30120140502017

International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 2, February (2014), pp. 149-161, © IAEME
149
MOLDING PROCESS INDUCED ANISOTROPY EFFECT ON BUCKLING
ANALYSIS OF FIBER- FILLED PLASTIC CRC PUSH ROD
R. Joseph Bensingh, M. Santhosh, S. Ilangovan
Advanced Research School for Technology and Product Simulation (ARSTPS),
Central Institute of Plastics Engineering and Technology, Guindy, Chennai-600032
ABSTRACT
Fiber-filled plastic materials are commonly used in metal replacement applications. The
combination of low weight and high stiffness makes fiber-filled plastics ideal for high-performance
applications. The key to unlocking the potential of these plastics lies in the orientation of the fibers.
The orientation direction and the degree of orientation of the fibers determine the mechanical
properties of the molded part. The injection moluding process for fiber-filled parts can cause great
variation in strength throughout a part, the effects of the injection process should be considered in the
design of such a part. In order to enable product designers to incorporate the strength variations of
fiber filled, injection-molded components into mechanical analyses of those components by coupling
of Moldflow injection molding simulation tools together with finite element analysis (FEA)
software. By using this approach Design engineer can explore different design scenarios that will
produce cheaper parts, while ensuring sufficient strength in highly loaded areas. In this paper, a Non
Linear Anisotropic buckling analysis is carried out on CRC push rod component of hydraulic clutch
actuation systems by coupling Moldflow with ANSYS. A comparison is made between the results
from non linear isotropic and non linear anisotropic analysis with experimental results to understand
the mechanical performance of the part. Simulation results are able to predict the observed
mechanical behavior of fiber filled plastic components when the anisotropy of the material is taken
into consideration. Traditional approach of treating the material property as isotropy overestimates
the stiffness of the part. Also, modeling of flow is able to quantify the anisotropy generated in the
part during its fabrication process.
Keywords: Fiber Filled Plastic, Anisotropic, Buckling Analysis, CRC Push Rod, ANSYS –
Moldflow Interface.
INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING
AND TECHNOLOGY (IJMET)
ISSN 0976 – 6340 (Print)
ISSN 0976 – 6359 (Online)
Volume 5, Issue 2, February (2014), pp. 149-161
© IAEME: www.iaeme.com/ijmet.asp
Journal Impact Factor (2014): 3.8231 (Calculated by GISI)
www.jifactor.com
IJMET
© I A E M E

150
ABBREVIATIONS
CAD Computer-Aided Design
CAE Computer-Aided Engineering
CRC Clutch Release Cylinder
MISO Multi linear Isotropic material
MPI Moldflow Plastics Insight
1. INTRODUCTION
Because of the many advantages of using plastic materials, there is an ongoing trend of
replacing metal with injection-molded plastic parts in variety of applications. Plastics are
lightweight, durable and corrosion-resistant; have a high strength-to-weight ratio; and, when used in
transportation applications, for example, offer one of the easiest ways to increase fuel savings by
making vehicles more lightweight. Lightweight plastics allow automotive designers and engineers
the freedom to deliver innovative concepts cost effectively. From an aesthetic perspective, plastics
and plastic composites offer the automotive designers distinct advantages in many applications.
Fiber-filled plastic materials are commonly used in metal replacement applications. When glass or
carbon fibers are added to plastics, the elastic modulus can increase significantly with a negligible
effect on part weight. This combination of low weight and high stiffness makes fiber-filled plastics
ideal for high-performance applications. The key to unlocking the potential of these plastics lies in
the orientation of the fibers. The orientation direction and the degree of orientation of the fibers
determine the mechanical properties of the molded part. In areas where fibers are strongly aligned,
the material will have higher strength characteristics in that direction, but will be relatively weak in
the perpendicular direction (across the fibers). In areas where the fibers are more randomly oriented,
the material will not achieve maximum strength, though the strength properties will not depend as
much on the loading direction, creating a more isotropic like material. But fiber reinforced plastics
typically show anisotropic mechanical, thermal and rheological properties. Therefore, prediction of
fiber orientation during the transient mold filling is important for the prediction of such anisotropic
properties of final plastic part.
During the injection molding process, the fibers in the plastic melt will orient in different
directions under the influence of shear forces that are driven by the flow patterns .Figures 1 and 2
show the velocity profile and fiber orientation for a melt flow across thickness. The degree of
orientation and the dominant direction of the fibers change throughout the part. The fibers in the mix
get oriented along the local velocity vector and because of the variation of velocity across the
thickness the fiber orientation also varies across the thickness of the part. This will result in material
properties being different at different locations of the part i.e. anisotropy of modulus of the part
based on the local orientation of the fibers.
Fig. 1: Velocity and shear rate profile of melt Fig. 2: Fiber orientations along thickness

