To improve the load capacity, energy absorption, and recoverability of cushioning pads under repeated compression, this study proposes a silicone rubber-based cushioning pad with a bioinspired multidirectional chevron layer (MCL). Inspired by the herringbone-modified architecture of the mantis shrimp dactyl club, the MCL structure is constructed from staggered half-honeycomb units to form angled and interlaced load-transfer paths. The MCL pad was fabricated by mold casting and thermal curing, and its compression behavior was investigated through quasi-static compression tests, cyclic loading tests, and finite element simulations. The results show that the MCL pad exhibits a staged compression response involving ordered cell-wall bending, rotation, contact, and densification. Increasing material hardness raises the mean compression force from 1884.62 N to 2904.49 N and the specific energy absorption from 0.041 J/g to 0.065 J/g. Cyclic loading results show low energy dissipation coefficients of 0.12-0.17, indicating good recoverability and stable repeated-compression response. Finite element analysis further shows that wall thickness is the dominant parameter controlling load capacity and energy absorption, while wall spacing and wall angle regulate cell-wall contact and compression hardening. This work provides a bioinspired structural strategy for recoverable cellular cushioning pads.
Composite helmets must balance ballistic resistance, deformation control, energy absorption, and low structural weight. This study presents a comparative numerical investigation of CFRP, GFRP, stitched CFRP (SCFRP), and UHMWPE helmets under ballistic impact. A transient explicit finite element (FE) model was developed in ANSYS using an orthotropic progressive-failure formulation based on the Chang-Chang criteria. The projectile was modeled as rigid, and the helmet rim was fully constrained to ensure identical boundary conditions. Impact velocities of 250 and 350 m/s were considered. Load-deformation response, peak contact force, kinetic and internal energy histories, mesh sensitivity, global energy balance, and compressive fiber and matrix failure distributions were evaluated. Increasing impact velocity raised peak contact force by 29.6-41.2% across all configurations. SCFRP produced the highest peak forces, reaching 7380 and 10100 N at 250 and 350 m/s, respectively, whereas UHMWPE exhibited the largest deformation at peak force, increasing from 0.622 to 1.279 mm. At 350 m/s, UHMWPE developed the highest maximum internal energy (40.835 J), followed by CFRP (27.499 J) and GFRP (13.774 J). The mesh study indicated deformation stabilization at approximately 14,370 elements, and global energy-balance error remained below 3.95%. These results show that peak force, deformation, energy evolution, and failure distribution provide complementary measures of ballistic response. However, this study is a deterministic numerical comparison, not experimental validation or ballistic-standard certification. Projectile deformation, strain-rate effects, head-helmet interaction, padding, retention systems, and experimental uncertainties require further investigation.
This study introduces an innovative mathematical framework for examining functionally graded thermoelastic nanobeams (FGNBs), incorporating spatial-temporal nonlocal effects and memory-dependent dynamics. The governing equations are formulated using Hamilton's principle, grounded in Euler-Bernoulli beam theory, and combined with a two-phase-lag heat conduction model that includes a customizable kernel function and associated time delays. FGNBs feature material properties that transition from ceramic at the base to metal at the top, under the influence of time-dependent heat flux. To account for nonlocal thermoelastic stresses, a Klein-Gordon-type operator is utilized, integrating spatial and temporal nonlocality through internal length and time scales. Analytical solutions are derived using the Laplace transform. The study graphically assesses the impact of kernel functions, time delays, nonlocal parameters, and periodic heat pulses on temperature, displacement, deflection, and moment distribution. The findings are compared with existing thermoelastic models, revealing the significant progress in understanding FGNB behavior. This thorough analysis deepens the understanding of thermoelastic interactions and lays a robust groundwork for future research and applications in nanoscale engineering.
