Investigation On Thermo-mechanical Behaviors Of Corrugated-core Sandwich Structures For Integrated Thermal Protection And Load Bearing

Focusing on the thermal protection demands of hypersonic vehicles,a kind of double-layer corrugated-core sandwich integrated thermal protection system(ITPS)is designed based on the classical singlelayer corrugated-core sandwich ITPS.The thermo-mechanical behaviors such as heat conduction,load bearing,thermal buckling,vibration,and impact responses of the ITPS under reentry thermal environment are studied by the finite element simulation.The influences of thermal environment on the thermo-mechanical responses are discussed by numerical examples,and the light-weight design of the ITPS is also carried out.The main substances of this paper are as follows:Firstly,the quasi-static thermo-mechanical behaviors of a single-layer corrugated-core sandwich ITPS under reentry thermal environment are studied,and then the effects of geometric parameters and boundary conditions on its heat transfer and mechanical properties are explored.Three kinds of double-layer ITPSs are designed based on the single-layer one.The thermal insulation and load bearing properties of the three schemes under thermal environment are analyzed.Results show that stress level of the double-layer ITPS with orthogonal arrangement is the lowest.According to thermal buckling analyzing results,critical buckling factor of the double-layer ITPS with parallel arrangement is the highest,and the buckling position of each ITPS is at the web.Secondly,free vibration characteristics of the ITPS panel in thermal environment are researched.Separately considering the uniform and actual non-uniform temperature field,the influences of structural thermal stress and material parameters on vibration responses are analyzed.Results show that the ITPS with orthogonal arrangement has the highest average natural frequency and its stiffness characteristic is the best.Thermal stress will produce negative additional stiffness,and the decrease of elastic modulus will cause material nonlinearity.The random vibration analysis is carried out based on the modal analysis,and influences of thermo-mechanical coupling on random responses of the ITPSs are studied.The research shows that the root mean square(RMS)values and acceleration power spectral density(PSD)curves of each scheme are different,and the resonance occurs near a certain natural frequency.The change of temperature load affects various RMS values of ITPS panel.Thirdly,aiming at investigating the impact responses of ITPSs under thermal environment,four kinds of impact velocities of an aluminum bullet are given,and the temperature condition of heating or cooling is separately applied.It is found that the thermal load changes the impact kinetic energy absorption characteristics of the ITPS and affects the contact force between the aluminum bullet and the panel.Thermo-mechanical coupling effect on the impact process is also studied according to the total plastic dissipation(ALLPD)curve.The plastic strain energy stored in ITPS generates thermal stress,and the double-layer orthogonal(DLO)ITPS has the best impact resistance.Finally,a dimensionless factor to evaluate the structural efficiency of the corrugated-core sandwich ITPS is proposed.The DLO one with the highest structural efficiency is selected for topology optimization under single and multiple weighted working conditions.The thermo-mechanical properties of the final optimized ITPS are obtained.On the premise of 9.59%weight reduction,the structural efficiency is significantly improved.