:Elastomer :Reinforced Plastic:Honeycomb Material Topic
Members • Imtiaz Ahmad(BSME01113115) • Khawer Saeed(BSME01113139)
Elastomer• Synthetic-rubber like material which, at room temperature, can be easily bent, stretched, twisted, or deformed and, when released, quickly returns to its approximate original dimensions and shape.
Elastomeric Materials• Highly amorphous• Highly random orientation• High elongation
Elastomeric Materials Metals Strain Conventional Plastics Stre ss Elastomers
Elastomeric Materials No Stress Stressed In tension
Elastomer Unsaturated rubber that can be vulcanized (Thermosets) are 1=>Natural rubber(NR) 2=>Polyisoprene(IR) 3=>polybutadiene(PB) 4=>choloprene rubber(CR) Saturated rubber 1=>Epichlorohydrin rubber(ECO) 2=> Silicone rubber(SI) 3=Flourosilicone rubber(FVMQ) Thermoplastic
Aliphatic Thermoset Elastomers• These are the most common elastomers• These have a double bond after polymerization has occurred• These are noncrystalline• These are highly flexible
Thermoplastic Elastomer (TPE)• These materials are not crosslinked, have some distinct processing advantages over traditional thermoset elastomers and physical properties of vulcanised elastomers• TPEs are able to be molded like thermoplastic (injection molding, extrusion, etc)• Thermoplastic elastomers are more temperature sensitive• Scrap and reject of these materials can be recycled-environmetal friendly behavior• Normal crosslinked polymers cannot be recycled because they dont melt. They dont melt because the crosslinks tie all the polymer chains together, making it impossible for the material to flow.
PROCESSING OF ELASTOMER Common machine used for rubber compounding:- 1. Banbury mixer 2. 2-roll mill
Manufacturing of Elastomer• Calendaring• Extrusion screw extrusion ram extrusion• Compression molding Horizontal injection molding• Transfer molding
calendaring• Calendar is consist of rollers(known as Bowls) by using this we can control the thickness of elastomer sheat.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. typical calendar
Extrusion• Screw ExtrusionTheelastomer is first fed into the barrel via ahopper and then forced down the barrelby the screw whilst heat is added (createdby the shearing action and via the heatedbarrel and screw). At the end of the barrel,in the extruder head, is a die throughwhich the material is forced out.
ExtrusionRam ExtrusionFor a ram extruder theelastomer needs to be rolled and warmed,usually by placing it in a bath of hot wateror taking it directly from the mill/calender.This roll is then placed into the cylinderhousing the ram. The head of the extrudercontaining the die is then locked in placeat the front of the extruder and the ramtraversed forward, forcing the materialout of the die orifice.
Compression MoldingCompression moulding describes theforming process in which an elastomerprofile is placed directly in a heatedmould, then softened by the heat, andforced to conform to the shape of themould as the press closes the mould.
Injection Molding• Injection molding is a process whereheated elastomer is injected into a closedcavity via a runner system. Uncuredelastomer is fed into the injection cylinderwhere it is preheated and accuratelymetered into the mould. This is done bycontrolling the pressure, injection timeand temperature.
Transfer MoldingElastomer of setweight is placed in the transfer pot, and,as with compression moulding, the pot isclosed by the press forcing the elastomerdown the sprues and into the cavity.A small amount of excess materialflows out of the cavity through vents, withother excess material lying in the sprue grooves and a mat of material left in the transfer pot.
Application of Elastomers• AutomotiveTuned mass dampers, rubbers seals, tyre and tube manufacturing, pipes and hoses, boots, sleeves and covers.• AerospaceAir management ducts, diaphragms, interior foils, hose and hoselines, air spring systems.• DefenseCoating for radar and other defense equipments
Application Of Elastomer• Biomechanics and the medical/dental professionsSurgery devices, prostheses, orthopedics, orthodontics, dental implants, artificial limbs, artificial organs, wheelchairs and beds, monitoring equipment• Highway safety and flight safetySeat belt design, impact absorbers, seat and padding design, passenger protection• Sports and consumerHelmet design, shoe design, athletic protection gear, sports equipment safety• Others• Dental Products, paints and coatings, cement and concrete adhesives, special wood protection coatings, biocompatible materials, medical and dental adhesives
Comparison B/W thermoplastic and Thermo setsThermoplastic Thermosets• These soften and melt on heating. • These do not soften on heating but rather• These can be remolded recast and reshaped become hard in case prolonged heating is done• These are less brittle and soluble in some these start burning. organic solvents. • These can not be remolded or reshaped.• These are formed by addition polymerization. • These are more brittle and insoluble in organic• These have usually linear structures.Ex. solvents. Polyethylene, PVC, Teflon. • These are formed by condensation polymerization. • These have three dimensional cross linked structures. Ex. Bakelite, urea, formaldehyde, resin.
