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

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(a) (b) Fig. 4. Quasi-static longitudinal compressive stress-strain behavior the reference and the modified UD carbon/epoxy laminates using (a) a standard IITRI compression fixture, and (b) a comparison between both test typologies.

Table 2. Longitudinal compressive behavior of UD carbon/epoxy composites under static loading condition. Test Typology Results No. tests Reference Modified Strength [MPa] Failure strain [%] Strength [MPa] Failure strain [%] Standard (ISO 14126) Mean 5 604.24 0.46 660.50 0.55 STDV 106.89 0.03 32.23 0.09 Non-standard Mean 3 765.06 0.57 619.80 0.55 STDV 152.53 0.11 109.82 0.10

4.2. Dynamic results Five dynamic tests were performed per material arrangement. Fig. 5 shows a typical output from the oscilloscope, including the incident, reflected and transmitted signals for both material configurations. The use of the reflected pulse, particularly for hard brittle materials, is generally considered to be a less accurate approach to deduce the strain history of the test sample [12]. Thereby, the strain value was directly acquired from a strain gauge bonded on the sample´s gauge section, which was recorded using the same acquisition system as the SHPB. The corresponding strain values of each sample are also included in Fig. 5. As mentioned, a rubber pulse shaper was inserted on the impact end of the incident bar to minimize the wave dispersion, and to increase the rise time of the incident pulse, leading to a ramped pulse, which is an ideal profile for testing the brittle materials [12]. It also facilitates achieving a nearly constant strain rate.