Mechanical behavior and failure mechanisms of boron carbide based three-layered laminates with weak interfaces

Abstract

The effect of weak interfaces on failure mechanisms of a three-layered composite was studied. Three-layered B 4C/B 4C–C nanofibers laminates have been produced using a hot pressing technique. The laminates were designed with thick (∼2.6 mm) outer layers of B 4C and a thin (∼90 μm) center layer of B 4C–70 wt.% C nanofibers. Based on the difference in coefficients of thermal expansion and Young's moduli of the pure B 4C and B 4C–70 wt.% C nanofibers layers, it was estimated that low tensile thermal residual stress with a magnitude of 11.3 ± 2.5 MPa was developed in the thick B 4C outer layers, and compressive residual stress with a magnitude of 455.7 ± 5 MPa was developed in the thin central B 4C–70 wt.% C nanofibers layer. The apparent fracture toughness of laminates was measured and based on the estimated fracture toughness values, a threshold stress was calculated.