PSI - Issue 28

Anurag Singh et al. / Procedia Structural Integrity 28 (2020) 2206–2217 Anurag Singh/ Structural Integrity Procedia 00 (2019) 000 – 000

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3. Results and discussions 3.1. Tensile tests

Figure 4 shows the tensile test result as stress vs strain values. The load applied to the specimen in the uniaxial direction divided by the measured section of each sample gives the stress values; DIC calculates the strain field during the tensile test. Table 1 shows the corresponding average values of tensile properties; the standard deviation values show the consistency in the test results. Ec specimens showed a decrease of 15.17 % in the value of Young's modulus as can also be seen from the slope of ref and ec specimens in figure 4. Figure 5 shows ruptured specimens at the end of the test; type of failure seems to be the matrix failure; hence the fibrils bonded with the matrix got separated after reaching the maximum tensile strength. Both ref and ec specimens achieved equivalent maximum tensile strength. However, ec specimens showed higher tensile strain values at the end of the test. Therefore, the ultimate strength, in this case, is the virtue of the strength of the matrix and is independent of the polymer veil interlaced between the carbon fibres. Table 1: Mechanical properties of the ref and ec specimen from the tensile tests

Tensile properties

Ref specimen

EC specimen

% increase/decrease with respect to ref specimen

Average

Std. Dev.

Average

Std. Dev.

Young’s Modulus (GPa)

148.46

3.65

125.93

4.71 0.13

-15.17 % 13.24 %

Max. Strain (%) Max. Stress (MPa)

1.51

0.098

1.71

2407.7405

294.4498

2440.9299

151.9966

1.38 %

3.2. Flexural tests Ref and ec specimens tested using the test method described above. Figure 6 shows the stress vs strain graph from the flexural test. A non-contact displacement measurement technique which uses the image processing algorithm in the MATLAB computes the displacement through the series of pictures taken during the experiment. The displacement of the loading support (figure 2) generates the displacement from the MATLAB programme. Table 2 reports the average

Figure 4: Tensile test result of reference and electrical conductive specimens