Composites manufacturing sanjay mazumdar pdf download

The most common reinforcements are glass, carbon, aramid and boron fibers. Typical fiber diameters range from 5 mm 0. Because of this thin diameter, the fiber is flexible and easily conforms to various shapes. In general, fibers are made into strands for weaving or winding operations.

The matrix gives rigidity to the structure and transfers the load to fibers. Fibers for composite materials can come in many forms, from continuous fibers to discontinuous fibers, long fibers to short fibers, organic fibers to inorganic fibers. The most widely used fiber materials in fiber-reinforced plas- tics FRP are glass, carbon, aramid, and boron. Glass is found in abundance and glass fibers are the cheapest among all other types of fibers.

There are three major types of glass fibers: E-glass, S-glass, and S2-glass. The properties of these fibers are given in Table 2.

Carbon fibers range from low to high modulus and low to high strength. Three spools of glass yarns are shown at the center and four roving spools are shown at edges. Courtesy of Saint-Gobain Vetrotex America. Glass rovings and yarns are shown in Figure 2. Continuous fibers are used with most thermoset and thermoplastic resin systems. Chopped fibers are used for making injection molding and compression molding compounds. Chopped fibers are made by cutting the continuous fibers.

In spray-up and other processes, continuous fibers are used but are chopped by machine into small pieces before the application. Woven fabrics are used for making prepregs as well as for making laminates for a variety of applications e. Preforms are made by braiding and other processes and used as reinforcements for RTM and other molding operations. The next section provides a brief description of manufacturing techniques for glass, carbon, and Kevlar fibers.

The raw materials used for making E-glass fibers are silica sand, limestone, fluorspar, boric acid, and clay. By varying the amounts of raw materials and the processing parameters, other glass types are produced.

The melt flows into one or more bushings containing hundreds of small orifices. The filaments are then pulled over a roller at a speed around 50 miles per hour. The roller coats them with sizing. The amount of sizing used ranges from 0. All the filaments are then pulled into a single strand and wound onto a tube. Sizing is applied to the filaments to serve several purposes; it promotes easy fiber wetting and processing, provides better resin and fiber bonding, and protects fibers from breakage during handling and processing.

The sizing formulation depends on the type of application; for example, sizing used for epoxy would be different than that used for polyester. The precursor undergoes a series of operations. In the first step, the precursors are oxidized by exposing them to extremely high temperatures.

Later, they go through carbonization and graphitization processes. During these processes, precursors go through chemical changes that yield high stiff- ness-to-weight and stength-to-weight properties. The successive surface treat- ment and sizing process improves its resin compatibility and handleability.

Pitch fiber is obtained by spinning purified petroleum or coal tar pitch. PAN-based fibers are most widely used for the fabrication of carbon fibers. Pitch-based fibers tend to be stiffer and more brittle.

The cost of carbon fiber depends on the cost of the raw material and process. The fabrication method for the production of carbon fibers is slow and capital intensive. Therefore, higher tow count is produced to lower the cost of the fibers.

There is a limitation on increasing the tow size. For example, a tow size more than 12K creates processing and handling difficulties during fila- ment winding and braiding operations. Pitch-based carbon fibers are produced in the same way as PAN-based fibers but pitch is more difficult to spin and the resultant fiber is more difficult to handle.

Pitch itself costs pennies a kilogram, but processing and purifying it to the fiber form are very expensive. Generally, pitch-based fibers are more expensive than PAN-based fibers. The cost of carbon fibers depends on the strength and stiffness properties as well as on the tow size number of filaments in a fiber bundle. Fibers with high stiffness and strength properties cost more.

The higher the tow size, the lower the cost will be. For example, 12K tow 12, filaments per fiber bundle costs less than 6K tow. They provide good impact strength. Like carbon fibers, they provide a negative coefficient of thermal expansion.

The disadvantage of aramid fibers is that they are difficult to cut and machine. Aramid fibers are produced by extruding an acidic solution a proprietary polycondensa- tion product of terephthaloyol chloride and p-phenylenediamine through a spinneret.

The filaments are drawn through several orifices. During the drawing operation, aramid molecules beome highly oriented in the longitu- dinal direction. Matrix surrounds the fibers and thus protects those fibers against chemical and environmental attack.

