Fabrication, analysis, and experimentation of a practically constructed laminated composite I-beam under pure bending

Seven I-beams constructed of AS4/3501 graphite/epoxy were tested and analyz ed. The I-beams, having a layup sequence of [45/-45/0(3)/-45/45](T) with va rious flange widths varying from 3/4 to 2 1/2 inches and a web height of 1 inch, were fabricated. The beams were tested under 4-point bending, produci ng results for the pre-buckled stiffness, buckling moment, and ultimate mom ent. Results indicate that wider flange beams exhibit buckling at lower moments than narrower flange beams. The flange width also affects the buckling mode . Wider flanged beams show larger edge displacements and lower mode values than narrower flanged beams. The ultimate moment capability appears to be o nly slightly increased by increased stiffness. Typically, increasing the fl ange width does not contribute significantly to the ultimate strength of th e beam. For wider flanged beams, delamination occurs at the flange and then propagates to the web causing final failure. However, narrower flanged bea ms fail due to fiber/matrix crushing at the flange-web intersection.