A system for manufacturing a thermoplastic prepreg product includes a belt or conveyor, a prepreg applicator that positions a thermoplastic prepreg atop the belt or conveyor, a foam applicator that applies a foam mixture atop the thermoplastic prepreg, a heating mechanism that heats the thermoplastic prepreg and the foam mixture to cause the foam mixture to react atop the thermoplastic prepreg, and a laminator that is configured to press the thermoplastic prepreg and foam mixture to control a thickness of the resulting thermoplastic prepreg product. The thermoplastic prepreg includes a fabric, mat, or web of fibers and a thermoplastic material that is impregnated within the fabric, mat, or web of fibers. The thermoplastic material is formed from in situ polymerization of monomers and oligomers. The foam mixture includes an isocyanate, a polyol blend, and a blowing agent.