonstrated PEKK's superior ablation performance compared to poly(ether ether ketone) (PEEK) and polyetherimide. The aerothermal performance of neat PEKK can be further enhanced with reinforcement materials. This work explores PEKK composite materials reinforced with additives such as carbon nanotubes (CNTs), carbon fibers (CFs), and glass fibers (GFs). The CNT-reinforced (10%wt) PEKK exhibited the highest char yield (69%wt) during thermogravimetric analysis (TGA) in nitrogen, superior to the short CF-reinforced PEKK. Various CF and GF loadings (10% and 20%wt) were tested for their thermophysical and aerothermal performance. Oxyacetylene tests (OTBs) under fuel-rich conditions further validated the results. Except for 10% CF PEEK, the mass loss in OTB tests correlated with TGA and thermal diffusivity measurements. The addition of CF/GF in PEKK enhanced thermal effusivity, but it also led to significant swelling due to increased conductive flux and reduced ablated heat flux. Among the tested materials, CNT-reinforced PEKK displayed the highest char yield, lowest mass loss, and minimal swelling. The unique porous structure of CNTs minimized char expansion and erosion during the OTB tests, making a promising material for reentry flights.