Residual stresses and failure behavior of GFRP/Al-Li laminates after single and multiple shot's indentation under quasi-static

Residual stresses and failure behavior of 3/2 GFRP/Al-Li laminates after single and Multiple shot's indentation under quasi-static condition were investigated to better reveal the characteristics of residual stresses after shot-peening forming. Single shot's indention behavior was analyzed with the finite element model using the Johnson-Cook material model and customize damage initiation criterion then validated by experiments of single shot's indentation. Results indicated that the fiber layers hindered the deformation of aluminum-lithium layer. Moreover, the layup of fiber layers and the shot diameter (more than 2 mm) affected the shape of the crater which reflected characteristics of residual stresses around the crater. In addition, the pressing depth of shot was related to GFRP/Al-Li laminates' failure. Residual stresses increased with the pressing depth of shot. Excessive residual stresses led to the FMLs' failure. Depth of failure (the pressing depth of shot when failure occurred) was affected by shot size and the corresponding failure form changed with the shot size. Based on the results on single shot's indentation, the residual stress field of the FMLs under multiple shot's indentation was simulated and the forming curvatures of the FMLs with different shot peening coverage were calculated. The prediction values were consistent to the experimental results with the overall error being about +/- 10%.