A homogenized structural model for shear deformable composites with compliant interlayers

Abstract

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Mode II dominant fracture of layered composite beams and wide-plates: a homogenized structural approach

“…They have also been used to simulate delamination damage progression and fracture by degrading the properties of the thin layers, using for instance a continuum damage approach. As recently noted in [37,38], however, the models which use this strategy and are based on the refined zigzag theories in [25,26] have some limitations in plates with in-plane discontinuities in the material properties and yield inconsistent and unacceptable results, also for the global variables of the system, in the presence of delaminations.…”

Local zigzag effects and brittle delamination fracture of n-layered beams using a structural theory with three displacement variables

“…This problem cannot be solved by increasing the order of the ESL theory used as global model and, in our opinion, could be solved only by modifying the zigzag formulation and leaving the displacement jumps as part of the unknowns of the problem, as it has been done for instance in [29]. Another approach to solve this problem could be through the use of the refined zigzag theory [7]; however, preliminary analyses in [20,30] highlight other still unresolved difficulties of the approach in dealing with in-plane discontinuities. The effects of neglecting shear deformations along the delaminated portions of the beam, however, are not relevant in all problems dominated by bending defomations (as in the fracture analyses of the cross ply laminated ELS specimen in Fig.…”

“…This implies that continuity is not satisfied at the local level and displacements and force sub-resultants within the single layers may differ. This typically occurs near the crack tip and clamped ends, within boundary regions whose size depends on the mismatch of the elastic constants of the layers and on the stiffness of the interfaces and is very small when the mismatch is small and the interfacial stiffness is very large or very small [20,22]. The model and analyses presented here are limited to mode II dominated problems, were transverse extensibility of the layers and interfacial openings may be neglected.…”

“…The local fields are accurately captured also in very thick beams and wide plates. Predictions are less accurate near clamped edges, due to the presence of boundary regions which will be discussed later [19,20,22]. The diagrams in Fig.…”

“…Following the approach which is commonly used for the structural low order theories, accurate shear stresses and strains can be obtained a posteriori through the imposition of local equilibrium: . On the other hand, the absence of shear strains in the delaminated regions induces under-predictions of the transverse displacements in shear deformable plates and the need for corrections or adjustments [19,20]. The problem will be discussed later.…”