Thermoplastic prepreg with partially polymerized matrix: Material and process development for efficient part manufacturing

Extensive use of thermoplastic composites has been restricted by processing challenges emerging from high melt viscosities. We demonstrate the feasibility of thermoplastic prepreg with partially polymerized poly(methyl methacrylate) (PMMA) matrix and carbon fiber reinforcement. The low viscosity pre-polymer resin allowed part consolidation at low temperature and pressure. The chemical kinetics and rheology of PMMA polymerization were characterized, and an aging study was conducted to assess pre-polymer stability. Prepregs were fabricated using lab-scale methods, and a fabrication map was constructed to determine the optimal extent of polymerization for the prepreg. The prepregs were tested for tack and drape at ambient temperature, and thermoformed for microstructural and chemical analysis. The results show that auto-acceleration drives both the rate of polymerization and viscosity evolution, while refrigeration delays pre-polymer out-time effects. The thermoformed laminates exhibited near-zero porosity. This work establishes material and process development guidelines for reactive thermoplastic prepreg, and highlights potential advantages of the proposed prepreg.