PSI - Issue 54

Norman Osa-uwagboe et al. / Procedia Structural Integrity 54 (2024) 44–51 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 2. Moisture absorption of FRPSS.

3.2. Force-Displacement behaviour The force-displacement graphs of the FRPSS samples before and after exposure to seawater degradation are presented in Fig 3. Apparently, the indenter force increased until the first peak, corresponding to the penetration of the top face sheet, followed by a drop in load. As the indenter progressed through the structure, the load increased due to the damage resistance of the bottom face sheets until the second peak before catastrophic damage to the structure. It is worth noting that due to the small thickness and the nature of the core, the core provided very limited resistance to the indenter. It was observed that the specimens experienced a drop in the overall load-bearing capacity from 20.8 % and 11.4 % for GS and CS respectively. It was found that the load variation in the top face sheet was not significant, indicating that the seawater degradation effect is intensified after the onset of plastic deformation in FRPSS. This could be ascribed to the plasticization, hydrolysis, and swelling of the epoxy resin, thereby weakening the bonds between the constituents of the structure as well as the reduced shear strength of the core as the indenter proceeded through the sample.

Fig 3. Load and energy absorption-displacement curves: (a) GS and (b) CS before (0) and after 16 weeks-long (16) exposure to seawater.