Investigation of Parachute Fabric Permeability Under Cyclic Loading

Permeability [ft/(ft-min)] is a key property of parachute fabrics. How fabric permeability changes with respect to cyclic pressure loading can provide valuable insight into parachute performance and lifecycle considerations. While field-testing can provide valuable data regarding parachute canopy permeability over time, controlled laboratory tests can provide synergistic insight into how environment, fabric mechanics and test parameters affect permeability over time. In this paper, cyclic permeability experiments using a computer numerically controlled, piston permeability apparatus (CNC-PPA) are presented for a variety of different experimental parameters including: test parameters (time vs. volume based testing), environmental as well as fabric conditioning, and fabric sample location on the roll. A series of additional tests using a TexTest permeability testing apparatus are also presented. Laboratory experiments indicate that the permeability of PIA-C-44378, type IV fabric tends to decrease over time under repeated cyclic pressure loading. Furthermore, the permeability results indicate a reasonably strong dependence on humidity and a moderate dependence on sample fabric roll location.