Experimental & Finite Element Analysis of Buckling Strength of Various Structural Cross Sections of Conventional and Composite Material for Weight Reduction

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Experimental & Finite Element Analysis of Buckling

Strength of Various Structural Cross Sections of

Conventional and Composite Material for Weight

Reduction

I. G. Bhavi

Assistant Professor Department of Automobile Engineering, V.P Dr P.G Halakatti College of Engineering & Technology

Vijaypur KARANATAKA, INDIA Email: igbhavi @gmail.com

Najeem M.

PG Student, Department of Mechanical Engineering, V.P Dr P.G Halakatti College of Engineering & Technology

Vijaypur KARANATAKA, INDIA Email: [email protected]

Abstract – The prime objective of this present work is to study compressive/buckling strength of different structural cross section like L, C, and Circular of composite material and convectional material mild steel as experimentally and FEM (Finite Element Method) analysis. The various parameters considered for this study are Young Modulus, Poisson ratio, compressive/ buckling strength for a constant weight per unit length ratio.

Also the prime objective of this present work is to study and reduce the weight of the sections keep the strength of composite material same as conventional material mild steel based on compression test which is carried by digital UTM (Universal Testing Machine) and as well as by FEM (Finite Element Method) software.

Keywords – Glass Fiber, Mild Steel, Buckling/Compressive Strength, Weight Reduction.

I. I

NTRODUCTION

Fibers or particles embedded in matrix of another material are the best example of modern-day composite materials, which are mostly structural. Laminates are composite material where different layers of materials give them the specific character of a composite material having a specific function to perform. Fabrics have no matrix to fall back on, but in them, fibers of different compositions combine to give them a specific character. Reinforcing materials generally withstand maximum load and serve the desirable properties. Further, though composite types are often distinguishable from one another, no clear determination can be really made. To facilitate definition, the accent is often shifted to the levels at. The demands on matrices are many. They may need to temperature variations, be conductors or resistors of electricity, have moisture sensitivity etc. This may offer weight advantages, ease of handling and other merits which may also become applicable depending on the purpose for which matrices are chosen. Zdenek Padovec et. al [1]He study that A derivation of the spring forward phenomenon for the unidirectional composite plate, and also for the laminated composite plate with symmetrical lay-up, both influenced with temperature, moisture and the volumetric change during recrystallization, is described in this paper. This method was used for analytical calculation of given laminated C/PPS plate. Residual stresses, which are set in

the fiber reinforced composites during the laminate curing in a closed form, lead to dimensional changes of composites after extracting from the form and cooling. One of these dimensional changes is called “spring forward” (also “spring-in” or “spring back”) of angle sections. Ashish A. Desai et. al[2] He work on Optimum axial stress of I-section beam can be analyzed by varying stacking sequence & fiber orientation. Carbon Epoxy / Glass Epoxy / Glass Epoxy / Glass Epoxy (900/450/450/900) are less than aluminum & steel I-section beam. The weight of composite beam is reduced up to 78% than steel & 66 % aluminum. This is intended to ensure for better designing options for composite laminates of I-beam In structural applications Pardeep Kumar, et. al [3] He study that investigations of mechanical behaviour of glass fibre reinforced epoxy composites revealed that the tensile strength and flexural strength is greatly influenced by the fiber content/ weight fraction of reinforcement in matrix. Kunlin Hsieh [4] He study that analytically investigate the torsional rigidity of laminated composite beams and compare the results with those from the finite element method, finite difference method, and a previous paper (Swanson, 1998).Torsion of cylindrical shafts has long been a basic subject in classical theory of elasticity.B.Ramesh et. al[5] This paper discusses to optimize the process parameter levels within the range examined based on minimum ovality of the drilled hole and thereby attaining high hole quality in drilling non laminated GFRP composite rods using a coated solid tungsten carbide drill.

II. M

ATERIALS AND

M

ETHOD

2.1 Glass Fibers

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chemicals, insulation capacity are other bonus characteristics, although the one major disadvantage in glass is that it is prone to break when subjected to high tensile stress for a long time. However, it remains break-resistant at higher stress-levels in shorter time frames. This property mitigates the effective strength of glass especially when glass is expected to sustain such loads for many months or years continuously.

