Unidirectional and continuous carbon fiber tin -matrix composites were used for the packaging
of the high -temperature superconductor YBa;
Cu,C),, by diffusion bonding at 170 °C and
500 psi. Tin served as the adhesive and to increase the ductility, the normal -state electrical
conductivity, and the thermal conductivity. Carbon fibers ssrved to increase the strength and
the modulus, both in tension along the fiber direction and in compression perpendicular to
the fiber layers, though they decreased the strength in compression along the fiber direction.
Carbon fibers also served to increase the thermal conductivity and the thermal fatigue
resistance. At 24 vol.
%
fibers, the tensile strength was approximately equal to the
compressive strength perpendicular to the fiber layers. With further increase of the
fiber content. the tensile strength exceeded the compressive strength perpendicular to the
fiber layers. reaching 134 MPa at 31 vol. % fibers. For fiber contents less than 30 vol. %,
the compressive ductility perpendicular to the fiber layers exceeded that of the plain
superconductor. At 30 vol. % fibers, the tensile modulus reached 15 GPa at room temperature
and 27 GPa at 77 K. The tensile load was essentially sustained by the carbon fibers and the
superconducting behavior was maintained after tension almost to the point of tensile fracture.
Neither 7', nor
was affected by the composite processing.