Studies of Carbon fibre compositesByDhanraj Desai

Introduction

CompositesEngineered or naturally occurring materials made from two or more constituent materials with significantly different physical or chemical properties which remain separate and distinct at the macroscopic or microscopic scale within the finished structure.E.g.- Concrete, Plywood.

Why composites?

Weight Saving Directionality Excellent fatigue Cost Ease of Assembly Don’t corrode

Ease of fabrication Wide range of shapes Inherent Mechanical Properties Tailor ability Special Features

Composites

Fibres used in composites

Carbon

Kevlar

Kenaf Bamboo Hemp

Glass Coir Jute

Sisal Flax

Why carbon fibre?

Light in weight, Strong and Durable

Good vibration damping and toughness

High dimensional stability Low co-efficient of thermal

expansion Low abrasion Electrical conductivity Biological inertness

X-Ray permeability Fatigue resistance Self lubrication property High damping Electromagnetic properties Chemical inertness High corrosion resistance

Why sisal fibre?

Exceptionally durable with low maintenance Minimal wear and tear It is recyclable Anti-static property It exhibits good sound and impact absorbing properties

Motivation of Work

Advantages of Sisal fibre Abundance and therefore low cost, Biodegradability, Flexibility during processing and

less resulting machine wear, Minimal health hazards, Low Density, Desirable fiber aspect ratio, Relatively high tensile and

flexural modulus

Advantages of Carbon fibre 70% Lighter than steel, 40%

lighter than aluminium High strength to weight ratio High corrosion resistance Application flexibility Low mass  It can be formed to most any

shape 

challenges

In Sisal Fibre Variable quality, depending on

unpredictable influences such as weather.

Moisture absorption, which causes swelling of the fibres.

Restricted maximum processing temperature.

Lower durability, fibre treatments can improve this considerably.

Poor fire resistance

In Carbon Fibre Carbon fibre in extremely

expensive Recycling in very difficult Once a carbon fibre structure

dinted or cracked cannot beat it back

Methods of Surface Modification

For Natural Fibre Physical methods of modification surface fibrillation, electric

discharge(corona, cold plasma)

Alkali Swelling and Substitution Reactions

Impregnation of Fibers

Chemical Modification

Silane TreatmentsFor Carbon Fibre Physical methods of modification Chemical modification Silane Treatment

Composite Manufacturing Methods

Hand Laminating Resin Injection Technique

Hot Press Method Pultrusion

Literature Survey

In 2009 Yunsheng Xu, D.D.L.Chung, treated carbon fibre with silane coupling agent and silane treated silica fumes.

And found the tensile strength of cement paste was increased by 56% and the modulus and ductility were increased by 39%. Silane treatment of fibers and silica fume contributed about equally to the strengthening. Silane treatment of fibres and silica fume also decreased the air void content and the drying shrinkage. The strengthening, air void content reduction and drying shrinkage reduction were less when the fibre treatment involved either potassium dichromate or ozone.Silane’s effectiveness is due to its hydrophilic nature.

Silane-treated carbon fiber for reinforcing cement, Carbon 39 (2001) 1995-2001

Cont…

Yanjun Xie, Callum A. S. Hill, Zefang Xiao, Holger Militz, Carsten Mai, carried out a variety of silanes (mostly tri alkoxy silanes) have been applied as coupling agents in the NFPCs to promote interfacial adhesion and improve the properties of composites,

And they found the interaction mechanisms between natural fibers and polymer matrices, and presents the effects of silane treatments on the mechanical and outdoor performance of the resulting composites.

Silane coupling agents used for natural fiber/polymer composites : A review,

Composites Part A 41 (2010) 806-819.

Cont.…

In 2007,P.Noorunnisa Khanam,H.P.S.Abdul Khalil, M. Jawaid, G.Ramachandra Reddy, C.Surya Narayana, S.VenkataNaidu, studied

1) The variation of mechanical properties such as tensile and flexural properties of randomly oriented unsaturated polyester based sisal/carbon fibre reinforced hybrid composites with different fibre weight ratios.2) The chemical resistance test of these hybrid composites to various solvents,acids and alkalies.3) The effect of NaOH treatment of sisal fibres on the tensile, flexural and chemical resistance properties of these sisal/carbon hybrid composites.And found1) The hybrid composites showed an increase in tensile and flexural properties with increase in the carbon fibre loading.2) The tensile properties and flexural properties of these hybrid composites have been found to be higher than that of the matrix.

3) Significant improvement in tensile properties and flexural properties of the sisal/carbon hybrid composites has been observed by alkali treatment.4) The resistance test results showed that these untreated and alkali treated hybrid composites are resistance to all chemicals except carbon tetrachloride.

Sisal/Carbon Fibre Reinforced Hybrid Composites :Tensile, Flexural and Chemical Resistance Properties, J Polym Environ (2010).

Cont.……

K.Bilba, M.-A. Arsene, describes the effect of two silane compounds on parameters such as the porosity, dimension, morphology and hygroscopic character of silane-coated sugar cane bagasse fibers.

They studied natural fiber reinforced composite setting times how the importance of the silane chemistry/structure, for fiber treatments with silane solution containing up to 6%(volume per cent) silane. In the case of composites reinforced with unpyrolyzed bagasse fibers, setting time increases with silane coating. Combining pyrolysis and silane treatment improve the water resistance of the fibers, which become more hydrophobic.

Silane treatment of bagasse fiber for reinforcement of cementitious composites, Composites :Part A 39 (2008) 1488-1495

Cont.……

Noor Sabah Sadeq, carried out reinforcing the matrix (Epoxy) resin with natural material (cane sugar fibers) and synthetic fibers (chopped carbon fibers). The natural fibers were exposure to chemical treatment before reinforcement.

The hybrid composites contain of chopped carbon and cane sugar fibers is produced using hand lay method. Each sample was reinforced with different volume fraction such as 30%, 20%, and 10%.Cane sugar composite has the higher values (of flexural strength 490.77 MPa and of impact strength 93.92 KJ/m2) than chopped carbon composites (flexural strength 93.19 MPa and impact strength 23.92 KJ/m2). It was found that the additions of natural fibers (cane sugar) to chopped carbon fibers improve of the mechanical properties of hybrid composites.

Influence of Natural Fiber on the Mechanical Properties of Epoxy Composites.

Cont.….

IIn 1999 L.Y.Mwaikambo and M.P.Ancell treated hemp, sisal, jute and kapok varying concentrations of caustic soda and acetylated with and without an acid catalyst to graft acetyl groups onto the cellulose structure.

And found After treatment the surface topography of hemp, sisal and jute fibres is clean and rough. The surface of kapok fibres is apparently not affected by the chemical treatments. X-ray diffraction shows a slight initial improvement in the crystallinity of the fibres at low sodium hydroxide concentration.

Plan of Work

FibresCarbon Fibres, Sisal, Jute and Coir (As per the availability) ResinPolyester, Polypropylene, Epoxy Surface modification method Mercerisation, drying, silane treatment. Manufacturing Process Hand lay up/ compression moulding.

Properties of Composites

Scan Electronic Microscopy(SEM) FTIR Tensile property Thermal (TGA,DSC) Moisture Swelling in water Compression

Applications

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