Effects Of Parasitic Shear In The Representation Of The Mechanical Behavior Of Laminated Composites

João E. Abdalla, Florentino A. Fagundes, Roberto D. Machado


This paper presents a study of the deleterious effects caused by the presence of
parasitic shear in the polynomial expansions of finite elements for modeling laminated
composite plates and beams. It is shown that spurious terms are responsible not only for
artificial stiffening, but also cause qualitative errors in the behavior of laminated composites.
That is, parasitic shear is capable of causing the finite element to misrepresent the nature of a
given deformation. The sources of parasitic shear are discussed in the context of beams and
plates. Through the use of strain gradient notation, the parasitic shear terms are precisely
identified, and a sensitivity analysis can reveal the strength of each and every term in the
deleterious effects of the group of spurious terms. Correction of the elements is possible by
removing these spurious terms. Numerical analysis demonstrates the convergence
characteristics of the elements contaminated by parasitic shear and that in certain cases the
only definite remedy is the removal of the spurious terms a-priori.

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