Process-Induced Residual Stress Analysis by Resin Transfer Molding

The objective of this study is to investigate the residual stress development during the resin transfer molding process. The analysis was based on the strain measurement tests during the entire cure process of unidirectional carbon fiber–epoxy matrix composite laminate using aluminum mold. The investigation efforts were particularly focused on the verification of the strain development mechanism. Although complex interference between the mold structure and the composite laminate was observed during the process, it was found that the final residual strain of the laminate was induced only by thermal mismatch during the cooldown stage. Based on the observation, the residual stresses were calculated by a viscoelastic classical laminated plate theory. The viscoelastic modulus in the calculations was obtained by a series of stress relaxation tests of the material. The curvatures of [0°/90°] asymmetric laminate were calculated, and the results were compared with the experimental data. The results showed that the residual stress developed by the resin transfer molding could be calculated by considering only the cooldown stage of the process.