2. textile reinforced composites

By: Granch Berhe2015

Textile Reinforced Composites

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Textile-Reinforced Composite Materials

Composite materials, Textile reinforcement, Woven fabric-reinforced composites, Braided reinforcement, Knitted reinforcement, Stitched fabrics;

Textiles in Filtration: Introduction, Dust collection, Fabric construction, Finishing treatments, Yarn types and fabric constructions, Fabric constructions and properties, Production equipment, Finishing treatments, Fabric test procedures;

Introduction to compositesWhat is a composite Material ? Two or more chemically distinct materials which when

combined have improved properties over the individual materials.Example: Wood, Bamboo, Bricks.

Composites are combinations of two materials in which one of the material is called the reinforcing phase, is in the form of fibers, sheets, or particles, and is embedded in the other material called the matrix phase. It is the main constituent of composites materials mainly responsible for its mechanical properties. Its percentage in the composite may be up to 70% by volume.

Composition of composites

Components of composite materials

Reinforcement: fibers

GlassCarbonOrganicBoronCeramicMetallic

Matrix materials

PolymersMetalsCeramics

Interface

Bonding surface

Classification of compositesFirst Level (Matrix Material)

Polymer Matrix composites (epoxides, polyesters, nylons, etc)Ceramic Matrix Composites (SiC, glass ceramics, etc)Metal Matrix Composites (aluminum alloys, magnesium alloys,

titanium, etc)

Second Level (reinforcement form)

Fibre -short or long fibre ((S-glass, R-glass, carbon fibres, boron fibres, ceramic fibres and aramid)

YarnFabric Composites (woven , knitted , nonwoven and braided)

Polymer Matrix Composites On the basis of type of polymer resin used, composite materials can be classified into two categories.

• Thermoplastic Composites• Thermo-set Composites

Thermoplastic Composites:This is type of composite material with thermoplastic resin like polyester, HDPE etc. They are lesser used as high-tech materials due to their higher viscosity which cause problem during their penetration into the reinforcement.

Thermo-set Composites:In these composites thermo-set polymers like epoxy, unsaturated polyester and vinyl-ester are used as resin. They are most used type of composites materials in automotive, naval, aeronautical and aerospace applications.

Polymer Matrix Composites Polymer matrix composites (PMC) and fiber reinforced plastics (FRP) are referred to as Reinforced Plastics. Common fibers used are glass (GFRP), graphite (CFRP), boron, and aramids (Kevlar). These fibers have high specific strength (strength-to-weight ratio) and specific stiffness (stiffness-to-weight ratio)

Matrix materials are usually thermoplastics or thermosets; polyester, epoxy (80% of reinforced plastics), fluorocarbon, silicon, phenolic.

Ceramic Matrix Composites Ceramic matrix composites (CMC) are used in applications where resistance to high temperature and corrosive environment is desired. CMCs are strong and stiff but they lack toughness (ductility).

Matrix materials are usually silicon carbide, silicon nitride and aluminum oxide, and mullite (compound of aluminum, silicon and oxygen). They retain their strength up to 3000 oF.

Fiber materials used commonly are carbon and aluminum oxide.

Applications are in jet and automobile engines, deep-see mining, cutting tools, dies and pressure vessels.

Metal Matrix Composites The metal matrix composites offer higher modulus of elasticity, ductility, and resistance to elevated temperature than polymer matrix composites. But, they are heavier and more difficult to process.

Classification on the Basis of Reinforcements

The reinforcements used during manufacturing may be in form of laminates which are combined to get certain thickness or in the form of thick woven cloth. So on the basis of reinforcement composites can be categorized in two categories :

1. Laminated Composites2. 3-D woven Composites

Laminated Composites: In laminar composites the layers of reinforcement are stacked in a specific pattern to obtain required properties in the resulting composite piece . These layers are called plies or laminates. Laminates can be composed of reinforcement material which may be

• Woven• Knitted • Non woven• Braided• Fiber reinforced• Matt• Uni-directional fibers or UDs

Woven fabric-reinforced composites

Woven fabrics, characterized by the interlacing of two or more yarn systems, are currently the most widely used textile reinforcement with glass, carbon and aramid reinforced .woven composites being used in a wide variety of applications, including aerospace (Fig. 11.4).Woven reinforcement exhibits good stability in the warp and

Optical micrograph of woven composite- side view


The mechanical properties of woven fabric-reinforced composites are dominated by the type of fibre used, the weaving parameters and the stacking and orientation of the various layers.

Woven reinforcement exhibits good stability in the warp and weft directions and offers the highest cover or yarn packing density in relation to fabric thickness. Glass-reinforced woven fabrics give rise naturally to composites with lower mechanical properties because of the much lower value of the glass fibre modulus compared to carbon.

Prepreg manufacturers were able, by the early 1980s, to supply woven fabrics in the prepreg form familiar to users of nonwoven material.