Fig.1. Types of glass fibers Table 1: Constituents of glass fibers

Constituents E Glass S Glass C Glass

SiO2 54 64 65

Al2O3 15 25 4

CaO 17 <0.1 14

MgO 4.5 10 3

B2O3 8 - 5

Others 1.5 .8 8

2.2 Epoxy Resin

Epoxy resin widely used in industrial applications because of their high strength and mechanical adhesive characteristic. Araldite CAMELET-3321 is a liquid solvent free epoxy resin. It has versatile applications in technical and industrial applications. Curing takes place at room temperature and atmospheric pressure after addition of hardener.

Fig.2. Epoxy Resin CAMELECT 3321

2.3 Hardener

Hardener CAMCURE-2411.It has been used as curing agent. In present investigation 10% per unit Kg weight of Epoxy used in all material developed. The weight percentage of hardener used in the present investigation is as per recommendation.

Fig.3. Hardener CAMCURE 2411

2.4 Mould Preparation

First of all the mould for the composite is prepared. We have to prepare moulds of size 42 x 42 mm for the preparation of required L-section composite. A clean smoothed surfaced wooden is taken and washed thoroughly. We give a cover to the wooden L-section with a non-reactive thin plastic sheet. Then the glass of equal size (thickness 3mm) that of the mould is taken. We place the glass on the wooden L-section. Rectangle bits are cut in required dimensions and are apply surrounding the glass. These bits should be nailed in such a way that no polymer leaks out while casting. The bits are carefully held so that the glass does not move aside, so that the dimension of the mould is not distorted. After nailing the bits, the glass is smoothly taken out leaving behind the mould

2.4.1 C Section mould

Fig.4. C Section mould

2.4.2 Circular Section mould

Fig.5. Circular Section mould

2.4.3 L Section mould

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2.5 Casting of Composite Section By Hand Lay-Up

Technique

Hand lay-up technique is very simplest technique of composite processing. The components requirement to this method is also minimum. First of all, we will spray the gel on the mold surface to avoid the sticking of glass fiber to the surface. Thin plastic sheets are used at top and bottom of the wooden mold plate to get good surface finish of the product. Reinforcement in the form of woven mats or chopped strand mats are cut as per the mold size and placed at the surface of mold after Perspex sheet. Then thermosetting polymer in liquid form is mixed thoroughly in suitable proportion with a prescribed hardener (curing agent) and poured onto the surface of mat already placed in the mold. The polymer is uniformly spread with the help of brush. Second layer of mat is then placed on the polymer surface and a roller is moved with a mild pressure on the mat-polymer layer to remove any air trapped as well as the excess polymer present. The process is repeated for each layer of polymer and mat, till the required layers are stacked. After placing the plastic sheet, release gel is sprayed on the inner surface of the top mold plate which is then kept on the stacked layers and the pressure is applied. After curing either at room temperature or at some specific temperature, mold is opened and the developed composite part is taken out and further processed. The schematic of hand lay-up is shown in figure 1. The time of curing depends on type of polymer used for composite processing. For example, for epoxy based system, normal curing time at room temperature is 24-48 hours. This method is mainly suitable for thermosetting polymer based composites. Capital and infrastructural requirement is less as compared to other methods. Production rate is less and high volume fraction of reinforcement is difficult to achieve in the processed composites. Hand lay-up method finds application in many areas like aircraft components, automotive parts, boat hulls, daises board, deck etc. Generally, the materials used to develop composites through hand lay-up method are given in table 1.

