PSI - Issue 28

Sahand P. Shamchi et al. / Procedia Structural Integrity 28 (2020) 1664–1672 Sahand Shamchi et al. / Structural Integrity Procedia 00 (2020) 000 – 000

1670

7

(a) (b) Fig. 5. Representative incident, reflected and transmitted signals along with the specimen´s strain value directly measured from the gauge section for the (a) reference, and the (b) electrically modified UD carbon/epoxy system.

The recorded images from the high-speed camera confirms a valid failure of all the specimens within the gauge section during the first stress pulse. The generated compressive stress wave was around 320 μs for all t he high-rate experiments. Fig. 6 presents the sequential high-speed images for a reference material subjected to an impact of 6.5 m/s. The failure initiated with a crack at the vicinity of the adapter at around 100 μs, progressing to an axial splitting along the fiber direction, followed by crashing at the end of the loading duration. The same failure process was observed for all the dynamic experiments, regardless of the material configuration.

0 μ s

50 μ s

100 μ s

150μ s 318μ s Fig. 6. Failure process of non-modified UD carbon/epoxy sample upon the impact loading of 6.5 m/s recorded at 160000 fps. 200μ s

Fig. 7 shows the material ’ s response, in terms of stress and strain, subjected to high strain rate compressive loading along the 0º fiber orientation using the SHPB apparatus. Mean strain rate, ̇ , of 113 and 133 s -1 was achieved for non modified and modified laminates, respectively. The findings from quasi-static standard tests were also included in the graph for the sake of comparison. A significant strain rate effect on the compressive strength and failure strain values were observed. At high loading