Effect of interface and configuration on dynamic mechanical properties of bilayer B₄C/Al composites

Layered materials have gained widespread attention in armor protection due to their unique designability, structure-function integration, and cross-scale synergistic effects. The interface and material configuration are key determinants of the dynamic mechanical properties of layered materials. This study focuses on these factors by fabricating bilayer B₄C/Al composites with a continuous aluminum matrix and varying reinforcement content gradients. The resulting bilayer structure exhibited an interfacial tensile strength of up to 326 MPa, significantly surpassing the bonding strength of epoxy resin. Under dynamic loading, the continuous matrix structure demonstrated superior compressive strength and energy absorption capacity, due to efficient strain transfer and coordinated deformation facilitated by strong interfacial bonding, which enhanced the synergy between layers. Digital image correlation (DIC) analysis revealed that the strain transfer efficiency near the interface in the continuous matrix structure reached 78 %, markedly higher than the 19 % observed in bonded structures. Finite element simulations further elucidated the influence of reinforcement gradients on stress-strain distribution and failure mechanisms. A larger reinforcement gradient intensified strain mismatch near the interface, inducing premature shear failure in the hard layer due to transverse volumetric expansion. For optimal material configurations, the compressive strength of the soft layer should exceed the yield strength of the hard layer to facilitate plastic zone expansion during compression and promote continuous strain hardening. These findings highlight the critical role of interface design and structural configuration in governing the dynamic mechanical performance of layered materials.