Fatigue Issues of Polymeric Foam Sandwich Core Materials in Simple Shear
Abstract
Obtaining the fatigue properties of sandwich core materials is a particularly difficult issue. This work evaluates the ASTM C 394 test procedure for determining the fatigue properties of core materials using compression-compression loading. The stress concentration at the ends of the specimen where the specimen meets the fixture has been suggested to lead to premature failures. A geometric optimization of specimen ends was attempted to minimize the effects of the stress concentration. This resulted in removing a circular arc of material from the specimen ends. While this allowed the stress concentration to be shifted away from the corner interface of the specimen and fixture, it did not seem to positively influence the fatigue life for the load levels tested. Fatigue results obtained using the compression-compression loading compared well with data obtained using other test methods, including four-point bending. This suggested that the current ASTM C 394 test standard, when used with compression-compression loading, allows acceptable fatigue data to be obtained for foam core materials.