MEASUREMENT BY LASER GENERATED ULTRASOUND OF THE STIFFNESS TENSOR OF AN ANISOTROPIC MATERIAL AT ELEVATED TEMPERATURES

摘要

A method to measure the stiffness tensor of anisotropic materials, based on LASER ultrasonic generation and detection has been used. The device is connected with an oven, and the changes of the coefficients induced by temperature are measured up to 300℃. The method shows a good sensitivity and an anisotropic change of the mechanical properties is detected. This anisotropy is connected with the differential behaviour of the matrix and fibers. It is pointed out that the tensile coefficient in the direction normal to the fibre axes C_(11), and in plane shear coefficients, C_(55) and C_(66), respectively, exhibit the same important relative variation of about 30 %. This coupled tensile-shear effect could not be measured using classical stress-strain metrology.