Abstract
A variety of glass fibers (GF) and Polyamide 12 (PA 12) resins were selected to study fiber-matrix wetting and adhesion in thermoplastic composites. The fibers differed in the nature of their surface treatment, the PA 12 resins in their content of amine terminal groups and melt viscosity. The wetting behavior and the interfacial adhesion were investigated by conducting contact angle and interfacial shear strength measurements on fiber-droplet specimens. Depending on the fiber surface finish, variations in contact angle of up to 600 and differences in interfacial shear strength of up to 7 M Pa were obtained. Slight variations in contact angle and interfacial shear strength were also observed as a function of the resin viscosity and the chain termination chemistry. These results are of practical relevance for tailoring the fiber-matrix interface, to minimize the fiber impregnation time during processing and optimize the mechanical performance of the composite during service. The results also allow a correlation to be established between the contact angle and the interfacial shear strength, in agreement with an existing model. The validity of the experimental methods suggested for the determination of contact angle and interfacial shear strength in thermoplastic composites is thus confirmed.