Internal Friction and Residual Thermal Stress in Composite Materials

Abstract

The problem of relationship between the thermal stress and the internal friction spectrum are discussed here on the basis of the examples of studying the temperature, amplitude, time and strain relationships of the internal friction of the aluminum alloys strengthened by the fibers of boron, carbon, silicon carbide and aluminum oxide, by filamentary crystals and particles. The frequency of the torsional, flexural and longitudinal oscillation during the measurements was 1 Hz, 1 kHz and 100 kHz, respectively. The studies show that: when the thermal stress in the composite matrix exceeds the yield point the internal friction temperature curve features inelastic effect; the plastic thermal deformation of the composite matrix results in hysteresis of the internal friction temperature dependence in the case of torsional oscillation while in the case of lower temperatures certain “deformation” maximums of damping become detectable; the temperatures at which the amplitude-dependent internal friction of the composites become prominent are always lower than those of the components.