Description:
OBJECTIVE: Create and develop new CMC manufacturing approaches such as Field Assisted Sintering Technology (FAST) that offers flexibility, robustness, and reduces manufacturing costs of CMC components. DESCRIPTION: Silicon carbide matrix reinforced with silicon carbide fibers (SiC-SiC) composite is a very attractive material due to high-temperature oxidation resistant properties, low density, and good creep properties needed for turbine applications. Significant progress has been made in the processing of SiC-SiC composite. Over the past 10 to 15 years, significant investments have been directed towards the development and manufacturing of CMC components. Manufacturing costs for CMC components are still very high however with long lead times that must be reduced by 50% to enhance process viability. The requested research will conduct fundamental investigations of processes such as sintering to view phenomena of the CMC including interface between fiber, coating, and matrix under the concurrent application of high current density, pressure temperature, and time. Processing-structure-properties relationships will be established to allow complete exploitation of the benefits of this novel processing approach. Mechanical properties including tensile, flex strength, and creep will be examined at room and elevated temperatures. The three processes for manufacturing CMC components have been: (a) Chemical Vapor Infiltration: a very slow process (100s of hours to densify preform), requiring tight parameter control that is not conducive to thick preform components, (b) Melt Infiltration: a comparatively fast process (few days), that lowers manufacturing cost, but is limited by liquid Si migration, and (c) Polymer Impregnation Pyrolysis: where pre-ceramic polymer precursors and multiple impregnations result in poor quality SiC matrix. The purpose of this SBIR topic is to develop a basic materials technology that would enable the production of more affordable 2700 degrees F capable CMCs which could translate to a 2% decrease in fuel or a 2.1% increase in mission range for limited engine parts. Expanded CMC use would augment greater fuel efficiencies or mission range for military aircraft. PHASE I: In the Phase I effort, conduct fundamental investigations of the phenomena of the CMC including interface between fiber, coating and matrix under the concurrent application of high current density, pressure temperature, and time. Processing-structure-properties relationships should be established to allow complete exploitation of the benefits of novel processing approaches. The proposed research should utilize an integrated, science-based framework to underpin and advance the development of integrally woven SiC CMC structures and should seek to identify and build a modeling framework to encompass manufacturing process simulation and quantitative processing-structure relationships, for assessment of process or product optimization. PHASE II: In the Phase II effort, the investigators shall evaluate and validate the process models and acquire missing thermodynamic data if needed. The processing-structure-properties relationships will be validated to verify complete exploitation of the benefits of the novel processing approach. Mechanical properties (tensile, flex strength, and creep) should be characterized at room temperature and elevated temperatures. The effort should analyze the defects in tow architecture arising during various stages of manufacturability and matrix processing. It is desirable to be able to analyze strain and temperature distributions in textile composites with non-periodic architectures and asymmetric boundary conditions and develop a modular structure to accept mechanistic continuum damage models to describe matrix cracking, fiber fragmentation, and bundle rupture as well as other inelastic processes. PHASE III: The investigators should connect with various original equipment manufacturers (OEMs) of aviation gas turbine components and materials to provide either support services for process optimization or license the process to allow the OEMs to exploit the benefits of this processing method for SiC CMC turbine components. PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The major barrier to more extensive usage of SiC CMC components for gas turbine engines has been the cost of fabrication. Development of a most cost-effective manufacturing method for CMCs would lead to more extensive adoption and usage of CMCs components in both military and commercial aircraft that would lead to greater engine efficiencies and less fuel usage. REFERENCES: 1. B.N. Cox, D.B. Marshall, and O. Sudre."Novel Textile Architectures and Robust Matrices for SiC/SiC Composites for Turbine Engines,"U.S. Air Force Report (VAATE) AFRL-RX-WP-TR-2011-4251. 2. S. Gephart, J. Singh, A. Kulkarni."Field Assisted Sintering of Submicron SiC using Extreme Heating Rates."Journal of Materials Science, 2011, 36593663.
