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CWPAN: coupled wavelength postbuckling analysis

Zhao, Kai 2021. CWPAN: coupled wavelength postbuckling analysis. PhD Thesis, Cardiff University.
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Abstract

Laminated composite plates are used extensively in the aerospace industry because of theirnlight weight, high strength and stiffness. Additionally, the use of panel structures leads to a reserve of postbuckling strength which allows more load to be carried than the initial critical buckling load. This enables the weight of the aircraft to be further reduced by fully utilising this stable postbuckling phase. Postbuckling is a highly nonlinear process incurring high computational costs for conventional numerical methods particularly when the plate is manufactured from composite material or subject to shear loading. For many years, researchers and engineers have been searching for a fast yet reliable analysis technique to extend the design envelope as far as possible into the postbuckling region. However, most of the commercial design software is characterized by either low computational efficiency or lack of accuracy. This work is motivated by the need for an alternative to such software. The coupled wavelength postbuckling analysis (CWPAN) presented in this thesis is based on the use of a series of sinusoidal solutions representing in-plane displacements, strains and stresses for a composite plate under any combination of in-plane loading based on the exact strip method. By incorporating classical plate theory and large deflection theory, the governing equilibrium equations are assembled and solved analytically at each postbuckling equilibrium state. The in-plane distributions of displacements, strains and stresses are therefore obtained as a means of observing postbuckling behaviour. A convergence procedure consisting of a modified Newton iteration scheme and its supporting strategies is also developed to capture progressive postbuckling behaviour. With such a procedure, successive equilibrium states can be connected and enabling a full postbuckling analysis considering postbuckling stiffness. Postbuckling behaviours such as stress redistribution can therefore be observed. CWPAN is illustrated using appropriate practical examples and numerical results including symmetric balanced, unsymmetric, unbalanced composite plates under in-plane compression, shear and combined loading under three different in-plane boundary conditions, and is validated against the most widely used numerical technique, finite element analysis (FEA).

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Engineering
Uncontrolled Keywords: Postbuckling_analysis, Composite _Plate, Laminate, VICONOPT, CWPAN, Shear loading,
Date of First Compliant Deposit: 25 February 2022
Last Modified: 01 Mar 2022 08:05
URI: https://orca.cardiff.ac.uk/id/eprint/147817

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