Nonlinear Behaviour Analysis of Composite Thin Beams and Plates.

Abstract

In engineering applications, it is well known that the minimum weight criteria with high performance is essential in the design of certain structures like aircraft components, aerospace vehicles and civil structures.. etc. This task could be a challenge especially when the design of wing structures such as aircraft wings, rotor blades, robotic arms is the subject. The behavior of such structures is highly nonlinear due to the deformation of their geometry. The solution of such problems becomes very complex, especially with the use of composite materials. The effects of large displacements may play a primary role in the correct prediction of the behavior of these structural members, which continue to be modeled as a flexible beams. In this way, another difficult task can be imposed here when some structural elements like plates and shells which can undergo inplane thermo-mechanical stresses that affect their dynamic and static behaviors. This problem has stimulated several researchers to work on the subject to provide accurate predictions of free vibration of laminated plates, subjected to inplane thermal or mechanical stresses. The main aim of the present work is the contribution in the analytical, experimental and numerical analysis of nonlinear behavior of some structural elements. The nonlinearities considered in this thesis are geometric nonlinearities arising from the large displacements and nonlinearities arising when a part of structure as plates, may lose their stiffness under inplane thermal or mechanical loading effect. An analytical model has been developed for beams large deflection analysis followed by an experimental program for the same purpose. Furthermore, a beam finite element based on Euler-Bernoulli beam theory, taking in consideration composite material has been formulated for nonlinear bending analysis. A four noded finite element based on first order shear deformation theory has been used to study the effect of thermal and mechanical inplane loading on dynamic behavior of laminated plates.The obtained results have been verified and validated with the available results in the literature.