Composites Part C: Open Access (Jul 2022)
Intimate contact development for automated fiber placement of thermoplastic composites
Abstract
The consolidation step in the automated fiber Placement (AFP) of thermoplastic composites is crucial for development of interlaminar bonding strength. Two mechanisms contribute to the interlaminar bond strength development in the interface between the incoming tow and the substrate: (a) the development of intimate contact between the two surfaces and (b) the formation of a fusion bond across those contacting surfaces known as healing. So far, a number of different theoretical intimate contact models have been proposed in the literature to study intimate contact development for different manufacturing processes. However, very limited experimental methods are available to measure degree of intimate contact. To fill this gap, a new experimental approach based on topology of the tape surface is introduced to quantify the degree of intimate contact for the AFP process. The new approach is based on the Bearing Area Curve (BAC) of the surface profile of the tape. To implement the new procedure, an unidirectional strips of carbon fiber/PEEK were laid down on the polished steel tool with different placement rates, compaction forces, hot gas torch (HGT) temperatures, and tool temperatures. The degree of intimate contact is calculated based on the proposed experimental approach and compared with prediction models from the literature. Furthermore, the effect of AFP process parameters on the degree of intimate contact is studied using BAC method and the effective intimate contact model. The results showed that the development of intimate contact is significantly governed by the torch and tool temperature.
