Investigation into the use of Adhesive Fillers and Soft Start Curing to Reduce the Distortion of a Work-piece Supported by PAAW Joints

Fractional thickness reduction is a critical measure of localized distortion for a part held within a PAAW fixture. The maximum fractional thickness that may result is the fractional volumetric shrinkage of the adhesive. However, this will only occur under the special conditions that the work-piece interface stiffness is very small and the joint aspect ratio is large.This research has shown that for conditions that vary from this, adhesives with comparable values of fractional volumetric shrinkage can lead to significantly different fractional thickness reduction. This is due to variations in the ability of these adhesive to form a neck and to elastically stretch after polymerization. Neck formation is a critical factor for all joint conditions. Elastic stretching is only relevant for cases in which the workpiece interface is very stiff.This research has also shown that soft start curing is an effective means of reducing fractional thickness reduction. It works by facilitating neck formation. As joint conditions become more favorable for neck formation, the effectiveness of soft start curing increases. Alternatively, for conditions in which the work-piece interface stiffness is very low and the joint diameter-to-thickness ratio is very large, soft start curing provides no advantage over conventional curing.