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2018 3rd SEM WORKSHOP PROJECT AT TAML

DEVARAJU V TATA ADVANCED MATERIAL PVT LTD 10/29/2018

AN ISO 9001:2008 CERTIFIED TRAINING INSITTUTION

NETTUR TECHNICAL TRAINING FOUNDATION

NEEM PROGRAM CONDUCTED BY NTTF AND TATA ADVANCE MATERIAL

LEARNINGS AT A TATA ADVANCED MATERIAL DURING THREE YEARS PROGRAM

DIPLOMA IN AEROSPACE MANUFACTURING TECHNOLOGY

(ADVANCE COMPOSITE) NTTF LEARN AND EARN TRAINING CENTER NEC BANGALORE - 560 100 2016-2019

AN ISO 9001:2008 CERTIFIED TRAINING INSITTUTION

NETTUR TECHNICAL TRAINING FOUNDATION

Certificate This is to certify that the project titled 3rd SEM TAML WORKSHOP

Is a bonafide record of the project work done by

DEVARAJU V

ID no LE/TAML /B1/08

In partial fulfillment of the requirement for the award of DIPLOMA IN AEROSPACE MANUFACTURING TECHNOLOGY under the institution Nettur Technical Training Foundation, NEC Training Centre, during the Academic year 2016– 2019

UNIT HEAD

GIRIDHAR

EXTERNAL EXAMINER

TAML

CO-ORDINATOR

KIRAN MH

ABSTRACT

As part of our diploma in aerospace manufacturing technology(advanced composite) curriculum, we have selected the COMPOSITE INTRODUCTION project named “ADVANCE COMPOSITE”. The main aim of the project is to make the Robotic arm, which comprises of three stepper motors, to interface with the PIC16F877A-based micro-controller Our project comprises of three main areas: 

ELECTRICAL DESIGNS

ACKNOWLEDGEMENT We feel privileged to acknowledge the contribution of several peoples for the successful completion of THIRD SEM TAML WORKSHOP OF THE PROJECT We are grateful to Mr. KIRAN MR (DT-COO, NTTF) for formulated the notion of the project work and facilitated us to know something more besides our regular practical curriculum. We would like to use this opportunity to thank Mr. SURESH.N, (PRINCIPAL, NTTF-NEC) for extending his official support for the progress of the project. We sincerely thank Mr. SHIJU GANGADHARAN (Section In charge, project in charge & STO, NEC-NTTF) & Mrs. SIREESHA DEVI M.M (Assistant TRG Manager) & Mr. A. PALANI KUMAR (CP15 Course Head) for their co-operation and hard work in arranging this project work. We would like to utilize this opportunity to express our gratitude to all the staff members of NTTF for supporting us during all the activities, proceedings and successful completion of our project.

TAML WORKSHOP 3rd SEM Content…………… 1. Thermoplastic 2. Introduction to composite 3. Raw materials 4. Reinforcement materials 5. Matrix materials 6. Resin system 7. Consumables used in composite 8. Fabrication method 9. Mechanical fastener 10. Adhesive bonding

11. Inspection method 12. FAI PROCESS 13. Importance of material testing 14. Case study of P8i BY-DEVARAJU V

THERMOPLASTIC A thermoplastic material it can be compared to a set of strings that are mixed on a table, each of these string is represents a polymer, the greater degree of mixing of the strings greater the effort will be made to separate the strings from each other, due the friction that occurs between each of the cords offers resistance to separate, in this example the friction represents the intermolecular forces that holds together the polymer.

Depending on the degree of the intermolecular interactions that occurs between the polymer chains, the polymer can take two different types of structures, amorphous or crystalline structures, being possible the existence of both structures in the same thermoplastic material: 

Amorphous structure - polymer chains acquire a bundled structure, like a ball of thread disordered, amorphous structure that is directly responsible for the elastic properties of thermoplastic materials.



Crystal structure - polymer chains acquire an ordered and compacted structure, it can be distinguished mainly lamellar structures and micelle form. This crystal structure is directly responsible for the mechanical properties of resistance to stresses or loads and the temperature resistance of thermoplastic materials. If the thermoplastic material has a high concentration of polymers with amorphous structures, the material will have a poor resistance to loads but it will have an excellent elasticity. But on the contrary, if the thermoplastic material has a high concentration of polymers with a crystalline structure, the material will be very strong and even stronger than thermoset materials, but with a little elasticity that provides the characteristic fragility of these materials.

Properties of thermoplastic materials are: 

It may melt before passing to a gaseous state.



Allow plastic deformation when it is heated.



They are soluble in certain solvents.



Swell in the presence of certain solvents.



Good resistance to creep. Examples and applications of thermoplastic plastic materials:



High pressure polyethylene as applied to rigid material covered with electrical machines, tubes, etc...



Low pressure polyethylene elastic material used for insulation of electrical cables, etc...



Polystyrene applied for electrical insulation, handles of tools...



Polyamide used for making ropes, belts, etc...



PVC or polyvinyl chloride for the manufacture of insulation materials, pipes, containers, etc... Examples of thermoplastic adhesives:



Acrylates



Cyanoacrylates



Epoxy cured by ultraviolet radiation



Acrylates cured by ultraviolet radiation

     

Thermoplastic Advantages Highly recyclable High-Impact resistance Reshaping capabilities Chemical resistant Aesthetically superior finishes Hard crystalline or rubbery surface options

 

Thermoplastic Disadvantages Expensive Can melt if heated

    

Thermoset Plastic Advantages More resistant to high temperatures Highly flexible design Thick to thin wall capabilities High levels of dimensional stability Cost-effective

  

Thermoset Plastics Disadvantages Can’t be recycled More difficult to surface finish Can’t be remolded or reshaped

INTRODUCTION TO COMPOSITES

Composite

material is a macroscopic combination of two or

more distinct materials, having a recognizable interface between them. Composites are extending the horizons of designers in all branches of engineering, and yet the degree to which this is happening can easily pass unperceived. The eye, after all, does not see beyond the glossy exterior or the race performance of a GRP1 yacht, nor does it sense the complexity of the structure of a composite helicopter rotor blade or of a modern CFRP2 tennis racket. Nevertheless, this family of synthesized materials offers the possibility of exciting new solutions to difficult engineering problems.

