Shell on shell bonding of composite heat shield

Abstract

Heat shield of a guided rocket experiences severe thermo-structural loads during flight especially during its re-entry phase. To meet the above requirement, Carbon Fibre Reinforced Plastic (CFRP) composite is the ideal choice of material which not only has high specific strength, stiffness, good thermal properties and light weight but also exhibits these properties at elevated temperatures. Heat shield is a two layered CFRP composite structure. Carbon Phenolic (CP) layer is an outer thermal member realized by tape lay-up method taking advantage of better ablation characteristics and Carbon Epoxy (CE) is an inner structural load bearing member fabricated by wet filament winding process to get tailor made structure. Each layer (CE & CP) is designed to meet its unique and distinct role. Realization of heat shield needs special attention as it is an assembly of multiple composite sections and also it is process intensive. The aim of this paper is to provide an insight into the established bonding methodology of two layered heat shield structure viz. selection of bonding material , qualification at coupon level both with metal and composite as substrate, tools and fixture, detailed established process and parameters, non-destructive testing of bonded structures, acceptance and qualification. It can be concluded that the structure bonded with the above established process methodology exhibits good bond quality post testing