Comparative Analysis of Crack Resistance of Fiber-Metal Laminates with HS2 Glass/T700 Carbon Layers for Various Stress Ratios.

Fiber-metal laminates (FMLs) composed of metal lamina and reinforcing fibers exhibit an improved crack growth resistance as compared to conventional aircraft materials. The crack resistance of a hybrid FML composite consisting of LY12M aluminum alloy lamina and prepreg layers of HS2 glass fibers and T700 carbon fibers has been experimentally investigated on tensile specimens at stress ratios R = - 1, 0.1, and 0.5. The crack growth rate data at positive stress ratios demonstrate a significant scatter and a large difference between specimen's back and front surfaces formed by 1-mm thick outer aluminum layers. This violation of the test standard requirements for metal materials in the performed FML tests presents a problem of determining a proper failure criterion for the engineering applications of FMLs. Based on the comparative analysis of FML crack resistance results obtained, some qualitative conclusions are drawn on solving this problem. [ABSTRACT FROM AUTHOR]