DEFLECTION-FORCE MEASUREMENTS AND OBSERVATIONS ON KEVLAR-29(R) PARACHUTE FABRICS

Deflection-force relations for plain weave Kevlar(R) fabrics have been determined under conditions of uniaxial loading. In these experiments, the loading is stopped at a given level and a portion of the fabric is encapsulated. The fabric is then unloaded, sectioned, and photographed. Measurements on the photographs reveal the changes in weave geometry and yam cross section with loading. The initial geometrical data are used in a large deformation mechanical model, which couples yam bending and stretching effects to predict theoretical displacement-force relations for the fabric. Experimental and theoretical deflection-force curves are in good agreement; they show that during initial loading the response is dominated by yam bending, while for large loads the response is dominated by yarn stretching.