Fracture behaviour of SiC monofilament reinforced copper – an acoustic emission study

Abstract

SiC monofilament-reinforced copper is a potential heat sink material for the divertor of future fusion reactors, where heat loads up to 15 MW/m2 must be removed. The composite combines high mechanical strength (300 MPa at 300℃) with sufficient thermal conductivity (at least 200 W/mK) at temperatures up to 550℃. The bonding between fibres and matrix is essential for the mechanical behaviour. We investigated two different fibre types (SCS0 and SCS6, Specialty Materials Inc.) with different interlayers in a galvanic copper matrix. Tensile tests in combination with acoustic emission analysis showed the dependence of fracture behaviour of the composite material on the fibre type. The average ultimate tensile strength of composite samples with 20% fibre reinforcement was in the range of 600 MPa, with a Young's modulus of 160 GPa. The tensile tested composite with SCS6 fibres generated roughly twenty times the number of acoustic emission events in comparison with the SCS0 fibres composite. Acoustic emission events in tensile test specimens with SCS6 fibres are correlated with the failure of the carbon-enriched surface layer of the fibre. In the case of SCS0 fibre-reinforced specimens, acoustic emission events were only caused by fibre failure. Fracture area analysis after tensile tests showed the failure of the SCS6 fibres at the interface between the two outer carbon layers and no interface failure for the composite with SCS0 fibres.