L-shaped composite structures are increasingly replacing metal ribs and box structures especially in recent civil aerospace structures and wind turbine blades. Delamination of these L-shaped composite laminates occur by interlaminar opening stresses at the curved region under perpendicular loading to one arm. In this study, delamination at the curved region is studied experimentally and computationally by using a simplified model material consisting of two L-shaped polycarbonate plates bonded together. The effect of precrack size at the curved region on the initiation and propagation of delamination under loading perpendicular to one of the arms is studied. Experimental observations are carried out using photoelasticity to visualize the isochromatic stress patterns in the model. Finite element analysis (ABAQUS) is carried out using static (implicit) analysis during elastic loading followed by dynamic (explicit) analysis during crack growth in conjunction with a bilinear cohesive zone model. For precracks smaller than 40mm, a sudden drop in load-displacement plot is observed corresponding to dynamic crack growth at 80 m/s crack tip speed from the corner to the arms. Afterwards, a generally monotonic increase in load-displacement behavior is observed albeit with a lower stiffness corresponding to continued stable crack growth. For larger pre-cracks, load-displacement increases monotonically even after crack initiates with stable stick-slip type crack growth. These two regimes of crack growth are consistent with the observations of Wimmer et al (2009) on cross-ply composite L-beams.

This content is only available via PDF.
You do not currently have access to this content.