In composites, materials are combined in such a way as to enable us to make better use of their virtues while minimizing to some extent the effects of their deficiencies. This process of optimization can release a designer from the constraints associated with the selection and manufacture of conventional materials. He can make use of tougher and lighter materials, with properties that can be tailored to suit particular design requirements. And because of the ease with which complex shapes can be manufactured, the complete rethinking of an established design in terms of composites can often lead to both cheaper and better solutions. The ‘composites’ concept is not a human invention. Wood is a natural composite material consisting of one species of polymer — cellulose fibers with good strength and stiffness — in a resinous matrix of another polymer, the polysaccharide lignin. Nature makes a much better job of design and manufacture than we do, although Man was able to recognize that the way of overcoming two major disadvantages of natural wood — that of size (a tree has a limited transverse dimension), and that of anisotropy (properties are markedly different in the axial and radial directions) — was to make the composite material that we call plywood. Bone, teeth and mollusk shells are other natural composites, combining hard ceramic reinforcing phases in natural organic polymer matrices. Man was aware, even from the earliest times, of the concept that combining materials could be advantageous, and the down-to-earth procedures of wattle-and-daub (mud and straw) and ‘pied’ (heather incorporated in hard-rammed earth) building construction, still in use today, pre-date the use of reinforced concrete by the Romans which foreshadowed the pre-tensioned and post-tensioned reinforced concretes of our own era. But it is only in the last half

century that the science and technology of composite materials have developed to provide the engineer with a novel class of materials and the necessary tools to enable him to use them advantageously. The simple term ‘composites’ gives little indication of the vast range of individual combinations that are included in this class of materials. We have mentioned some of the more familiar ones, but the diagram Figure 1.1 gives a clearer idea of the scope for ingenuity which is available to the Materials Scientist and his customer, the Design Engineer. First, within each group of materials — metallic, ceramic and polymeric — there are already certain familiar materials which can be described as composites. Many members of the commonest and largest group of engineering materials, the family of steels, consist of combinations of particles of hard ceramic compounds in a softer metallic matrix. These particles are sometimes plate-like, sometimes needle-shaped, and sometimes spherical or polygonal. Polymers, too, are often two-phased, consisting of a matrix of one polymer with distributions of harder or softer particles contained within it; wood is a perfect example of this, as we have seen. And concrete is a classic example of a ceramic/ceramic composite, with particles of sand and aggregate of graded sizes in a matrix of hydrated Portland cement. These materials have been well known for many years, and Materials Scientists have learned to control their properties by controlling their microstructures; that is to say, the quantity, the form, and the distribution of what we might refer to as the ‘reinforcing phase’. The idea of mixing components across the materials class boundaries is a natural extension of this idea. Making additions of hard, or fire-resistant, or simply cheap, ceramic powders to plastics to make filled polymers; and making additions of very hard, or abrasive, or thermally stable ceramic particles to metals to make the class of materials known as ‘cermet’ to produce machine tool tips capable of cutting hard metals at high speeds or high temperatures; are only two examples of important developments in our exploitation of these materials. But even more significant is the extension of this principle to incorporate filamentary metals, ceramics and polymers into the bulk forms of any of these three classes of materials to make fiber composites — reinforced plastics, like CFRP and GRP, metal-matrix composites (MMCs) like silicon-carbide-fiber-reinforced aluminum, and ceramic-matrix composites (CMCs) like carbon fiber-reinforced glass. Classification of Composites

Figure 1: Classification of composites Definition: An advanced composite material comprises at least two chemically different materials (heterogeneity): reinforcement, and a matrix that binds the reinforcement and is separated from it by a sharp interface.

Phases of Composites  Matrix Phase: Polymers, Metals, Ceramics Also, continuous phase, surrounds other phase (e.g.: metal, ceramic, or polymer)  Reinforcement Phase: Fibers, Particles, or Flakes Also, dispersed phase, discontinuous phase (e.g.: metal, ceramic, or polymer) → Interface between matrix and reinforcement

Examples: – Jell-O and Cole slaw/mixed fruit – Peanut brittle – Straw in mud – Wood (cellulose fibers in hemicellulose and lignin) – Bones (soft protein collagen and hard apatite minerals) – Pearlite (ferrite and cementite)

Factors in Creating Composites Factors in creating composites: – Matrix material – Reinforcement material

RAW MATERIALS

 Typical Composite Materials  Typically, basic composite parts or components are made up of at least two parts – a reinforcement material substrate e.g. fiberglass, carbon fibers or aramid (Kevlar™) fibers and a resinous binder.  The relatively brittle and firm resin matrix transfers forces acting on the part to the load-capable flexible fibers.  The low weights of both resin and fibers lend these parts extremely high strength-to-weight ratios.  Furthermore, simple composite “skins” may be fixed to the top and bottom of so called “core materials” to form sandwich structures, e.g. composite beams, still holding true to exceptional strength characteristics of these parts.

Structural fibers and fab

When compared to an unreinforced cured resin system, the mechanical characteristics of reinforcement fibers are tremendously higher. The mechanical performance of a composite part is therefore dictated in most part by that of the structural fibers. The following factors determine the ultimate mechanical properties of a cured composite part:   Basic mechanical characteristics of the reinforcement fibers   Bond / surface interaction between resin system and fibers   Amount of fibers per volume in the composite (fiber count)  Orientation of fibers in cured part Note:

The bond between fibers and resin can be improved by surface treatment. This is especially important when bonding composite parts. See SWP 12 on Adhesive Bonding.

