A practical method for predicting thermal residual deformation in RTM-manufactured large-scale composite structures

Abstract

Thermal stresses and residual deformations in composite structures arise from the mismatch in the coefficients of thermal expansion (CTE) between fibers and the resin, chemical shrinkage during curing, and non-uniform temperature distributions through the laminate thickness. These effects cause shape distortions such as spring-in, spring-out, and warpage, which increase tooling correction effort and manufacturing time. In large-scale composite structures, repeated mold modification is particularly costly, and therefore a practical prediction method is required.

This study proposes a practical methodology to predict the thermal residual deformation of a 4 m-scale composite structure manufactured via the resin transfer molding (RTM) process. The approach employs coupon-level segment panels fabricated under processing conditions identical to those of the full-scale structure. The fiber volume fractions (FVFs) of the segment panels were experimentally characterized and used to establish an effective segment-level calibration procedure that accounts for manufacturing-induced ply-wise variability. The calibrated FVF distributions were then transferred to the full-scale finite element model without further adjustment using the full-scale deformation data. The proposed methodology was validated using a 4 m-scale composite main wing structure, achieving a maximum prediction error of 5.4% (approximately 0.214 mm), thereby demonstrating its practical applicability and reliability for large-scale composite structures.