METHOD FOR THERMOMECHANICAL CHARACTERIZATION OF SINGLE FIBERS

A method has been developed for measuring the longitudinal Young's modulus and longitudinal coefficient of thermal expansion of flexible fibers as a function of temperature. A length of the fiber specimen is fixed at the ends on a plate of very low thermal expansion material inside an oven. The fiber is loaded by small incremental weights at the center and the corresponding deflections recorded photographically. The fiber stiffness is calculated from the stress and strain which are related to the applied loads and measured center deflections. For the measurement of the coefficient of thermal expansion, thermal strains are obtained from deflection measurements under a constant load at various temperatures. A modified method was also developed for the case of stiff or semi-rigid fibers. The fiber is hinge-supported at the ends and its deflection at various temperatures is related to thermal strains from which the coefficient of thermal expansion is obtained. Good results were obtained for a number of materials.