A high-precision apparatus for dimensional characterization of highly stable materials in space applications

We present an apparatus for high-accuracy and high-resolution absolute measurement of the linear coefficient of thermal expansion (CTE). Based on a displacement measuring interferometer (DMI) system, dimensional changes of a tubular shaped specimen under controlled thermal conditions can be characterized. Our measurement apparatus was located in a vacuum where the test specimen could be controlled in a temperature range from 20 to 40 degrees C. We measured the CTE of a quartz tube by using the DMI system with a temperature variation close to 4 degrees C. The test result was (3.888 +/- 0.1292) x 10(-7)/degrees C with 99% confidence probability. The measured value of 3.89 x 10(-7)/degrees C of the specimen taken from the above-mentioned quartz tube (DIL402 Expedis, NETZSCH) was within the confidence interval, which indicates that our apparatus not only has excellent repeatability but also has the correct absolute CTE value. The measurement uncertainty reached the 1.3 x 10(-8)/degrees C level. Finally, a CTE test of carbon-fiber reinforced plastic (CFRP) tubes was conducted. The test result was (1.218 +/- 0.0822) x 10(-7)/degrees C with 99% confidence probability. The results show that we can manufacture CFRP tubes with a CTE of 0.12 x 10(-6)/degrees C, which could be used for aeronautical and space structures.