As mentioned above, the orientation of fibers play an important role. In almost all cases reinforcement fibers are available in different types of weaves, making up a fabric. The following are typical commercially available reinforcement fibers and weaved fabrics:

Glass fibers Many unique chemical compositions of glass fibers are manufactured worldwide. These different compositions are designated by an alphabet letter and each display varying mechanical and chemical properties. The most common are:   E-glass   C-glass   S-glass  H-glass. The E denotes high Electrical resistance, the C Chemical resistance, S high Strength characteristics and the H stands for Hollow glass (extremely light fibers). Many more types of glass fiber exist, too numerous to all be mentioned here. Refer to a supplier’s catalogue and datasheets for fiber-specific information. As an example the properties of the already mentioned E-, C- and S-glass are listed below:

Property

E-glass

C-glass

S-glass

2540 kg/m3

2490 kg/m3

2480 kg/m3

Physical

Density

Hardness

6.5

6.5

6.5

Tensile strength 25°C

3.447 GA

3.309 GA

4.585 GA

Tensile strength 350°C

2.620 GA

-

4.447 GA

Tensile strength 550°C

1.724 GA

-

2.413 GA

Young’s Modulus

72.395 GA

68.948 GA

85.495 GA

Mechanical

Raw Materials

Chemical Composition

Silicon oxide

54.3%

64.6%

64.2%

Aluminum oxide

15.2%

4.1%

24.8%

-

-

0.21%

Calcium oxide

17.2%

13.2%

0.01%

Magnesium oxide

4.7%

3.3%

10.27%

Sodium oxide

0.6%

7.7%

0.27%

-

1.7%

-

8.0%

4.7%

0.01%

Iron oxide

Potassium oxide Boron oxide

Properties of single-fiber E-, C- and S-glass

Carbon fibers Carbon fibers are usually made by taking strands of poly-acrylonitrile (PAN) in the form of multifilament yarn and then oxidizing, carbonizing and graphitizing it to form carbon fiber filaments. These are then usually given a surface oxidation treatment to promote bonding with resins.

Other properties of carbon fiber include:   High thermal conductivity   Conducts electricity  Electrically opaque to radio waves

Aramid (Kevlar) fibers Also a relative newcomer, aramid fiber has many of the characteristics of carbon fiber but sets itself apart from carbon and glass with its unique degree of toughness. Several types of aramid fibers can be found commercially. Some benefits include:   Electrically non-conductive   Heat resistant  Transparent to radio waves One big drawback of using aramid fiber in a composite part is that it cannot be sanded after curing. Be sure to leave gaps between the edges of aramid fabrics and part ends. Important:

Special shears, sharpened at a specific angle are needed in order to cut aramid fabrics correctly.

Aramid fibers are hygroscopic (absorbs moisture from the atmosphere) and UV sensitive. Fibers should therefore be stored in a dry, darkened storage room. Moisture will adversely affect its bonding properties with resins. It should also be noted that aramid only bonds satisfactorily with epoxy and vinyl ester resin systems. Using aramid fabrics with polyester resins is not recommended – poor interlaminated bonding can be expected.

Other fiber types Many exotic, experimental and classified fibers are in existence around the world, each having unique properties still being explored and tested. Many of these fibers are either very rare or very expensive and are therefore beyond the scope of this manual.

Types of fabrics Different fabrics are mainly recognized by varying strand thickness and type of weave. Consult with manufacturers on their unique fabrics with different yarn thicknesses and weaves for specific purposes. In general, the following types of woven fabric can be found commercially:

PLAIN WEAVE

TWILL WEAVE

LENO WEAVE

BASET WEAVE

SATIN WEAVE

Sandwich structure core materials Sandwich structures are made by “sandwiching” a core material between two skins. The basic idea behind these structures is to significantly increase a structure’s bending stiffness whilst only marginally increasing the overall weight. With this in mind there are 2 basic characteristics a core material should display:   Low weight  High volume This basically means any core should have a low density (other than the skin material consisting of heavier resin and fibers). Several compounds are suitable as cores and can be placed under 3 main categories:   Foams   Honeycombs  Woods

Refer to SWP 18 on Sandwich Structures, where core materials are discussed in greater detail.

Foams Foamed plastic materials are affordable and easy to use as cores. The mechanical and physical properties of different foams vary greatly and their specific datasheets should be consulted for more detail. Examples are: o PVC foam o Polystyrene foams o Polyurethane foams o Polymethyl meth acrylamide foams o Styrene acrylonitrile (SAN) co-polymer foams o Metallic foams o Other thermoplastics Important:

Polystyrene “bead foam” is not suitable for use as a sandwich core material. This is foam made by exposing polystyrene granules to steam which then expand in a mould. The bonds between these beads are weak and varied. Air might also become trapped in the structure. These factors make this type of foam unusable.

Honeycombs Composite honeycombs are made from a variety of materials. Used mostly in the aerospace industry, honeycombs can also be found in stage flooring sandwich structures, marine vessels. Of all the core materials, honeycomb has the best compressive strength (next to balsa, see section 4.2.3)

Examples are: o Aluminum honeycomb o Nome honeycomb o Thermoplastic honeycomb o Glass fiber / plastic honeycombs o Carbon fiber / Kevlar honeycombs o Stainless steel, titanium and super-alloy honeycombs

Woods Balsa wood offers good strength whilst having a very low density. If the grain is orientated perpendicular to the sandwich skins, balsa wood’s compressive strength is better than most honeycombs.

Examples are: o Balsa (most common because of low density) o Cedar o Spruce o Mahogany o Redwood o Pine o Fir o Many others Woods are normally cheaper than foams, but prone to the attack from insects, mildew and will deteriorate when exposed to moisture. Proper sealing and treatment is therefore necessary where woods are used.

