Blister appearance in thermoplastic composites

Blisters were observed in thermoplastic composite materials after a thermal shock during the manufacturing process of electronic parts. The aim of thi s paper is to describe the blister appearance and its mechanism. First, an experimental study is presented about the environmental conditions and the evolution of blister appearance on the specimen; then the mechanism of thei r formation and propagation in the material is suggested, and finally an at tempt is made to explain the origin of the phenomenon. Experiments show tha t the water content of the material, the time and the temperature of the th ermal shock play an important role. Observations made by SEM show the blist er progression in the core of the material. A crack is initiated and then p ropagates on the interface fiber-matrix. After a crack reaches a sufficient length, the internal stress field opens it and a blister appears.