For fibers to carry maximum load, the matrix must have a lower modulus and greater elongation than the reinforcement. Matrix selection is performed based on chemical, thermal, electrical, flam- mability, environmental, cost, performance, and manufacturing require- ments. The matrix determines the service operating temperature of a composite as well as processing parameters for part manufacturing.

Maxi- mum continuous-use temperatures of the various types of thermoset and thermoplastic resins are shown in Table 1. During curing, they form three-dimensional molecular chains, called cross-linking, as shown in Figure 2. Due to these cross-linkings, the molecules are not flexible and cannot be remelted and reshaped. The higher the number of cross-linkings, the more rigid and thermally stable the material will be. In rubbers and other elastomers, the densities of cross-links are much less and therefore they are flexible.

Thermosets may soften to some extent at elevated temperatures. This characteristic is sometimes used to create a bend or curve in tubular structures, such as filament-wound tubes. Thermosets are brittle in nature and are generally used with some form of filler and reinforcement. Thermoset resins provide easy processability and better fiber impregnation because the liquid resin is used at room temperature for various processes such as filament winding, pultrusion, and RTM.

Thermosets offer greater thermal and dimensional stability, better rigidity, and higher electrical, chem- ical, and solvent resistance. The most common resin materials used in ther- moset composites are epoxy, polyester, vinylester, phenolics, cyanate esters, bismaleimides, and polyimides. Some of the basic properties of selected thermoset resins are shown in Table 2. TABLE 2. It exhibits low shrinkage as well as excel- lent adhesion to a variety of substrate materials. Epoxies are the most widely used resin materials and are used in many applications, from aerospace to sporting goods.

There are varying grades of epoxies with varying levels of performance to meet different application needs. They can be formulated with other materials or can be mixed with other epoxies to meet a specific performance need. By changing the formulation, properties of epoxies can be changed; the cure rate can be modified, the processing temperature requirement can be changed, the cycle time can be changed, the drape and tack can be varied, the toughness can be changed, the temperature resistance can be improved, etc.

Epoxies are cured by chemical reaction with amines, anhydrides, phenols, carboxylic acids, and alcohols. An epoxy is a liquid resin containing several epoxide groups, such as diglycidyl ether of bisphe- nol A DGEBA , which has two epoxide groups.

In an epoxide group, there is a three-membered ring of two carbon atoms and one oxygen atom. In addition to this starting material, other liquids such as diluents to reduce its viscosity and flexibilizers to increase toughness are mixed. The curing cross- linking reaction takes place by adding a hardener or curing agent e. These cross-links grow in a three-dimensional network and finally form a solid epoxy resin. Each hardener provides different cure characteristics and different properties to the final product.

The higher the cure rate, the lower the process cycle time and thus higher production volume rates. Epoxy-based composites provide good performance at room and elevated temperatures. For high-tempera- ture and high-performance epoxies, the cost increases, but they offer good chemical and corrosion resistance.

Epoxies come in liquid, solid, and semi-solid forms. Liquid epoxies are used in RTM, filament winding, pultrusion, hand lay-up, and other processes with various reinforcing fibers such as glass, carbon, aramid, boron, etc. Semi-solid epoxies are used in prepreg for vacuum bagging and autoclave processes.

Solid epoxy capsules are used for bonding purposes. Epoxies are more costly than polyester and vinylesters and are therefore not used in cost-sensitive markets e. Epoxies are generally brittle, but to meet various application needs, tough- ened epoxies have been developed that combine the excellent thermal prop- erties of a thermoset with the toughness of a thermoplastic.

Toughened epoxies are made by adding thermoplastics to the epoxy resin by various patented processes. They are used for aircraft interiors, stowbins, and galley walls, as well as other commercial markets that require low-cost, flame-resistant, and low- smoke products. Phenolics are formed by the reaction of phenol carbolic acid and form- aldehyde, and catalyzed by an acid or base.

Urea, resorcinol, or melamine can be used instead of phenol to obtain different properties. Their cure characteristics are different than other thermosetting resins such as epoxies, due to the fact that water is generated during cure reaction.

The water is removed during processing. In the compression molding process, water can be removed by bumping the press. Phenolics are generally dark in color and therefore used for applications in which color does not matter. The phenolic products are usually red, blue, brown, or black in color. To obtain light- colored products, urea formaldehyde and melamine formaldehyde are used. Phenolics are used for various composite manufacturing processes such as filament winding, RTM, injection molding, and compression molding.

