The measurement of non-linear damping in metal-matrix composites

This thesis is concerned with the measurement of non-linear (i.e. strain amplitude dependent) intrinsic material damping in continuous fiber reinforced metalmatrix composites. The particular MMC studied is a 4-ply, [O︢]S, (O = 0, 15, 30, 45, 60, 75 degree), P55Gr/Al-6061 composite. A popular method for measuring damping is the free-decay of flexural vibrations of a cantilevered beam. The strain field in a cantilevered beam is inhomogeneous. For materials whose damping is non-linear, the measured damping is not equal to the intrinsic material damping. Using an elementary algorithm developed by Lazan, we extract non-linear intrinsic material damping from non-linear specimen damping. In general, damping is a function of temperature, strain amplitude and strain rate. For the measurements reported herein, the range of these parameters is: [ ] where T is the absolute temperature, Er is the root strain and f is the frequency in Hz.