Compressive Properties and Laser Absorptivity of Unidirectional Metal Matrix Composites

摘要

Metal matrix composite use has been impeded because there is no well qualified property data base. Elevated temperature compressive properties and laser absorptivity data are in great demand in the design, modelling, and analysis of MMC structures in elevated temperature applications and survivability assessment. Testing methods were developed for room temperature and elevated temperature compressive modulus and strength measurements of single-ply unidirectional graphite-aluminum (Gr/Al) and graphite-magnesium a(Gr/Mg), and to generate laser absorptivity data for these two types of materials. An effective gage length was established for valid compression tests to eliminate buckling failure. The measured failure strength values for Gr/Al and Gr/Mg are approximately 50 to 60% lower than the material tensile strength. Small gage strain gages are being used to measure the compressive modulus as a function of temperature. The laser absorptivities of Gr/Al and Gr/Mg were measured by the use of an in-house developed differential calorimeter. The calorimeter has been used to measure total hemispherical emittance and normal laser absorptance of specimens as a function of temperature from 200 to 700 C. Test results indicated that the laser absorptances of Gr/Al and Gr/Mg at 10.6 micrometer wavelength remain more or less constant over most of the temperature range tested. 888