Measurement of Thermal and Mechanical Properties of Graphiteepoxy Composites for Precision Applications

Results are reported on an investigation to evaluate the usefulness of selected graphite-epoxy composite structures for applications requiring precision tolerancing and dimensional control. GY-70/X-904 laminate composites in the double symmetric design (0/ ± 45/90)_2s were tested, as well as a honey-comb design having two singly symmetric GY-70/X-904 faceplates bonded to an aluminum core.

Measurements were made to evaluate the coefficient of thermal expansion and its directional variations at 0, 45, and 90 deg to the outermost fiber orientation. Additional measurements of the coefficient included variations normal to the surface. Nondestructive testing employing holography was conducted to determine microcreep behavior.

Optical processing methods were investigated and mirrors with three types of reflector surfaces were fabricated. Environmental testing, including thermal cycling, thermal stability, humidity/vacuum effects, and temporal stability, was done on mirrors representing the various processing methods.

Data, discussion of results, and recommendations for applicable areas are given for the specific material and design types tested.