Free-Edge Effects in the Characterization of Composite Materials Available to Purchase

In the use of flat specimens for the characterization of composite materials, stress free edges often are encountered. In the case of laminated tension specimens, such free edges induce interlaminar stresses which can disturb the desired state of stress. Large stress concentrations can be induced by free edges, such as in the rail shear test. Other examples include the sandwich beam test. A general review of free-edge problems as related to composite characterization is presented, including a discussion of narrow versus wide specimens. Particular attention is given to the sandwich beam test where a preliminary analysis of the free-edge problem reveals a state of stress which differs from a tensile coupon.