Fatigue Life Predictions of Adhesive Joint of Sheet Steels

Structural adhesive is widely employed in vehicle structures to enhance noise-vibration and crashworthiness performance. It is also known that structural durability is enhanced with application of structural adhesive. Many researchers have reported the fatigue performance of adhesive joints, but the test results showed noticeable scatter, making it hard to develop a fatigue life prediction method. This study fabricated cross-tension specimens joined with either adhesive only or adhesive with a spot-weld joint. These specimens were subjected to a 45-degree loading direction with respect to adhesive joint plane. The materials used for the specimens were various sheet steels, including mild steel, DP, and ultra-high strength steel. Fatigue tests were conducted for the specimens and a stress-life curve was constructed using a structural stress method. The test results were also correlated with a fracture mechanics approach. Both of the approaches showed reasonable correlation with the test results.