Abstract
This research work has two main objectives, being the first related to the characterization of variable stiffness composite plates’ behavior by carrying out a comprehensive set of analyses. The second objective aims at obtaining the optimal fiber paths, hence the characteristic angles associated to its definition, that yield maximum fundamental frequencies, maximum critical buckling loads, or minimum transverse deflections, both for a single ply and for a three-ply variable stiffness composite. To these purposes one considered the use of the first order shear deformation theory in connection to an adaptive single objective method. From the optimization studies performed it was possible to conclude that significant behavior improvements may be achieved by using variable stiffness composites. Hence, for simply supported three-ply laminates which were the cases where a major impact can be observed, it was possible to obtain a maximum transverse deflection decrease of 11.26%, a fundamental frequency increase of 5.61%, and a buckling load increase of 51.13% and 58.01% for the uniaxial and biaxial load respectively.
Highlights
Fiber-reinforced polymers have been used over the years in many different application areas [1], wherein the use of straight fibers with selected orientations within each ply deserved a significant research attention
A similar elongation pattern is observed in Figure 8, for the biaxial critical buckling load, more balanced when compared to the constant stiffness composite plate
Due to their known fiber curvilinear paths, variable stiffness (VS) composites can provide greater design flexibility when compared to constant stiffness laminates, as they may enable for an eventual adjustment to geometrical specificities, such as holes, and contribute for a better load redistribution
Summary
Fiber-reinforced polymers have been used over the years in many different application areas [1], wherein the use of straight fibers with selected orientations within each ply deserved a significant research attention. This study was performed for a linear fiber angle and a flow field fiber angle variation for different ply quantities, geometric parameters, boundary, and loading conditions being the results compared with the ones obtained by finite element analysis. The application case studies are divided in two parts: The first one, wherein a set of static and buckling analyses aim at complementing a free vibrations analysis considered in the context of the verification case studies; and the second part and the main part of the present work, where a complete and transversal set of optimization studies are presented In this last context, one performs a set of constrained optimization processes focused on a single layer and on three layers VS composite plates, where the objective functions are the minimization of the maximum transverse deflection, the maximization of the fundamental frequency, and the maximization of the critical buckling load. The design variables are the characteristic angles associated to the fibers’ path in each ply
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