PSI - Issue 81

Anandito Adam Pratama et al. / Procedia Structural Integrity 81 (2026) 58–65

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S3

X3

U3

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Fig. 6. Final deformation contour of the sandwich panel in the 3rd SF variation.

6. Conclusions • This study demonstrates that maintaining a constant Shock Factor (SF) does not produce equivalent UNDEX loading conditions. For identical SF values, variations in explosive mass and stand-off distance result in significantly different maximum deflection and total impulse, demonstrating that SF alone cannot adequately represent UNDEX load severity for operational safety assessment. • Structural response is strongly governed by core geometry. The X-core and U-core configurations exhibit the highest resistance, reducing the maximum deflection by nearly 80% compared to the S-core, while the Y-core shows intermediate behavior. • Independent of load equivalence, the structural response is predominantly governed by core geometry. Cellular core configurations, particularly X-core and U-core designs, substantially improve blast resistance and hull crashworthiness, underscoring the critical role of structural design in fluid – structure interaction beyond load-intensity metrics. • Limitations: The present results are based on coupled acoustic – structural analysis implemented in Abaqus. Structural responses may differ when alternative UNDEX modelling approaches or more advanced fluid – structure interaction methods are employed. • Future work: Further studies will extend the analysis by incorporating corrosion-induced material degradation in marine environments and conducting sensitivity analyses to assess the influence of key parameters on UNDEX-induced structural damage. Acknowledgements This work was supported by the RKAT Universitas Sebelas Maret - Year 2025, under the Research Scheme of "PENELITIAN FUNDAMENTAL B (PFB-UNS), with research grant/contract no. 369/UN27.22/PT.01.03/2025. The authors highly acknowledge this support. References Alsos, H.S., Amdahl, J., 2009. On the resistance to penetration of stiffened plates, Part I – Experiments. International Journal of Impact Engineering 36(6), 799 – 807. Arons, A.B., Yennie, D.R., 1948. Energy Partition in Underwater Explosion Phenomena. Reviews of Modern Physics 20(3), 519 – 536. Cole, R.H., Weller, R., 1948. Underwater Explosions. Physics Today 1(6), 35 – 35. Fajri, A., Prabowo, A.R., Muhayat, N, 2022. Assessment of ship structure under fatigue loading: FE benchmarking and extended performance analysis. Curved and Layered Structures, 9(1), pp. 163 – 186. Fathallah, E., Qi, H., Tong, L., Helal, M., 2015. Numerical investigation of the dynamic response of optimized composite elliptical submersible pressure hull subjected to non-contact underwater explosion. Composite Structures 121, 121 – 133. Fhandy, B.A., Prabowo, A.R., Tuswan, T., Zubaydi, A., Smaradhana, D.F., Baek, S.J., Fitri, S.N., 2025. Crashworthiness behaviour of the stiffened panel in idealized penetration test: A developed stiffening configuration against impact loading. Brodogradnja, 76(2), 76205. Fuadi, A.P., Muttaqie, T., Nugroho, A.C.P.T., Kusuma, Y.F., Mukti, S., Kurniawan, M.A., Firmandha, T., Ismail, M., 2024. Patrol Boat Strengthening Against a Collision with COLL Notation Based on Class Rules and Regulation in Indonesia – An Overview. Mekanika: Majalah Ilmiah Mekanika, 23(1), 1-11. Guo, J., Ji, X.B., Wen, Y.Y., Cui, X.W., 2017. A new shock factor of SWATH catamaran subjected to underwater explosion. Ocean Engineering 130, 620-628. Gupta, N.K., Kumar, P., Hegde, S., 2010. On deformation and tearing of stiffened and un-stiffened square plates subjected to underwater explosion — a numerical study. International Journal of Mechanical Sciences 52(5), 733 – 744. Jen, C.Y., 2009. Coupled acoustic – structural response of optimized ring-stiffened hull for scaled down submerged vehicle subject to underwater explosion. Theoretical and Applied Fracture Mechanics 52(2), 96 – 110. Keil, A.H., 1961. The response of ships to underwater explosions. Kumar, R., Patel, S., 2019. Failure analysis on octagonal honeycomb sandwich panel under air blast loading. Materials Today: Proceedings 46, 9667 – 9672.