Experimental analysis of formulation and coating process of LDAM for thermal protection systems

Abstract

The Thermal Protection System (TPS) is a membrane used to avoid aerodynamic heating of metallic and plastic surfaces during flight of missile. Between a heat source and the protected entity, the thermal protection system is interposed. Although the Orbiter’s re-entry surface heating is primarily convective, ample energy in the air molecules disassociated from the shock layer and given the potential for additional heating. Various composite materials are used in thermal insulation systems to achieve higher backwall temperatures in order to maintain high temperatures and pressure upon re-entry. A Low-Density Ablative Material (LDAM) is prepared and coated using the High Velocity Low Pressure (HVLP) method of coating. The process of applying the chemical composition of the present invention shall ideally require spraying at room temperature, without the need to add heat to the treatment of the composition in order to affect the repair and to obtain the optimum dry film thickness specifications. In this present research, the configuration of the Taguchi experiments is considered and a series of experiments are carried out for the coating process using the L9 orthogonal array by varying the control factors such as air pressure, spray time and nozzle size (lock no.) and the performance parameters are optimized such as Dry Film Thickness (DFT) and Back Wall Temperature (BWT) using Taguchi optimization technique to get the optimal input levels. Finally, a validation test is carried out according to the optimal levels obtained from the optimization technique of Taguchi and the most influential parameters are found using ANOVA.