Effect of Fibre Orientation on the Properties and Functional Performance of Ablative Materials for Solid Rocket Motors

Abstract

Ablative materials are polymeric composites where the reinforcement is generally a fibre with high melting point like Carbon or Silica and the matrix is a high char yielding resin like phenolics. These composites are used as thermal protection systems in Solid rocket motor nozzles, liquid engine throats, control thrusters, re-entry nose caps etc. They encounter extremely hostile conditions during their service conditions. The high temperature, pressure, velocity of hot exhaust gases, heat flux, particle impingement of the solid propellant particles etc. contribute to harsh environment inside the nozzle. These high performance composites are synthesised using specially developed processes using sophisticated equipments. In this paper, the process of ablation, the physical and chemical changes and the process of synthesis of ablatives are clearly elaborated. In the present work, the factors affecting the thermo-mechanical properties and functional performance of ablatives are investigated. Based on the selected parameters, detailed study was done on a few key factors. The fiber orientation in the reinforcement and the process of orienting the fibers during the prepreg tape layup were chosen for detailed study. Composites were processed under carefully controlled conditions and detailed characterisation was done. The details of processing operations, characterisation and Non-destructive evaluation have been explained in this paper. The critical process parameters and the special processing conditions needed to realise a defect-free composite have also been addressed. The details of these tests, the post test evaluation and analysis etc. are explained in this paper.