Failure behavior of an epoxy matrix under different kinds of static loading

The yield and fracture behavior of an unreinforced epoxy resin has been investigated. The parabolic Mohr failure criterion was applied to experimental results under different loading conditions. From a plain resin slab, specimens for tensile, torsion and compression tests were manufactured and the failure behavior of the resin was tested and discussed in detail. The results of the mechanical tests and a fractographic study of the fracture surfaces were correlated with the stress-state-dependent strength and fracture stress of the epoxy resin. This plays an important role in fiber-reinforced composites because just after cooling to room temperature the resin matrix is under a tri-axial residual stress state. From the mechanical properties of the plain resin and by using the parabolic failure criterion it is possible to explain the low strain to failure of unidirectional laminates under transverse tensile loading.