Dynamic tensile stress–strain characteristics of carbon/epoxy laminated composites in through-thickness direction

Abstract

Abstract. The effect of strain rate up to approximatelyε = 10 2 /s on the tensile stress-strain properties of unidirectional and cross-ply carbon/epoxy laminated composites in the through-thickness direction is investigated. Waisted cylindrical specimens machined out of the laminated composites in the through-thickness direction are used in both static and dynamic tests. The dynamic tensile stress-strain curves up to fracture are determined using the split Hopkinson bar (SHB). The low and intermediate strain-rate tensile stress-strain relations up to fracture are measured on an Instron 5500R testing machine. It is demonstrated that the ultimate tensile strength and absorbed energy up to fracture increase significantly, while the fracture strain decreases slightly with increasing strain rate. Macro-and micro-scopic examinations reveal a marked difference in the fracture surfaces between the static and dynamic tension specimens.

Image-Based Inertial Impact Test for Composite Interlaminar Tensile Properties

“…Comparison of the current measurements to those in other studies shows the robustness of the IBII test for measuring interlaminar strength. For example, a similar strain rate sensitivity was measured by Nakai & Yokoyama (+ 77%) [6,7]. However, the scatter on measured strength was significantly higher (39% COV), and measurements were made at much lower strain rates (50 s −1 ).…”

“…It is worth noting that comparisons to quasi-static values need to be interpreted with some caution because quasi-static interlaminar tensile tests are quite sensitive to experimental factors such as misalignment, gripping and volume effect. Typical scatter in the literature for quasi-static strength measurements ranges from 10 to 50% [6,7,40,41]. Therefore, the reported coefficient of variation for quasi-static interlaminar strength of this material is comparatively low.…”

“…A similar situation exists for tensile strength measurements at high strain rates. Most studies report moderate increases in strength of around 30% compared to quasi-static values [3,5], while others report much more significant increases of up to several hundred percent [6][7][8]. Therefore, much ambiguity remains regarding the effect of strain rate on interlaminar stiffness and tensile strength.…”