Experimental characterization of multiscale solidification in thermoset CFRP during gelation for flow and stress modeling

Two types of flow mechanisms consisting of unidirectionally arrayed fibers and uncured thermoset resin exist in prepreg materials. These mechanisms are percolation flow where resin flows out of the gaps between fibers, and shear flow where resin and fibers flow together. Based on our previous study, we assumed that percolation flow is controlled by the rheology of the matrix resin, whereas shear flow is controlled by the rheology of prepreg. Based on this assumption, we experimentally evaluated the ‘multiscale’ solidification (solidification of matrix resin and that of prepreg) process using dynamic mechanical analysis during gelation. The solidification of matrix resin was examined by observing the development of loss angle, which provides a continuous description of the solidification process. On the other hand, the solidification of prepreg was characterized by analyzing the relationship between the shear storage modulus of prepreg and that of the matrix resin. Finally, we examined the difference in the solidification process between prepreg and matrix resin during gelation.