Mechanical and ballistic properties of graphene platelets reinforced B4C ceramics: Effect of TiB2 addition

This study reports the experimental investigations on the mechanical properties and ballistic performance of the dual-phase (GPLs-B₄C) and trio-phase (GPLs-B₄C–TiB₂) ceramic composites. Both graphene platelets (GPLs) reinforced ceramic composites were fabricated by the hot-pressing method. The influences of the sintering additive, TiB₂, on the hardness, flexural strength, fracture toughness, static and dynamic compressive strength, and ballistic performance of the GPLs-B₄C composite were studied. Results ascertained the beneficial effect of adding the TiB₂ as a sintering phase for the GPLs-B₄C ceramic composite. The hardness, flexural strength, fracture toughness, dynamic strength (at 900 s⁻¹) and ballistic efficiency of the GPLs-B₄C–TiB₂ composite reached 27.98 $\pm$ 0.69 GPa, 555.48 $\pm$ 7.50 MPa, 4.80 $\pm$ 0.31 MPa$\cdot$m^1/2, 4.99 GPa and 6.72, which are 19.7%, 24.1%, 19.7%, 31.6% and 18.1%, respectively, higher than that without the TiB₂ addition. Experimental results showed that both GPLs-B₄C and GPLs-B₄C–TiB₂ are strong rate-dependent composites with nonlinearities in their constitutive behaviours under quasi-static and dynamic compressive loadings. In-depth SEM investigation revealed that the enhanced performances under dynamic compression and impact loading are due to the combination of failure mechanisms of the GPLs-B₄C–TiB₂ ceramic composite – it is a mixed inter/trans-granular fracture mode – and the toughening mechanisms offered by the reinforcing phase (GPLs). The anchoring effect of GPLs was identified, which attributes to its toughening mechanisms for the current composites through crack deflection and crack bridging. This work may be served as an experimental basis for the design and application of GPLs-B₄C–TiB₂ composite for ballistic protection.