PSI - Issue 79

H.G.E. da Silva et al. / Procedia Structural Integrity 79 (2026) 97–104

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Fig. 4. Refined mesh for the 4PB numerical model and detail at the punch zone.

3. Results 3.1. Experimental test data

Fig. 5 presents the P -  curves of the PMI core compression tests, where repeatability is notorious (Fig. 5). The maximum load ( P m ) was 1880.67±30.37 N, the compressive strength (  ) was 1.26±0.02 MPa and modulus of the foam ( E c ) was 35.94±0.85 MPa, and the elastic slope ( S ) average was 5359.67±157.81 N/mm.

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Fig. 5. Core compression P -  test curves.

Fig. 6 presents the P -  curves extracted from the 4PB tests for configurations 1 (a) and 2 (b). In addition, Table 5 presents the summary of 4PB results for configurations 1 and 2, where  is the shear stress in the core,  f is the flexure stress in the skins, and s 1 is the elastic stiffness of the specimen. Overall, configuration 2 specimens present lower deviation values than in configuration 1. Comparing the mechanical performance, marginally deviations were found, i.e., P m increases 18.6%,  increases 26.5%,  at P m increases 22.5%, while  f and s 1 decreases 5.2 and 1.8%, respectively. Consequently, one can conclude that the orientation of the glass fibre plies has small effect in the overall structure behaviour.

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8

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Fig. 6. P -  curves extracted from 4PB tests: for configuration 1 (a) and configuration 2 (b).