Flexing behaviour of high strength coated fabrics

Flexing characteristics of three varieties of thermoplastic polyurethane (TPU) coated high strength fabrics (nylon 6,6, polyester and kevlar) have been evaluated by subjecting them to 5000 cycles in a De-Mattia flex tester. The flexing damage is assessed in terms of % loss of strength by evaluating the residual tensile strength of flexed fabrics. Statistical analysis has been carried out at 95% significance level for assessing the influence of flexing cycles and variation in thermoplastic polyurethane concentration on the residual strength of coated kevlar fabrics. Accordingly, the specific trend exhibited is established. The study shows that the coated kevlar fabric has suffered with maximum strength loss, while nylon and polyester show excellent flex damage resistance with negligible strength loss. Further, the sensitivity to damage of kevlar fabric has been studied by varying the number of flex cycles from 1000 to 5000 and the extent of damage that happened within the structure is thoroughly analyzed using field emission scanning electron microscope. Finally, the possible mean of improving strength retention (22%) of coated kevlar fabric subjected to repeated flexing by the application of a proprietary high viscosity polymer coating has been proposed.