The impact properties and damage tolerance and of bi-directionally reinforced fiber metal laminates

Fiber metal laminates are an advanced hybrid materials system being evaluated as a damage tolerance and light weight solution for future aircraft primary structures. This paper investigates the impact properties and damage tolerance of glass fiber reinforced aluminum laminates with cross-ply glass prepreg layers. A systematic low velocity impact testing program based on instrumented drop weight was conducted, and the characteristic impact energies, the damage area, and the permanent deflection of laminates are used to evaluate the impact performance and damage resistance. The post-impact residual tensile strength under various damage states ranging from the plastic dent, barely visible impact damage (BVID), clearly visible impact damage (CVID) up to the complete perforation was also measured and compared. Additionally, the post-impact fatigue behavior with different damage states was also explored. The results showed that both GLARE 4 and GLARE 5 laminates have better impact properties than those of 2024-T3 monolithic aluminum alloy. GLARE laminates had a longer service life than aluminum under fatigue loading after impact, and they did not show a sudden and catastrophic failure after the fatigue crack was initiated. The damage initiation, damage progression and failure modes under impact and fatigue loading were characterized and identified with microscopy, X-ray radiography, and by deply technique.