REINFORECEMENT Reinforcement The role of the reinforcement in a composite material is fundamentally one of increasing the mechanical properties of the neat resin system. All of the different fibers used in composites have different properties and so affect the properties of the composite in different ways. However, individual fibers or fibre bundles can only be used on their own in a few processes such as filament winding. For most other applications, the fibers need to be arranged into some form of sheet, known as a fabric, to make handling possible. Different ways for assembling fibers into sheets and the variety of fibre orientations possible lead to there being many different types of fabrics, each of which has its own characteristics.

Properties of Reinforcing Fibres The mechanical properties of most reinforcing fibers are considerably higher than those of un-reinforced resin systems. The mechanical properties of the fibre/resin composite are therefore dominated by the contribution of the fibre to the composite. The four main factors that govern the fibre’s contribution are: 1. The basic mechanical properties of the fibre itself. 2. The surface interaction of fibre and resin (the ‘interface’). 3. The amount of fibre in the composite (‘Fibre Volume Fraction’). 4. The orientation of the fibers in the composite. The basic mechanical properties of the most commonly used fibers are the surface

interaction of fibre and resin is controlled by the degree of bonding that exists between the two. This is heavily influenced by the treatment given to the fibre surface.

Styles of reinforcement Many reinforcing fibers are marketed as wide, semi-continuous sheets of ‘prepreg’ consisting of single layers of fibre tows impregnated with the required matrix resin and flattened between paper carrier sheets. These are then stacked, as discussed in chapter 3, the orientations of each ‘ply’ being arranged in accordance with design requirements, and hot pressed to consolidate the laminate. This process is able to cope with curved surfaces, provided the degree of curvature is not too great, but there may be a possibility of local wrinkling of the fibers when prepregs are pressed into doubly curved shapes. One means of overcoming this problem is to use the reinforcement in the form of a woven cloth since textile materials can readily be ‘draped’ over quite complex formers. Many of the fine filamentary reinforcing fibers like glass, carbon and SiC can be readily woven into many kinds of cloths and braids, the fibers being effectively placed by the weaving process in the directions required by the designer of the final composite structure. In simple designs, this may call for nothing more elaborate than an ordinary plain weave or satin weave, with fibers running in a variety of patterns but in only two directions, say 0° and 90°, but weaving processes to produce cloths with fibers in several directions in the plane of the cloth are all readily available. Fibres of different types may also be intermingled during the weaving processes to produce mixed-fibre cloths for the manufacture of some of the ‘hybrid’ composites that will be discussed later.

Most of the continuous fibers that we have considered are expensive raw materials, and it is often only the fact that the overall cost of a manufactured composite product may nevertheless be lower than a competing product made from cheaper, conventional materials by more costly processes that makes a composites design solution an attractive alternative. Thus, although large quantities of glass fibers are supplied in chopped form for compounding with both thermoplastic and thermosetting matrix polymers, it may not seem economical to chop the more expensive types of reinforcement.

Nevertheless, there are some advantages in using even these fibers in chopped

form, provided they can be arranged in the composite in such a way as to make good use of their intrinsically high strengths and stiffnesses. Parratt and Potter (1980) described a process for producing both chopped fibers, like glass and carbon, and naturally short filaments, like whiskers or asbestos fibers, in the form of prepreg sheets with fibers that were very well aligned in either unidirectional or poly-directional patterns. These prepregs also have excellent ‘drapability’ and can be used to form complex shapes, as discussed by Tsuki et al. (1997). As will be seen in chapter 4, provided the short fibers are well above some critical length, which for carbon, for example, may be of the order of only a millimetre, they are able to contribute a high fraction of their intrinsic properties to the composite without the loss that occurs with woven reinforcements as a result of the out-of-plane curvature of the fibers.

MATRIX MATERIALS Matrix Matrix materials • Fibers and whiskers in composites are held together by a binder known as matrix. This is required since fibers by themselves: – Given their small cross‐sectional area, cannot be directly loaded. – Further, they cannot transmit load between themselves. • This limitation is addressed by embedding fibers in a matrix material. • Matrix material serves several functions, the important ones being: – Binds fibers together. – Transfers loads and stresses within the composite structure. – Support the overall structure – Protects the composite from incursion of external agents such as humidity, chemicals, etc. – Protects fibers from damage due to handling. • Matrix material strongly influences composite’s overall transverse modulus, shear properties, and compression properties. • Matrix material also significantly limits a composite’s maximum permissible operating temperature. • Most of the matrix materials are relatively lighter, more compliant, and weaker vis‐à‐vis fibers and whiskers.

• However, the combination of fibers/whiskers and matrix can be very stiff, very strong, and yet very light. – Thus most of modern composites have very high specific strengths, i.e. very high strength/density ratios. – This makes them very useful in aerospace applications, where weight minimization is a key design consideration. Choosing the Right Matrix Materials While selecting matrix material for a composite system, several considerations have to be factored into, principal ones being: – Physical properties such a specific gravity. – Mechanical properties such as modulus, strength, CTE, conductivity, etc. – Melting of curing temperature for the matrix material – Viscosity: It strongly affects processing attributes of the composite, and also uniform flow of matrix material into the composite system. – Reactivity with fibers: One would certainly not desire possibility of chemical reactions between fibers and matrix material. – Fabrication process compatible with matrix and fibers – Reactivity with ambient environment –Cost Functions of the matrix

• The matrix binds the fibers together, holding them aligned in the important stressed directions. Loads applied to the composite are then transferred into the fibers, the principal load-bearing component, through the matrix, enabling the composite to withstand compression, flexural and shear forces as well as tensile loads. The ability of composites reinforced with short fibers to support loads of any kind is dependent on the presence of the matrix as the load-transfer medium, and the efficiency of this load transfer is directly related to the quality of the fibre/matrix bond. • The matrix must also isolate the fibers from each other so that they can act as separate entities. Many reinforcing fibers are brittle solids with highly variable strengths. When such materials are used in the form of fine fibers, not only are the fibers stronger than the monolithic form of the same solid, but there is the additional benefit that the fibre aggregate does not fail catastrophically. Moreover, the fibre bundle strength is less variable than that of a monolithic rod of equivalent load-bearing ability. But these advantages of the fibre aggregate can only be realized if the matrix separates the fibers from each other so that cracks are unable to pass unimpeded through sequences of fibers in contact, which would result in completely brittle composites.

