Inner Layer Material Identification of Two Layer
- Publication date
- Publisher
- RTU
Abstract
For the identification of the elastic modulus of the inner layer E2 the TWCS method
(Method for the Identification of the Elastic Properties of Polymer Materials by Using
Thin-Walled Cylindrical Specimens) is considered. The method is based on the solution of
the problem of compression of a thin-walled cylindrical tube by two parallel planes. The
contact problem is solved by using the Finite Element Method. The deformation of a thin
polymer shell is characterised by great displacements and relatively low elastic
deformations in a large range of movement of parallel planes.
In this paper the cylindrical shell consisting of two layers with different elastic
modulus is considered. The outer layer (bandage) of the cylindrical shell is made from a
rigid polymeric material with relatively high Young's modulus (10J MPa). The inner layer
is made from a softer polymer - Young's modulus 102 MPa or even 10 MPa. Poisson's
ratios of both layers are 0.35. The average radius R, the length L, the Young's modulus of
the outer layer E\ and the thickness of both layers t\ and tj of the cylindrical shell are
assumed to be known. The parameter to be identified is the elastic modulus of the inner
layer £2-
According to the above mentioned method at first the so-called reduced elastic
modulus Epriv (modulus of inelastic buckling) is determined from the compression
experiment of a cylindrical shell. The cylindrical shell is assumed to be single-layered with
thickness t=t\+t2. Then the step-down ratio for the elastic modulus K=E\/Epnv is introduced.
Further a Finite Element model for the problem of compression of a two-layer cylindrical
shell is built by using software package ANSYS. The Finite Element model is built by
using SHELL181 element which allows multi-layer properties.
Further the series of calculations of the cylindrical shell with different elastic
modulus of the inner layer are carried out. Obtained results are tabulated and then on the
basis of theses tables the graph of the dependence of the relative Young's modulus E\/Epi^
from the logarithm of the ratio of the elastic modulus of layers lg{E\IEi) is constructed