Tensile strength of unidirectional CFRP laminate under high strain rate

Abstract

The tensile strength of unidirectional carbon fiber reinforced plastics under a high strain rate was experimentally investigated. A high-strain-rate test was performed using the tension-type split Hopkinson bar technique. In order to obtain the tensile stress-strain relations, a special fixture was used for the impact tensile specimen. The experimental results demonstrated that the tensile modulus and strength in the longitudinal direction are independent of the strain rate. In contrast, the tensile properties in the transverse direction and the shear properties increase with the strain rate. Moreover, it was observed that the strain-rate dependence of the shear strength is much stronger than that of the transverse strength. The tensile strength of off-axis specimens was measured using an oblique tab, and the experimental results were compared with the tensile strength predicted based on the Tsai-Hill failure criterion. It was concluded that the tensile strength can be characterized quite well using the above failure criterion under dynamic loading conditions.

Experimental characterization and constitutive modeling of the non-linear stress–strain behavior of unidirectional carbon–epoxy under high strain rate loading

“…In the proposed elastic-viscoplastic extension A is used in the formulation of the viscoplastic creep function and the viscoplastic potential, which are analogous to the plastic yield function and the plastic potential, respectively. However, the model should also take into account the strain rate dependence of the elastic and strength properties observed in carbon-epoxy composites [2,[12][13][14][15][16][17][18]. The elastic free energy density for the proposed transversely isotropic model reads:…”

Static and high-rate loading of single and multi-bolt carbon–epoxy aircraft fuselage joints

“…Most high rate testing studies on carbon-epoxy composites suggest enhancement of matrix-dominated ply properties with increased loading rate [6][7][8][9][10][11][12][13][14][15]. All of these studies pointed to an enhanced nonlinear shear response (elevated stress-strain curve) for increased loading rates.…”

“…Koerber [14] analysed data from multiple studies ( [8,11,12,16]) and found the strain rate effect on the tensile, compressive and shear strength of neat epoxy resin to be approximately equal to the strain rate effect on the transverse tensile, transverse compressive and in-plane shear strength of a unidirectional (UD) carbon-epoxy laminate. However, it was highlighted that transverse tension failure in a UD composite can be caused by fibre-matrix de-bonding rather than by failure of the matrix [12], necessitating studies on carbon-epoxy material systems such as those in [6][7][8][9][10][11][12][13][14][15]. Extensive high rate testing was carried out on off-axis carbon-epoxy specimens with varying off-axis ply orientation in [13,15].…”

The Use of 2D and 3D High-Speed Digital Image Correlation in Full Field Strain Measurements of Composite Materials Subjected to High Strain Rates

“…As a result, local strain measurement on the sample is necessary during split Hopkinson tensile experiments. Very often, strain gauges are used for local strain measurement on the surface of the sample [5]. However, strain gauges provide only average strain data, and do not provide full field strain information of the samples which might reveal strain heterogeneities including strain localizations.…”