Stiffness properties of triaxially braided glass/ epoxy composites

The stiffness properties of t riaxially braided glass/ epoxy composites , considering the effect of braid
angle and specimen width , were tested. The differences between tensile and compressive stiffness properties were also discussed. The test result s show that the longitudinal modulus of the specimens decreases a lit tle with the increasing braid angle in the same fiber volume f raction , and so dose the Poisson ratio (when the braid angle is approximately greater than 35 degree) . As the specimen width changes f rom double to threefold the unit cell width , the stiffness properties of the specimen are almost equal . The longitudinal modulus and Poisson ratio are much greater than the t ransverse modulus and Poisson ratio. Furthermore , tensile specimens almost equal compressive specimens in modulus and Poisson ratio. It is found that the t ransverse tension and compression stress 2strain curves are highly nonlinear. The test result s can provide a reference for the braided composite st ructure design.