Damage tolerance analysis of double strap joints with composite adherends

Damages in composite structures are typically repaired using external bonded patches. In this work, the damage tolerance within external patches is studied using double strap joint (DSJ) with carbon fibre reinforced plastic (CFRP) specimens. The damage tolerance in this work refers to bond-line manufacturing-related defects such as debond or dry area. Both intact and pre-cracked DSJ specimens are numerically analysed using experiments for comparisons. DSJ specimens' adherends were CFRP laminates with AS4/3501–6 plies and bonded using adhesive film FM 300–2. The pre-cracked specimens are monitored during experiments using high-speed digital image correlation to visualize damage propagation. The unsymmetric pre-crack influences in a clear way as shown by experiments. The numerical analyses reveal the effect of failure mechanisms on final failure and the maximum force during a test. The included parametric sensitivity analysis is performed using statistical methods. The normally distributed parameters are sampled using separate distributions for each analysed interface and fracture mode. UNCLASSIFIED Based on Foreground Information under EDA Contract No B.PRJ.RT.670 covering the Ad Hoc Project entitled "PATCHBOND II".