Mechanical modeling of a stitched sandwich thermal protection structure with ceramic-fiber-reinforced SiO₂ aerogel as core layer

Ceramic-fiber-reinforced SiO2 aerogel (CFRSA) composite was used as core layer to prepare a stitched sandwich thermal protection structure (SSTPS). Mechanical properties of the SSTPS were experimentally investigated and compared with that of CFRSA, including flatwise tension, flatwise compression, edgewise compression and shear. Research results showed that the SSTPS can greatly improve the mechanical properties of CFRSA. To further understand the non-linear, tension-compression asymmetric and transversely isotropic properties of the SSTPS, inner configurations were investigated by X-ray computed tomography and scanning electron microscopy. Mechanical models were established to predict the overall properties of the SSTPS through performance of each component, including theoretical model and finite element analysis (FEA) model. Mixed series-parallel spring models were constructed to theoretically predict the effective elasticity modulus of the SSTPS. Representative volume element (RVE) was selected for FEA modeling of the SSTPS, which can not only predict the equivalent elastic modulus of SSTPS, but also predict the nonlinear flatwise compression behavior. In order to verify whether the mechanical properties of large area SSTPS under complex stress can be represented by the properties of uniform materials through RVE analysis, four-point bending test and FEA modeling were carried out on a large scale SSTPS specimen. Results showed that when analyzing the macro bending behavior of large area SSTPS, the method of equivalent SSTPS to uniform material were of relatively high accuracy and efficiency.