Phenolics provide easy processability, tight tolerances, reduced machining, and high strength. Because of their high temperature resistance, phenolics are used in exhaust components, missile parts, manifold spacers, commuta- tors, and disc brakes. The operating service temperatures for polyesters are lower than for epoxies. Polyesters can be a thermosetting resin or a thermoplastic resin. Unsaturated polyesters are obtained by the reaction of unsaturated difunc- tional organic acids with a difunctional alcohol.

The acids used include maleic, fumaric, phthalic, and terephthalic. The alcohols include ethylene glycol, propylene glycol, and halogenated glycol. The carbon-carbon double bonds in unsaturated polyester molecules and styrene molecules function as the cross-linking site. In recent methods, catalysts are used for curing polyesters with reduced styrene. They offer good chemical and corrosion resistance and are used for FRP pipes and tanks in the chemical industry. They are cheaper than epoxies and are used in the automotive and other high-volume applications where cost is critical in making material selection.

Vinylesters are formed by the chemical reaction of an unsaturated organic acid with an epoxide-terminated molecule. In vinylester molecules, there are fewer unsaturated sites for cross-linking than in polyesters or epoxies and, therefore, a cured vinylester provides increased ductility and toughness.

If they are formulated correctly, their high-temperature properties are similar to bisma- leimide and polyimide resins. They are used for a variety of applications, including spacecrafts, aircrafts, missiles, antennae, radomes, microelectron- ics, and microwave products.

Cyanate esters are formed via the reaction of bisphenol esters and cyanic acid that cyclotrimerize to produce triazine rings during a second cure. Cyanate esters are more easily cured than epoxies. The toughness of cyanate esters can be increased by adding thermoplastics or spherical rubber particles. These values are much higher than for epoxies and polyesters.

The lack of use of BMIs and polyimides is attributed to their processing difficulty. They emit volatiles and moisture during imidization and curing. Therefore, proper venting is necessary during the curing of these resins; otherwise, it may cause process-related defects such as voids and delaminations. Other drawbacks of these resins include the fact that their toughness values are lower than epoxies and cyanate esters, and they have a higher moisture absorption ability.

The automotive industry is a big market for these processes. Polyurethane is currently used for automotive applications such as bumper beams, hoods, body panels, etc. Unfilled polyurethane is used for various applications, including truck wheels, seat and furniture cushions, mattress foam, etc. Polyurethane is also used for wear and impact resistance coatings. Polyurethane can be a thermosetting or thermoplastic resin, depending on the functionality of the selected polyols.

Thermoplastic-based polyurethane contains linear molecules, whereas thermoset-based resin contains cross- linked molecules. Polyurethane is obtained by the reaction between polyisocyanate and a polyhydroxyl group. There are a variety of polyurethanes available by select- ing various types of polyisocyanate and polyhydroxyl ingredients.

Polyure- thane offers excellent wear, tear, and chemical resistance, good toughness, and high resilience. Thermoplastics can be melted by heating and solidified by cooling, which render them capable of repeated reshaping and reforming.

Thermoplastic molecules do not cross-link and therefore they are flexible and reformable. Thermoplastics can be either amorphous or semi- crystalline, as shown in Figure 2. In amorphous thermoplastics, molecules are randomly arranged; whereas in the crystalline region of semi-crystalline plastics, molecules are arranged in an orderly fashion. Some of the properties of themoplastics are given in Table 2. Their lower stiffness and strength values require the use of fillers and rein- forcements for structural applications.

Thermoplastics generally exhibit poor creep resistance, especially at elevated temperatures, as compared to thermo- sets.

They are more susceptible to solvents than thermosets. Thermoplastic resins can be welded together, making repair and joining of parts more simple than for thermosets. Repair of thermoset composites is a complicated process, requiring adhesives and careful surface preparation.

Thermoplastic compos- ites typically require higher forming temperatures and pressures than com- parable thermoset systems. Thermoplastic composites do not enjoy as high a level of integration as is currently obtained with thermosetting systems.

The higher viscosity of thermoplastic resins makes some manufacturing pro- cesses, such as hand lay-up and tape winding operations, more difficult.

As a consequence of this, the fabrication of thermoplastic composite parts have drawn a lot of attention from researchers to overcome these problems.

