Transverse Shear Stiffness of T300/5208 Graphite-Epoxy in Simple Bending

摘要

Buckling and crippling of a structural element is governed by its elastic properties. Nevertheless, a complete definition of the elastic constants of a graphite/epoxy laminate, including the transverse shear moduli (important under high compressive stress), has never been accomplished. For this purpose, tension, compression, and bending tests were conducted on square-section specimens cut 0-degrees and 90-degrees to the fiber axis from 64-ply unidirectional T300/5208 laminate. Axial test specimens were instrumented with tee gages to obtain data on extensional moduli and Poisson's ratios. Bending deflections were measured with high precision and analyzed using a rigorous finite difference solution for stress distribution to derive the shear moduli along with the extensional moduli acting in bending. Redundant determinations were obtained for the nine elastic constants of Hooke's law as generalized for specially orthotropic material. Extensional moduli obtained under axial load and in bending agreed with each other to within one percent. A self-consistent set of properties was determined which were generally in accordance with published data, and which established the material as being transversely isotropic and conforming to the linear theory of elasticity.