• The matrix should protect the reinforcing filaments from mechanical damage (eg. abrasion) and from environmental attack. Since many of the resins which are used as matrices for glass fibers permit diffusion of water, this function is often not fulfilled in many GRP materials and the environmental damage that results is aggravated by stress. In cement the alkaline nature of the matrix itself is damaging to ordinary glass fibers and alkali-resistant glasses containing zirconium have been developed (Proctor & Yale, 1980) in an effort to counter this. For composites like MMCs or CMCs operating at elevated temperature, the matrix would need to protect the fibers from oxidative attack. • A ductile matrix will provide a means of slowing down or stopping cracks that might have originated at broken fibers: conversely, a brittle matrix may depend upon the fibers to act as matrix crack stoppers. • Through the quality of its ‘grip’ on the fibers (the interfacial bond strength), the matrix can also be an important means of increasing the toughness of the composite. • By comparison with the common reinforcing filaments most matrix materials are weak and flexible and their strengths and moduli are often neglected in calculating composite properties. But metals are structural materials in their own right and in MMCs their inherent shear stiffness and compressional rigidity are important in determining the behaviour of the composite in shear and compression. The potential for reinforcing any given material will depend to some extent on its ability to carry out some or all of these matrix functions, but there are often other considerations. We consider now the likely qualities of various classes of matrix materials.

Polymer matrix materials Polymers as Matrix Materials • Polymers: Most widely used matrix materials – Common examples: Polyesters, vinylesters, PEEK, PPS, nylon, polycarbonate, polyacetals, polyamides, polyether imides, polystyrene, epoxies, ureas, melamines, silicones. • Advantages: – Low cost – Easy to process – Low density – Superior chemical resistance

• Limitations: – Low strength – Low modulus – Limited range for operating temperature – Sensitivity to UV radiation, specific solvents, and occasionally humidity

Thermoplastics • Soften or melt when heated. This process is reversible. • Their structure has long chains of molecules with strong intra‐molecular bonds, but weak inter‐molecular bonds. • When exposed to heat, these inter‐molecular bonds breakdown, and the material starts “flowing”. • Semi‐crystalline of amorphous in structure • Examples: polyethylene, PEEK, polyamides, polyacetals, polysulfone, PPS, nylon, polystyrene.

Thermosets • These polymers do not melt, but breakdown (decompose) when heated. • Amorphous structure • They have networked structures with strong covalent bonds linking all molecules. • These networks permanently breakdown upon heating. Hence, these polymers, once “set”, cannot be reshaped. • Examples: epoxies, polyesters, phenolics, urea, melamine, silicone, polyimides.

Thermosets: Epoxies • Epoxy thermosets, like polyester thermosets, are produced from epoxy resins. These resins come in viscous liquid form, and have low molecular weight. • The viscosity of these resins strongly depends on the extent of polymerization of its molecules. • Common epoxy resins are produced through a reaction between epichlorohydrin and bisphenol‐A. Alternative formulations replace bisphenol‐A with other chemicals. • A “curing agent” (or hardener, or activator) triggers the polymerization process amongst resin molecules, thereby generating a very dense network of cross‐ linked polymer. Diethylene triamine is a very commonly used curing agent.

• The exothermic reaction between hardener (curing agent) and resin (compound) does not produce a by‐product. Further, like polyesters, epoxies also undergo shrinkage during the curing process. • Epoxies, like polyesters, can be produced at room temperatures. However, by proper selection of curing agents, the curing process can be conducted at elevated temperatures as well. • The curing process time strongly depends on the choice of resin as well as curing agent. It can vary between minutes to 24 hours. • Many a times, heat is applied to accelerate the curing process. Typically, curing time decreases, almost exponentially, with increasing temperature.

Thermosets: Phenolics • Produce less smoke during oxidation/charring process • Very low flammability • Dimensionally stable when subjected to changes in temperature • Good adhesion properties • Good candidates for public transportation systems, where flammability and smoke concerns are very significant • Also used in aircraft applications for similar reasons

Resin systems Typically material composites include at least two parts – a reinforcement material substrate e.g. fibreglass, carbon fibers or aramid (Kevlar™) fibers and a resinous binder. The sole purpose of the hardened (cured) resin system is to keep the fibers in place and along their correct orientation. Thus a resin should also be able to chemically connect to the different layers

of material. Resin systems fall in the thermosetting plastic category can be classified under the following groups, according to their chemical composition:   Epoxy resin   Polyester resin   Vinyl-ester resin  Polyurethane resin Other binding materials categories (for information purposes) are:    

    

Thermoplastic (e.g. Perspex) Phenolics Unsaturated Silicones polyesters  Polyimides

In this SWP only the thermosets will be discuss

Epoxy resin systems Epoxy resins are nearly transparent after curing. They are commercially available in hardware stores for small scale repairs as well as in large quantities (resin and different hardeners) for aerospace and marine applications. Epoxies are used as either a structural matrix material reinforced with fibers (glass, carbon, aramid, boron) or as a structural adhesive. Some properties of epoxy resin systems:      

      

Resin-to-hardener ratio is usually between 1:1 and 5:1 Excellent chemical- and corrosion resistance Excellent thermal properties Better mechanical properties compared to polyester resins Good gap filling properties when mixed with additives (see section 4.4) Offers excellent adhesive properties (including to polyester resin surfaces) Low shrinkage compared to Polyester resins.