Composites• Composites can cut weight by not being isometric and still maintain the strength in the desired directions• Composites are, by definition, solid materials composed of more than one substance in more than one phase
Processes• Thermoplastic processes –Very short fibers• Matched die/compression molding• RTM• Spray-up• Hand lay-up for wet and prepreg materials• Filament winding and fiber placement• Pultrusion
Matrix Materials• Resins – Both thermosets and thermoplastics can be used – Short fibers are generally used in thermoplastics – Long fibers are generally used with thermosets
Matrix Materials• Short fiber composites – Less than 0.2 inches (whiskers) – Processed through standard thermoplastic processes • Must pass through gates, runners, and gap between processing screw and barrel walls – Thermoplastics generally benefit greatly from even the short reinforcement materials
Matrix Materials – FRP• Intermediate length fiber reinforcement – The longer the fibers, the more difficult it is to coat the fibers enough to reap strength benefits – Low viscosity thermosets ―wet-out‖ the materials better than high viscosity thermoplastics – Generally use unsaturated polyester and vinylester resins for FRP
Reinforcements• Three main types of fibers – Fiberglass – Carbon fiber or Graphite – Organic fibers, aramids (kevlar)
Fiberglass• Spin molten glass• Different types of glass can be made – E-glass (improved electrical resistance) – S-glass (high strength) – C-glass (high chemical resistance)
Carbon or Graphite Fiber• Originally some distinction was made—now the two refer to the same material• Made from PAN fibers, pitch or rayon fibers• Through heating, raw material looses most non-carbon atoms in the chain• Processing also aligns carbon chains• Carbon fibers have very high modulus (stiffness)
Organic Reinforcement Fibers• Aramid fibers have greatest strength and modulus properties of organic fibers• Kevlar is the most commonly used aramid fiber• Aramids are strong and stiff but their greatest value is in impact applications – Front of airplane wings – Armor applications
Reinforcement Forms• Fiber manufacturers package the fibers on spools called tows• Fibers are generally converted to other forms after manufacturing – Chopped fibers (including whiskers) – Mat (random) – Woven fibers – Tapes – Prepregs
Manufacturing Methods• Thermoplastic processes using short fibers – Injection molding – Extrusion – Minor changes are made to accommodate the fiber reinforcements • All gaps in flow path should be increased • A resin viscosity decrease may be necessary
Manufacturing Methods• Matched die or Compression molding – Reduced flow path over injection or extrusion – SMC compression molding allows for continuous fibers, mats or weaves – These processes offer parts that are finished on both sides where most other composite processes do not
Manufacturing Methods• Resin transfer molding – Fiber preform is placed in the mold cavity – Preform doesn’t move—resin is pulled/pushed in
Manufacturing Methods• Spray-up – Fibers are chopped, coated with resin and sprayed onto the mold
Manufacturing Methods • Hand Lay-up (wet and prepreg) WetPrepreg
Fiber Orientations• Isometric materials have equal strength in all directions• Composites can be lighter weight by not having strength in the directions that it is not needed• Lay-up still has to have some balance and symmetry
Vacuum Bagging• Provides for increased part consolidation• Reduces matched die mold costs
Manufacturing Methods• Filament winding and fiber placement – Fiber placement has greater accuracy – Fiber placement can wind on less symmetrical and even partially concave mandrels• Tubes, tanks, wind turbine blades and rockets
Manufacturing Methods• Roll wrapping – Faster than filament winding – Limited to symmetrical mandrels
Manufacturing Methods• Pultrusion – High volume production – Comparable to extrusion but the main processing force is tension – Profile is pulled from the machine
Plant Concepts• Many of the processes require considerable space• Curing equipment for large parts can be very large (and expensive)• Controlling volatiles (solvents and resins) must be taken care of• Molds can be both expensive and fragile
Honeycomb structures are natural orman-made structures that have thegeometry of a honeycomb to allow theminimization of the amount of usedmaterial to reach minimal weight andminimal material cost. The geometry ofhoneycomb structures can vary widelybut the common feature of all suchstructures is an array of hollow cellsformed between thin vertical walls.
Today honeycomb cores are manufactured via theexpansion process and the corrugation process fromcomposite materials such as glass-reinforced plastic(also known as fiberglass), carbon fiber reinforcedplastic, Nomex aramide paper reinforced plastic, orfrom a metal (usually aluminum)
Recently a new process to produce thermoplastichoneycombs has been implemented, allowing acontinuous in-line production with direct lamination ofskin to cost efficient sandwich panel production.Continuous in-line production of metal honeycomb canbe done from metal rolls by cutting and bending.Today, a wide variety of materials can be formed into ahoneycomb composite. For example paperboardhoneycomb is used in paper pallets and packagecushioning, blocking and bracing
Manufacturing methodExpansion methodcorrugation processslotted metal strips
Expansion method• In this process thin metal sheet is first cut into panels and strip bonded• This 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• In this approach, a metal sheet is corrugated, and then stacked into a block. The sheets are bonded by welding (or any suitable method) together and the core sliced to the desired thickness and the corrugated layers either adhesively bonded or welded to face sheets.
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
Slotted metal strips• slotted metal strips can be assembled in the form of square and triangular honeycombs• Since no metal bending is required, this slotted sheet process is also well suited for making honeycombs from low ductility materials. The honeycomb cores are bonded by welding/brazing (or any suitable method) together and bonded to face sheets to form a sandwich structure. Even brittle composite or ceramic honeycombs can in principle be made by this approach.
Application of honeycombComposite honeycomb structures have been used in numerous engineering and scientific applications.
Application of honeycombLightweight honeycomb solutions are used in a wide range of industries, including the aerospace, marine, military, construction and automotive markets. Aluminum honeycomb, for example, is used as flooring material in various aircrafts, as it provides exceptional strength and low weight. It is also suitable for use at high temperatures and can withstand a variety of environmental factors
Application of honeycomb• Aramid fiber honeycomb is also used in aerospace applications, but often in more advanced capacities, such as missile and hull components. This type of honeycomb also finds use in various marine and military structures. Polypropylene honeycomb, on the other hand, is used in various noise and vibration reduction applications, such as acoustical panels. It also offers relatively high strength for its weight and is easily formed by various thermoforming techniques.
Application of honeycomb• Honeycombs utilize far less material than a solid panel but still provide exceptional strength, making it a highly economical option for many applications. In addition, the strength of the honeycomb increases with its thickness, meaning it is well suited to structures needing considerable core materials. Honeycombs are available in a wide range of standard and custom shapes and sizes.
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