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FRACTURE TOUGHNESS ANALYSIS OF SISAL FIBER REINFORCEMENT POLYESTER COMPOSITE

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NAGA SUNDARAM.B.S ABSTRACT This project titled FRACTURE TOUGHNESS TEST OF SISAL FIBRE REINFORCEMENT POLYESTER COMPOSITES has been conceived having studying about the utilization of natural fibres in polymer composites. Due to the establishment of disposal methods for glass fibre reinforced plastics. Among various natural fibres, sisal fibre is of particular interest in that its composites will have high tensile strength, high tensile modulus, and low elongation at break beside its low cost and ease of availability.Now the project mainly concentrated on reinforcement of polymer plastics with same proportions of sisal fibre composites .These composites are subjected to the shear stress to find the fracture. Thermosetting resins, namely polyester, are commonly used in natural fiber composites.WHAT IS A COMPOSITE MATERIAL?A broad definition of composite is: Two or more chemically distinct materials which when combined have improved properties over the individual materials. Composites could be natural or synthetic.Wood is a good example of a natural composite, combination of cellulose fiber and lignin. The cellulose fiber provides strength and the lignin is the "glue" that bonds and stabilizes the fiber.FRACTURE TOUGHNESS : Fracture toughnessis a property which describes the ability of a material containing a crack to resistfracture, and is one of the most important properties of any material for virtually all design applications. It is denoted KIcand has the units ofN/mm3/2.

Mode I crack Opening mode (atensile stressnormal to the plane of the crack)

WHAT IS RESIN?In polymer chemistry and material science, resin is a solid or highly viscous substance ,which are typically convertible into polymers. such viscous substance can be plant derived or synthetic in origin.Unsaturated Polyester resin are the simplest most economical resin systems that are easiest to prepare and show good performance. Millions of ton of this material is used annually around the world.

WHAT IS FIBER?A thread or filament from which a vegetable tissue, mineral substance, or textile is formed.Synthetic fibers can often be produced very cheaply and in large amounts compared to natural fibers, but for clothing natural fibers can give some benefits, such as comfort, over their synthetic counterparts.

WHAT IS SISAL?Sisal, with the botanical name Agave sisalana, is a species of Agave native to southern Mexico but widely cultivated and naturalized in many other countries. It yields a stiff fiber used in making various products. The term sisal may refer either to the plant's common name or the fiber, depending on the context. It is sometimes referred to as "sisal hemp", because for centuries hemp was a major source for fiber, and other fiber sources were named after it.

SISAL FIGURE

Plant descriptionSisal plants, Agave sisalana, consist of a rosette of sword-shaped leaves about 1.52 meters (4.96.6 ft) tall. Young leaves may have a few minute teeth along their margins, but lose them as they mature.The sisal plant has a 710 year life-span and typically produces 200250 commercially usable leaves. Each leaf contains an average of around 1000 fibers. The fibers account for only about 4% of the plant by weight. Sisal is considered a plant of the tropics and subtropics, since production benefits from temperatures above 25 degrees Celsius and sunshine.

ENVIRONMENTAL IMPACTS:Sisal farming initially caused environmental degradation, because sisal plantations replaced native forests, but is still considered less damaging than many types of farming.No chemical fertilizers are used in sisal production, and although herbicides are occasionally used, even this impact may be eliminated, since most weeding is done by hand. The effluent from the decortication process causes serious pollution when it is allowed to flow into watercourses. In Tanzania there are plans to use the waste as bio-fuel.ACIDS USED: Sodium hydroxide Potassium permanganate Malic acid Stearic acidCATALYST A Substance that increases the rate of chemical reaction without itself undergoing any permanent chemical change.The catalyst used in this process is Methyl ethyl ketone peroxide.

