Dynamic mechanical response of a thermoplastic sheet molding compound‐glass fiber composite

The dynamic mechanical properties of nylon 6/continuous glass fiber composites at four levels of fiber volume content were studied between ‐180 and 130°C using a free resonance torsion pendulum. The composites were produced by anionically polymerizing caprolactam monomer within a swirl type glass fiber mat using a vacuum injection technique. In addition to the expected strong dependence of shear storage modulus on fiber volume content, the glass transition temperature of the nylon 6 was observed to increase slightly and the mechanical damping decrease with fiber volume fraction. Introduction of about 7 weight percent water (i.e., equilibrium hygroscopic state) into the composite led to a considerable broadening of the transition peaks and a much lower plasticizing action of water in the composite relative to the pure nylon 6 matrix.