Abstract

Internal insulation in a solid rocket motor is a layer of heat-barrier material placed between the internal surface of the case and the propellant. The primary function of internal insulation is to prevent the rocket motor case from reaching temperatures that may endanger its structural integrity. An extensive experimental and theoretical work in the development and characterization of asbestos-free rubbers for use as rocket motor insulators has been performed. The insulation is based on chopped carbon fiber and/or aramid fiber in the pulp form as fillers for Ethylene Propylene Diene Monomer (EPDM). The first aim of the research is to provide an understanding of the mechanism, the principle, and the process for making polymeric thermal insulants. The second aim is to produce thermal insulants based on polymers with different fillers having different compositions which are capable of working under extreme thermal conditions of 2760 °C (5000 °F). This is through an investigation on the processing, installation, physical, mechanical, thermal and ablative properties of these materials. A hybrid of chopped carbon fiber and Kevlar pulp filled EPDM has been shown to exhibit better thermal, mechanical, physical and ablative properties than its asbestos containing counterpart. Also the prediction of thermal conduction of multiphase thermal insulation composite materials was done using series, parallel, Maxwell Euken and effective medium theory models. Comparison with the measured values allows determining which model estimates best the thermal conductivity of composite insulation material. Development of a suitable optimization technique to reach the best parameters of the selected material was done by doing transient dynamic analysis to determine the response of these materials under a time-varying thermal load. A new type of insulation material using prepregs was developed for the first time. This consists of the development of the prepregs and their assembly to make insulant laminates. This laminate has been shown to exhibit better physical, mechanical, thermal and ablative properties than a hybrid of chopped carbon fiber and Kevlar pulp filled EPDM.