Presentation on theme: "Manufacturing with Composites"— Presentation transcript:
1 Manufacturing with Composites Chapter 19Manufacturing with Composites
2 Composite - Definition Structures made of two or more distinct materialsThe materials maintain their identity during the processThe materials maintain their identity after the final component is fully formed.
3 Key Points Fabric Types Resin Types Manufacturing Techniques Curing TechniquesSandwiches and HoneycombsJoining of CompositesPros and Cons of Composites
4 Where are Composites Used? Recreational boatsCarsAirplanes and other aircraftsAerospaceHigh performance sporting goodsAppliances, tools, and machineryTanks and pipes
5 What is a Composite? First produced about 50 years ago A “Judicious” combination of two or more materials that produces a “Synergistic” effectFocusing on using glass, graphite and Kevlar and impregnated with a plastic resin for manufacturing. Areas used recreational
6 JudiciousImplies that the components are carefully selected to provide the desired physical and chemical characteristics
7 SynergisticThe whole product is better than the sum of its individual componentsWord coined by Buckminster FullerIllustrated concept by using a rope as an exampleThe term synergy was coined by Buckminster Fuller. He illustrated his concept of synergy with the following analogy. “If one has one hundred individual strings, each is capable of lifting one pound therefore the maximum load of the strings would be 100 pounds. However, if those same strings are twisted, braided, or woven into a rope, the rope will lift far more than a 100 pounds.
8 Composites are made up of a fiber and a matrix Fiber can be short or long strands of materialMatrix is a the material that holds the fibers togetherNatural composites – celery, corn stalks, and sugar caneManmade composite – reinforced concreteReinforced concrete can be considered a composite with the steel as the fiber and the concrete as the matrix.
9 Composite Classification MatrixMaterial that surrounds the other componentsFillersRandomly oriented equally dispersed particlesFiber ReinforcementUsually the main component in differing forms
10 Simple and Advanced Composites Simple Composite (Reinforced plastic) – Fiber laid in random directions or very shortAdvance Composite – Long fibers are laid in a given direction, long, and continuous
11 Fiber orientation Unidirectional Biaxial (Cross-ply) Laminates Random orientationLaminatesCross layering of unidirectional composites
12 Composite System Categories Fiber – ResinFiber – CeramicCarbon – MetalMetal – ConcreteMetal – ResinMetal – ElastomerFiber – ElastomerWood – ResinWhen adding fibers to a resin matrix, one cannot predict the properties of the composite by analyzing the components. When a composite is created the fibers and resin create new properties. Example, glass fibers are strong but are vulnerable to damage and a certain plastic weak but, versatile and tough. Combining the two will strengthen the strengths and hide the weaknesses.
13 Typical Fabrics Used in Composites GlassCan be long and continuous or shortCan use many different types ex: Soda lime – easy and low costFiberglass white color can be dyed to any colorKelvarCan be long and continuousSame family as nylonDistinctive yellow colorGraphite (carbon)Made by burning a material in the absence of oxygen, other elements burn off leaving carbonShould be called carbon fiberAlways black
16 Why Chose Glass? Excellent thermal and impact resistance High tensile strengthGood chemical resistanceOutstanding insulating propertiesLower cost
17 Glass Types E-glass Low cost - $1 per pound Used in 90% of glass reinforcementGood electrical resistanceUsed in aircraft radomes and antennae and computer circuit boardsGood resistance to sodium carbonate (base)Good high temperature performanceHigh strength glass$6 per poundS-glass or S2-glass(U.S.)R-glass (Europe)T-glass (Japan)Contains more silica oxide, aluminum oxide, and magnesium oxide40% to 70% strongerOriginally used for military applications (S2 for commercial)Good resistance to hydrochloric and sulfuric acidGood resistance to sodium carbonate (base)Good high temperature performanceC-glassCorrosion resistantGood resistance to hydrochloric and sulfuric acidPoor high temperature performance
