Effect of low temperature on interlaminar fracture toughness of multi-directional CFRP and CFRP-steel interfaces

Abstract

Delamination is the dominant failure type in FMLs, particularly when combining CFRP and steel. Practical applications usually contain multi-directional interfaces. Therefore, delamination of multi-material and multi-directional interfaces is investigated using the DCB and ENF setups. Analysis of such interfaces requires asymmetric layups. Thus, thermal residual stresses (TRS) build up. Effects of TRS are corrected to compare true fracture toughness values, since neglecting TRS can result in mispredictions of up to 200 %. The ply orientation at the delamination interface affects the fracture toughness of monolithic and hybrid interfaces. In general, hybrid interfaces exhibit slightly lower interface properties compared to monolithic interfaces. While mode I behavior appears mostly unaffected by temperature, mode II fracture toughness slightly increases with decreasing temperature.