MECHANICAL PERFORMANCE OF CARBON-FIBER-REINFORCED AND GLASS-FIBER-REINFORCED EPOXY I-BEAMS .1. MECHANICAL-BEHAVIOR

This paper is the first in a series which detail the mechanical behavi our, finite element predictions and fractographic observations of the failure of composite I-beams. Experimental investigations into the beh aviour under static load of both unnotched and web- and flange-notched continuously reinforced carbon-fibre/epoxy and glass-fibre/epoxy I-be ams are discussed. A four-point flexural configuration is used. The gl obal static response and ultimate failure are described in terms of st rains, compliance, buckling and final fracture. A mode of buckling tha t is antisymmetric across the width of the compressive flange is obser ved prior to failure in all cases. Failure of the unnotched I-beams is concentrated around a buckle on the compressive flange whilst failure of the notched I-beams initiates from a shear-loaded circular cutout within the web. Buckling of the unnotched beams occurs at loads that a re approximately 50% of the failure loads. Failure of the notched beam s occurs at loads that are approximately 75% of the failure loads of t he unnotched beams. Buckling and failure of the glass/epoxy beams occu r at loads that are approximately 75% of the corresponding loads in th e carbon/epoxy beams.