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

The effect of weak interfaces on failure mechanisms of a three-layered composite was studied. Three-layered B(4)C/B(4)C-C(nanofibers) laminates have been produced using a hot pressing technique. The laminates were designed with thick (similar to 2.6 mm) outer layers of B(4)C and a thin (similar to 90 mu m) center layer of B(4)C-70 wt.% C(nanofibers). Based on the difference in coefficients of thermal expansion and Young\u27s moduli of the pure B(4)C and B(4)C-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(4)C outer layers, and compressive residual stress with a magnitude of 455.7 +/- 5 MPa was developed in the thin central B(4)C-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. (C) 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved