Affordable Low Dielectric Ceramic Composites with Improved Interlaminar Strength

Hot structures fabricated from ceramic composite materials are an attractive design option for selected components of future aerospace vehicles and propulsion systems to reduce weight and increase survivability. Fabric-laminated ceramic composite components have been determined to suffer from low interlaminar strength properties, making them vulnerable to delamination when subjected to high thru-thickness thermal gradients and/or normal loads. Under Phase I SBIR funding, Hyper-Therm HTC demonstrated increasing the interlaminar shear strength of novel low dielectric Nicalon/CVI-Si3N4 composites by over 400% using an affordable angle-interlock fiber perform to overcome the inherent limitations of fabric-based laminates. The objective of this proposed Phase II effort is to continue the development and evaluation of improved low dielectric composites utilizing the low-cost 3D angle-interlock fiber preform architecture and Hyper-Therm HTC’s exclusive high-stability silicon-doped boron nitride (Si-BN) interphase in combination with a novel CVI-derived SiNC matrix. Panels of 2D and 3D Nicalon/SiNC composites will be produced and destructively evaluated at both Hyper-Therm HTC and Southern Research Institute (SoRI) to determine the relevant in-plane and interlaminar mechanical properties of the material system. The experimental results will be compared to the “baseline” 2D Nicalon fabric-laminated SiNC-matrix composite system to establish the overall viability of the proposed approach. Samples from the various materials produced will be delivered to the NAVY for additional evaluation.