MSE FINALS

• Why study Composites?


  Knowledge of different composite types and how their behavior depends on constituent characteristics allows designing materials with better properties than monolithic metals, ceramics, or polymers
• Composites


  Artificially produced multiphase materials with desirable combinations of the best properties of the constituent phases
• Main divisions of composite materials

  • Particle-reinforced
  • Fiber-reinforced
  • Structural
  • Nanocomposites
• Particle-reinforced composites


  • The dispersed phase consists of equiaxed particles
• Fiber-reinforced composites


  • Feature a dispersed phase with fiber geometry, characterized by a high length-to-diameter ratio
• Structural composites


  • Multilayered and engineered for low densities and high structural integrity
• Nanocomposites


  • Contain dispersed phase particles with dimensions on the order of nanometers
• Particle-reinforced composites


  Feature a matrix that surrounds dispersed equiaxed particles
• Types of particle-reinforced composites

  • Large-particle composites
  • Dispersion-strengthened composites
• Fiber-reinforced composites


  The matrix surrounds dispersed fibers
• Types of fiber-reinforced composites

  • Continuous and aligned
  • Discontinuous and aligned
  • Discontinuous and randomly oriented
• Hybrid composites


  Combine at least two different fiber types, allowing us to design materials with better all-around properties
• Composite Processing Techniques


  • Pultrusion
  • Layup (hand or automated)
  • Filament winding
• Why study imperfections in solids?

  Studying imperfections in solids is crucial because they significantly impact material properties
• Imperfections in crystalline materials

  Irregularities that occur on the atomic scale
• Types of imperfections in crystalline materials

  • Point defects
  • Linear defects
  • Interfacial defects or boundaries
• Point defects


  Little hiccups in the regular arrangement of atoms within the crystal lattice, involving missing atoms (vacancies), extra atoms (interstitials), or atoms that have swapped places with neighboring atoms (substitutional defects)
• Linear defects


  Defects that occur along lines or planes within the crystal lattice, such as dislocations, which can affect how materials deform under stress and influence properties like material strength and ductility
• Interfacial defects or boundaries


  Occur at the boundaries between different crystalline regions or between the crystal and its surroundings, such as grain boundaries, which can affect properties like corrosion resistance and mechanical behavior
• Studying imperfections in crystalline materials


  Exploring the deviations from perfect order and how these deviations impact material properties
• Point defects


  The smallest unit of imperfection, involving just one or two atomic positions within the lattice
• Linear defects


  Also known as one-dimensional defects, occur along lines within the lattice structure, such as dislocations
• Interfacial defects


  Two-dimensional imperfections found at the interfaces between different regions of the crystal lattice, such as grain boundaries
• Impurities in crystalline materials

  Atoms that are not part of the original crystal lattice, but can have a significant impact on the material's properties
• Solid solutions


  Blends of two or more elements, typically metals, that come together to form a new metallic substance, where impurity atoms integrate into the existing crystal structure of the metal
• Types of solid solutions

  • Substitutional
  • Interstitial
• Dislocations


  One-dimensional crystalline defects, categorized into edge and screw types
• Edge dislocations


  Involve lattice distortion along an extra half-plane of atoms
• Screw dislocations


  Resemble a helical planar ramp
• Burgers vector


  Specifies the magnitude and direction of lattice distortion
• Interfacial defects


  Occur at grain boundaries and twin boundaries, where atomic mismatches exist between adjacent grains or mirror-image positions of atoms on either side
• Microscopy techniques


  • Optical microscopes
  • Electron microscopes (Transmission (TEM) and Scanning (SEM))
  • Scanning probe microscopes
• Fracture Mechanics


  Studying how materials respond to stress when flaws or cracks are present, essential for understanding the integrity of structures and components
• Fatigue


  Examining how materials behave under cyclic loading, the wear and tear a material experiences over time due to repeated stress cycles
• Creep Behavior


  Investigating how materials deform under constant stress at elevated temperatures, particularly important in industries like aerospace and power generation
• Toughness


  A measure of a material's ability to absorb energy before fracturing
• Fracture toughness


  How well a material resists failure when there's already a flaw present, like a crack, often quantified using parameters like KIc (plane strain fracture toughness)
• Fatigue testing


  Simulating the wear and tear a material experiences over time due to repeated stress cycles, using tools like the S-N curve to understand the correlation between stress levels and the number of cycles a material can endure before failure
• Creep behavior


  Slow, steady deformation under prolonged stress at high temperatures, a critical consideration in industries where materials are exposed to extreme conditions over long durations
• Why study Electrical Properties of Materials?

  Understanding the electrical properties of materials is crucial for making informed decisions during component and structure design