Fig.7. Hand layup technique

2.6 Experimental testing specimen section of

composite and convectional (mild steel) material

Convectional Composite

Fig.8. C Section

Convectional Composite

Fig.9. L Section

Fig.10. Circular Section

2.7 Experimental testing setup

Fig.11. UTM

III. R

ESULTS AND

D

ISCUSSION

3.1 Material Properties

Mild Steel

Young Modulus E = 206 x 105MPa Poisson ratio µ = 0.28

Composite

Young Modulus for glass Ef = 0.85 x 105MPa Poisson ratio for glass µf = 0.20

Young Modulus for resin Er = 0.03 x 105MPa Poisson ratio for resin µr = 0.30

For 60% of Glass Fibers and 40% of Epoxy Resin Em = 0 .6 Ef +0.4 Er

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Stress σ≡ Resisting force

Cross sectional area N/mm2

For Same Strength % of weigth reduction =

weight of mild steel − weight of composite weight of mild steel

3.2 For Mild Steel

Table 2: Result for Mild Steel

FEM EXPERIMENTAL

Load KN Stress N/mm2 Dis mm Load KN

Stress N/mm2

Dis mm

L section 123 246.85 8.916 122.6 239.92 8.645

C section 180 355.60 13.383 178.2 348.04 12.436

Circular section 85 174.71 12.532 84.8 169.38 11.83

3.3 For Composite

Table 3: Result for Composite

FEM EXPERIMENTAL

Load KN Stress N/mm2 Dis mm Load KN

Dis mm

L section 123 65.242 8.338 122.6 58.38 8.783

C section 180 72.946 13.28 178.2 68.75 12.73

Circular section 85 42.377 12.09 84.8 38.38 12.02

3.4 Fem Results for Mild Steel and Composite

3.4.1 L section

Table 4: FEM results for L section Material Load KN Stress

N/mm2

Displacement Mm Mild steel 123 246.854 8.916 Glass fiber

Composite

123 65.242 8.338

Fig.12. L section displacement for mild steel

Fig.13. L section displacement for composite

Fig.14. L section stress for mild steel

Fig.15. L section stress for composite

3.4.2 C section

Table 5: FEM results for C section Material Load KN Stress

N/mm2

Displacement Mm Mild steel 180 355.607 13.383 Glass fiber

Composite

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Fig.17. C section displacement for composite

Fig.18. C section stress for mild steel

Fig.19. C section stress for composite

3.4.3 Circular section

Table 6: FEM results for Circular section Material Load

KN

Displacement mm

Mild steel 85 174.71 12.532

Glass fiber Composite

85 42.377 12.099

Fig.20. Circular section displacement for mild steel

Fig.21. Circular section displacement for composite

Fig.22. Circular section stress for mild steel

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3.5 Experimental Results for Mild Steel and

Composite

3.5.1 C section

Table 7: Experimental results for C section Material Load

KN

Displacement mm Mild steel 178.20 348.04 12.436 Glass fiber

Composite

195.95 75.59 12.732



For Same Strength Weight Reduction of

Composite

Table 8: Weight reduction based on strength for C section Material Load

KN Stress N/mm2 Weight Kg % of weight reduction Mild steel 178.20 348.04 1.084

9.1 Glass fiber

Composite

178.20 68.75 0.986

Mild Steel Composite

Fig.24. C section under compression test, both composite and mild steel

3.5.2 Circular section

Table 9: Experimental results for Circular section Material Load

KN

Displacement mm Mild steel 84.8 169.50 11.830 Glass fiber

Composite

111.94 50.66 12.026

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For Same Strength Weight Reduction of

Composite

Table 10: Weight reduction based on strength for Circular section

Material Load in KN Stress in N/mm2 Weight in Kg % of weight reduction Mild steel 84.8 169.50 1.082

24.30 Glass fiber

Composite

84.8 38.38 0.819

Fig.25. Circular section under compression test, both composite and mild steel

3.5.3 L section

Table 11: Experimental results for L section Material Load

in KN

Stress in N/mm2

Displacement in mm

Mild steel 122.6 239.92 8.654

Glass fiber Composite

127.10 60.52 8.783



For Same Strength Weight Reduction of

Composite

Table 12: Weight reduction based on strength for L section Material Load

in KN Stress in N/mm2 Weight in Kg % of weight reduction Mild steel 122.6 239.92 1.084

7.5 Glass fiber

Composite

122.6 58.38 1.000

Fig.26. L section under compression test, both composite and mild steel

3.6 GRAPHS

3.6.1 Experimental and fem results for

Load Vs

Displacement



C section

Experimental 0 20 40 60 80 100 120 140 160 180 200

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

L section

Experimental

FEM



Circular section

Experimental

FEM

3.6.2 Comparison of Experimental and FEM Results



Mild Steel

Experimental 0 20 40 60 80 100 120 140 160 180 200

0 5 10 15 20 25 30 35 40 45 50

Composite Load mild steel load L o a d ( K N) Displacement (mm) 0 20 40 60 80 100 120 140 160

0 5 10 15 20 25 30 35 40 45 50

Composite Load mild steel load L o a d (K N) Displacement (mm) 0 20 40 60 80 100 120 140

0 5 10 15 20 25 30 35 40 45 50

Composite Load mild steel load L o a d (K N) Displacement (mm) 0 20 40 60 80 100 120 140

