A study is undertaken to investigate the response of a representative integrated thermal protection system structure under combined thermal, aerodynamic pressure, and acoustic loadings. A two-step procedure is offered and consists of a heat transfer analysis followed by a nonlinear dynamic analysis under a combined loading environment. Both analyses are carried out in physical degrees-of-freedom using implicit and explicit solution techniques available in the Abaqus commercial finite-element code. The initial study is conducted on a reduced-size structure to keep the computational effort contained while validating the procedure and exploring the effects of individual loadings. An analysis of a full size integrated thermal protection system structure, which is of ultimate interest, is subsequently presented. The procedure is demonstrated to be a viable approach for analysis of spacecraft and hypersonic vehicle structures under a typical mission cycle with combined loadings characterized by largely different time-scales.
This paper is concerned with homogenization of a corrugated-core sandwich panel, which is a candidate structure for integral thermal protection systems for space vehicles. The focus was on determination of thermal stresses in the face sheets and the web caused by through-the-thickness temperature variation. A micromechanical method was developed to homogenize the sandwich panel as an equivalent orthotropic plate and calculate the equivalent thermal forces and moments for a given temperature distribution. The same method was again used to calculate the stresses in the face sheets and the core. The method was demonstrated by calculating stresses in a sandwich panel subjected to a temperature distribution described by a quartic polynomial in the thickness direction. Both constrained and unconstrained boundary conditions were considered. In the constrained case the plate boundaries are constrained such that there are no deformations in the macroscale sense. The unconstrained case assumes that there are no force and moment resultants in the macroscale. The results for stresses are compared with that from a three-dimensional finite element analysis of the representative volume element of the sandwich structure, and the comparison was found to be within 5% difference. The micromechanical analysis, which is less time consuming, will be useful in the design and optimization of integral thermal protection system structures.
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