The influence of electrophysical activation of the components on interphase-boundary strength in fiber-reinforced composites based on thermoplastic polymers was studied. Investigation of the relaxation processes in the composites indicated that the structure and properties of the boundary layers depend strongly on the electrical state of the components during forming. Introduction of an excess charge during prepregging raises the strength of the adhesive joints and improves the mechanical properties of the resulting prepregs and plastics. It is suggested that the principal cause of the adhesion improvement is an increase in the molecular component of the adhesion forces that is induced by the electric charges and fields.