Interlaminar contact development during thermoplastic fusion bonding

Abstract

AbstractFabrication of layered thermoplastics and thermoplastic‐matrix composites using processes such as tow placement, tape laying, and resistance welding is fundamentally based on the principle of fusion bonding, which involves applying heat and pressure to contacting thermoplastic surfaces. One of the important processing steps—intimate contact development—is considered in this paper. Interlaminar intimate contact development has a strong dependency on the thermoplastic surface geometry. Profilometric measurements of common thermoplastic prepreg tows, such as AS4/PEEK and IM7/PIXA, show that surface roughness features appear at several length scales and that the surfaces have fractal asperity structures. In this paper, principles of fractal geometry are used to describe prepreg surfaces. Based on this description, a microscale fluid flow model is developed to relate a degree of intimate contact to the process parameters (pressure, temperature, and time) and the fractal parameters of the surface. The model development and comparisons with experimental data are presented and discussed.