MECHANICAL DEFORMATION MECHANISMS IN KNITTED FABRIC COMPOSITES

Knitted fabric composites have certain advantages over woven composite s, particularly in their ability to conform to complicated contours. A s a consequence, however, they demonstrate inferior mechanical charact eristics compared to woven materials as a direct result of the presenc e of bent fibers. Such a knitted fabric composite made from, for examp le, glass fibers in a polyurethane matrix, can be used as an orthopaed ic splinting bandage for immobilizing fractures of the upper and lower limbs. Relatively little research has been reported on knitted fabric composites; therefore, a study on the mechanical deformation mechanis ms of knitted fabric composites was initiated. It was observed that kn it patterns, type of fiber, size of fibers used, size of loops, coatin gs and lay-up procedure were all variables that could affect the struc ture/property relationship of knitted fabric composites. Tensile testi ng with optical measurement of strain was performed on knitted substra te and coated bandages in both the course and wale directions. Results indicated that the knitted fabrics function as link mechanisms at the microscopic level, with knitted loops straightening and bending befor e the individual elements of the knitted yarn take up significant load and material deformation. Theoretical modeling of the glass knit stru cture, in both the course and wale directions, agrees well with experi mental testing.