SEDL / STP / STP546-EB / STP35481S

Analysis of the Flexure Test for Laminated Composite Materials

Whitney, JM
Materials research engineer, research chemist, and graduate student, Air Force Materials Laboratory, Wright-Patterson Air Force Base, Ohio

Browning, CE
Materials research engineer, research chemist, and graduate student, Air Force Materials Laboratory, Wright-Patterson Air Force Base, Ohio

Mair, A
Materials research engineer, research chemist, and graduate student, Air Force Materials Laboratory, Wright-Patterson Air Force Base, Ohio

Pages: 16    Published: Jan 1974

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Abstract

Equations applicable to a general class of symmetrically laminated beams are derived by considering a beam as a special case of a laminated plate. The beam bending stiffness thus becomes a function of all the bending stiffness coefficients of a laminated plate. The validity of this approach is verified by comparing theoretical results to flexure data on graphite/epoxy angle-ply and quasi-isotropic laminates. In addition, it is shown that flex strength on general composite laminates is extremely difficult to interpret, even though the stresses can be calculated from the modified beam theory. Discontinuities in the in-plane stresses at layer interfaces lead to a state of stress which is difficult to compare to standard laminate tensile coupons.