Composites

• Composite


  Combination of two or more different materials that are bonded together
• Composite properties


  • Mechanical properties
  • Physical properties
• Mechanical properties


  • Tensile and compressive strength
  • Stiffness and toughness
  • Plasticity and elasticity
  • Ductility and malleability
• Physical properties


  • Mass
  • Weight
  • Volume
  • Density
  • Hardness
  • Electrical conductivity and resistivity
  • Thermal conductivity and expansion
• Enhanced properties of composites

  • Improve physical, mechanical, working properties
  • Create 3D forms that impossible with traditional methods
  • Easier and more efficient to work with
  • Lead to improved product performance
• Carbon fibre


  Several times thinner than human hair, lightweight, high tensile strength
• Making carbon fibre fabric

  1. Fibres woven into fabric

  2. More complex weave, more durable material

  3. Carbon fibre fabric built up in layers and formed in moulds to make complex shapes
• Carbon fibre reinforced plastic (CFRP)


  • Layer carbon with resin to make CFRP
  • High tech bike frames, race cars, crash helmets, prosthetics
  • Corrosion and chemical resistant, lightweight, stable in hot conditions
  • Tough, hardwearing, good tensile strength
• CFRP


  • Ferrari F1 2000's car chassis made from carbon-fibre reinforced plastic
• Glass reinforced plastic (GRP)

  • Fibreglass - polyester or epoxy resin combined with fibre made of glass
  • Glass fibre strong with little compressive strength
  • Resins strong in compression but weak in tension
• Properties of GRP


  • Lightweight
  • High compressive and tensile strength
  • Resistant to UV and corrosion
  • Highly durable and water tight
  • Can be formed into 3D shapes such as boats, car body panels and sculptures
• Making GRP


  1. GRP formed on moulds and layered up as CFRP

  2. Labour intensive

  3. GRP far cheaper than carbon fibre
• Engineered wood


  Wood based composites designed to enhance properties of natural timber
• Wood composites


  • All manufactured boards combine wood sheets, chips or particles with bonding agent
  • Engineered flooring combined ply or HDF with hardwood veneer
  • Offers stability, durability and natural aesthetic
  • Melamine formaldehyde often added to particle boards to achieve hard wearing finish
  • Glulam made from layers of laminated timber formed around mould, can be used as alternative to steel for beams, bridges and archways
• Smart material


  One or more property dramatically altered by external stimulus
• Modern materials


  Developed by engineers and scientists through research and experimentation, sometimes discovered by accident but usually developed to perform particular function, developed for specialist applications, many make way into range of products due to enhanced properties
• Smart materials


  • Stimulus + property linked to smart material affect how and where
  • External stimuli affect all material in the environment
  • Smart materials change with subtle environment differences like temperature, light, moisture, pressure
• Kevlar


  High performance aramid fibre spun into thread, woven fabric can stop bullets and offer thermal protection over 120 C, lightweight, hardwearing and extremely strong, stiff, heat and chemical resistance 5 times stronger than steel
• Kevlar discovered by Stephanie Kwolek at DuPont laboratories


  1965
• Shape memory alloy (SMA)

  • Programmed to remember a specific shape
  • SMA bent out of shape, returned to shape at given temperature
  • SMA activated by change in weather, body temperature, electrical current
  • Common alloy is nitinol (nickel + titanium)
• Purpose of discovering Kevlar


  • Wanted strong, stiff and lightweight material could be used alternative to steel reinforcements in tyres, as fabric used for high performance protective clothing, as fibre additive to enhance performance of composite materials
• Programming SMA into a shape

  1. Held in desired shape using jig, then heated in furnace or with flame

  2. With electric current above transformation temperature, deformed SMA will return to shape
• Benefits of Kevlar


  • Excellent impact resistance as well as tensile and torque strength, allows faster and further travel without refuel in high performance vehicles for land, sea and air, used to create tougher, safer and lighter products
• Polymorph


  Thermoplastic modern material which becomes malleable at low temperatures, when heated in hot water to 62, easy to mould by hand, remoulded many times, cooled, extremely tough, durable similar properties nylon, non-toxic and biodegradable
• Activation temperature of SMA

  Dedicated by subtle changes in composition of alloy
• Uses of Polymorph


  • Used safely and easily at home, create personalised and ergonomic products and parts such as handles, orthodontic moulds, gum shields, particularly used for elderly or disabled or deformities
• Uses of SMA


  • Glass frames
  • Orthodontic braces (body heat affects wire which pulls teeth into position)
  • Expensive, only commercially viable in high cost commodities
• Precious Metal Clay (PMC)


  Made from precious metal particles held in water based, non-toxic organic binder, shaped by hand or with moulds, formed like modelling clay, moisture and binding agents burnt off during the firing process, finished product contains 90% precious metal, PMC shrinks around 5-15% during firing
• Thermochromic pigment


  • Changes colour or opacity with temperature
  • Pigment mixed into materials and finishes like varnishes, paints, dyes, polymers
  • Transforms from opaque to transparent or changes colour
• Pros and Cons of PMC

  • Accessible material used with minimal tools, metalsmithing skills, easy and quick to work with, can be fired in a kiln or with a butane torch, used to set stones and slip can be used to join PMC parts, dry out if worked or stored for too long, not as strong as sterling silver, more expensive than traditional materials, set up costs are minimal
• High Density Modelling Foam (HDMF)


  Rigid, lightweight, strong material, used for high quality 3D models, holds good surface detail and fillers, primers and paints create high quality finish, can be CNC milled or routed or shaped by hand, cheap and quick ways make moulds for vacuum forming and casting metals at low temp
• Quantum tunnelling composites (QTC)

  • Flexible material with amazing electrical properties
  • Perfect insulator, when squeezed becomes near perfect conductor allowing high current to pass with little resistance
  • Composites of rubbery polymer material embedded with metal particles
  • Electrons can leap between particles without contact due to quantum tunnelling, improving conductivity
  • Used in tunnel diodes (semiconductor with negative resistance)
• Photochromic pigment


  • Changes colour or opacity with level of UV light
  • Used in spectacles, clothing
  • Used as additive to affect properties of other materials and finishes
• Electroluminescent (EL) wire


  • Copper wire coated in phosphor which glows when alternating current applied
  • Pliable plastic coating so flexible and suitable for outdoors
  • Produces 360 degree unbroken thread of light
  • Used in lighting, accessories for bicycles, vehicles and costumes
• Piezoelectric materials


  • Convert mechanical energy into electrical energy
  • Pressure or vibrations converted to electrical charge
  • Include crystals, ceramics, bone, viruses
  • Can create spark, trip burglar alarms, generate sound for fire alarms
• Piezoelectric materials in ultrasound

  1. Grid of quartz crystals held between two steel plates resonates when electric current applied

  2. Cell emits sound underwater, timing the return echo measures underwater terrain

  3. Basis of all sonar and ultrasound technology
• Piezoelectric materials in wearable technology

  • Digital watch contains quartz crystal component which helps keep time