Multiscale cure process modeling of an advanced 3D-woven composite for thermal protection systems applications

As-manufactured woven polymer matrix composites often exhibit in-situ cracking due to residual stresses that arise from curing. NASA’s Heatshield for Extreme Entry Environment Technology (HEEET) is a state-of-the-art 3D-woven composite thermal protection system featuring a highly porous phenolic matrix, blended fiber yarns, and a complex woven architecture. To predict residual stresses in HEEET due to curing, a bottom-up hierarchical multiscale cure process modeling framework was engineered. The modeling framework spanned three length scales: nanoscale, microscale, and mesoscale. A novel application of molecular dynamics was developed to generate microstructure models with characteristic cross-sections of the blended yarns. Cure- and temperature-dependent properties of the phenolic matrix were established to serve as homogenization inputs at the nano and microscales. Residual stresses predicted by virtual curing of HEEET at the mesoscale were compared quantitatively to simple, relatively low computational cost thermal cooldown simulations and qualitatively with micro-computed tomography imaging data.