Thermal Conductivity of 34-700 Carbon Fiber Composites at Cryogenic Temperatures

A steady-state test rig for measuring the thermal conductivity of thin carbon fiber composites at cryogenic temperatures has been constructed and calibrated using a 304 stainless steel sample. Thermal conductivity measurements were carried out on both unidirectional and multi-directional 34-700 carbon fiber-NCT 301 epoxy composite samples from 8 K up to 150 K using the test rig. Thermal diffusivity measurements were made at 295 K and were then used to calculate the thermal conductivity. Unidirectional samples with fibers oriented at 0, 90, and 45 degrees to the direction of heat flow have been evaluated. The thermal conductivity of a sample with laminate plys in the configuration ±45/90/0(3)/90/±45 has also been measured. At room temperature, the thermal conductivity in the 0° direction is 7 times that in the 90° direction. For the multidirectional sample, the thermal conductivity ranges from 0.22 W/(mK) at 5.7 K to 2.98 W/(mK). The general trend of the data is similar to that of the T-300 carbon fiber samples.