Compression of Oriented Nylon Parallel to Fiber Axis

Abstract

A method was developed for preparing small specimens of oriented nylon 6-10 bristle suitable for the measurement of the behavior in compression parallel to the direction of orientation. The stress-strain curve in compression differed markedly from the tensile curve, being sharply bent toward the elongation axis. At room temperature, the stress reached a maximum of 0.45 g/den at about 10% strain, and at 100°C this maximum was reduced to 0.18 g/den at 6% strain. Con trary to the indications of the stress-strain curves, the elastic recoveries from up to 20% strain in compression and tension were quite similar. At 100°C, however, the elastic recovery in compression was greatly reduced, strains above about 5% being unrecoverable. The rate of stress relaxation in tension and compression were compared. Both the tensile and compression relationships must be known to predict bending behavior. An example analyzed indicates that, in a bend of radius of curvature 10 times that of the fiber, the maximum strain in compression on the inside of the bend is 50% greater than that in tension on the outside.