Volume Fiber fraction effect on stress concentration factor of a finite plate with different hole
geometries
Abstract
The main objective of this paper is to study volume fiber fraction effect on stress concentration factor of a composite
lamina. Volume fiber fraction is an important parameter for evaluating stress concentration factor for a hole in a composite lamina.it
has been studied in commercial software named Ansys APDL. By taking different materials graphite-epoxy, glass-epoxy and
aramid-epoxy same results are obtained.to make a parametric study MATLAB GUI is used as a tool for generating APDL code.
Keywords: Stress concentration factor, fiber volume fraction, APDL
1. Introduction:
2 . Review of literature:
A composite is a structural material that
consists of two or more combined constituents that are
combined macroscopic level and are not soluble in
each other[1-autar kaw] .Composite plates are used in
many engineering applications like automobile,
aircraft, aerodromes, space structure technology, Gas
turbine engine components(high temperature and
oxidation resistant applicaton).[1,2LNM11.PDF
Nptel].the main advantage of using composites is its
high strength to weight ratio as well as high stiffness
to weight ratio. various studies have been done in
composite field in terms of plates with hole. For
Various joints holes or cut-outs are made on composite
plates which reduces strength of material. So it is very
essential to study hole or cut-out effect on stress
concentration. Stress concentration factor can be
found using three approaches:1) Finite element
Analysis 2) Experimental (Photo Elasticity, Strain
gauge etc.) 3) Analytical formulation.
Dheeraj Gunwat and J.P. singh have studied
stress and displacement analysis of a rectangular plate
with Central Elliptical Hole. [3]. They studied effect
using Finite element approach. Dharmendra S. Sharma
has studied effect of stress distribution around
polygonal holes under biaxial loading for isotropic and
anisotropic material [4]. he used complex variable
approach and after finding general solution for
different boundary conditions analyzed in ANSYS. He
has studied effect of the hole geometry and loading
pattern on stress concentration factor for infinite plate.
Generalized formulation to determine the stresses
around the polygonal shaped hole in anisotropic finite
plate was studied by Mihir M. Chauhan and
Dharmendra S. Sharma [5]. They formulate analytical
equation using complex variable approach with the
help of boundary collocation method.it was also
validated using ANSYS approach for both anisotropic
and isotropic material. Hole location, load direction,
no of sides in polygon, orientation of polygon greatly
influences on stress concentration factor [5]. The
corners of the polygonal shaped holes are the points of
stress concentration in the plate. [5]. Prabhu et al.
experimentally investigated effect of fiber orientation
around circular hole in symmetrically laminated
hybrid composite plate in uniaxial tensile. [6] The SCF
was found to be least for 00 for ply orientation and
maximum for 900 ply orientation.M.yasar & M.Arslan
studied SCF around a hole for layers having different
oriented fibers using different material with different
E1/E2 ratio.(ratio of elastic modulus of longitudinal to
transverse).[7].the ratio of bi-axial loading (ratio of xdirection loads to y-direction loads) is also important
to calculate desing characteristic of a layer.it was
found that as the fiber orientation changes, maximum
stress value around the hole and angular location of
that stress value changes in a laminated composite
plate.[7].Lotfi Toubal et al. has studied the effect of
stress concentration in a circular hole in composite
plate.[8].he
used
all
three
approaches
Here the objective is to study the effect of one
of the different parameters which was volume fraction
of the fiber on Stress concentration factor in finite
lamina under the application of unidirectional load.
FEA technique was used for this work. Different
variations like hole shape, size, length and width of
plate and its location, materials, volume fraction of
fibers has been included in GUI. MATLAB GUI was
prepared for doing parametric studies which will give
the code that is to be fed in ANSYS APDL.the analysis
is done under plane stress condition. PLANE182
element is used for analysis. The Stress concertation
factor was obtained for different hole geometries like
circle, ellipse, rectangle etc. By varying fiber volume
fraction corresponding Stress concentration factors are
found and the graphs are plotted for different hole
geometries and materials. We have used three
materials: graphite-epoxy, glass epoxy and aramid
epoxy. All three materials show the same behavior.
experimental,ansys analysis and theroretical approach
using Lekhnitski’s et al equation.[8]. In experimental
work, three sequences of orientation are used in a uniaxial tensile test. Near of the hole , the stress obtained
in experimens is definitely lower compared to the
anaylatical and numerical models[8] .