Model Development for Estimation of Failure Loads: A Case Study of Composite Plates with Single Pin-Loaded Hole

IJSRD - International Journal for Scientific Research & Development| Vol. 1, Issue 05, 2013 | ISSN (online): 2321-0613
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Model Development for Estimation of Failure Loads:
A Case Study of Composite Plates with Single Pin-Loaded Hole
K. Sridevi1
A. Satyadevi2
1, 2
Mechanical Engineering Department
1
Faculty of Tech. & Engg.(M. S. University),Baroda 2
G. I. T. A. M. University, Hyderabad
Abstract--- This paper deals with the study of failure loads
of glass vinylester composite plates with a circular hole
subjected to a traction force by a rigid pin. These are
investigated for two variables, the ratio of distance from the
free edge of the plate (E) to the diameter of the hole (D) and
the ratio of width of the plate (W) to the diameter of the hole
(D). The work consists of a numerical study of different
specimens using finite element analysis package ANSYS.
Also, a mathematical model has been developed to
determine the failure loads of different geometry plates. The
results obtained from the numerical study and the
mathematical models are compared with experimental
results from the existing literature and the correlations are
observed for both. A comparison of the experimental results
with the numerical model shows that the numerical model
gives results with correlation co-efficient 0.96. A
comparison of the experimental results with the
mathematical model shows that the mathematical model
gives results with correlation co-efficient 0.99. For
estimation of the failure loads within the range of E/D and
W/D considered for the study, the mathematical model
developed, i.e., Full Cubic Model proves to be more
efficient with the observed values of correlation co-efficient,
Root Mean Square Error and Maximum Absolute Error.
Keywords: composite plates, pin joint, failure load.
I. INTRODUCTION
Composite materials have become very popular and are used
in almost all fields due to their light weight, high strength to
weight ratio, good fatigue resistance, corrosion resistance
etc. compared to metals. The applicability of composite
materials has increased the demand for high reliability
materials in various industries like aerospace, aircraft, and
automobile. In building complex structures several parts
must be joined together. Mechanical joining using bolt or a
rivet is one method for joining parts. The difficulty with this
method is that the presence of a hole in a laminated plate
subjected to external loading introduces a disturbance in the
stress field. Stress concentrations are generated in the
vicinity of the hole making the joint a weak one. The
knowledge of failure strength of a joint helps in selecting the
appropriate joint size in a given application. The capability
of a composite structure to withstand any physical load can
be evaluated either by physical testing or any advanced
computational method. Performing physical tests on
composites is destructive and costly. So, implementing
advanced computational techniques to determine the failure
loads and failure modes are preferred after some
experiments are done.
Many investigators have studied the strength of
mechanically fastened joints in composite structures. Chang
et al. (1982) developed a computer code, which can be used
to calculate the maximum load. Icten et al. (2003)
investigated the mechanical behaviour and damage
development of woven glass fiber-epoxy composite pinned
joint. Vyasaraj and Kakhandki (2005) obtained analytical
solutions for an irregular shaped hole in an orthotropic
laminate. Karakuzu et al. (2006) predicted the failure loads
experimentally and numerically on glass vinylester
composite plates subjected to pin loading. In the numerical
analysis, they used the Hashin failure criterion in order to
determine failure loads and failure modes. LUSAS
commercial finite element software was utilized during their
analysis. Sridevi and Satyadevi (2006) carried out
numerical analysis to determine failure loads and failure
modes using ANSYS and then compared it with the
experimental results. Later the numerical analysis was done
to find the effect of different geometric parameters on the
failure loads and failure modes of specimens. Whitworth et
al. (2008) investigated the characteristic dimensions in
tension and compression using point stress failure criteria
and Yamada-Sun failure criteria. Nanda et al. (2009) studied
the effects of various geometric parameters on the behaviour
of three and four-pin joints in glass fiber/epoxy composite
laminate with emphasis on pitch-to-diameter ratio.
Numerical analysis was performed using a two-dimensional
finite element model to study the propagation of damage by
implementing Tsai–Wu failure criteria to predict failure load
and to differentiate failure modes. Experiments were
conducted to validate the results obtained from finite
element analysis. Aktas (2011) has done experimental and
numerical study to determine the failure behaviour of glass
epoxy composite plates with single and two holes. The
numerical study was performed by using ANSYS and
Yamada-Sun failure criteria were used. Ozen and Sayman
(2011) investigated experimentally and numerically the first
failure load and the bearing strength behaviour of pinned
joints of glass fibre reinforced woven epoxy composite
prepregs with two serial holes subjected to traction forces by
two serial rigid pins. Ondurucu (2012) has studied the
effects of joint geometry and stacking sequence on the
bearing strength and damage mode experimentally. Damage
progression was examined by using scanning electron
microscopy on specimens loaded up to ultimate failure.
Rahimi et al. (2012) has performed the Last Ply Failure
analysis of a laminated composite plate. The analysis is
carried out by employing Maximum Stress and Tsai-Wu
failure criteria. Khashaba et al. (2013) has dealt with the
failure and reliability analysis of composite pinned-joints
using theoretical models based on Weibull distribution
functions with experimental results for a guideline of safe
design strength. In the present work both numerical and
mathematical models are developed to determine the failure
loads of different pin loaded glass vinylester composite

