PSI - Issue 77

Claudia Barile et al. / Procedia Structural Integrity 77 (2026) 3–10 Barile and Kannan/ Structural Integrity Procedia 00 (2026) 000 – 000

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Two major failure modes are observed in the flexural test specimens: compressive failure below the loading cylinder and interlaminar failure. The interlaminar damage progression, which contributes to the catastrophic failure of the specimens are discussed. Fig. 4 shows the representative micrographs of the fractured damaged (DS-1 and DS-2) and healed (DS-1-Healed and DS-2-Healed) specimens. In the damaged specimens shown in Fig. 4(a) and 4(b), the failure is dominated by shear band formation in the mid plies, which leads to the delamination by kink band formation in the upper plies. Some evidence of longitudinal cracking and wedge splitting are also present. In the healed specimens shown in Fig. 4(c) and 4(d), resin bleed is observed between the damaged plies. Heat allows the healing agent to flow and fill the crack planes. This possibly have resulted in the resin bleeds. The damage progression appears to originate from the resin rich areas (Barile et al., 2025). The failure in the healed specimens is dominated by through thickness and longitudinal crack growth stemming from the resin bled areas. In addition, through thickness shear and local shear failure also contributed to the failure. The results highlight that the healing process have not only recovered the flexural properties but also changed the failure progression paths in the composites.

3.3. Acoustic Emission Results

Fig. 5. Classified Acoustic Emission Data recorded from (a) Damaged Specimen Groups and (b) Healed Specimen Groups.

The AE data are classified based on their WPF and PA values. It is reported in several literatures that the AE signals associated with matrix-dependent failure modes such as matrix cracking, delamination, and longitudinal crack are characterised by low WPF and PA values. On the contrary, the fibre-dependent failure modes such as shear cracks and through thickness crack growth are characterised by high WPF and PA values (Barile et al., 2020, 2019; De Groot et al., 1995).