Session: 04-09-01: Materials and Structures for Extreme Environments

Paper Number: 71934

Start Time: Monday, 11:45 AM

71934 - Processing and Characterization of Continuous Carbon Fiber Reinforced Silicon Oxycarbide Ceramic Matrix Composites 

Abstract

There are significant challenges for materials in extreme environments for a variety of applications such as aircraft engines, gas turbines, nuclear reactors, rocket launch pad, and hypersonic structures. Ceramic matrix composites (CMCs) could be ideal candidates to meet these stringent requirements for materials due to their excellent mechanical the thermal behavior in extreme environments. Particularly, continuous fibers can bridge cracks in CMCs and therefore improve the strength and fracture toughness of composites. CMCs are traditionally manufactured by melting infiltration method. Composites manufactured by this method present typically high porosity and brittle structure, and their mechanical properties are not high enough to stand high mechanical loads. Alternatively, polymer derived ceramic composites are fabricated by incorporating carbon fibers into polymer derived ceramic matrix to achieve high fracture toughness. With the aid of protective coatings of metallic or ceramic materials, such as Nickel and boride nitride, carbon fiber could potentially withstand high temperatures without oxidation. In this study, continuous fiber reinforced silicon oxycarbide composite was manufactured with the polycarbosilane (PCS) resin and woven carbon fabrics through the polymer infiltration and pyrolysis process (PIP). Carbon fabrics was infiltrated through the flow of polycarbosilane resin under vacuum or pressure to form prepregs with laminated structure, followed by curing and post-curing procedures in autoclave under controlled temperature, vacuum and pressure. After the formation of a green part, high temperature pyrolysis process was applied in an inert (Argon) atmosphere to further decompose the PCS into silicon oxycarbide to form the composites. Through re-infiltration of the PCS resin into the composites, curing in autoclave, and pyrolysis for additional 2 to 10 cycles to increase the yield of ceramics in the composites. A dense structure of the composites was observed by SEM, indicating good bonding between carbon fiber and ceramic matrix, and the crack generated by flexural strength testing. The EDS results showed that elemental composition of the composites mainly consisted of carbon, silicon and oxygen. The crystalline structure of the composites was examined through XRD to illustrate the degree of polymer pyrolysis. The results of 4-point bending testing of the composites showed a flexural strength of 68MPa, a flexural modulus of 52GPa, and a fracture of toughness of 140kJ/m³. The flame torch test was conducted on the CMCs panels under different heat flux. The ablation rate, mass loss rate, ablation temperature, and insulation indexes were characterized to evaluate ablation performance of the Polymer Derived Ceramic Composites.

 

Presenting Author: Haonan Song University of Central Florida

Authors:

Haonan Song University of Central Florida
Derek Saltzman University of Central Florida
Jayanta Kapat University of Central Florida
Jihua Gou University of Central Florida