 

Gelcoat does not readily adhere to epoxy surfaces Deteriorates when exposed to UV light

 

Polyester resin systems

Polyester resins may have a slightly yellow, transparent colour and are also known as thermosetting plastics (will set at high temperatures.) Because of their sensitivity to UV light and degradation over time, polyester resins are often coated with a protective layer. Properties of polyester resin systems:    

     

  

The hardener and accelerator agents are pre-mixed in the resin - the system only requires a catalyst to set off the reaction. MEKP (Methyl-ethyl-ketone-peroxide) is used as the abovementioned catalyst Usually requires only 2% catalyser by weight Offers good resistance against chemicals, corrosion and exposure to the environment

   

Flame retardant (self-extinguishes) Very easily processed in low cost equipment Usually cheaper than epoxy systems Typical shelf life of less than 6 months



Storage containers for these resins must be tightly closed to slow down the natural hardening process Hygroscopic (draws in moisture from surrounding air) High shrinkage compared to epoxies.

 

Polyurethane resin systems Polyurethane is widely used in flexible and rigid foams, heavy duty adhesives and sealants, fibers and hard plastic parts. Products containing polyurethane are often referred to as "urethanes,” but should not be confused with the specific substance, urethane (ethyl carbamate). Polyurethane system properties:    

    

Offers excellent thermal insulation Resists the spreading of flames Results in parts with high strength-to-weight ratios Easily processed Usually cheaper than epoxies

Vinyl-ester resin systems Vinyl-ester resins may have a coloured tint, ranging from green to blue to purple. They are also slightly more transparent then polyester resins and flows more easily. A Vinyl-ester system is a good alternative to a polyester or epoxy resin system, having inferior characteristics to those of epoxies, but better compared to those of polyester. Properties:

     

      

Vinyl-ester resins are more flexible than polyester resins Also catalyzed with MEKP, at a similar mixing ratio Better corrosion and temperature resistance Better strength properties Resists water absorption They degrade faster than polyester resins Shelf life less than three months

Hardeners Hardeners are substances or a mixture added to a plastic composition to promote or control the curing action by taking part in it. Resins are sometimes referred to as “Part A” while hardeners are referred to as “Part B”. The reaction can normally not be controlled by modifying the mixing ratios. Mixing ratio must be used as per the manufacturer’s datasheets. Different hardeners can be found for specific types of resins. As explained above in section 4.3, some resin systems only require a catalyzing agent. Furthermore different hardeners (as in epoxy systems) differ normally only in respect to the pot life of each different hardener-resin mixture.

Applications of resin systems The different applications for which specific resins can be used allow us to reclassify different sub-types of resin systems. Therefore common applications will be listed and described in the following sections, along with a few examples of resins available on the market.

Laminating resins Laminating resins easily wet any cloth, due to their low viscosity. They also chemically connect to the weave, resulting in a strong composite material. Examples of laminating resins include:    

    

SP Systems Ampreg 20, 22, Axon Epolam 2015, 2020, 2022 Axon Epolam 2080 (high temperature epoxy) Hexion L285 (LBA aircraft certified system) NCS and Scott Bader Polyester resins

Bonding resins Bonding materials have to have a higher viscosity to prevent the material from flowing off the area being bonded A few examples:

 

  

SP Spabond 345 Axson H 9940 Laminating resins (mixed with cotton flocks and carb-o-sil, see section 4.4)

Gelcoats Gelcoats can be divided into spray-paintable gelcoats and mould surface gelcoats. Whereas the mould surface gelcoat is usually black or some darker colour, the spray-painting Gelcoat can have any colour, although it is frequently white. Spray-paint Gelcoat: Properties: Thick when mixed according to standards but can be diluted. Examples:   

   

SP 127 Hexion, T 35 Azko Nobel, Schwabellack NCS Ultra gel P1075

Mold surface Gel coat: Properties: Develops a hard and durable surface. Examples:  

  

Axon GC1050 Hex ion F 200/F 15 (polish able surface) Hex ion F 260/F 16 (non- polish able surface)

Casting resins Casting materials can be used for both high and low density foams or to form polyurethanebased rubbers. Examples:  

  

Axon F16 Axon 3034 Axon 5056

Resin additives (fillers) By augmenting a resin-hardener mixture with a variety of additives, a wide range of different properties can be obtained. These additives work well when mixed with epoxy resin systems

Cotton flocks This additive is made from natural cotton and appears as fine fibers. A mixture of cotton fibers and epoxy is referred to as “flux”. Other names: “Micro fibers”, “Cotton flakes” The mixture is used in structural joints and in areas where a very hard, durable build-up is required. Preparation: Flux is normally mixed with 1 part cotton and 1 part carb-o-sill to one part resin. Effects: Turns resin into a tough bonding compound Examples where used:   Bonding of parts   Filler material  To create chamfers when needed

Carb-o-sill Carb-o-sill or fused quartz is a non-crystalline form of silicon dioxide, also called silica. Other names are:  Aerosol (German)   Fused silica   Colloidal Silica (SP Systems) Carb-o-sill can be used to reduce the flow of epoxies on vertical surfaces, as well as for filling pinholes. Uses:   Carb-o-sill can be mixed with epoxies or gel coats to modify the flow characteristics  Carb-o-sill can be mixed with micro balloons or cotton flocks to give non-sag properties to fillers. Effects: It decreases the viscosity of resin. Examples where used:   Sealant in water tanks   As a bonding adhesive when mixed with laminating resin and other fillers (see 4.3.1)   A filler material, when combined with micro balloons.  Sealing paste on vacuum bag edges

Micro balloons Micro balloons are hollow spheres made from either glass or phenolic. The differences are:

