高分子固体の非線形動的粘弾性測定に基づく疲労挙動の解析

抄録

Fatigue behavior of polymeric solids has been paid great attention these days, since various high performance polymers and polymer composites have been ap-plied for structural components. However, little investigation on polymer fatigue has been made on the basis of dynamic viscoelastic behavior. The purpose of the present study is to analyze the fatigue behavior of polymeric materials on the basis of nonlinear dynamic viscoelastic measurement during the fatigue process and to reveal the fatigue mechanism of polymeric solids. A fatigue tester which enables continuous measurement of dynamic viscoelasticity and the surface temperature under sinusoidal strain has been designed. Fatigue tests have been carried out for various polymeric solids including amorphous glassy polymers, crystalline polymers, oriented polymers, elastomers and polymer composites. It was revealed that the dynamic viscoelastic behavior and surface temperature rise during the fatigue process can be classified into brittle and ductile failures. The amount of energy dissipated for irreversible structural change was calculated from the viscoelastic energy loss and the amount of heat generation. The fatigue criterion on the basis of viscoelastic energy loss dissipated for irreversible structural change has been established for various polymeric solids. The fatigue analysis procedure mentioned above has been successfully applied to glass-fiber reinforced polymer composite. In order to reveal the effect of nonlinear viscoelasticity on the fatigue behavior, a quantitative measurement of nonlinear viscoelasticity has been carried out based on Fourier analysis of response stress. It was revealed that the degree of nonlinear viscoelasticity was closely related to the fatigue strength. Finally, the origin of nonlinear viscoelasticity has been discussed.