A New Testing Machine for the Dynamic Characterization of High Strength Low Damping Fiber Materials

Abstract

This work describes a novel method for measuring the damping, the elastic modulus and the non-linear behavior of high strength low damping fiber materials such as para-aramids, silicon carbide (SiC) and carbon. The method is based on resonant response characterization of a spring-mass system excited by a sine-wave forcing term which is applied as a vertical force to the suspended mass. The damping is obtained from the measured resonance quality factor Q, the elasticity modulus is calculated from the resonance frequency, and the non-linear coefficient is obtained with the backbone approach from resonance profile variations as a function of the forcing term amplitude. It is argued that the method is very sensitive, to the point that a maximum excitation amplitude of the order of a few percent of resistance is sufficient to obtain an estimate of the non-linear coefficient. This claim is supported by experimental results. A testing machine is also discussed, which provides the necessary sensitivity at such small excitation amplitudes and the capability of evaluating very small damping values, as expected in high strength low damping fiber materials. The sensitivity is guaranteed by an optical position sensor with sub-micron resolution. To evaluate small damping values,

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“…Unfortunately, mechanical characterization of fibers is less than complete in the open literature, particularly for what concerns mechanical losses summarized by Q f . Therefore, tests were carried out in the laboratory with a purposely built apparatus [17] on promising candidates, mainly aiming at characterization of mechanical losses, creep, and linearity [18]. Para-aramid, SiC, basaltic, and carbon fibers were analyzed [19], as well as steel and tungsten metal wires.…”