Model Development for Estimation of Failure Loads: A Case Study of Composite Plates with Single Pin-Loaded Hole
(IJSRD/Vol. 1/Issue 05/2013/056)
plates. The results are later compared with experimental data
given by Karakuzu et al. (2006).
II. PROBLEM DEFINITION
In the present work a composite rectangular plate, shown in
Fig. 1, of length L+E, width W and thickness T is
considered. A hole of diameter D is present at a distance E
from one edge of the plate. A rigid pin is located at the
centre of the hole. A load P is applied to the plate along the
longitudinal axis. The plate is symmetric with respect to the
longitudinal axis. The diameter of the hole is taken as 5mm,
total length of the plate L+E as 200mm and thickness of the
plate T as 2.8mm.
The material properties considered are shown in
Table 1 given by Karakuzu et al. (2006). Different models
are obtained by varying E/D and W/D but keeping the
parameters D and T as constant. These models are analyzed
using Finite Element package ANSYS. Also, a mathematical
model is developed to obtain the failure loads of different
specimens. A comparison of both models with experimental
results is made and correlations are observed.
E1=E2
MPa
G12
MPa
µ12 Xt =Yt
MPa
XC=YCMPa S
MPa
Vf
%
20769 4133 0.09 395 260 75 63
Table. 1: Material properties of the plate.
III. NUMERICAL ANALYSIS
The Finite Element method was chosen for numerical
analysis of the model due to its unique capability to analyze
structures of complex material behaviour. The model was
developed by using ANSYS software. The Maximum Stress
theory is used to check the failure criterion. A two
dimensional model of the specimen is built. The specimen
has symmetry about the longitudinal axis. Therefore one
half of the model is created. A symmetry condition is
applied on the model along the longitudinal axis. The pin
located at the centre of the hole tries to compress one half of
the hole because of the load acting in the other direction. It
is considered as a radial constraint on the hole. The
boundary conditions applied on the finite element model are
as shown in Fig. 2 and Fig. 3. The model is meshed using
PLANE42 from the ANSYS element library.
Fig. 2: Model showing the boundary conditions
Fig. 3: Enlarged view of the hole showing the radial
constraint
The Failure of the specimen takes place either due to
tension, compression or shear. To check whether failure has
occurred, the failure criterion option available in ANSYS is
used. At this point the maximum induced stress in the
specimen reaches one of the permissible stresses viz. tensile,
compressive and shear stresses. The failure mode is decided
depending on which stress has reached its permissible limit
first. This procedure is continued with different specimens.
Different specimens are obtained by varying the geometric
proportions of the model. The geometry is varied by taking
W/D as 2, 3, 4 and 5 and for each W/D, E/D varying from 1
to 5. These specimens are analyzed for their failure loads
and compared with the available experimental results.
IV. MATHEMATICAL MODELING
A mathematical model has been developed to predict the
failure loads of specimens with different geometries using
curve expert. The model has been built with the available
experimental results. The equation has two independent
variables in W/D ratio as x1 and E/D ratio as x2. The
dependent variable considered here is the failure load P. The
thickness of the specimen and the diameter of the hole are
constant for all the specimens. A Full Cubic polynomial
equation is found to be best suited to determine the failure
loads for the existing problem. This equation can be used to
predict the failure load of specimens with other geometric
parameters within the given range i.e. for E/D and W/D
ratios for which experiments have not been done. The
limitation with the model is that the failure mode is not
predicted. But, we know that for higher values of E/D and
W/D the shear strength and normal strength of the plates
increase, so specimen tends to fail in bearing mode only.
Hence, the mathematical model is best suited to obtain the
results for failure loads. The equation developed is found to
be
P = a + b*x1 + c*x2 + d*x1
2
+ e*x2
2
+ f*x1
3
+ g*x2
3
+
h*x1*x2 + i*x1
2
*x2 + j*x1*x2
2
Where in the values of the co-efficients a, b, c, d, e,
f, g, h, i and j are given in Table 2 and graphical
representation of the model is shown in Fig. 4.
a b c d e
-2196.31 2636.96 1515.40 -670.57 -404.52
f g h i j
58.20 33.94 54.48 -12.08 7.44
Table. 2: Co-efficients of the Full Cubic Model Developed