151
In normal Design engineers typically solve this kind of problem by using highly non isotropic
materials by applying generous safety factors to their designs, making them thicker than is actually
required. This led to not only waste of raw materials and cost, but also on cycle time. A simple rule
of thumb for injection molding is that when the thickness is doubled, the production time quadruples.
For effective design of short-fiber reinforced polymer based composites; CAE (Computer Aided
Engineering) can play an important role. Characteristics of polymer and particle-contained
suspensions being highly nonlinear and complex, only CAE can provide reasonable solutions. This
technique offers a detailed and accurate simulation of processes in shorter time and lesser cost than
traditional experiments and tests. The results can be used to identify the areas where orientation of
the fibers is not suitable for a design. However, most commercial packages use rather simplified
models and approximate numerical algorithms to calculate fiber orientation distribution. Refinement
in modeling and numerical prediction of fiber suspension for better prediction is one area of focus for
current research activities.
2. LITERATE REVIEWS
A number of researchers have studied the flow induced anisotropy in fiber-filled plastics
employing analytical and experimental methods. Recently, linear orthotropic analysis is carried out
on ash tray door component by coupling Moldflow with ANSYS by [1] P. Satheesh Kumar, S.
Srikari, N. S. Mahesh, S. Reddy. Based on there work the following points are drawn from there
paper.
1) A finite element modeling approach can be used to predict the influence of process induced
anisotropy in fiber-filled plastic parts.
2) Anisotropy induced due to manufacturing process has a major impact on mechanical
performance of a component.
3) In a molded part, fiber orientation and density, both governed by flow pattern in the mold,
result in modulus value different at different points in the part, and also, different in three
principle directions at the same point.
4) Anisotropy can change the stiffness characteristics of a part by more than 50%.
5) Material anisotropy is affected by the flow pattern in mold. Hence, change in mold design can
be used to tailor the stiffness characteristics of a part.
[2] Ashok K Kancharla, Harindranath Sharma K, and Paul Nugent are carried outed the
Experimental techniques and numerical studies to compare the isotropic and anisotropic behaviors of
a fiber-filled plastic bolt. They conducted flow and structural analysis on a plastic bolt, using
Moldflow and Abaqus. Their results showed that the simulation results with anisotropic property
were within 4% of experimental results (Fig. 3). According to them this proves the capability of
anisotropic structural analysis in predicting the results accurately for a short fiber filled thermoplastic
material.
Fig. 3: Variation of deflection with pressure

