Response of braided composites under compressive loading

Abstract

Four triaxially braided composite architectures were tested in uniaxial and biaxial compression. Three stiffness models were compared to the experimental results. Laminated plate theory provided good stiffness predictions for architectures with low crimp angles, while a fiber-inclination model worked well for all architectures, provided the experimentally observed braid pattern was sufficiently described for the architecture with the greatest crimp angle. Axial yarn undulation was observed in two architectures which had uneven braider coverage. Using failure strains from uniaxial tests, a maximum fiber strain failure criterion was able to predict biaxial failure for the specimens tested biaxially. Failure strains in the braider yarns were significantly lower than failure strains in the axial fibers (on average −0.46% compared to −1.1%, respectively).