Fig. 4: Full Cubic Model Developed
V. RESULTS AND DISCUSSION
The failure loads of specimens obtained by varying the E/D
and W/D ratios are found by numerical technique and also
from mathematical model. Numerical models are developed
using ANSYS. A comparison of the failure loads obtained
from experimental, numerical and mathematical model have
been made. Shown in the Fig. 5 and Fig. 6 are the graphs
plotted for the failure loads of specimens obtained from
experimental, numerical and mathematical models for
different W/D ratios and E/D ratios. All the three methods
show the same trend in the failure loads but the results
obtained by the mathematical model are close to the
experimental results. It is observed from the results obtained
that For a constant W/D ratio, the failure strength of the
specimen increases with increase in E/D. This is because
keeping the diameter of hole constant, when E/D increases,
the distance of the hole from one edge of the plate increases
which increases the shear strength of the specimen.
 With the increase in W/D ratio, keeping E/D ratio
constant, the failure load of the specimens increase.
This is because as W/D increases and hence the
width of the specimen, the normal strength of
specimen increases.
 Both numerical and mathematical models show the
same trend in failure loads with varying E/D and
W/D ratios.
 A comparison of the experimental results with the
numerical model shows that the numerical model
gives results with Correlation Co-efficient 0.96,
Maximum Absolute Error as 286N and Root Mean
Square Error as 162N.
A comparison of the experimental results with the
mathematical model shows that the mathematical model
gives results with Correlation Co-efficient 0.99, Maximum
Absolute Error as 176N and Root Mean Square Error as
80N.
Fig. 5: Comparison of results for constant W/D ratios

Fig. 6: Comparison of results for constant E/D ratios
VI. CONCLUSIONS
In the present work, failure loads of glass vinylester
composite plates with singe pin holes were studied by
mathematical modelling and numerical analysis using finite
element method for the geometrical parameters W/D and
E/D. Maximum stress theory was used to predict failure
loads by finite element analysis using ANSYS and a
mathematical model has also been developed for the same
using Curve Expert. A comparison of the both with the
experimental results show that
 The specimen is weak for lower values of E/D and W/D
and so failure occurs at small loads.
 E/D ratio has a greater effect on the failure load of the
specimen.
 As for higher values of E/D and W/D ratios, the
specimen generally fails in bearing mode only, and
hence the failure loads are the important parameters to
be analyzed, wherein the mathematical models prove to
be more efficient.
 The numerical model when compared with the
experimental results gives results with Correlation Co-
efficient 0.96, Maximum Absolute Error as 286N and
Root Mean Square Error as 162N.
 The mathematical model when compared to
experimental results gives results with Correlation Co-
efficient 0.99, Maximum Absolute Error as 176N and
Root Mean Square Error as 80N.
 For estimation of the failure loads within the range of
E/D and W/D considered for the study, the
mathematical model developed, i.e., Full Cubic Model
proves to be more efficient with the above given values
of Correlation Co-efficient, Maximum Absolute Error
and Root Mean Square Error.
REFERENCES
[1] Aktas, A., 2011, Failure analysis of serial pinned joints
in composite plates, Indian Journal of Engineering and
Material Sciences, Vol 18, 102-110
[2] Chang., F.K., Scott, R.A., Springer, G.S., 1982,
Strength of mechanically fastened composite joints,
Journal of Composite Materials; 16:470-494
[3] Icten, B.M., Okutan, B., Karakuzu, R., 2003. Failure
strength of woven glass fiber-epoxy composite pinned
joint. Journal of Composite Materials, vol. 37, no. 15,
1337-1351
[4] Karakuzu, R., Gulem, T., and Icten, B.M., 2006, Failure
analysis of woven laminated glass-
vinylestercomposites with pin loaded hole, Composite
Structures, 72 (1), 27-32
[5] Khashaba, U.A., Sebaey, T.A., Alnefaie, K.A., 2013,
Failure and reliability analysis of pinned-joints
composite laminates: Effects of stacking sequences,
Composites: Part B, 45 (2013) 1694–1703
[6] Nanda, A.K., Malhotra, S.K., Prasad, N.S., 2009,
Failure analysis of multi-pin joints in glass fibre/epoxy
composite laminates. Composite Structures, 91:266–77
[7] Ondurucu, A., 2012, Progressive failure analysis of
glass–epoxy laminated composite pinned-joints,
Materials and Design 36, 617–625
[8] Ozen, M., Sayman, O., 2011, Failure loads of
mechanical fastened pinned and bolted composite joints
with two serial holes, Composites: Part B 42, 264–274
[9] Rahimi, N., Hussain, A.K., Meon, M.S., Mahmud, J.,
2012, Capability Assessment of Finite Element
Software in Predicting the LastPly Failure of Composite
Laminates, International Symposium on Robotics and
Intelligent Sensors 2012 (IRIS 2012), Procedia
Engineering 41, 1647 – 1653
[10] Sridevi, K., Satyadevi, A., 2006, Failure analysis of
pin-loaded composite plates, Proceedings of 51st
Congress of The Indian Society of Theoritical and
Applied Mechanics (ISTAM),College of Engineering,
Andhra University, 18-21 Dec.,2006
[11] Vyasaraj and Kakhandki, 2005, Stress analysis of an
orthotropic plate with an irregular shaped hole for
different in-plane loading conditions-Part 1, Composite
Structures, 70, 255-274
[12]Whitworth, H.A., Aluko, O., Tomlinson, N.A., 2008,
Application of point stress criterion to the failure of
composite pinned joints, Engineering Fracture
Mechanics 75, 1829-1839.

Model Development for Estimation of Failure Loads: A Case Study of Composite Plates with Single Pin-Loaded Hole

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Model Development for Estimation of Failure Loads: A Case Study of Composite Plates with Single Pin-Loaded Hole