Pressure Effect on Molding of Rod Piercing Type 3D-Composites

Rod piercing type three-dimensional fabric composites (3D composites) have rigid preform structures, which are responsible for aggravation of defects generation during molding. In this study, a model is proposed that the internal strain produced during composite molding is expressed as the difference between the specific volume of cured resin at room temperature and that of resin at the stage which the resin has lost its fluidity during cure. Then the relation between curing pressure and generated defects is examined. This experiment yields the following results. 1) No defects are observed for the inner part of the epoxy resin matrix of 3D composites molded at the pressure of no less than 29 MPa. 2) The numerical estimation of resin compressibilities, the changes of resin specific volume, and internal strains in 3D composites quantitatively explains the defect generation, and shows that the experimental results are in good agreement with the model.