0 5 10 15 20 25 30 35 40 45 50

Composite Load mild steel load L o a d (K N) Displacement (mm) 0 10 20 30 40 50 60 70 80 90 100

0 5 10 15 20 25 30 35 40 45 50

Composite Load mild steel load L o a d(K N) Displacement (mm) 0 20 40 60 80 100 120 140 160 180 200

0 5 10 15 20 25 30 35 40 45 50

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

Composite material

Experimental

FEM

3.7 Percentage of Weight Reduction in Composite

Section for Same Strength

Percentage of Weight Reduction in Composite sections

IV. C

ONCLUSION

Based on the results obtained from the FEM and experimental for composite and mild steel following are the conclusions drawn for the present study.

1. The strength of composite material sections is more than the mild steel based on weight per unit length ratio 2. For same strength there will be weight reduction in composite material sections are

Circular section = 24.03 % L section = 7.50 % C section = 9.10 %

3. In the C section there will be more compressive strength based on that C section is more better than all section

4. In the Circular section there will be more weight reduction percentage that is 24.03 based on that Circular section is more better than all section

5. All through the composite material sections are better for the used in industry because it give more strength than the mild steel based on weight per unit length ratio

A

CKNOWLEDGEMENT

We would like to thank our principal and management for their support and help towards this work.

R

EFERENCES

[1] Spring forward phenomenon of angular sections of composite materials analytical, numerical and experimental approach Journal: BULLETIN OF APPLIED MECHANICS 7(26), 31-36(2011)

[2] Investigation of Structural Analysis of Composite Beam Having I-Cross Section under Transverse Loading Journal: IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE) e-ISSN: 2278-1684, p-ISSN: 2320-334X, Volume 6, Issue 5 (May. - Jun. 2013), PP 43-49

[3] An experimental and numerical investigation of mechanical properties of glass fiber reinforced epoxy composites Journal: Published online by the VBRI press in 2013 ADVANCED MATERIALS Letters Adv. Mat. Lett. 2013, 4(7), 567-572 Received: 23 November 2012, Revised: 28 December 2012 and Accepted: 07 January 2013

[4] Numerical Modeling and Analysis of Composite Beam Structures Subjected to Torsional Loading Journal: Thesis submitted to the faculty of the Virginia Polytechnic Institute and State University 0 20 40 60 80 100 120 140 160 180 200

0 5 10 15 20 25 30 35 40 45 50

C Section Circular Section L Section L o a d (K N) Displacement (mm) 0 50 100 150 200

0 5 10 15 20 25 30 35 40 45 50

C Section Circular Section L Section Displacement (mm) L o a d (K N) 0 20 40 60 80 100 120 140 160 180 200

0 5 10 15 20 25 30 35 40 45 50

C Section Circular Section L Section L o a d (K N) Displacement (mm) 7.5 9.1 24.3 0 10 20 30

L SECTION C SECTION CIRCULAR

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composites with coated tungsten carbide tool Journal: International Journal of Innovative Research in Science, Engineering and Technology Vol. 2, Issue 7, July 2013 ISSN: 2319-8753

[6] Sisal Fiber / Glass Fiber Hybrid Nano Composite: The Tensile and Compressive Properties Journal: 5th International & 26th All India Manufacturing Technology, Design and Research Conference (AIMTDR 2014) December 12th–14th, 2014, IIT Guwahati, Assam, India

[7] Thermal and Mechanical Behavior of the Angle Section of Composites with a Single and Double Curvature Journal: 18th International Conference on Composite Materials

[8] Experimental Studies on Mechanical Properties of Glass Fiber Reinforced Ceramic Matrix Composites Journal: International Journal of Emerging Technology and Advanced Engineering (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 6, June 2014)

A

UTHOR

'

S

P

ROFILE

I. G. Bhavi

Completed BE in Automobile Engg in july, 2002, secured 5th rank to university (VTU, Belgaum). Joined Kirloskar Oil Engines Ltd, Pune on 1st August, 2002 as Member-R & D. Did M.Tech in Machine design in 2005. At present from last 10 years working as Associate Professor, in BLDEA's College of Engineering, Bijapur, India. Published more than 16 research papers in international conferences and referred international journals. Presently pursuing Ph.D in the fatigue life estimation of gear tooth, in VTU, Belgaum

Experimental & Finite Element Analysis of Buckling Strength of Various Structural Cross Sections of Conventional and Composite Material for Weight Reduction