ACCELERATOR A substance that speeds up a chemical processThe accelerator used in process is Cobalt(II) naphthenate

MATERIAL SELECTIONSisal fiberUnsaturated polyester Resin Methyl ethyl ketone peroxideSilicon RubberCobalt(II) naphthenate

OBJECTIVE OF THE PROJECT WORK:

Fabrication of sisal fiber composite.Evaluation of fracture toughness of the sisal fiber composite.Comparison of Experimental result. Preparation of Mould . Fabrication of composites. Testing of Composite as per ASTM Standard. Prediction of Fracture toughness. Comparison the fracture value VOLUME FRACTION CALCULATION :Volume fraction is defined as the ratio between volume of fiber to the volume of composite.

Vf = Vfi / Vc Vfi - Volume of fiber Vc- Volume of composite

STRESS INTENSITY FACTOR:Stress intensity factor K can be considered as a estimate of fracture toughness.It depends on the 1. Load 2.Flow depth 3.Geometry

Where P- load at which crack propagate B- Thickness of the test specimen W- Length of the specimen A - crack length Critical stress intensity factor for mode-1FORMULA:

MODE-ICALCULATION: Density of sisal fiber s = 1.4 g/ccDensity of unsaturated polyester resin p = 1.13g/ccTotal volume of mold =300x300x3 = 270000mm3Mass of sisal fiber = 75.6 gWeight of sisal fiber Wb = 0.756NTotal weight of fiber Wf = 0.756NMass of resin used = 300gWeight of resin Wm = 3NWeight of composite = Wf+Wm = 0.756+3= 3.756NWeight fraction = Weight of the fibre/weight of the composite Wsfi = 0.756/3.756=0.20

23Weight fraction of fiber + Weight fraction of matrix=1So that, Wfi + Wmi = 1 Wfi = Wsfi =0.20 Wmi = 1- Wsi= 1-0.20= 0.80

Wfi / f = Wgfi / g = 0.756/1.4 = 0.54 Vf = 0.54/(0.54+0.707) = 0.54/1.247 = 0.433x100=43.3%

MODE-I

DIMENSIONS: Total length (L) = 90mm, Length from the centre of hole = 67.5mm, Crack length (A) = 22.5mm Half height (H)= 50mm, Thickness (B)= 3mm

CALCULATION FOR EXPERIMENTAL ANALYSIS ::

f (a/w)= 6.068 29 f(a/w) =6.068 b*w^0.5 = 3*(67.5)^0.5 = 24.647

f(a/w) /b*(w^0.5)= = 6.068/24.647 = 0.2461sodium hydroxide 1 P = 0.900KN KIC = P/0.2461 = 0.9/0.2461 = 0.2215KN/mm3/2sodium hydroxide 2 P = 0.660KN KIC = P/0.2461 = 0.660/0.2461 = 0.0.1624KN/mm3/2

Potassium permanganate 1 P = 0.895KN KIC = P/0.2461 = 0.895/0.2461 = 0.220.KN/mm3/2Potassium permanganate 2 P = 0.825KN KIC = P/0.2461 = 0.825/0.2461 = 0.2030KN/mm3/2

Unsaturated sisal 1 P = 1.065KN KIC = P/0.2461 = 1.065/0.2461 = 0.0.2621KN/mm3/2Unsaturated sisal 2 P = 0.550KN KIC = P/0.2461 = 0.550/0.2461 = 0.1353KN/mm3/2

Malic acid 1 P = 0.805KN KIC = P/0.2461 = 0.805/0.2461 = 0.1981KN/mm3/2Malic acid 2 P = 0.540KN KIC = P/0.2461 = 0.540/0.2461 = 0.1329KN/mm3/2

Stearic acid 1 P = 1.545KN KIC = P/0.2461 = 1.545/0.2461 = 0.3802KN/mm3/2Stearic acid 2 P = 1.130KN KIC = P/0.2461 = 1.130/0.2461 = 0.2780KN/mm3/2

