Collapse load evaluation of pinned-joint composite plates Aurora Pisano, Paolo Fuschi DASTEC, University Mediterranea of Reggio Calabria, Italy E-mail: [email protected], [email protected] Keywords: Limit Analysis Theory, Linear Matching Method, Mechanically-Fastened Composite Joints. SUMMARY. A numerical procedure for limit analysis is presented and applied to evaluate upper and lower bounds to the collapse load of pinned-joint composite plates. The procedure is an extension, in the context of orthotropic materials, of a method known in the literature as Linear Matching Method. To show the validity of the method, the numerical predictions are compared with available experimental data in terms either of collapse loads or of collapse mechanisms. 1 INTRODUCTION Joints between composite laminates, among several techniques, can be made by using mechanical fasteners like bolts, rivets or pin-connectors. Mechanical fastened-joints are employed in many advanced engineering fields and this mainly because they are relatively inexpensive to manufacture as well as easy to assemble or disassemble. Nevertheless, such type of connections are characterized by an high stress concentration near the hole area which becomes a source of weakness; the structural joint failure usually begins at the fasteners sites. A great deal of research has therefore concentrated on the evaluation of the strength as well as on the prediction of the failure mechanism of these joints between composite plates or components and this with different approaches, see e.g. [1] and references therein. In the present study, far off the will of furnishing an exhaustive solution of the above problem, a limit analysis numerical approach for pinned-joint orthotropic composite laminates in plane stress conditions is proposed. The mechanical problem is treated in terms of evaluation of an upper and a lower bound to the collapse load multiplier giving also a prediction of the failure mode. The examined structural elements are composite laminates obeying, by hypothesis, to a Tsai-Wu type yield criterion defined as a second order tensor polynomial form of the Tsai-Wu failure criterion for composite laminates [2]. This criterion is one of the best known showing a very good capability for predicting the failure of composite laminates [3]. The treated numerical approach, recently proposed by the authors in [4,5], can be viewed as an extension, in the context of orthotropic materials, of a method known in the relevant literature as Linear Matching Method (LMM), see e.g. [6]. The LMM here employed basically solves a sequence of linear analyses on the structure assumed, by hypothesis, as made of a fictitious linear viscous orthotropic material with spatially varying moduli and suffering a distribution of given initial stresses. With this conjecture, at each iteration, by varying (rescaling) the fictitious material parameters at each sampling point of the structure (namely at each Gauss point of the adopted FE mesh), the computed fictitious solution is used to define a collapse mechanism for the real structure and eventually an upper bound to the collapse load multiplier. The whole method has
Collapse load evaluation of pinned-joint composite plates
Jun 24, 2023
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