Abstract:
This thesis deals with the stress analysis of sandwich structured composite materials.
Materials under consideration are assumed to be perfectly bonded together. Finite
difference method is used for the solution of two dimensional elastic problems. A
numerical model for rectangular geometry based on displacement potential function
has been developed to investigate the problem. In each layer of the composite the
mechanical properties are assumed to be isotropic.
At the interface, there is a single value for each displacement component but two
different values for each stress component of the laminated composite having
different mechanical properties in layers. Like usual critical zone of a sandwich
structured composite under mechanical loading, the two interfacial zones are also
zone of critical stresses. Changing the Poisson’s ratio in any layer (case or core) has
significant effects on the results of all layers of the sandwich structured composite.
Due to the mathematical expressions of stresses and displacements for two
dimensional elastic problems, the study of the effects of Poisson’s ratio is intricate
rather the study of the effects of Modulus of elasticity is straightforward. In general,
the material having higher modulus of elasticity experiences higher stresses.
Finite difference scheme has been developed for the management of boundary
conditions so that all possible mixed boundary conditions can be applied in any
boundary points as well as at the interfaces of isotropic layers. Special numerical
formulations yield to new formula structures are employed at the interfaces. An
effective programming code has been developed by FORTRAN language to solve
the problems of sandwich structured composites. In order to compare the results by
the present finite difference method, another numerical technique namely finite
element method is used. Validation of the results is performed by using
commercially available FEM package software. It is observed that the results agree
well within the acceptable limit, which also confirms to the reliability of the finite
difference method.
