Temperature Effects on the Fatigue Behavior of Foam Core Sandwich Structures

The effects of temperature on the fatigue behavior of foam core sandwich structures have been investigated. Two types of PVC cores of the same nominal density were used; one was linear HD foam and the other a slightly cross-linked H foam. In both cases the face sheet material was S2-glass/vinylester. Fatigue tests were conducted on these sandwich structures at room temperature (RT), 40° and 80 °C. The tests were conducted on an MTS machine equipped with an environmental chamber. The stress ratio was set at R=0.1 and the frequency, f=3Hz. S-N diagrams were generated and revealed that fatigue life increased with decreased stress and decreased with increased temperatures. At RT, HD structures revealed much longer fatigue life compared to H structures however at elevated temperatures, a complete reversal of this trend was seen. Further, significant differences in the failure between H and HD structures were observed. Details of the experimentation, the analysis of the fatigue data, and damage mechanisms are presented.