Thermostructural Behavior of Polymer and Ceramic Matrix Composites Under Extreme Short Term Thermal Loads

Future supersonic missiles can be improved through the use of polymer matrix composites (PMCs) for structural airframes. However the severe aerodynamic heating conditions will expose the structure to short term temperatures and stresses that are beyond those typically seen by these materials. Nevertheless because the airframes are required to survive these conditions for very short times, it may be possible to employ PMCs as primary structural materials. Designs using these materials are presently limited by the lack of a consistent database that reflects the property degradation caused by severe short term thermal exposure. Materials Research & Design, Inc. (MR&D) proposes to continue the Phase I effort to develop a design method and supporting database that will enable the use of PMCs in short term, high temperature applications. The overall goal of the Phase II program is to demonstrate the use of PMCs as a missile structure that is exposed to extreme, short term thermal loads. The structure may include the Phase I ra-dome, or the fuselage, fairings, control surfaces, strakes, or fins. Specific objectives of the Phase II effort are separated into Part A and Part B. The goal of Part A will be to compare a degraded PMC design to a baseline design in terms of weight, cost, and performance to show that the use of PMCs offers real system benefits. The goal of Part B will be to fabricate a PMC subcomponent suitable for government sponsored testing in a high temperature wind tunnel. The Phase II program will include tasks that address design and analysis, material fabrication, assessment of high heating rate behavior, creation of a thermostructural database, and manufacture of a representative missile subcomponent. Another important outcome of the project will be a micromechanical model for use by the Navy and its contractors to design degrading PMCs with other fiber architectures, heating rates, etc. The program will be performed by a team of MR&D, Raytheon Missile Systems, Physical Sciences, Inc. (PSI), and Southern Research Institute (SoRI). MR&D will manage the program, develop the material model, design and analyze the missile component, and prepare the reports. Raytheon will guide the study, provide system information, and fabricate a selected high temperature PMC materials and subcomponents. PSI will simulate aerodynamic heat loads using the Laser Hardened Materials Evaluation Laboratory (LHMEL) at Wright-Patterson and define effective properties under high heating rates SoRI will generate the database by characterizing the material under conditions of short term, high temperature thermostructural loads. The MR&D team is uniquely suited to perform the proposed effort because of previous experience on the SM-3 Gr/BMI nosecone and in-depth knowledge of the thermal degradation of PMCs under severe aerothermal loads.