On experimental versus theoretical incipient buckling of narrow graphite/epoxy plates in compression

Abstract

Most stiffeners in aerospace structures are composed of narrow plate elements with the unloaded edges usually being either simply-supported or free. This paper is concerned with the difficulties encountered in attempting to predict the incipient buckling strength for narrow (low width to thickness ratio) angle-plied graphite/ epoxy plates in compression. Numerous available test data was compared to analytical predictions. The tested plates were of two types: both unloaded edges supported by steel V-blocks (no-edge-free); one unloaded edge supported by a steel V-block and the other edge free (one-edge-free). Nondimensional plots for both types of tests are presented which can be used to predict incipient buckling strengths for plates with laminate configurations other than those tested. For completeness, nondimensional crippling plots are presented where the incipient (initial) buckling stress is employed in the nondimensional parameters. This approach is an interesting ramification of previously published crippling plots where the theoretical buckling stress was employed in the nondimensional parameters. Nomenclature length of plate width of plate elastic flexural stiffness of plate theoretical elastic buckling stress incipient buckling stress Southwell plot buckling stress postbuckling failure (crippling) stress ultimate compressive strength overall length of test specimen effective column length of test specimen L/X, where C is the end fixity coefficient and is equal to approximately 3.6 for fixed ended test specimens in testing machine theoretical elastic buckling load incipient buckling load postbuckling failure (crippling) load thickness of plate