152
[3] Chung and Kwon carried out finite element analysis for fiber suspensions using Pseudo
Concentration method as a melt-front capturing technique. They found that including fountain flow
effect induces wide core layers of orientation distributions and consequently simulation results match
experimental data. Also, the coupling effect between fluid and fiber is important near the core and
transition layers, even far downstream in the flow direction. The numerical studies of viscoelastic
polymer dynamics must accompany with general 3D geometry because of the importance of melt
front or gate region on the orientation states. Also, experimental data for various complex geometries
must be obtained to understand detailed orientation dynamics and rheology. It was stated that
suspension rheology and particle dynamics must be understood for more highly concentrated
suspensions in the near future, then fiber to fiber interaction could be better understood
The literature reveals the need for analysis of flow induced anisotropy for improving design
and performance of fiber-filled material. Due to the complex flow behavior very few computational
studies have been reported previously. In the current work, numerical simulations of a CRC push rod
component of hydraulic clutch actuation have been carried out to provide an insight into the physics
of the flow characteristics and structural performance of a filled material.
There is only some simulation technique available for the simulation of thermoplastics
because of their material nonlinearity. In this paper repeated use will be made of the finite element
method to identify significant issues and provide evidence of the accuracy with which engineering
analysis of plastic parts can be conducted. Although it is not within the scope of this work to provide
a detailed description of this analysis approach, some general level of understanding of this analysis
method will be useful. There is a significant difference between simulation and test results for
thermoplastics necessitating comparison studies as in the scope of this paper to increase the
correlation between test and simulation.
In this paper, results of modeling and simulation of fiber-filled plastics with process induced
anisotropy have been presented. Moldflow has been used to simulate the manufacturing process
(injection molding) and ANSYS has been used to simulate the structural Buckling performance of
the CRC push rod component At Two different cases, as described below, and results have been
compared with test results.
Case 1: Simulation technique based on material models (Multi-linear isotropic material model)
Case 2: Simulation technique based on interface based simulation tools (Mold flow-ANSYS
interface)
3. GEOMETRIC MODELS AND ANALYSIS METHODOLOGY
The model used for this study is a push rod which is the part of the Clutch release Cylinder
(CRC) of a hydraulic clutch activation system show in Fig 4. The Function of Push rod is to
transfermation the motion from CRC cylinder piston to clutch Fork .Push rod is subjected to only
axial loads so it behave like column. In normal short column under the action of an axial load will
fail by direct compression before it buckles, but a long column loaded in the same manner will fail
by buckling (bending), the buckling effect being so large that the effect of the direct load may be
neglected. Buckling is characterized by a sudden failure of a structural member subjected to high
compressive stress, where the actual compressive stress at the point of failure is less than the ultimate
compressive stresses that the material is capable of withstanding.

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Fig. 4: Location of push rod in Clutch release Cylinder
The Geometric model of the push rod is created in CATIA V5 as for the dimensions as
shown in Fig.5.
Fig. 5: Geometric model of the CRC Push Rod
Figure 6 shows the Details of the analysis methodology to conduct the flow and structural
analysis in the first case of the methodology, CAD model was imported into ANSYS and loading,
boundary conditions are applied for isotropic material model for find out the buckling load. In the
Second case material Flow Simulation of the component is carried out by using Moldflow. The result
of this analysis, which includes information about fiber orientation, is then exported to ANSYS
where finite element model for structural analysis is created. For anisotropic analysis, Information
about fiber orientation, obtained from Moldflow analysis, is used to determine the buckling load of
push rod.
Fig .6: Methodology for Push rod buckling analysis

154
3.1 Details of the numerical models for analysis
ANSYS was used to carry out the structural analysis. The CAD model was imported into
ANSYS and meshed with solid 187 tetrahedral elements. Boundary conditions were specified in
ANSYS and first an analysis with Multi-linear isotropic material model was carried out to get the
Buckling load (Case 1). The material specified for the analysis was PA66 GF50% (Zytel73G50
HSLABK416) from DUPONT engineering polymers with a elastic modulus of 11688 MPa at
temperature of 230
.
3.2 Boundary conditions for analysis
Boundary condition used for non linear buckling analysis of push rod are described below
and are shown in Fig .7
1) At pilot node UZ displacement is applied axially and all other DOF are locked to achieve the
buckling load.
2) At bottom face of the push rod all DOF are locked.
3) For reducing the computational time of analysis, some disturbance load is applied in positive
x and negative y direction to initiate the buckling.
To determine the buckling load, axial displacement is applied instead of force on the pilot
node. Based on reaction force that is developed on the pilot node buckling load is determined.
Fig .7: Boundary Conditions used for structural analysis
4. STRUCTURAL ANALYSIS AND FLOW SIMULATION
4.1 Case 1: Simulation technique based on material models
Thermoplastic exhibit complex behavior when subjected to constant, increasing or cyclical
mechanical loads. As these materials begin to be used more in load-bearing designs, we must be able
to predict the structural performance of actual modeled parts. The design element involves creating
geometry and performing analysis to predict part performance. Engineering design requires
mechanical properties to define material behavior adequately and accurate analysis techniques to
predict generic part performance based on those data. For this type of simulation technique the
material property provided for simulation, will be taken from standard data provided by the
manufacturers after conducting some tests on the standard specimen. Simulation technique based on
material model is given below.

