Experimental Study On Tensile Properties Of Carbon-aramid Hybrid Three-dimensional Braided Composites

The co-braided hybrid 3D5d and 3D6d braided composites with carbon fibers as axial yarns,aramid fibers as braided yarns and aramid fibers as axial yarns,carbon fibers as braided yarns are designed and manufactured in this paper.The Digital Image Correlation(DIC)technique is used to record the surface full-field strain distribution during the axial tensile loading.The comparative tensile experiment between the co-braided hybrid composites and individual fibers(carbon fibers and aramid fibers)reinforced composites is utilized to analyze the effects of hybrid structure and braided architecture on the tensile properties and damage mechanisms for the carbon-aramid co-braided hybrid 3D braided composites.The axial tensile tests results shows that for the same braided architecture,the tensile strength and modulus of the co-braided hybrid 3D5d and 3D6d braided composites with aramid fibers as axial yarns,carbon fibers as braided yarns and carbon fiber as axial yarns,armid fibers as braided yarns are higher-2.71%,10.14%,21.21%,28.86%and 36.77%,62.68%,30.28%,74.26%than that of aramid fibers reinforced 3D5d and 3D6d braided composites.The ultimate tensile strain of the co-braided hybrid 3D5d and 3D6d braided composites with aramid fibers as axial yarns,carbon fibers as braided yarns and carbon fiber as axial yarns,armid fibers as braided yarns are higher 34.38%,11.96%,51.09%and 2.19%than that of carbon fibers reinforced 3D5d and 3D6d braided composites.For the same hybrid structure,the tensile strength of the 3D5d braided composites with individual fibers(carbon fibers and aramid fibers)as reinforcement and co-braided hybridization fibers(aramid fibers as axial yarns and carbon fibers as axial yarns)as reinforcement is higher 58.72%,59.29%,27.84%and 36.15%than that of 3D5d braided composites and the tensile modulus is higher 47.43%,36.28%,43.07%and 27.23%than that of 3D5d braided composites.The ultimate tensile strain has no difference between 3D6d and 3D5d braided composites.The Poisson's ratio is mainly influenced by the braided architecture.The Poisson's ratio of the 3D5d braided composites with individual fibers(carbon fibers and aramid fibers)as reinforcement and co-braided hybridization fibers(aramid fibers as axial yarns and carbon fibers as axial yarns)as reinforcemen is higher 293.75%,162.50%,228.57%and 344.44%than that of 3D6d braided composites.The time-longitudinal strain curves of the typical samples in each group are near linear.The surface full-field longitudinal contours present periodicity of the meso-strain and homogeneity of the macro-strain.At the same time,the hybrid structure and braided architecture have an influence on the in-plane axial strain distribution.For the same braided architecture,the strain distribution of the samples with carbon fibers and aramid fibers as braided yarns presents lattice and weave line characterization.For the same hybrid structure,the surface strain distribution of 3D5d braided composites is distributed at the surface braiding yarns.While,the surface strain distribution of 3D6d braided composites is distributed at the sixth directional yarns.The tensile fracture and longitudinal-section morphologies indicate that for the same braided architecture,the reduced uniformity of the fracture,the matrix cracking and fall-off during the failure are mainly caused by the addition of the aramid fibers.However,the infiltration of the fiber and matrix is also reduced by the addition of the aramid fibers.For the same hybrid structure,the 3D5d braided composites have zigzag and diagonal fractures.The internal damage is less serious with the increasing of the length from the fracture and the damage propagates far.However,the fractures of 3D6d braided composites are plane along with transverse direction.The internal damage is concentrated in the fracture and the damage propagates near.