PSI - Issue 77

Magdalena Mieloszyk et al. / Procedia Structural Integrity 77 (2026) 256–263 M.Mieloszyk & S.Bhadra / Structural Integrity Procedia 00 (2026) 000–000

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Fig. 4. A comparison of THz images of 4-layer GFRP samples intact (A) and after exposition to elevated temperature (B): (a) B-scan, (b) C-scan of top surface, (c) C-scan of FO plane, (d) C-scan of bottom surface.

polymer, which elevates the shear stresses at the interface, thus weakening the interfacial adhesion. The second image (Figure 5(b)) captures an adjacent matrix crack, which is likely an initiating factor of damage in GFRP. The crack openings propagate into the resin-rich zones, and once the interface is compromised, load transfer to the adjacent fibre filaments becomes uneven, making the fibre susceptible to bending and microbuckling. Also, fibre damage(fracture / filament splitting) is observed in the presented figures, which indicates the damage progression from matrix cracking to interfacial debonding, which led to final fibre failure. In addition to matrix cracking and interfacial debonding, hygrothermal ageing was observed, which is a combined e ff ect of moisture absorption and elevated temperatures. Figure 6(a) shows lamellar, striated features, which are a morphology typical of viscous flow and resolidification. The observed thermally induced reflow can seal microvoids formed during the manufacturing process in certain regions. Although in other areas it may generate shrinkage gaps and interfacial discontinuities, which in turn promote debonding and crack initiation during cooldown or under me-