155
Multi-linear isotropic material model
The non linear buckling analysis carried out for multi-linear isotropic material model with the
following Stress vs Strain curve data at 230
C for the material PA66 GF50% (Zytel73G50
HSLABK416) is shown in fig .8 and the stress strain data is listed in table 1.
Fig. 8: Stress vs Strain curve for MISO material model
Table .1 Stress vs Strain values for the MISO material model
Strain Stress
0.0032 37.4
0.0051 57.3
0.0066 72.2
0.008 84.4
0.0093 94.4
0.0121 112
0.0149 127
0.0165 134
0.0182 141
0.0218 152
0.0366 167
Buckling load obtained from this analysis was about 7255 N is shown in fig.9 .This curve is
draw for the reaction force obtained at pilot against to the displacement at the pilot node in z
direction
Fig .9: Displacement vs. Load curve at pilot node for MISO material model

156
Buckling mode shape of the push rod for MISO material model is shown fig.10
Fig .10: buckling mode shape of push rod for MISO material model
Von mises stress contour for push rod is shown in Fig.11.From this contours we can see that
the max von mises stress of push rod reached max stress value definde by stress vs strain curve.
After this value the part will strart get fail (plastic defromed).
Fig. 11: Von mises stress contour MISO material model
4.2 Case 2: simulation technique based on interface based simulation tools (Mold flow-ANSYS
interface)
The results of a Moldflow simulation include calculations of material properties with fiber
orientation and residual stresses in the plastic part. These data's are given as a input for structural
analysis in Ansys. The work flow of this interface is shown in below Fig.12

157
Fig .12: Work Flow between Moldflow and ANSYS
4.2.1 Flow Simulation
The CAD model of the Push rod is imported in Hypermesh and surface of the push rod
was meshed very fine and after checking quality, exported in Moldflow readable format. The surface
meshed model from Hypermesh is imported in to Moldflow insight software for the mouldflow
simulation. In Mold flow the Push rod with 2D surface mesh is converted into 3D mesh to do flow
simulation. The meshed Push rod model with The injection gate location used for flow stimulation is
show in Fig 13.
Fig.13: Injection gate location for Push rod mold stimulation
Process boundary condition like filling time, packing pressure, holding pressure, injection
time, velocity etc. are directly affect the component material properties in molding process .So
proper process condition are needed to accurate mold flow stimulation. The process boundary
condition used for CRC push rod mold flow stimulation are listed in Table 2
Table 2: Moldflow process boundary conditions for Push rod molding
Material PA66 GF50% (Zytel70G50
HSLA BK039B)
Melt temperature 2870
c
Mold temperature 100 0
c
Injection time 0.6 s
Switch-over Velocity/Pressure ( By %volume filed) 99
Packing/Holding
Pressure
Packing Pressure 50Mpa
Time 7s

158
The material processing of the Push rod component for the specified process boundary
conditions is simulated using Moldflow (MPI). Mold flow has the capability to predict the fiber –
orientations and then calculate the mechanical properties based on these orientations. The random
fiber orientation of the push rod after the molding stimulation are shown in Fig.14
Fig: 14: Random fiber orientation tensor contour of the push rod
The stimulation results generated by MPI are binary files. In order to be used in ANSYS,
these files need to be converted to ASCII format. An API script is available that automatically
converts the necessary result and mesh files into a format that ANSYS can use. API uses the
mpi2ans.vbs, command to convert the files for ANSYS readably format. The MPI results are
exported in *.mts,* ist format the 3D mesh is exported in ANSYS input *.cdb format. The exported
files are imported in to ANSYS to do the Buckling analysis.
For this material model the Von mises stress contour shown in fig.15.Based on Von misses
failure criteria. The von misses stress of push rod is reached failure stress value (250) at
displacement 0.699 mm and the corresponding load that is cause this displacement is consider as
buckling load.
Fig. 15: Von mises stress contour for interface material model
The obtained Buckling load for causing of 0.699mm displacement was about 5732 N is
shown in fig.16.This curve is draw for the reaction force obtained at pilot against to the displacement
at the pilot node in z direction.

