Damage tolerance and durability of GLARE laminates

The damage tolerance and durability including impact and fatigue behavior of GLARE laminate is studied. The post-impact fatigue behavior and residual strength after post-impact fatigue test of GLARE 4-3/2, GLARE 5-2/1 and 2024-T3 aluminum alloy were investigated experimentally. Drop-weight impact was applied at a variety of energy levels to inflict damages such as barely visible impact damage (BVID), clearly visible impact damage (CVID) and penetration damage. After impact test, constant-amplitude tension-tension fatigue was conducted to delineate influence of loading parameters on impact damage initiation, accumulation during fatigue loading and their effect on life and residual properties was identified. The results showed that GLARE laminates exhibit superior post-impact fatigue durability when compared with the monolithic 2024-T3 aluminum alloy. In the investigation of residual strength, the tensile strength of GLARE laminates is decreased by 30% or 35% after 1x10 6 cycles. However, if no fatigue crack growth is observed in the impacted aluminum layer of the GLARE laminates, no strength reduction was observed.;The FE (finite element) simulation work was performed to predict impact behavior of GLARE laminates. The commercial finite element software ABAQUS was used for the simulation work. And VUMAT (the user material subroutine) based on two- and three-dimensional Hashin failure criteria was develop to present the model stiffness degradation in the composite layer. Through look into load-time history, the maximum deflection and damage progression, good agreement is obtained between the experimental results and the finite element model predictions.;The experiment and FE (finite element) simulation for low-velocity multiple impacts was performed on GLARE laminate. Drop-weight impact was applied two times at a variety of energy levels to inflict multiple impacts damages for aluminum 2024-T3 and GLARE 5-2/1. As well as single impact behavior, the commercial finite element code ABAQUS and user subroutine VUMAT were used to predict all dynamic impact behavior. Finite element predictions show good agreement with experimental results for multiple impact behavior.;Finally, a database for the damage tolerance and the durability of FMLs (fiber metal laminates) has been developed. The database is used to identify specific features of damage tolerance and durability of fiber metal laminates.