Thermomechanical Homogenization of Corrugated Core Sandwich Structures of Reusable Launch Vehicles

The corrugated core sandwich structure is a potential candidate for the integrated thermal protection system (ITPS) of reusable launch vehicles (RLVs). The sandwich structure can develop a significant thickness-wise thermal gradient during operation, resulting in a temperature-dependent property variation along the cross section as well as thermal stresses. In this work, a homogenization method has been developed that incorporates these effects into the first-order shear deformation plate theory to facilitate thermomechanical structural analysis of RLV components such as wings, fuselage, etc., with the ITPS sandwich panels represented as thick orthotropic plates. The formulation expands the classical plate theory by assuming a polynomial form of thickness-wise temperature variation, as well as a linear dependence of elastic moduli and thermal expansion coefficients on temperature. This expansion introduces unknown constants into the homogenized model that could then be evaluated from unit-cell analyses with periodic boundary conditions and beam analyses of the corrugated core sandwich structure. The accuracy of the homogenized plate has been demonstrated by comparing its response with a full-scale model for a uniform and spatially varying in-plane temperature field. For both cases, a thickness-wise linear temperature variation has been used. The comparisons show that the homogenization approach is reasonably accurate in capturing the midplane deflections as well as stresses on the face sheets. An error of less than 1% could be seen in the maximum midplane transverse deflection for the problem with a spatially varying in-plane temperature field.