Thermal conductivity of various CFRPs from 100 mK to 20 K

Carbon-fiber-reinforced polymers (CFRPs) are some of the most useful materials for building spacecraft and aerospace tools. They are especially valuable for systems that work at extremely cold (cryogenic) temperatures because they are strong, lightweight, and don’t transfer heat easily. In this study, researchers measured how well heat moves through several different types of carbon fiber samples, specifically T300, T700, HS40, M55J, and IMA, at different fiber layouts and densities. These measurements were taken at ultra-cold temperatures ranging from 100 mK to 20 K. The team used a newly developed analysis method to calculate the thermal conductivity for each sample. Finally, they shared how each material behaved at different temperatures and compared their findings to previous research.

💡 Research Summary

The paper presents a comprehensive experimental study of the thermal conductivity of carbon‑fiber‑reinforced polymers (CFRPs) over the ultra‑low temperature range of 100 mK to 20 K. Nine commercially available CFRP laminates were investigated: T300, T700, HS40, M55J, and IMA, each supplied with two or more lay‑up configurations that differ in fiber volume fraction (60 %–67 %) and fiber orientation relative to the heat flow (0° – parallel, 90° – transverse). All samples were rectangular plates roughly 200 mm × 20 mm × 2 mm, and their geometric dimensions were measured with sub‑percent accuracy.

The measurements were performed in the DRA CuLA dilution refrigerator (BlueFors LD400) at the Institut d’Astrophysique Spatiale. A dedicated sample holder placed the laminate on a gold‑plated copper cold plate. Two Cernox resistance thermometers (RX‑102A at the bottom, CX‑1010 at the top) were mounted using a linear contact scheme to minimise uncertainty in the distance L between them. A thin‑film 10 kΩ heater, embedded in a gold‑plated copper block and thermally bonded to the top surface, supplied controlled heating powers ranging from nanowatts to milliwatts. Heater voltage and current were monitored with a Keithley 2602A, yielding an injected power uncertainty of 0.1 %.

Data acquisition consisted of stepping the heating power and recording the temperature response of both thermometers over three‑hour intervals. Each temperature‑versus‑time trace was fitted with an exponential relaxation model T(t)=A−B exp(−t/τ) to extract the equilibrium temperatures T₁ (bottom) and T₂ (top) without waiting for full steady‑state. The fit quality was quantified by χ², with values below 10 deemed excellent. A parasitic background heat load Q₀, significant only at the lowest powers (<100 nW), was introduced into the heat‑flow equation to correct the measured power.

Thermal conductivity κ(T) was modelled using a Callaway‑type expression κ = a T³ /