Research on compression properties of unidirectional carbon fiber reinforced epoxy resin composite (UCFREP)

Abstract

To research the axial compression properties of unidirectional carbon fiber reinforced epoxy resin composite (UCFREP), the compression experiments at different strain rates were carried out by using the MTS universal electronic testing machine and the equipment of split Hopkinson pressure bar (SHPB). Furthermore, the finite element analysis (FEA) was also used to study the compression properties of UCFREP with different conditions. The true stress-strain curves in quasi-static and dynamic compression were obtained, and the relationship between yield limit and strain rate was coupled. The microstructure of the failure area was observed by scanning electron microscope (SEM). A formula for predicting compression strength of combined buckling under the quasi-static condition was presented. The application range of Chang-Chang failure criterion was discussed by FEA, and the compression failure of UCFREP with different fiber directions was predicted. The results show that UCFREP has the obvious strain rate effect, the mechanical properties at dynamic compression are nonlinear. Shear is the main compression failure mode, which includes the shear cracking of matrix between fibers and the shear buckling of fiber. The direction of the fiber is the main factor that causes the shear cracking, such as the shear cracking shows the feature of 45° when the direction of the fiber is 45°. As a conclusion, increasing the shear strength of matrix and fiber will be a way to increase the compression strength of UCFREP. This paper could be used as a reference to develop the new constitutive model, especially considering the nonlinear effect.

The effect of model dimensionality on compression strength of fiber reinforced composites

“…Microbuckling is divided into an extensional/symmetrical/tensile mode and a shear mode. [5][6][7] However, shear mode MB is of interest as it occurs in most of the industrial scale, high volume fraction FRPs. Other failure modes such as longitudinal splitting may compete with MB in low volume fraction FRPs, however, MB is the dominant failure mode in high volume fraction FRPs.…”

“…Other failure modes such as longitudinal splitting may compete with MB in low volume fraction FRPs, however, MB is the dominant failure mode in high volume fraction FRPs. 5,[7][8][9] The MB failure is controlled by the matrix shear nonlinearity and the manufacturing induced fiber misalignment. The MB failure is initiated when geometric softening at a location of a critical fiber misalignment outpaces the material hardening inside the incipient shear band.…”