Stress-based fatigue life prediction of adhesively bonded hybrid hyperelastic joints under multiaxial stress conditions

The joining of dissimilar materials like aluminium and carbon fiber reinforced polymer using hyperelastic adhesives to reduce high stress gradients at the overlapping ends in bonded joints is becoming progressively important. The design of these adhesively bonded joints with complex mechanical behaviour requires a valid and efficient method for virtual lifetime prediction. In following, a concept for stress-based fatigue life prediction with associated experimental parameter identification of adhesively bonded joints using hyperplastic adhesives under multiaxial stress conditions is presented. Furthermore, a possibility of optical crack monitoring for adhesively bonded test specimens is demonstrated and a method for crack detection based on amplitude compliance is proposed. Based on these results, the presented lifetime prognosis concept will be validated experimentally and numerically for inhomogeneous stress fields in the adhesive layer using technological test specimens. In addition to the number of cycles to failure, the expected cycles to crack initiation is considered as the prediction variable.