Mixed Mode Delamination Creep Crack Growth of Unidirectionally Reinforced AS4/PEEK Laminate at Elevated Temperature
Yoshihiko UEMATSU, Atsushi SUGETA, Kohji EGAWA and Masahiro JONO
Abstract:Mixed mode I + II delamination crack growth tests at elevated temperature (473K) were carried out on unidirectionally carbon fiber reinforced thermoplastics (CFRTP) under static creep condition. Asymmetric end loaded splitiAELSjspecimens were used in order to investigate the effect of mixed mode ratio, GI/GII, on crack growth. The creep crack growth rate, da/dt, became higher in terms of mode I component of total energy release rate, GI, as GI/GII decreased. This implies that the crack propagation rate was accelerated by mode II component, GII. The measurement of the load point displacement rates due to mode I or mode II component of total load revealed that the creep deformation at the crack tip by mode II component was larger than that by mode I component and the size of creep deformation area depended on GI/GII. It is considered that the creep deformation by mode I component, which was perpendicular to carbon fibers, was constrained strongly by fibers, while the creep deformation by mode II expanded along carbon fibers. The crack growth rate under mixed mode loading was governed by the creep J integral, , regardless of the mixed mode ratio. Fractographic observation showed that matrices were elongated along carbon fibers and fracture occurred at the interface between fibers and matrix. Key Words:CFRP, Mixed mode, Delamination, Crack growth, Creep, Creep J integral, Elevated temperature