Design and Manufacturing Strategies to Eliminate Visible Adhesive-Induced Surface Distortions in Bonded Automotive Class 'A' Assemblies

摘要

Bond-line read-through (BLRT) is a distortion in the "Class "A" surface of a bonded assembly caused by differential shrinkage between the substrates and the adhesive. When these distortions are severe enough to be visible customers consider them to be unacceptable. In automotive applications in which a structural inner panel is bonded to a Class "A" outer panel, the coefficient of thermal expansion of the adhesive is higher than that of the substrate. This difference in thermal expansion between the two materials causes the outer panel to be distorted at room temperature if the assemblies were bonded at elevated temperature. The distortions become visible when other factors exacerbate the severity of these naturally occurring distortions. The material and process factors that determine the severity of BLRT-induced distortions, and the experimental and analytical work from which those relationships were determined, have been reported previously. Understanding of the cause of and the factors that contribute to BLRT allows one to then develop design and manufacturing strategies for minimizing the severity of adhesive-induced surface distortions in bonded assemblies. The design and manufacturing strategies that are the final outcome of the Automotive Composite Consortium's BLRT project are presented.