Vibration characteristics of thermal insulation tile with material and geometric nonlinear effects

Abstract

Thermal protection system (TPS) composed of ceramic insulation tile and strain-isolation pad (SIP) tends to be destroyed by excessive inner strain arises from aerodynamic load or substructure deformation/vibration. Both material nonlinearity and geometric nonlinearity affect the static and dynamic strength of TPS, and the nonlinear effects of SIP need to be considered in the strength analysis. By considering both the material nonlinearity and geometric nonlinearity of SIP, the effect of external static load on the dynamic characteristics of tile-SIP system is investigated. Firstly, a theoretical model is established to calculate the natural frequency of tiles under static load with material and geometric nonlinearities. The analysis procedure is separated into two steps. The first step is the nonlinear analysis to determine the static large deformation. The second step is the linearized dynamic analysis on the base of static deformation with small vibration amplitude assumption. The complexity is reduced by introducing a nonlinear coefficient parameter. The theoretical results have good agreement with COMSOL simulation. Numerical results show that large deformation is found in the flexible SIP when uniform static load applied on the surface of the tile, which introduces significant material and geometric nonlinearities and changes the dynamic characteristics of the tile. 9% increase of intrinsic frequency is found for the static load of 80kPa when considering material nonlinearity, while 16% increase of intrinsic frequency is found when considering both material and geometric nonlinearities. It is concluded that the uniform static load has important effect on the nature frequency of tile-SIP systems when introducing the material and geometric nonlinearities into the calculation. The nonlinearities of the SIP need to be considered in the tile-SIP dynamic strength analysis.