Shear debonding behavior of a carbon-coated interface in a tungsten fiber-reinforced tungsten matrix composite

One of the crucial issues related to structural application of tungsten for fusion reactor components is its brittleness. To improve tungsten toughness we explored a novel toughening method based on W fiber reinforcement. The idea is to utilize the effective energy dissipation caused by controlled cracking and friction at fiber/matrix interfaces. To realize this, the interfaces need to be engineered by means of adequate coating. In this work we investigated fracture behavior of a carbon-coated (0.6 μm) interface in a single-filament mini-composite using fiber push-out test. The composite was fabricated by CVD process. Mechanical parameters were determined by fitting the related theoretical models with the experimental data. Calibrated fracture energy and debonding strength was 7.4 J/m2 and 285 MPa, respectively. This fracture energy value satisfied the theoretical criterion of controlled crack deflection. The result of the carbon coating was compared to the case of uncoated interface which exhibited stronger friction.