YIELD OF ADHESIVE JOINTS

The yield strengths of polyethylene-stainless-steel lap joints and of polyethylene samples having the same thermal history have been measured over a range of strain rates at temperatures between 245 and 323°K. A yield mechanism based on the motion of dislocation loops through crystalline regions of the polymer is preferred to one based on the jumping of polymer segments into adjacent free volume in an amorphous region. The size of the dislocation loops may be derived from the time dependence of yield strength, and it is found that the ratio of these sizes for the polymer when in the joint and when free is constant under all conditions examined.