JOINING OF CARBON-FIBER-REINFORCED SILICON-NITRIDE COMPOSITES WITH 72AG-26CU-2TI FILLER METAL

Unidirectionally reinforced carbon fibre/Si3N4 matrix composites were joined with 72Ag-26Cu-2Ti filler metal. Joining interfaces were observ ed by SEM and analysed by energy dispersive spectroscopy. The strength of the joints was evaluated by four-point bending tests. Most of the interfaces of Si4N4 matrix/filler metal were firm without cracking and separation. At the interfaces, reaction between the composites and fi ller metal was limited. Only a concentration of titanium at Si3N4 matr ix/filler metal interface was confirmed. On the fracture surfaces, man y holes left as traces of pull-out of carbon fibres and pulled out fib res could be observed. The maximum joining strength and the average st rength, measured by the bending test, were 159 MPa and 107 MPa, respec tively. The pull-out process of fibres from the matrix and the reasons for the large scatter in the strength of joints, were discussed. The fibre pull-out behaviour could be related to fibre distribution densit y at the joining interface.