The Effects of Shear on Mode II Delamination

Abstract

ABSTRACT. The paper focuses on the effects of shear deformation and shear forces on the mode II contribution to the energy release rate in delaminated beams. A critical review of the relevant literature is presented, starting from the end-notched flexure test as the prototype of delaminated laminates subjected to pure mode II fracture. Several models of the literature are recalled from simple beam theory to more refined models. The role of first-order shear deformation in line with the Timoshenko beam theory is investigated as distinct from the local crack-tip deformation related to the shear modulus of the material. Then, attention is moved on to a general delaminated beam with an arbitrarily located through-the-width delamination, subjected to mixedmode fracture. Several fracture mode partition methods of the literature are reviewed with specific attention on the effects of shear on the mode II contribution to the energy release rate.KEYWORDS. Delamination; Mixed-mode fracture; Mode II fracture; Beam theory; Shear deformation; End-notched flexure test.Citation: Valvo, P.S., The effects of shear on Mode II delamination: a critical review,

The Effect of Transverse Shear in Symmetric and Asymmetric End Notch Flexure Tests–Analytical and Numerical Modeling

“…Thus, the compliance becomes: where is the specimen half length. This expression is consistent with the well-known expression in the literature [ 14 ].…”

“…where l = L/2 is the specimen half length. This expression is consistent with the well-known expression in the literature [14]. For a = 0, we obtain the well-known expression of a beam deflection in a three-point bending test:…”

“…Carlsson et al [ 12 ] presented an analysis of the ENF specimen based on the Timoshenko beam theory (TBT) [ 13 ], which on the contrary to the SBT, enables for the kinematic cross-section rotation of the beam, with respect to their neutral plane and resulted in increased beam compliance. As noted in a critical review by Valvo [ 14 ], in the literature, conflicting reports may be found addressing the effect of shear deformation on the fracture toughness of the laminates [ 15 , 16 , 17 , 18 ]. Anyway, shear deformation clearly influences the compliance of both symmetric and asymmetric ENF test specimens, whereas the energy release rate is influenced only for asymmetric specimens.…”

Experimental investigation of Mode II fracture properties of parallel strand bamboo composite by end notched flexure test

“…At this point, the ENF test method for mode II fracture was basically improved. Recently, Valvo (2018) presented a critical review of the relevant literature on mode II fracture starting from the ENF test, and theoretically investigated the effects of shear on mode II delamination. Several extensions of mode II fracture flexural specimens have been proposed since the introduction of the ENF specimen.…”