Development of Superior Carbon/Carbon Composites with Enhanced Oxidation Resistance at High Temperatures for Aerospace Application

Abstract

Ablative Materials are at the base of the entire aerospace industry. It pushes the boundaries of what materials and components can endure. An increasingly important innovation in the aerospace industry is the use of composite materials as ablators, as these enable designers to overcome the barriers created by using metals. Carbon Fiber reinforced carbon composites also known as Carbon-carbon composites (C/C or CCC) and Carbon Fiber Reinforced Polymer (CFRP) composites have played a major role in weight reduction. These are used as ideal structural materials capable of applications in ultra-high temperature environments due to their suitable thermal shock resistance and high-temperature mechanical properties. Unfortunately, the carbonaceous materials tend to be dramatically oxidized above 500oC meaning C/Cs are susceptible to ablation environments at high temperatures. Here, we have focused on the aerospace components with extremely high service conditions like stress, speed, and temperature. The synergic technique of matrix modification, fiber modification, or combined modification and/or multiphase modification of the ablative composites is a promising method to provide effective oxidation and ablation protection for C/C composites. Low-dimensional micro/nanoscale materials including graphene, CNTs/CNFs, ceramic NPs, nanowires, and whiskers exhibit special properties that could be used as reinforcements and functional fillers. An interesting technique for modifying advanced composites for aerospace is through hybridization with ultrahigh-temperature ceramics creating multiscale hybrid micro-nano composites. This work proposes an innovative approach towards the manufacturing and dual modification of C/Cs. The reinforcement strategy for modified C/C in this study relies on the incorporation of Multiwalled Carbon Nanotubes (MWCNTs) and hybridization of Ultrahigh-temperature ceramics (UHTCs). The MWCNTs modified composites (CNT-C/C) involve single-phase reinforcement while the UHTCs modified composites (UHTC-C/C) involve multiphase reinforcement with a duality of fiber modification and matrix modification. In this study, different properties of the three categories of samples including MW-C/C, and C/C-UHTCs were investigated in comparison to a control C/C sample. The thermal properties of UHTC-C/C were found to be greatly enhanced as compared to pristine C/C. The phase composition, microstructure, and elemental analysis were done by XRD, SEM, and EDS respectively. The chemical structures and their possible changes after processing were studied xxiii by FTIR. Fracture was done by a three-point bend test which indicated brittle fracture furtherance. The trend in Flexural strength of the composites was found to be FSUHTC-C/C < FSMW-C/C < FSC/C. Thermogravimetric Analysis and Differential Scanning Calorimetry were performed to study the thermal behavior of the samples whereby the UHTC-C/C with an increased content of HfB2 shows the lowest mass loss in weight percentage. The ablation test by Oxyacetylene Torch was done to simulate the severe environments these materials will encounter in real-world applications. It exhibits that UHTC-C/C outperforms the CNT-C/C and non-modified/pristine C/C. Through this technological research effort, the designed ablatives/ablators based on CarbonCarbon composites will likely endure operation temperatures up to 3000oC or higher in hyperthermal environments and superheated gases.