Glass-filled and carbon-filled nylons in pellet form are available for injection molding purposes. Nylons are most widely used for injection molding purposes, but are also available as prepregs with various reinforcements. Nylons have been used for various pultruded components. Nylons are also called polyamides. There are several types of nylon, includ- ing nylon 6, nylon 66, nylon 11, etc.

Nylons provide a good surface appearance and good lubricity. The important design consideration with nylons is that they absorb moisture, which affects the properties and dimensional stability of the part. Glass reinforcement minimizes this problem and produces a strong, impact-resis- tant material. Impact resistance of long glass-filled nylon is higher than conventional engineering materials such as aluminim and magnesium, as shown in Figure 1. It has the lowest density 0.

PP is used for machine parts, car components fans, fascia panels, etc. As well, PEEK has the advantage of almost 10 times lower water absorption than epoxies. The water absorption of PEEK is 0. The toughness offered by PEEK is 50 to times higher than that of epoxies. PPS-based composites are used for appli- cations where great strength and chemical resistance are required at elevated temperature.

These fabrics are woven yarns, rovings, or tows in mat form in a single layer. Common weave styles are shown in Figure 2. The amount of fiber in different directions is controlled by the weave pattern. Courtesy of Cytec Fiberite. For lightning strike purposes, conductive wires are woven into fabric forms to distribute the energy imparted by lightning, thus minimizing damage to the structure.

Woven fabrics have the advantage of being inexpensive. Warp unidirec- tional fabric is used when fibers are needed in one direction only, for example, in stiffness-critical applications such as water ski applications where the fabric is laid along the length of the ski to improve resistance to bending. Quadraxial fabrics are quasi-isotropic, pro- viding strength in all four fiber axial directions.

Noncrimp fabrics offer greater flexibility compared to woven fabrics. Noncrimp fabrics are available in a thick layer and thus an entire laminate could be achieved in a single-layer fabric. This is useful in making thicker laminates such as boat hulls and reduces the num- ber of fabrication steps. A larger yield number denotes a finer roving and, therefore, more yards are required to achieve a given weight. The selection of yield number is determined by the physical, mechanical, and aesthetic requirements of the laminate.

The finer filaments mean higher fiber content and less resin. This improves strength and can reduce weight. To meet the market need for heavier fabrics, stitched fabrics with various combinations of plies are produced. Unidirectional tape provides the ability to tailor the composite properties in the desired direction.

Woven fabric prepregs are used to make highly contoured parts in which material flexibility is key. It is also used to make sandwich panels using honeycomb as a core material.

Preimpregnated rovings are primarily used in filament winding applications. Epoxy-based prepregs are very common in industry and come in flat sheet form in a thickness range of 0. Reinforcements in a prepreg can be glass, carbon, or aramid, and are used in filament or woven fabric or mat form in either type of prepreg.

Table 2. Properties of thermoset- and thermoplastic-based prepreg tapes with unidirectional fibers, as well as plain weave fabric forms, are also shown in the table. The table presents a wide range of material possibilities and performance potentials, which pro- vides easy and quick assessment of the various prepregs.

They eliminate the need for weighing and mixing resin and catalyst. Various types of drape and tack are provided with prepregs to meet various application needs.

Drape is the ability of prepreg to take the shape of a contoured surface. For example, thermoplastic prepregs are not easy to drape, whereas thermoset prepregs are easy to drape.

Tack is the stickiness of uncured prepregs. A certain amount of tack is required for easy laying and processing. Because thermoplastic tapes do not have any tack, they are welded with another layer while laying up. Thermoset prepregs have a limited shelf life and require refrigeration for storage. Refrig- eration minimizes the degree of cure in the prepreg materials because heat causes thermoset prepregs to cure. Unidirectional prepreg tapes are available in a wide variety of widths, ranging from 0.

By laying unidirectional tapes at desired ply orientations, the stiffness, strength, and coefficient of thermal expansion properties of the structure can be controlled. Fabric prepregs are available in a number of weave patterns in standard widths ranging from 39 to 60 in. Fabric prepregs are made by preimpregnating woven fabrics with resin via a hot melt process or by solution treatment.

They provide a good amount of flexibility in highly contoured and complex parts. Shelf Life Temp. Prepregs in roving form are also available for filament winding purposes. Prepregs are used in a wide variety of applications, including aerospace parts, sporting goods, printed circuit boards, medical components, and industrial products.

The advantages of prepreg materials over metals are their higher specific stiffness, specific strength, corrosion resistance, and faster manufacturing.