159
Fig .16: Displacement vs. Load curve at pilot node for interface material model
4.3 Experimental test
The experimental test is carried out on the UTM (universal testing machine) for the push rod
component. Sample parts for testing are prepared by injection moulding. Then those test sample parts
are placed in UTM and compression load is gradual applied to find out the buckling load of the push
rod. After experimental Tested push rod parts are sown in Fig .17.
Fig. 17: push rod mode shapes after experimental test
Average buckling load obtained for this experimental test is about 6120 N shown in Fig
18.This curve is drawn against the time vs applied load
Fig. 18: Time vs applied load curve for the experimental test

160
5. RESULTS AND DISCUSSIONS
Buckling load obtained for two cases with two different material models are compared with
test results is shown in table 3 and Fig. 19
Table.3: Comparison of buckling load with test result for different material models
Fig. 19: Comparison of buckling load for different material models
From above results following observation is drawn.
1) The buckling load is varying for different material models to cause the same amount of
displacement.
2) From curve we can also observe that in MISO material model the load is decreasing with respect
displacement after buckling load is reached .This is due to the plasticity affect of the non liner
material model.
3) But in anisotropic material the load is increase linear with displacement after buckling load
Because of the material strength in other direction are capable of carrying load even through the
material get plastic deformation in one direction
Results presented above demonstrate the necessity and accuracy of Anisotropy Buckling
analysis over isotropic buckling analysis for glass fiber filled thermoplastics. Precise modeling of the
experimental setup is necessary to predict the results accurately. The CAE analysis results
considering Anisotropy material properties, closely match with the experimental data within a
variation of 6%. This proves the capability of Anisotropy Buckling analysis in predicting the results
accurately for a glass fiber filled thermoplastic material.

161
6. CONCLUSIONS
Based on above results, it can be observed that the simulation tools, for molding process and
for structural analysis with anisotropic material properties, can be successfully used in tandem to
predict the Buckling behavior of molded components made out of glass fiber filled thermoplastic
material. It is important that this approach is used, rather than designing the component assuming the
material property to be isotropic, because the approximation can be very erroneous.
Based on the simulation results presented above, the following conclusions were drawn
1) As analyzed, it will be inappropriate to consider isotropic material properties for the simulation
of short fiber filled thermoplastics.
2) By using the interface simulation technique we can accurately predict the structural analysis
occurs.
3) A finite element modeling approach can be used to predict the influence of process induced
anisotropy in fiber-filled plastic parts.
4) Anisotropy induced due to manufacturing process has a major impact on mechanical
performance of a component.
5) Material anisotropy is affected by the flow pattern in mold. Hence, change in mold design can
be used to tailor the stiffness characteristics of a part.
REFERENCES
1. P. Satheesh Kumar, S. Srikari, N. S. Mahesh, S. Reddy, structural analysis of fiber- filled
plastics With moulding process induced anisotropy, SASTECH Journal Volume 9, Issue 2,
September 2010.
2. Ashok K Kancharla, Harindranath Sharma K, and Paul Nugent, Orthotropic Structural
Analysis of Short Fiber Filled Thermoplastics: Abaqus- Moldflow Interface, Experimental
Validation, SIMULIA India Regional Users Meet, 2009.
3. Du Hwan Chung and Tai Hun Kwon, Fiber Orientation in the Processing of Polymer
Composites, Korea-Australia Rheology Journal Vol. 14, No. 4, pp. 175-188, December 2002.
4. José Luis Manzanares Japón, Ignacio Hinojosa Sánchez-Barbudo, Non-linear plastic analysis
of steel arches under later buckling, journal of construction steel research volume 67, Issue 12,
December 2011, Pages 1850-1863.
5. Santhosh M, Joseph Bnsingh R, “Structural analysis of fiber- filled plastics with molding
process induced anisotropy: Ansys - Mold flow Interface and Experimental Validation”
International conference ANTEC Mumbai 2013 held on December 06-07, 2012 at Mumbai.
6. Autodesk, Moldflow reference manuals and help files, Autodesk Moldflow 2010.
7. Ramesh Chandra Mohapatra, Antaryami Mishra and Bibhuti Bhushan Choudhury,
“Investigations on Tensile and Flexural Strength of Wood Dust and Glass Fibre Filled Epoxy
Hybrid Composites”, International Journal of Mechanical Engineering & Technology
(IJMET), Volume 4, Issue 4, 2013, pp. 180 - 187, ISSN Print: 0976 – 6340, ISSN Online:
0976 – 6359.
8. M.G. Rathi and Manoj D. Salunke, “Reduction of Short Shots by Optimizing Injection
Molding Process Parameters”, International Journal of Mechanical Engineering & Technology
(IJMET), Volume 3, Issue 3, 2012, pp. 285 - 293, ISSN Print: 0976 – 6340, ISSN Online:
0976 – 6359.

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