Glass Micro balloons

Phenolic Micro balloons

Other names

Micro balloons

Glass bubbles

Color

White

Reddish/brown

Particle Size

40-80 microns

50 microns

Density

250g/liter

200g/liter

Sand ability

Good

Moderate

Waterproof

Moderate

Good

Cost

Expensive

Less expensive

Raw Materials

Also known as glass bubbles, micro balloons are used in composites to fill polymer resins for specific characteristics such as weight, sand ability and sealing properties. The term “micro” or “micro balloons” was applied to the mixture of solid microspheres and epoxy early in the development of composite structures. Although microspheres have been replaced by glass bubbles, “micro” is still commonly used to refer to a micro balloon and resin mixture. Effects: Lightens resin and eases its processing and application

CONSUMABLES CONSUMABLES:Capable of being consumed. Industrial consumables are those products that help to manufacture the final product. Eg:Release film, breather etc. *Note:-

 A product that is typically used .  Goods that get used up in manufacturing but are not considered a material. Consumables Inventory planning, Procurement, Management and Feeding Consumables for Assembly or production is a non-core, but a complex activity for OEM to spend on human resources and on management systems. Besides, if it is not focused and managed efficiently it would cost OEM from several thousand dollars a day to Hundreds of thousand dollars. Seine can offer solutions from being a simple demand supplier to a complete Line Feed Management Solutions Provider. Seine structured its consumables business as a demand supplier in its early stages and gradually grown in to a life cycle management solution provider to OEM Clients.

Hazards such as falling debris, excessive noise, electrical wiring, and chemical exposure can be prevalent on industrial sites. For those laboring among these potential safety threats, at least a minimal level of personal protective equipment (PPE) is necessary. Though all PPE should be selected based on the hazards involved, here is a list of five to wear: 1. Hard hats safeguard against falling objects and other flying debris and may be necessary for industrial and construction environments. Face shields and other head gear offer an additional barrier of protection. Full-face respirators are available for those exposed to harmful levels of chemicals or dust in the air. 2. Eyewear: Safety glasses help protect eyes from flying objects, radiation from hot objects, and other vision-threatening dangers. 3. Safety gloves for hand protection when working with sharp objects, chemicals, rugged or sensitive materials, and extreme temperatures. Gloves should fit well, be chemically compatible with the materials to be handled, and be suitable for the task involved. For example, heat-insulated

Neoprene gloves offer good chemical resistance. 4. Hearing protection: Earplugs and noise reduction tools are helpful in industrial facilities, construction, and transportation. Earmuffs can provide equal pressure distribution and maximum high-frequency attenuation. Some are crafted for use in high volume areas such as heavy industry facilities, jet engine environments, and near riveting activities. 5. Safety footwear so your feet and toes do not get crushed or damaged.

FABRICATION METHODS LAYUP Layup is a simple method for composite production. The process consists of building up or placing layers of composite fiber in a sequenced layup using a matrix of resin and hardener. There are several types of methods define.

· · · · · · · · ·

Hand Layup Method Autoclave Method Vacuum Bagging Method Filament Winding Pultrusion winding Resin Transfer Moulding Method Resin Infusion Moulding Method High Temperature Compression Moulding Low Temperature Compression Moulding

Hand Layup Method Resins are impregnated by hand into fibers which are in the form of woven, knitted, stitched or bonded fabrics. This is usually accomplished by rollers or brushes, with an increasing use of niproller type impregnators for forcing resin into the fabrics by means of rotating rollers and a bath of resin. Laminates are left to cure under standard atmospheric conditions

Advantages · · · · · ·

Design flexibility Large and complex items can be produced. Tooling cost is low. Design changes are easily effected. Sandwich constructions are possible. Semi-skilled workers are needed.

Disadvantages · · · ·

Only one molded surface is obtained. Quality is related to the skill of the operator. Low volume process. Longer cure times required.

Applications · Standard wind-turbine blades · Production boats · Architectural moldings.

Autoclave Method In the production of composite aerospace and aircraft components, autoclave curing has traditionally been used to achieve the desired fiber content (resin-to-fiber ratio) and the absence of resin voids to produce light weight and strong components. Autoclave curing achieves this by placing the part under vacuum in an autoclave and then pressurizing the autoclave during the heated cure cycle. The high pressure on the part (within the pressurized autoclave) helps to minimize resin voids and to achieve the desired resin/fiber ratio. Autoclaves are utilized where the highest of material performance standards are required such as a void content of less than 2% and high glass transition temperatures. Aerospace autoclaves normally operate from 120 to 230 degrees Celsius within a nitrogen environment at 7 bars of pressure. Liquid nitrogen is injected into the heated autoclave to create the internal pressure. Most common materials cured in an autoclave are advanced composites such as carbon fiber and epoxy resins. Curing cycles range from 90 minutes to 12 hours.

Controlled Variables · Temperature · Pressure · Vacuum

Autoclav

e curing chart

Applications · Vulcanization · Composite Curing · Sterilisation Vacuum Bagging Is a technique employed to create mechanical pressure on a laminate during its cure cycle. Pressurizing a composite lamination serves several functions. First, it removes trapped air between layers. Vacuum bagging techniques have been developed for fabricating a variety of aerospace components and structures. The process is principally suited to prepreg materials. This method utilizes a flexible film or rubber bag that covers the part lay-up. The bag permits evacuation of the air to apply atmospheric pressure. The primary limitation of this method is the limited pressure that can be applied. The bag used in this method has two fold objectives: · It provides a means for removing volatile products during cure; and · It provides a means for the application of a pressure of one atom which is adequate for some materials. The essential steps in the process are the lay-up, preparation of bleeder system and the bagging operation. The required number of plies are cut to size and positioned in a mold. When individual plies of a prepreg material are formed to the lay-up tool, certain amount of voids exists between layers. The lay-up is covered with a flexible membrane or vacuum bag, which is sealed around the edges of the mold by a sealant. An edge bleeder is also placed near the edges of the lay-up. Its function is to absorb excess resin, which may flow during curing. Requirement for proper bagging are:

p Bag to be impervious to air pressure, q Bag to uniformly apply the cure pressure, r Bag not to leak under over-pressure, and

Filament Winding Filament winding is a fabrication technique mainly used for manufacturing open (cylinder) or closed end structures (Pressure vessels or tanks). This process involves winding filament under tension over a rotating mandrel. Once the resin has cured, the mandrel is removed or extracted, leaving the hollow final product.

