Photoelastic and numerical investigation of thermally-induced restrained shrinkage stresses in plastics

A photoelastic analysis is used to determine stress distributions within an epoxy encapsulation material for idealized geometries. Experimental results are compared with analytical and numerical predictions based on actual material data. It is demonstrated that to determine quantitative stress levels using photoelasticity it is necessary to separate orientation effects from an elastically active portion of stress. These `elastic´ stress levels are predicted using linear elastic finite-element models, and agreement with experimental data is obtained when appropriate input parameters are chosen