Viscoelastic response of unidirectionally reinforced thermoplastic composites to off axis deformation

Abstract Measurements of dynamic viscoelastic in‐plane shear modulus have been made for unidirectional carbon fiber composites with amorphous engineering thermoplastics as the binder resins. The viscoelastic response is modeled by a three‐phase, finite‐element model in which fiber placement in the plane perpendicular to the fiber axes is largely disordered. In the model, fibers tend to chain with the distance of closest approach dictated by several factors, including the tendency for the resin to wet the entire fiber surface. Polished section microscopy supports the assumed microstructure. The model includes an adsorbed primer layer at the fiber interface with perturbed viscoelastic response. The model is useful throughout the temperature range up to and including the glass transition of the binder resin.