Design and multi-objective optimization of a double-V underbody blast protection structure for a space-constrained vehicle-mounted shelter

Underbody blast remains a major threat to vehicle-mounted shelters operating in high-risk environments. Compared with conventional armored vehicles, underbody protection design for vehicle-mounted shelters is subject to stricter constraints imposed by the driveline layout, chassis interfaces, available installation space, and weight budget. To address this problem, this study proposes a design and optimization framework for a double-V underbody blast protection structure for a space-constrained vehicle-mounted shelter, with occupant injury mitigation as the primary objective. First, a validated blast–vehicle–occupant finite element model was established using the arbitrary Lagrange-Euler coupling method, incorporating the blast field, carrier chassis, shelter body, mounting platform, seat restraint system, and a Hybrid III 50th percentile dummy. The model was validated against full-scale blast tests, with prediction errors of 4.1% and 2.9% for the peak forces in the left and right lower tibiae, respectively. Second, under a 6 kg TNT shallow-buried blast directly beneath the occupant, three candidate configurations, namely a single-V structure, a trapezoidal sandwich structure, and a double-V structure, were compared under equal-mass conditions. The double-V structure produced the lowest bilateral lower-tibia peak forces. Finally, multi-objective optimization of the double-V structure was carried out using design of experiments, a Kriging surrogate model, and the NSGA-II algorithm. The optimized design reduced the peak forces in the left and right lower tibiae by 23.97% and 19.63%, respectively, while reducing structural mass by 13.45%. The proposed approach provides a feasible design basis for underbody blast protection of vehicle-mounted shelters under spatial and weight constraints.