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

1671

8

rate, 60% and 91% increase in the longitudinal compressive strength was recorded for reference and modified UD carbon/epoxy composites, respectively. Likewise, the failure strain of both material arrangements was increased twofold as compared to the static values. The findings from the experiment are summarize in table 3. Taking into account that the compressive behavior of the polymeric composites is influenced by the properties of the resin matrix, the increase in the strength and failure strain values might be due to the rate sensitivity of the matrix. Additionally, a change in the failure mode under the dynamic loading condition could also attribute to the rate sensitivity observed for both materials. Regarding the stiffness values, the overall behavior of the material is consistent, showing a similar trend which was attained under static loading. This can, again, be attributed to the interleaved conductive veil in the laminate. Nonetheless, it appears that the loading rate has an insignificant effect on the elastic modulus of both material types.

Fig. 7. Longitudinal compressive stress-strain response of both material configurations under static and dynamic loading conditions.

Table 3. Longitudinal compressive behavior of UD carbon/epoxy composites under dynamic loading condition. Results No. tests Reference Modified Strain rate [s -1 ] Strength [MPa] Failure strain [%] Strain rate [s -1 ] Strength [MPa] Failure strain [%]

Mean

113

1156.4

0.95

133

1055

1.14

5

STDV

14.58

63.84

0.11

18.87

117.24

0.07

4. Conclusions The strain rate sensitivity of a UD carbon/epoxy composite system with enhanced electrical conductivity under longitudinal compressive loading was studied using a split Hopkinson pressure bar apparatus. Benchmarking was carried out against the non-modified carbon/epoxy laminate to examine the effect of the modification on the mechanical response of the material. The overall dynamic results were in good agreement. The employed compression test setup was successful in characterizing the UD fiber-reinforced composites, which oftentimes has its own pitfalls.