MEASUREMENTS OF THE INITIAL STRAIN-ENERGY OF LEATHER

This investigation was to establish an improved method to characterize the stiffness of leather associated with its resistance to a small de formation while taking into account the nonlinear viscoelasticity of l eather. Stiffness was quantitatively determined for a specimen by meas uring the energy needed to stretch it to 10 percent strain. This physi cal quantity, called initial strain energy, was observed to be easier to define and measure than the tensile modulus. Using Box-Hunter's exp erimental design method a second order polynomial equation was derived for the relationship between initial strain energy and three major in dependent variables: moisture content, strain rate, and sampling angle . The breaking elongation was observed to decrease as initial strain e nergy increased, whereas the tensile strength did not show a direct co rrelation with initial strain energy alone. However, regression analys is provided a significant statistical relationship between tensile str ength and a parameter that incorporates the effects of strain energy, moisture content and strain rate. Thus, a prediction of tensile streng th may become feasible based on measurements of initial strain energy without breaking the leather.