Investigation on interlayer phase morphology evolution of “ Ex‐Situ ” toughened composite laminate

The numerical simulation on the interlayer phase morphology evolution of “ Ex‐Situ ” toughened laminate was performed in this study. Specifically, the diffusion process of thermoset (TS) resin into thermoplastic (TP) resin was modeled incorporating the negative effect of resin curing reactions. The dynamic process of polymerization‐induced phase separation in TP/TS blends was predicted by the modified Cahn–Hilliard equation, in which the concentration‐dependent mobility was used to describe dynamic asymmetry between TP resin and TS resin, and the mixing free energy of the blends contained the contribution of resin curing reactions. The phase morphology evolution of polysulfone/epoxy blends in the interlaminar region was analyzed numerically, and the results indicated that the diffusion process resulted in the concentration‐gradient distribution of epoxy resin in interlayer, and when the concentration‐gradient decreased, the interlayer phase morphology developed from the coexistence of different microstructures to the presence of a single structural form. The post‐curing temperature played a more important role in the phase separation than that in resin curing reaction, and the separated structures were only observed in the local region of interlayer under low post‐curing temperature, due to small driving force of phase separation. Moreover, the movements of epoxy molecules dominated the microstructure formation process. POLYM. COMPOS., 40:3644–3656, 2019. © 2019 Society of Plastics Engineers