3D woven compositesThese composites have reinforcement of 3D woven or 2D+ multilayer interlock fabric. These composites have much better through the thickness properties as compared to laminated composites

Knitted fabric-reinforced composites

The major advantages of knitted fabric-reinforced composites are the possibility of producing net shape/near net shape preforms, on the one hand, and the exceptional drapability/formability of the fabrics, which allows for forming over a shaped tool of complex shape, on the other. Both of these features follow from the interlooped nature of the reinforcing fibres/yarns which permits the fabric to have the stretchability to adapt to complex shapes without crimp.


However, the advantages which the knitted fibre architecture brings also lead to the disadvantages, which are the reduced in-plane stiffness and strength of the composites caused by the relatively poor use of the mechanical properties of the fibre (glass, carbon or aramid).

The tensile and compressive properties of the knitted fabrics are poor in comparison with the other types of fabric. Hence both warp-knitted and weft-knitted reinforcements are under investigation.

Braided- reinforcement composites

Braided textiles for composites consist of intertwined two (or more) sets of yarns, one set of yarns being the axial yarns. In two-dimensional braiding, the braided yarns are intertwining in 1 x 1 or 2 x 2patterns.


The braided architecture enables the composite to endure twisting, shearing and impact better than woven fabrics. Combined with low cost fabrication routes, such as resin transfer moulding, braided reinforcements are expected to become competitor materials for many aerospace applications or automobile applications.

A variety of shapes can be fabricated for composite applications from hollow tubular to solid sections. The mechanical properties of composites fabricated using braided reinforcement depend on the braid parameters (braid architecture, yarn size and spacing, fibre volume fraction) and the mechanical properties of fibre and matrix.

Stitched fabric- reinforcement composites

Stitching of composites adds one further production step with the use of a sewing machine to introduce lock stitches through the full thickness of the laminate. The stitching can be performed on unimpregnated fibres or fibres in the prepreg form, although the latter is usually to be avoided owing to excessive fibre damage. Stitching in this way can be carried out with carbon, glass or aramid fibre yarns.

stitch

Other -reinforcement composites

• Laminar composite structure – conventional• Sandwich structure• Honeycomb sandwich structure

Composites manufacturing process

• Pultrusion• Spray method• Sheet molding• Bulk molding• Resin transfer molding• Hand Lay-up• Pre-preg forming• Pressure molding• Vacuum bagging• Filament winding

Pultrusion Method

Spray Method

Sheet molding

Hand Lay-up Method

Pre- perg Method

Pressure molding

Vacuum bagging method

Expansion method

In this process thin metal sheet is first cut into panels and strip bondedThis process is referred to as the “honeycomb before expansion” or HOBE method. This can be cut and stretched perpendicular to the strip bonds to create a hexagonal structure. The expansion process requires moderately high inter-sheet bond strengths (sufficient to enable sheet stretching). For low density honeycombs with very thin webs

Corrugated method

The process for forming a hexagonal honeycomb core; however this process may be used for numerous additional topologies including square and triangular shaped cells

Other methods

Calendar is consist of rollers(known as Bowls) by using this we can control the thickness of elastomer sheet. the bowls can be horizontal of vertical the material from the mixer is fed between the nips of the bowls. the desiered sheet thickness can achieved by adjusting the nips.

Production of fiber tapes by encasing fibers between metal cover sheets by diffusion bonding

Nano composites

Nanoparticulates (filler) introduced into a macroscopic sample material (matrix). Percentage by weight (mass fraction) of the nanoparticulates can remain very low on the order of 0.5% to 5%.

Nanocomposite may exhibit enhanced properties• electrical and thermal conductivity• optical properties• dielectric properties • mechanical properties • stiffness • Strength

…Or nanoparticles can impart new physical properties and behaviors to matrix (genuine nanocomposites or hybrids)

• flame retardancy • accelerated biodegradability

Nano composite: Under a microscope

Carbon

Nanotubes

Polymer

Matrix

Application of composites

• Aerospace• Missile tech• Automotive• High speed machinery• Equipment parts• Coolers• Office cabins• Room insulations

Application of composites

Application of composites in aircraft industry

Boeing 787 – case study

Boeing 787

Technological Benefits of 787 (aka. “Dreamliner”)I. Light weight-

a. Fuel efficientb. Longer range than comparable aircraft

II. Reduced maintenance costsa. $30-40 million in savings

i. High reduction in fatigueii. Highly corrosion resistant

III. Increased passenger comforta. Increase in cabin pressureb. Increased humidity

i. Result of high corrosion resistancec. Bigger windows due to increased strengthd. Less noise

i. Front engine cowl intake is made of a single piece of composite, reducing drag

IV. Decreased assembly time a. Parts arrive from suppliers as net-shape

b. Components are pre-installed in parts at supplier factory

Cost- Benefit Analysis of the Boeing 787I. Boeing estimates that 787 will consume $5 million less in fuel on a comparable route than 767

a. Savings = Price of planeII. Potentially longer life

a. Not proven yet, but likely due to the high reduction in corrosion and fatigue 47

Boeing 787

Cost- Benefit Analysis of the Boeing 787I. Boeing estimates that 787 will consume $5 million less in fuel on a comparable route than 767

a. Savings = Price of planeII. Potentially longer life

a. Not proven yet, but likely due to the high reduction in corrosion and fatigue

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2. textile reinforced composites

Engineering

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