Experimental study on the mechanical behavior and failure mechanism of 3d MWK carbon/epoxy composites under quasi-static loading

Abstract

Quasi-static tensile, out-of compression, in-plane compression, three-point-bending and shear tests were conducted to reveal the mechanical behavior and failure mechanisms of three-dimensional (3D) multiaxial warp-knitted (MWK) carbon/epoxy composites. The characterization of the failure process and deformation analysis is supported by high-speed camera system and Digital Image Correlation. The results show that tensile, bending, out-of-plane compression, in-plane compression stress–strain response exhibit obvious linear elastic feature and brittle fracture characteristics, whereas the shear response exhibits a distinct nonlinear behavior and gradual damage process. Meanwhile, 3D MWK carbon/epoxy composites have good mechanical properties, which can be widely used in the fields of engineering. In addition, the failure for tension behaves as interlayer delaminating, 90/+45/−45° interface debonding and tensile breakage of 0° fibers; the damage for out-of-plane compression is mainly interlaminar shear dislocation together with local buckling and shear fracture of fibers; the failure pattern for in-plane compression is 90° fiber separating along fiber/matrix interface as well as 0/+45/−45° fiber shear fracture in the shear plane. The main failure for bending is fiber/matrix interface debonding and fibers tearing on the compression surface, 0° fibers breakage on the tension surface as well as fiber layers delaminating. Although the shear behavior is characterized by a gradually growing shear matrix damage, 90/+45/−45° interface debonding, +45/−45° fibers shear fracture, and final 0° fiber compression failure. POLYM. COMPOS., 37:3486–3498, 2016. © 2015 Society of Plastics Engineers