1. Pratik Chaudhari MIS- 111210015 TY Mechanical div-1 Subject Advanced manufacturing techniques

2. Conventional materials Conventional materials are shows more crystallinity. Shows deflection under service load More crystallinity , harder, stiffer and less ductile Structure sensitive Problems with sophastication, machinability,tolerance, etc. Changed by small changes in chemical composition 3. Plastics Material of New age Its basic constituent is prepared synthetically or semi- synthetically from monomer. Easily machined , cast and joined Ease of manufacturing and versatility hardness, elasticity, breaking strength, temperature resistance, thermal dimensional stability, chemical resistance 4. Plastics - Classification Elastomers thermosets Thermoplastics 5. Thermoplastics Polymers which moulds above Glass transition temperature and returns to normal state upon cooling 6. Thermoplastics Most commonly used engineering thermoplastics as matrices Nylon Polycarbonate (PC) Polyethylene terephthalate (PET) Polypropylene (PP) Stronger and stiffer but lower toughness Have engineering as well as advanced applications 7. Glass transition temperature Amorphous polymers do not have a specific melting point. At low temp., they are hard, brittle, rigid and glassy and at a high temp. rubbery and leathery. The temperature at which this transition occurs is called Glass transition temperature (Tg). 8. Effect of temperature Above glass-transition temp. polymers become leathery and then rubbery At higher temperatures, polymers become a viscous fluid, with viscosity decreasing with increasing temperture. 9. Behaviour under temperature conditions Below temperature Tg, plastic polymers are glassy ,rigid, hard or brittle and behave as a elastic body. If the load exceeds the certain critical value, it fractures as a piece of glass 1. Elastic deformation 2. Viscous deformation 3. Maxwell Model of Viscoelastic deformation 4. Voigt or Kelvin Model of Viscoelastic deformation 10. Viscoelastic behavior When heated above Tg , It becomes leathery first and then rubbery with increasing temperature If we increase above Tm (melting point ), it becomes viscous and viscosity goes on decreasing with increase in temperature and strain rate As viscosity is not constant, thermoplastic shows visco-elastic behavior 11. Draw diagrams on page 569 12. Orientation When thermoplastics are permanently deformed by stretching, long chain molecules align in general direction of elongation. This is known as orientation. The polymer becomes stiffer and stronger in the elongation direction as compared to transverse direction This technique is used to enhance the strength and toughness of polymers 13. Crazing & stress whitening Some thermoplastics such as polystyrene develop localized,wedge shaped narrow regions of highly deformed material when subjected to high tensile stresses or bending Presence of various additives, solvents, water vapour favours crazing Stress whitening - When polymer subjected to tensile stresses such as by folding or bending, the plastic becomes lighter in color due to formation of micro-voids in the material. 14. Water absorption This is limitation of thermoplastics Water acts as plasticizing agent. Thus, it makes polymer more plastic It lowers the glass transition temperature, yield stress and elastic modulus of polymer Sometimes,Undesired dimensional changes occur 15. Classification 16. Amorphous thermoplastic polymers Molecule chains are completely chaotically arranged and tangled with each other like the threads of a cotton wool pad amorphous structure means that these materials cannot be subjected to loads above the glass transition point Properties : Low tendency to creep Good dimensional stability Tendency to brittleness Sensitive to stress cracking 17. Semi-crystalline thermoplastics Molecules form crystalline structure Due to the crystalline areas, the materials are extremely tough (strong intermolecular forces) and are capable of withstanding mechanical loads Properties : Opaque Good fatigue resistance Tendency to toughness Good chemical resistance Wear resistance 18. Some examples 19. Polyamides or Nylons (PA) 20. Acetals or Polyoxymethylenes (POM) 21. Mechanicaldo not embrittle, good impact strength Moisturevery little (shower heads) Chemical resistancevery high, resists stains, sensitive to strong acids and bases Electrical resistance - good Machininglike cutting brass Adhesionepoxy glues Acetals or Polyoxymethylenes (POM) and Polyamides characteristics 22. Thermoplastic Polyesters (PET/PBT) 23. Thermoplastic Polyester General Family Characteristics PET Higher mechanical stiffness Strength by orienting chains not by H-bonding Get 50% crystallinity forced by mechanical stretching PBT crystallizes rapidly processes faster lower overall properties 24. Polycarbonate 25. Flouropolymers 26. Other aspects 27. Costsin$/lb Automotive Structures $1 - $3/lb Innovative Materials and Processes $5 - $20/lb Typical Aerospace Structure $50 - $100/lb and more Materials: Glass Fiber / Polypropylene, SMC/BMC Processes: Compression Molding, Injection Molding Materials: Thermoplastic Woven Sheets, Glass, Carbon and Kevlar Fiber, Engineering Polymers Processes: Co-Compression Molding, Co- Injection Molding, Thermoforming Materials: Carbon Fiber / Epoxy, Carbon Fiber / BMI, Carbon Fiber / PEEK Processes: Hand Lay Up Apply Materials and Processing Techniques being Developed for Automotive Applications to Aerospace Applications Cost challenge 28. Short fiber, Long Fiber and Continuous Fiber Composites Typical short fiber thermoplastic material, granules with fiber length of approx. 2 to 4 mm, resulting fiber length in a part of approx. 0.4 mm Long fiber thermoplastic material, pellets of and 1 fiber length, resulting fiber length in a part of approx. 4- 6 mm in injection molding and approx. 20 mm in compression molding Continuous reinforced thermoplastic material, tape used for woven sheets (thermoforming), filament winding or pultrusion 29. Composite Performance versus Fiber Length 0.0 0.2 0.4 0.6 0.8 1.0 1.2 0.1 1 10 100 Length (mm) RelativePropertyLevel Modulus Strength Impact Processibility 30. Processing 31. Current Composite Materials and Processes Process Type of Application Injection Molding Compression Molding Thermoforming Hand Lay Up / Vacuum Bag / Autoclave Low-Structural Components Semi-Structural Components Structural Components 32. Thermoplastic Thermoforming Blanks Oven Clamp Clamping Pressing Press (in two modes) Finished Part 33. Extrusion 34. Injection Molding Machine Basics 34 35. 35 Blow Molding Extruded Parison- Mold Open Mold Closed and Bottle Blown Finished Bottle Removed from Mold Plastic 36. Plastic Materials and Pocesses 36 Compression Molding Platen Mold Plunger Guide Pins Mold Cavity Platen Hydraulic Plunger Heat and Cooling Heat and Cooling Hydraulic Pressure Compound to be molded 37. Applications 38. Applications For High-Performance Thermoplastics Aerospace and defense: Radomes, wing and fuselage sextions, anti-ballistics Infrastructure and Construction Window profiles, rebar, beams, structures, composite bolts Consumer / recreational Orthotics, safety shoes, sporting goods, helmets, personal injury protextion, speaker cones, enclosures, bed suspension slats Auto and truck Bumper beams, skid plates, load floor, seat structures Transportation Railcar structure, body structure and closures Energy production and storage Oil and gas structura tube, wind turbines 39. Future ? Thermoplastics polymers go to more structural applications using different technical thermoplastics in combination with glass, carbon and synthetic fibers. Thermoplastics will replace metal applications and reduce weight. Improved processing methods will be developed and applied. 40. Thank you