PSI - Issue 28

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

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values of the flexural properties; standard deviation values show the consistency in the flexural test results. Table 2 shows ec specimens having higher flexural stress and higher tangent modulus values compared to ref specimens. However, flexural strain value in the case of ec specimen decreases by 29%; this shows that ec specimens are more susceptible to failure in case of bending in comparison to the reference specimen.

Table 2: Flexural test properties of the ref and ec specimen from the tensile tests

Flexural properties

Ref specimen

EC specimen

% increase / decrease w.r.t. to ref specimen

Average 53.7162

Std. Dev.

Average 80.1178

Std. Dev.

Tangent modulus of elasticity (GPa) Max. Strain (%) Max. Stress (GPa)

1.1256

0.5345

49.15%

1.8123 0.9507

0.0468 0.0170

1.2799 1.0161

0.0871 0.0687

-29.38%

6.88%

3.3. DCB Mode-I fracture tests Figure 7 shows the force vs displacement graph as R-curve as per the procedure defined. Figure 8 shows the complete R-curve generated by extrapolating the initial loading and final unloading data points. The graph in figure 8 shows the permanent deformation is present in all the specimens. Energy release rate (ERR) and modulus values for ref and ec specimens are shown in figure 9 and figure 10, respectively. All graphs 7-10 shows the consistency and repeatability for ref and ec specimens. Figure 3 c) shows the DCB specimen after reaching the final delamination point. Fibres can be seen in the middle of two layers separated by the thin delamination film. G IC fracture initiation toughness for ref specimen is 138.83 J/m 2 , comparatively for ec specimen it increases to 276.12 J/m 2 .

Figure 5: Ruptured specimens at the end of the tensile test (a) ref specimen (b) ec specimen