EDGELESS COMPOSITE LAMINATE SPECIMEN FOR STATIC AND FATIGUE TESTING.

In the reported test program, a new type of edgeless cylindrical specimen was developed which is a flattened tube consisting of two flat sides connected by curved sections and it can be handled much like the standard flat coupon. Special fabrication techniques and fixturing were devised for quantity production of such specimens. The flat ends of the specimens are provided with crossplied fiberglass gripping tabs, the same as used for flat test coupons. As part of the tabbing the hollow ends must be plugged with inserts to prevent the crushing of the ends during specimen gripping for load introduction. A special insert design was developed which minimizes detrimental Poisson's effects ordinarily introduced by inserts. Angle-ply specimens of this type of construction, as well as corresponding flat coupon specimens, were fabricated from graphite/epoxy, S-glass/epoxy, Kevlar 49/epoxy materials and hybrid graphite/S-glass/epoxy. Static tensile fatigue and residual property tests after fatigue were conducted. The data obtained from the flattened tube specimen tests were compared with those from flat test coupons of the same material and laminate construction. Extensive test data are included.