Broadgoods for Improved Fatigue Performance

Modern carbon-fiber reinforced composites are superior in strength-to-weight ratio over most metal alloy materials. One major problem, however, is the susceptibility of composites to micro fractures and fatigue failure. Because composites cannot be annealed to eliminate stress risers, great care has to be taken during manufacture to avoid creating such. The US Navy is soliciting proposals for new materials that allow composite manufacture using dry broadgood carbon fiber and resin infusion. Unfortunately, current broadgoods are assembled by stitching together unidirectional carbon fiber tows. Upon composite cure, the stitching material acts as stress risers and reduces the fatigue performance below acceptable levels.Adherent Technologies has studied alternative composite manufacturing techniques for two decades. ATI has developed a powder tow impregnation technology to produce prepreg material directly from dry powders, known as towpreg. Based on this approach, we now propose to manufacture unidirectional tapes using a low-percentage of powdered binder to produce a dry broadgood. The binder will be selected to either seamlessly blend into the resin during cure or act as a randomly distributed toughening agent. Both approaches will eliminate the need for stitching yarn or resin-rich areas.