Fabrication, Analysis, and Experimentation of a Practically Constructed Laminated Composite I-Beam Under Pure Bending

Abstract

Seven I-beams constructed of AS4/3501 graphite/epoxy were tested and analyzed. The I-beams, having a layup sequence of 45/-45/03/-45/451T with various flange widths varying from ¾ to 2 ½ inches and a web height of 1 inch, were fabricated. The beams were tested under 4-point bending, producing results for the pre-buckled stiffness, buckling moment, and ultimate moment. 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 only slightly increased by increased stiffness. Typically, increasing the flange width does not contribute significantly to the ultimate strength of the beam. For wider flanged beams, delamination occurs at the flange and then propagates to the web causing final failure. However, narrower flanged beams fail due to fiber/matrix crushing at the flange-web intersection.