COMPOSITES

• First man made composites engineered by the Mesopotamians in Iraq


  3400 B.C
• Egyptians started to make death masks out of linen or papyrus soaked in plaster


  2181 B.C
• Mongols began to engineer composite bows


  1200 A.D
• Synthetic resins started to take a solid form by using polymerization

  1900s
• Glass fiber was introduced by Owens Corning who also started the first fiber reinforced polymer (FRP) industry


  1930s
• Composites offer many benefits such as corrosion resistance, design flexibility, durability, light weight, and strength
• Composite


  A multiphase material that exhibits a significant proportion of the properties of both constituent phases such that a better combination of properties is realized
• Particle-Reinforced Materials


  • A composite where the dispersed phase is approximately equal in all directions
  • Contain micro or nano-sized constituents of metallic and ceramic materials that are used to improve and strengthen ceramic-based matrices' properties

  
• Sub Classifications of Particle-Reinforced Materials

  • Large-Particle Composites
  • Dispersion-Strengthened Composites

  
• Large-Particle Composites


  Contain large particles, which are in millimeter sizes or more, and are the major load bearers and it tends to restrain the matrix deformation around their shared surfaces
• Dispersion-Strengthened Composites


  Materials that are strengthened by the fine particles that are uniformly dispersed throughout the matrix. Particles are much smaller than the particulate phase in large-particle composites, and ranges from 10nm to 100nm
• Fiber


  Thread-like structures that are thin, long, and flexible. Can be natural or synthetic
• Fiber-Reinforced Composites


  • Known to have fibers incorporated in its matrix structure. It is generally said to be the most promising type of composite due to its high strength and stiffness
  • Characteristics can be further subclassified by their fiber length, fiber orientation and concentration which defines the properties and structural behavior
• Matrix Phase


  Refers to the addition of reinforcing components to improve fracture toughness and ductility. In fiber-reinforced composites it helps bind the fibers together and act as a medium where externally applied stress is transmitted and distributed to the fibers
• Polymer Matrix Composites (PMCs)


  Refers to polymer resin or high-molecular-weight reinforcing plastic as the matrix with fibers as the reinforcement medium

  
• Matrix phase


  • Transmits and distributes externally applied stress to the fibers
  • Protects fibers from surface damage from mechanical abrasions or chemical reactions causing cracks
  • Helps prevent propagation of cracks which can cause catastrophic or material failure
• Polymer Matrix Composites (PMCs)


  Polymer resin or high-molecular-weight reinforcing plastic as the matrix with fibers as the reinforcement medium
• Types of PMCs


  • Glass Fiber-Reinforced Polymer (GFRP) Composites
  • Carbon Fiber-Reinforced Polymer (CFRP) Composites
  • Aramid Fiber-Reinforced Polymer Composites

  
• GFRP Composites


  • Produced in large quantities
  • Example is fiberglass, a composite material consisting of glass fibers contained within a polymer matrix
  • Glass is commonly used as a fiber reinforcement as it can be easily drawn into high-strength fibers, is relatively strong, and possesses chemical inertness good in preventing corrosion when exposed to corrosive environments
• CFRP Composites


  • Use carbon, a high-performance fiber material, as the reinforcement
  • Retain their high tensile modulus and strength at elevated temperatures
  • Not affected by moisture
• Aramid Fiber-Reinforced Polymer Composites

  • High-strength, high-modulus materials introduced in the early 1970s
  • Have outstanding strength-to-weight ratios, superior to metals
  • Applications include bullet proof vests, armors, biomedical applications
  • Challenged by the problem of slow degradation having an effect on the environment
• Metal Matrix Composites (MMCs)


  Ductile metal such as aluminum, magnesium, titanium, and copper, as the matrix material incorporated with fibers or whiskers acting as the reinforcement medium
• MMCs


  • Can withstand higher temperatures
  • Nonflammable
  • Have overall dimensional stability
  • More expensive than PMCs
  • May be highly reactive at certain temperatures and subject to composite degradation, but can be resolved by applying surface coatings
• Ceramic Matrix Composites (CMCs)


  Advanced form of ceramics that utilizes the use of fibers or whiskers of one ceramic material embedded into the matrix of another ceramic material
• CMCs


  • Traditional ceramics are resilient to oxidation, deterioration, hard but very prone to cracks
  • Increasing the fiber content helps improve fracture properties or toughness of ceramics, reducing fractures when high external forces are applied
• Fabrication of CMCs


  1. Hot pressing

  2. Polymer infiltration

  3. Pyrolysis
• Carbon-Carbon Composites (C/C composites)

  Uses carbon both as a reinforcement and as a matrix
• C/C composites


  • Lightweight
  • Exceptionally strong even at temperatures exceeding 2000°C, reaching up to 3000°C
  • High thermal conductivity and low thermal expansion, retaining structure and strength even with rapid temperature changes
  • High fracture toughness, avoiding brittle fracture like conventional ceramics
• Production of C/C composites

  1. Select carbon fiber cloth

  2. Inject with phenolic resin to serve as binding agent and matrix

  3. Cure resin through controlled heating

  4. Carbonize through high temperatures, decomposing resin and leaving carbon-based structure

  5. Fill any gaps through reinfusion if necessary

  6. Graphitize by heating to extreme temperatures, arranging carbon atoms into graphite-like arrangement
• Hybrid Composites


  Use multiple types of reinforcements or matrix
• Hybrid Composites


  • Offer a mix of properties like tensile modulus, compressive strength, and impact resistance, which single composites can't match
  • Widely used across industries for its ability to adapt, making products lightweight yet strong, corrosion resistant, and tough
• Classification of Structural Composites

  • By Matrix Material: Ceramic Matrix Composites (CMCs), Metal Matrix Composites (MMCs), Polymer Matrix Composites (PMCs)
  • By Reinforcement Geometry: Particles Reinforced Composites, Fiber-Reinforced Composites

  
• Laminar Composites


  Two-dimensional sheets or panels with a preferred high-strength direction, stacked and bonded together with varying orientation of the high-strength direction
• Laminar Composites


  • Offer strength in multiple directions, though lower than if all fibers were oriented in one direction
  • Properties are virtually isotropic in a two-dimensional plane, made possible by varying the high-strength direction in each successive layer
• Laminar Composites


  • Plywood
  • Modern skis
• Sandwich Panels


  Lightweight beams or panels with high stiffness and strength, consisting of two strong and stiff outer sheets bonded to a thicker core

  
• Sandwich Panel Core


  • Offers continuous support for the outer sheets/faces
  • Able to withstand transverse shear stress and has shear strength to do it
  • Thick enough to provide high shear stiffness

  
• Sandwich Panel Core


  • Rigid polymeric foams
  • Wood (balsa wood)
  • Honeycombs

  
• Honeycomb Core


  • Thin foils formed into interlocking hexagonal cells, with axes oriented perpendicular to the face planes
  • Normally made of aramid polymer or aluminum alloy
  • Strength and stiffness depend on cell size, cell wall thickness, and material
• Honeycomb panels are found in exterior claddings, roofs, walls, etc.