18 Why Chose Graphite? Higher tensile strength and stiffness than glass Used in high-tech applications where product needs exceptional fiber properties and customer is willing to pay premium
19 Why Chose Kevlar? Highest quality High breaking strength More impact resistantLightest weightHighest tensile strength
24 Resins Must be compatible with fibers Two types Thermoplastic Needs higher temperature processingRemains plastic and can be reheated and reshapedUsed lessHigh performanceHigher costsHigher temperature performanceBetter damage resistanceHigher compressive strengthHigh vibrational dampingViscoelasticityThermosettingCrosslinks during curingSets into final rigid formUsed widelyLower price tagEase of handlingGood balance of mechanical, electrical, and chemical resistance properties
26 Manufacturing Techniques Hand layup or Hand-layPre-pregFilament windingPultrusion
27 Open Mold ProcessesHand Lay-upSpray-upTape-layingFilament winding
28 Hand layup Oldest, Inexpensive, Little equipment required Repair technicians and backyard boat builders use this technique with fiberglassRequires some skill to doWasteful use of resinProduct heavier compared to using other techniquesGood for one of a kind products or prototypes
29 Hand layup MethodA form is coated with resin using a paintbrush, roller, swab, spatula or any other methodFabric is pressed into the resinAnother coat of resin is applied on top
30 Pre-preg Method Fabric saturated with resin Excess squeezed out by rollersCured to B stage, material tackyCan be stored a week to 10 days if not used right away. Refrigeration lengthens shelf lifeCan be wrapped around a mandrel, cut by computer controlled machines or laid up on forms by robotsMust be put under pressure to finish curing
31 Filament Winding Method Good for convex shapes having no indentationsIndividual fibers are drawn through the resin and wrapped around a mandrelWhen complete pressure cured, mandrel removedGood method for aircraft nose cones, radar domes and missile nose cones and bodies
32 Pultrusion Method Good method for selective placement composites A bundle of arranged fibers are drawn through a resin bathThen pulled through a selected shape heated dieCured and cut to sizeGood method to create channels, flange beams, T-bars, and other shapes in very long lengths
35 Pressure Form Method Uses a heated internal and external mold Can be used in mass production, but requires expensive equipment
36 Vacuum Bagging Method Simple and cheapest method Used after hand layup or pre-preg of materialPiece is placed in a polyethylene, rubber, or airtight flexible bagVacuum pull in the bag exerts equal pressure approximately 12 lb/in2Part or entire bag is heated to cure
37 Autoclaving MethodUsed when parts require more than one atmosphere of pressureAn oven that can be sealed and pressure is then applied by air or other gasses
38 Other Composite Forms Sandwiches Styrofoam, syntactic foam, or polyurethane foam wrapped in fiberglass, Kevlar, or graphite fibers and fused togetherBalsa wood could be used as a core to make sailboatsRecent developments using ceramic cores for heat resistance
39 Other Composite Forms Honeycombs Honeycombed aluminum, Nomex, fiberglass, graphite, or other material wrapped and bonded to composite materialsUsed in helicopter blades, truck and aircraft bodies, and some parts of aircraft wings and tail surfaces
40 Joining CompositesJoined in conventional methods by threads, pins, rivets, and other mechanical methodsThermoplastic polymers joined by fusion weldingChemical joiningAdhesives
41 Composites vs. Traditional Materials ProsConsLighterStrongerNo fatigue failureNo corrodingHard to breakComplicated shapesDelaminateBlistersFabric cutting difficultMaterial and curing costs high
42 Environmental Concerns Reduction of styrene emissionsExposure limited to 50 parts per million (OSHA)Hard to meet standards and costlyAchieved by reducing styrene, better transferring to molds, curing in closed systemsDevelopment of biodegradable reinforced plasticsFilling up landfills with computer and car parts, packaging, etc.Create matrices from soybean protein and use plant-based fibers such as ramie, pineapple leaves and banana stemsCould be used in car and train interiors, computers and as packaging materialsLow cost (when acceptance increases), biodegradable and renewable on a yearly basis
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