For sodium hydroxide Average = (0.2216+0.1624)/2 = 0.1919

For Potassium permanganate Average = (0.2203+0.2030)/2 = 0.2116

For unsaturated sisal Average = (0.2621+0.1353)/2 = 0.1987

For Malic acid Average = (0.1981+0.1329)/2 = 0.1655

For Stearic acid Average = (0.3802+0.2780)/2 = 0.3291 From the above values a graph is plotted below by taking FRACTURE TOUGHNESS value on the Y axis and the ACIDS on the X axis. Uses of sisal:Traditionally, sisal has been the leading material for agricultural twine (binder twine and baler twine) because of its strength, durability, ability to stretch, affinity for certain dyestuffs, and resistance to deterioration in saltwater. The importance of this traditional use is diminishing with competition from polypropylene and the development of other haymaking techniques, while new higher-valued sisal products have been developed.The sisal fiber is traditionally used for rope and twine, and has many other uses, including paper, cloth, wall coverings, carpets, and dartboards.

Apart from ropes, twines, and general cordage, sisal is used in low-cost and specialty paper, dartboards, buffing cloth, filters, geotextiles, mattresses, carpets, handicrafts, wire rope cores. Sisal has been utilized as an environmentally friendly strengthening agent to replace asbestos and fiber glass in composite materials in various uses including the automobile industry. The lower-grade fiber is processed by the paper industry because of its high content of cellulose and hemicelluloses. The medium-grade fiber is used in the cordage industry for making ropes, baler and binder twine. Ropes and twines are widely employed for marine, agricultural, and general industrial use. The higher-grade fiber after treatment is converted into yarns and used by the carpet industry.

Higher Specific Strength (strength-to-weight ratio)Composites have a higher specific strength than many other materials. A distinct advantage of composites over other materials is the ability to use many combinations of resins and reinforcements, and therefore custom tailor the mechanical and physical properties of a structure. Design flexibilityComposites have an advantage over other materials because they can be molded into complex shapes at relatively low cost. This gives designers the freedom to create any shape or configuration. Boats are a good example of the success of composites.Corrosion resistance

Advantages of CompositesDisadvantages of CompositesComposites are highly anisotropicThe strength in composites vary as the direction along which we measure changes (most engineering structural materials are isotropic). As a result, all other properties such as, stiffness, thermal expansion, thermal and electrical conductivity and creep resistance are also anisotropic. The relationship between stress and strain (force and deformation) is much more complicated than in isotropic materialsComposites materials are difficult to inspect with conventional ultrasonic, eddy current and visual NDI methods such as radiography43Sisal Advantages:100% biodegradable and sustainable.It is extremely hard wearing and strong. Antistatic due to natural fiber helping to control the humidity in the atmosphere.Natural sound insulation.Recommendation for those prone to allergies and asthmatic reaction.SISAL DISADVANTAGES:Like many other natural floor coverings, sisal is not especially comfortable to sit on however, it is very pleasant to walk on and provides a natural massage for the soles of your feet. Another drawback is that sisal cannot be used outdoors, not is it recommended in areas that are frequently wet, such as kitchens and bathrooms. It is also not a cheap flooring option.

We can obtain from the various tests, it is understanding that it can be used in applications of higher strength and less weight.Complicated shapes and size can also be developed with reduced material wastage.CONCLUSIONThank youREFERENCESK.G.Satyanarayana, K,Sukumaran, Kulkarni,A.G, Pillai S.G.K and Rohatgi (1984), Performance of banana fabric polyester composites in proceedings of Second international conference on Composite Structure 13-16 Sep 1983,ed.I.H.Marshall,Applied Science publishers, London :535-537.K.G.Satyanarayana, K. Sukumaran, P.S.Mukherjee, C. Pavithran and S.G.KPillai, (1990) natural Fiber-Polymer Composites, Journal of Cement & Concrete Composites, v 12: 117-136.Lightsey.G.R (1983),Polymer application of renewable resource materials,