Computational and analytical modelling of composite structures based on exact and higher order theories.
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Date
1995
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Abstract
The objective of the present study is the computational and analytical modelling of
a stress and strain state of the composite laminated structures.
The exact three dimensional solution is derived for laminated anisotropic thick cylinders
with both constant and variable material properties through the thickness of a
layer. The governing differential equations are derived in a such form that to satisfy
the stress functions and are given for layered cylindrical shell with open ends. The
solution then extended to the laminated cylindrical shells with closed ends, that is
to pressure vessels.
Based on the accurate three-dimensional stress analysis an approach for the optimal
design of the thick pressure vessels is formulated. Cylindrical pressure vessels are
optimised taking the fibre angle as a design variable to maximise the burst pressure.
The effect of the axial force on the optimal design is investigated. Numerical results
are given for both single and laminated (up to five layers) cylindrical shells. The
maximum burst pressure is computed using the three-dimensional interactive Tsai-:
Wu failure criterion, which takes into account the influence of all stress components
to the failure. Design optimisation of multilayered composite pressure vessels are
based on the use of robust multidimensional methods which give fast convergence.
Transverse shear and normal deformation higher-order theory for the solution of dynamic
problems of laminated plates and shells is studied. The theory developed is
based on the kinematic hypotheses which are derived using iterative technique. Dynamic
effects, such as forces of inertia and the direct influence of external loading on
the stress and strain components are included at the initial stage of derivation where
kinematic hypotheses are formulated. The proposed theory and solution methods
provide a basis for theoretical and applied studies in the field of dynamics and statics
of the laminated shells, plates and their systems, particularly for investigation of
dynamic processes related to the highest vibration forms and wave propagation, for
optimal design etc.
Geometrically nonlinear higher-order theory of laminated plates and shells with
shear and normal deformation is derived. The theory takes into account both transverse
shear and normal deformations. The number of numerical results are obtained
based on the nonlinear theory developed. The results illustrate importance of the
influence of geometrical nonlinearity, especially, at high levels of loading and in case
when the laminae exhibit significant differences in their elastic properties.
Description
Thesis (Ph.D.)-University of Natal, Durban, 1995.
Keywords
Composite materials--Mechanical properties., Laminated materials--Mechanical properties--Mathematical models., Strength of materials., Shells (Engineering), Composite construction., Theses--Mechanical engineering.