Process:The process of Filament Winding

· Uses a continuous length of fiber strand / roving (Called Direct Single end Roving), or tape · Patterns may be longitudinal, circumferential, helical or polar · Mostly requires thermal curing of work pieces · Filament winding processes can be either Continuous or Discontinuous type.

Continuous winding Process Continuous winding processes are used to manufacture low pressure, small to very large diameter pipes continuously on a mandrel formed out of an endless band (commonly known as the Drostholm Process).

Pipes manufactured through this process are primarily used for media (water, sewage, waste-water) transmission / distribution networks. Continuous winders are usually 2 axis machines capable of laying fibre, fiberglass cloth, veil in a continuous hoop pattern.

Discontinuous Winding Process Discontinuous winding process is used to manufacture high pressure parts, pipes, pressure vessels and complex components. Multi axes machine are used to customize the angle of lay for the fiberglass band.

Filament winding machines: · 2 axis Pipe winder – pipes of all sizes (up to ⌀6000m) · 2 axis multiple spindle - for small tubes under ⌀400m (higher productivity) · 4 axis bottle/ tank winder – general purpose winder · 4 axis multiple spindle – for small bottles & tubes (higher productivity) · 6 axis winder – Aerospace / R&D / Tape winding / Special applications

Pultrusion winding Pultrusion is a continuous process for manufacturing of composite material with constant cross section Pultruded FRP sections are usually made by pultrusion process. This process creates continuous composite profile by pulling raw composites through a heated die. Pultrusion combines words “pull” and “extrusion” where extrusion is pulling of material such as fiberglass and resin, through a shaping die. Many resin types can be used in pultrusion including polyester, polyurethane and vinyl ester epoxy resins etc. Fiber is wetted or impregnated with resin and is organized and then removed of excess resin. After that the composite is passed through a heated steel die. Precisely machined and often chromed, the die is heated to a constant temperature. Generally it is produced in sections of various profiles like Beams, Angles, Tubes, Hollow Square, solid Rods of various profiles.

Advantages: 1. Increased Strength (fiber processed under tension) 2. High Fiber Content 3. Highly Automated 4. Consistent Quality 5. High Production 6. Low Labor Required 7. Low Cost

Resin Transfer Molding RTM is a low pressure molding process, where a mixed resin and catalyst are injected into a closed mould containing a fibre pack or preform. When the resin has cured the mould can be opened and the finished component removed. A wide range of resin systems can be used including polyester, vinylester, epoxy, phenolic etc, combined with pigments and fillers including aluminium trihydrates and calcium carbonates if required. The fiber pack can be either, glass, carbon, aramid, or a combination of

these. There are a large variety of weights and styles commonly available. Working Process Reinforcement mat or woven roving is placed in the mold, which is then closed and clamped. Catalyzed, low-viscosity resin is pumped in under pressure, displacing the air and venting it at the edges, until the mold is filled. Molds for this low-pressure system are usually made from composite or nickel shell-faced composite construction.

Benefits of RTM There are several benefits to using the resin transfer molding process over the alternative processes available. Some key benefits include: p Good surface quality q Wide range of reinforcements r Large, complex shapes s Dimensional tolerances t Low capital investment u Less material wastage v Tooling flexibility w Low environmental impact x Labor savings

Application Small complex aircraft and automative componant, train sheeta.

Resin Infusion Method

Vacuum infusion, also called resin infusion, is a fabrication technique that uses vacuum pressure to drive resin into a laminate.Working Process Dry materials are laid into the mold and the vacuum pressure

is applied before resin is introduced. Once a complete vacuum is achieved, resin is forced into the laminate via vacuum tubing. The vacuum infusion process offers a better fiber-to-resin ratio than hand lay-up or vacuum bagging. In a typical hand lay-up, reinforcements are laid into a mold and manually wet out using brushes, rollers, or through other means. And resin out of the laminate, and results in a stronger and lighter product.

Benefits of Vacuum Infusion Vacuum infusion provides a number of improvements over traditionally vacuum bagged parts. These benefits include: • Better fiber-to-resin ratio • Less wasted resin • Very consistent resin usage • Unlimited set-up time • Cleaner

Compression Molding Method Compression molding is a forming process in which material is placed directly into a heated metal mold, then is softened by the heat, and forced to conform to the shape of the mold as the mold close. The advantage of compression molding is its ability to mold large, fairly intricate parts. Also, it is one of the lowest cost molding methods compared with other methods such as transfer molding and injection molding There are two types of compression molding are defined. · Low temperature compression molding. · High temperature compression molding.

High temperature compression molding It is a high-volume, high-pressure method suitable for molding complex, high-strength fiberglass reinforcements. Advanced composite thermoplastics can also be compression molded with unidirectional tapes, woven fabrics, randomly oriented fiber mat or chopped strand. In this method tool will only generate the heat, here no need to

use any other heater or heating machine.

Low temperature compression molding It is a method of molding in which the moulding material, generally preheated, is first placed in an open, heated mould cavity. The mold

is closed with a top force or plug member, pressure is applied to force the material into contact with all mold areas, while heat and pressure are maintained until the molding material has cured. The process employs thermosetting resins in a partially cured stage, either in the form of granules, putty-like masses, or preforms.