The major disadvantage of prepreg materials is their higher cost. Products made with prepreg materials provide a higher fiber volume fraction than those made by filament winding and pultrusion. Prepregs also provide more controlled properties and higher stiffness and strength properties than other composite products. These prepregs are generally stored in a low-temperature environment and have a limited shelf life.

Room-temperature prepregs are also becoming available. Usually, the resin is partially cured to a tack-free state called B-staging. Several additives e. Thermoset prepregs require a longer process cycle time, typically in the range of 1 to 8 hr due to their slower kinetic reactions. Due to higher production needs, rapid-curing thermoset prepregs are being developed.

Thermoset prepregs are more common and more widely used than ther- moplastic prepregs. They are generally made by solvent impregnation and hot melt technology. In the solvent impregnation method, the resin is dis- solved by a chemical agent, creating a low-viscosity liquid into which fibers are dipped. Due to growing environmental awareness, disposal of the sol- vent resulting from this process is becoming a concern.

The hot melt tech- nology eliminates the use of solvents. In this process, the matrix resin is applied in viscous form. The drawback of this process is that fiber wetting is not easily achievable due to the higher viscosity of the resin. Prepregs are generally used for hand lay-up, roll wrapping, compression molding, and automatic lay-up processes.

Once the prepregs are laid on a tool, it is cured in the presence of pressure and temperature to obtain the final product. The most common resins are nylon, polyetheretherketone PEEK , polyphe- nylene sulfide, polyimide, etc.

The process cycle time for thermoplastic com- posites is much faster than thermoset composites, in the range of a few minutes.

They provide some processing difficulties because of their poor drape capabilities. Thermoplastic prepregs are manufactured by solvent impregnation and hot melt coating techniques similar to thermoset prepreg manufacturing.

Solvent impregnation becomes difficult because thermoplastics offer more chemical resistance. The hot melt coating technique is similar to an extrusion process, wherein fibers and resins are extruded simultaneously in sheet form.

There are other manufacturing methods such as film stacking and dry pow- der deposition methods for prepreg fabrication. In the film stacking process, the thermoplastic resin film is stacked together with the reinforcements and consolidated under heat and pressure to fully imprepregnate the fibers.

This process is clean and solvent-free but requires proper care for the production of a void-free prepreg. In the dry powder deposition technique, the resin must be in powder form as a starting material. The powder is fluidized and charged to form a resin cloud. The fibers are passed through the cloud and coated with the charged resin as they get attracted to the fibers.

The coated fibers are then passed through a heat source to fully melt the resin and form a continuous sheet of material. Preforms are made in several ways. To make a preform by braiding and filament winding, dry fibers are laid over a mandrel as shown in Figure 2. Courtesy of Fiber Innovations Inc. Courtesy of Fiber Innovations, Inc. The braided preform is becoming common and is widely used for RTM processes. Braiding can be done over a mandrel of nearly any shape or size.

The cost estimating and production planning chapters are very comprehensive. It contains many references to sources of more detailed information. John O. Post a Comment. October 07, No comments.

Email This BlogThis! Share to Twitter Share to Facebook. Social Profiles. The most up to date publication from an extremely renowned wr Checking out makes you much better. Labels Ebooks. Subscribe to Posts [ Atom ]. More and more companies manufacture reinforced composite products. To meet the market need, researchers and industries are developing manufacturing methods without a reference that thoroughly covers the manufacturing guidelines. The author presents a fundamental classification of processes, helping you understand where a process fits within the overall scheme and which process is best suited for a particular component.

The book is well written and illustrated, logically organized and easy to follow. This book is a welcome to my library and is recommended to the readers with interest in the manufacturing of composites. It is a wonderful tool chest of knowledge that we all can use for review.

This book is very much needed in the industry, to help train new people in the craft that most of us learned by the school of trial and errorI no longer see this book as it is being read by everyone around herevery impressed with this new book. This book is an excellent source of information for all disciplines, bringing together both introductory and advanced resources in one publication.

It focuses on the fundamental processes an engineer or program manager must address when planning to employ advanced composites into his or her project.

The book encompasses the latest technology and design issues as composite design science matures. The cost estimating and production planning chapters are very comprehensive.

It contains many references to sources of more detailed information. John O. Reviews from 5 leading experts in the composites industry By A Customer This book is reviewed by several leading experts in the field of composites manufacturing.