Evaluation of Unidirectional Glass-Graphite Fiber/Epoxy Resin Composites

Abstract

As an all-fiberglass reinforcement is progressively replaced by graphite fiber, the longitudinal composite fracture stress and strain decrease rapidly for all loading modes except shear, accompanied by a substantial increase in the tensile and compressive stiffness. Conversely, upon introducing some fiberglass into a graphite composite, its strength declines in proportion to the decrease in graphite fiber content. The maximum torsional shear stress is approximately 8 ksi for all combinations of glass and graphite. Most of the transverse mechanical properties decrease linearly upon progressive replacement of the fiberglass by graphite. The transverse torsional shear properties are about 20 percent lower than the longitudinal ones. The magnitude of the flexural modulus, which depends not only on the graphite content but even more so on the distance of the graphitic plies from the center plane of the laminate, may be calculated by means of the existing theory of bidirectional laminates. It is concluded that the large increase in composite stiffness upon addition of a small amount of oriented graphite fiber is the most salient characteristic of glass-graphite hybridization.

Flexural and tensile moduli of unidirectional hybrid epoxy composites reinforced by S-2 glass and T700S carbon fibres

“…The mechanical properties of glass and carbon fibre reinforced hybrid epoxy composites have been studied extensively [4,5,[7][8][9][10][11][12][13][14]. Most studies were focused on the strength [7,[9][10][11][12][13][14].…”

“…Most studies were focused on the strength [7,[9][10][11][12][13][14]. Fu et al [10] showed that no hybrid effects for the tensile modulus, while a positive hybrid effect for the flexural modulus.…”

Effect of repeated impacts on the response of plain-woven hybrid composites

“…It is assumed that the mechanical properties of hybrid composites would be somewhere between single fiber reinforced composites. However, it has been reported widely that many hybrid composites show a synergistic effect, called hybridization, which causes the resultant mechanical property to deviate from the linear Rule of Hybrid Mixtures (RoHM) [18][19][20][21][22][23].…”

“…For instance, since the mechanical properties of glass-and carbon-fibers and the interfacial properties of a glass-fiber-reinforced polymer and a carbon-fiberreinforced polymer differ greatly, the hybridization effect would very likely exist for their hybrid composites. Several researchers found the hybrid effects of the tensile modulus and the strain at failure of glass-rich hybrids [18][19][20] to be positive. As interpreted by Zweben [19], on micromechanical level the high elongation glass fibers in the hybrid composite behave like crack arrestors hindering cracks to propagate through the composite.…”

Elastic properties of intermingled hybrid composites

“…3) falls above the upper bound of the theoretical curve. This nonlinear variation with relative fiber-volume fraction has been suggested by Kalnin (7) to be a hybrid effect. However, the cause of this behavior is not clear to.us.…”