Residual Stress and Warpage Development during the Automated Fiber Placement Process

摘要

The Automated Fiber Placement process is being investigated as a rapid affordable manufacturing technique for the fabrication of composite components. One of the potential probelms asosciated with this process is the process-induced residual stress and warpage in the part. In order to understand the interactions and the fundamental mechanisms of residual stress and warpage development during the automated fiber placement process, a simplified residual stress model has been implemented to study this phenomenon. This model is based on Classical Lamination Plate Theory. It models the resultant residual stresses and warpage due to the sequential laydonwn of each layer at some initial temperature T_i and cooled to a final temperature T_f before the next layer is laid down. The material properties are varied above and below the glass transition temperature T_g. Experimental observations have shown that the resultant curvature is changed if the laminate is constrained and prevented from warping during processing. hence, the effect of a constraint is being included in the modeling approach. Fiber tension may represent an important mechanism for controlling the warpage, and is also included in the model. Based on the current processing parameters used in the manufacture of K3B/IM7 composite laminates, three mechanisms have bene identified for the development of residual stress and warpage. The total process induced warpage of the laminate is the sum of the warpage resulting from these mechanisms. A parametric analysis using the model has identified possible techniques for controlling the process-induced warpage.