The paper presents an enhanced model of the mixed-mode bending (MMB) test, commonly used for assessing the mixed-mode interlaminar fracture toughness of composite laminates. The specimen is considered as an assemblage of two identical sublaminates, partly bonded together by an elastic interface. Each sublaminate is modelled as an orthotropic beam, deformable due to bending, extension and shear. The interface is thought of as a continuous distribution of normal and tangential springs, whose elastic reactions produce transverse and axial loads in the sublaminates, as well as distributed couples. The mechanical behaviour of the system is described by a set of eighteen differential equations, endowed with suitable boundary conditions. The problem is split into the superposition of two subproblems, where the applied loads are symmetric and antisymmetric with respect to the interface plane, respectively. This approach allows for a simpler analytical solution and leads to a natural separation of the fracture modes within the context of beam theory. Through lengthy yet elementary calculations, a complete explicit solution to the original problem is deduced, in terms of displacements, internal forces and interfacial stresses. In particular, the mode I and II contributions to the energy release rate and the mode mixity ratio are determined.
An enhanced beam model of the mixed-mode bending (MMB) test
BENNATI, STEFANO;VALVO, PAOLO SEBASTIANO
2007-01-01
Abstract
The paper presents an enhanced model of the mixed-mode bending (MMB) test, commonly used for assessing the mixed-mode interlaminar fracture toughness of composite laminates. The specimen is considered as an assemblage of two identical sublaminates, partly bonded together by an elastic interface. Each sublaminate is modelled as an orthotropic beam, deformable due to bending, extension and shear. The interface is thought of as a continuous distribution of normal and tangential springs, whose elastic reactions produce transverse and axial loads in the sublaminates, as well as distributed couples. The mechanical behaviour of the system is described by a set of eighteen differential equations, endowed with suitable boundary conditions. The problem is split into the superposition of two subproblems, where the applied loads are symmetric and antisymmetric with respect to the interface plane, respectively. This approach allows for a simpler analytical solution and leads to a natural separation of the fracture modes within the context of beam theory. Through lengthy yet elementary calculations, a complete explicit solution to the original problem is deduced, in terms of displacements, internal forces and interfacial stresses. In particular, the mode I and II contributions to the energy release rate and the mode mixity ratio are determined.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
