Effect of addition of fine sub-micron sized and thick glass fibers into epoxy matrix on fatigue life of plain-woven textile carbon fiber composite

Abstract

This study investigated the mechanism of the effect of addition of fine sub-micron sized (close to nano-sized) and thick (11μm) glass fibers into epoxy matrix on the fatigue life of plain-woven textile carbon fiber composite. Static bending strength and fatigue life of the coupon shaped composite with the modified matrix were investigated by three-point static and cyclic loading test. The resistance of interlaminar delamination was characterized with double cantilever beam of Mode-I fracture test and ENF (end notch flexure) of Mode-II fracture test. The effect of the size of the added glass fibers on those mechanical properties was discussed. To explain the effect of the modification on the observed interfacial strength around the intertwining point of the reinforcing textile cloth, model specimens were prepared where an embedded carbon fiber bundle was put between other two carbon fiber bundles oriented to the perpendicular direction in the modified resin. Test results in current study showed that the addition of glass fibers with fine size was rather effective to dramatically improve the fatigue life. The fatigue life was dramatically increased 10-100 times by the addition of nano-sized glass fibers into the matrix in contrast to the static case. Fracture toughness in Mode-II was also improved by the modification of the matrix, while that in Mode-I was improved slightly. Macroscopic crack propagation in fatigue was totally prevented when the matrix was modified with fine glass fibers of 500nm in diameter. Those effects in improvement of mechanical properties of the textile carbon fiber composite were explained by the prevention of interfacial crack propagation with large resistance between carbon fiber bundles in Mode-II and modified matrix around the texture points where comparatively large strain energy would be released, if the epoxy matrix was adequately modified with the fine glass fibers.