Understanding Composites: Properties and Classifications, Study Guides, Projects, Research of Engineering

An introduction to composite materials, explaining why they are studied and the principles behind their design. It covers the different phases of composite materials, their dispersed phase geometry, and classifications, including particle-reinforced and fiber-reinforced composites. Examples of common composite materials, such as concrete and fiber-reinforced composites, are also discussed.

Typology: Study Guides, Projects, Research

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10/13/2015
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Composites
Art Ian G. Bautista, ECE, ECT
Why Study Composites?
to design materials having property
combinations that are better than those found
in the metal alloys, ceramics, and polymeric
materials.
Many of our modern technologies require
materials with unusual combinations of
properties that cannot be met by the
conventional metal alloys, ceramics, and
polymeric materials. This is especially true for
materials that are needed for aerospace,
underwater, and transportation applications .2
Composite
- are artificially produced multiphase
materials having desirable combinations
of the best properties of the constituent
phases.
3
Principle of Combined Action
- better property combinations are
fashioned by the judicious combination of
two or more distinct materials
4
In designing composite materials, scientists
and engineers have ingeniously combined
various metals, ceramics, and polymers to
produce a new generation of extraordinary
materials.
Most composites have been created to
improve combinations of mechanical
characteristics such as stiffness, toughness,
and ambient and high-temperature
strength.
5
Phases of Composite Materials
Matrix is continuous and surrounds the
other phase.
Dispersed phase
(Reinforcements)
6
pf3
pf4
pf5

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Composites

Art Ian G. Bautista, ECE, ECT

Why Study Composites?

  • to design materials having property combinations that are better than those found in the metal alloys, ceramics, and polymeric materials.
  • Many of our modern technologies require materials with unusual combinations of properties that cannot be met by the conventional metal alloys, ceramics, and polymeric materials. This is especially true for materials that are needed for aerospace, underwater, and transportation applications.^2

Composite

  • are artificially produced multiphase materials having desirable combinations of the best properties of the constituent phases. 3 Principle of Combined Action - better property combinations are fashioned by the judicious combination of two or more distinct materials 4
  • In designing composite materials, scientists and engineers have ingeniously combined various metals, ceramics, and polymers to produce a new generation of extraordinary materials.
  • Most composites have been created to improve combinations of mechanical characteristics such as stiffness, toughness, and ambient and high-temperature strength. 5

Phases of Composite Materials

  • Matrix – is continuous and surrounds the other phase.
  • Dispersed phase (Reinforcements) 6

Dispersed Phase Geometry

  • is the shape of the particles and the particle size, distribution, and orientation 7 8 Classification of Composite Materials 9 Dispersed Phase Characteristics for Composite Classifications:
  1. Particle-Reinforced Composites equiaxed (i.e., particle dimensions are approximately the same in all directions)
  2. Fiber-Reinforced Composites has the geometry of a fiber (i.e., a large length-to diameter ratio)
  3. Structural Composites are combinations of composites and homogenous materials 10
  4. Particle-Reinforced Composites
  • Large particle is used to indicate that particle–matrix interactions cannot be treated on the atomic or molecular level; rather, continuum mechanics is used.
  • For most of these composites, the particulate phase is harder and stiffer than the matrix. 11 Large-Particle
  • These reinforcing particles tend to restrain movement of the matrix phase in the vicinity of each particle.
  • The matrix transfers some of the applied stress to the particles, which bear a fraction of the load.
  • The degree of reinforcement or improvement of mechanical behavior depends on strong bonding at the matrix particle interface. 12

19 Influence of Fiber Length

  • As fiber length l increases, the fiber reinforcement becomes more effective. Stress the critical length–position profiles when fiber length lc, (b) is greater than the critical length. l (a) is equal to 20 Continuous
  • Fibers for which l>>lc Discontinuous
  • or short fibers, have lengths shorter than this
  • Fibers for which l<<lc 21 22 Structural composites
  • A structural composite is normally composed of both homogeneous and composite materials, the properties of which depend not only on the properties of the constituent materials but also on the geometrical design of the various structural elements. 23 Laminar Composites
  • A laminar composite is composed of two- dimensional sheets or panels that have a preferred high-strength direction such as is found in wood continuous and aligned fiber-reinforced plastics. 24

25 The stacking of successive oriented, fiber reinforced layers for a laminar composite.

  • Laminations may also be constructed using fabric material such as cotton, paper, or woven glass fibers embedded in a plastic matrix. Thus a laminar composite has relatively high strength in a number of directions in the two-dimensional plane; however, the strength in any given direction is, of course, lower than it would be if all the fibers were oriented in that direction. 26 Sandwich panels
  • Consist of two strong outer sheets, or faces, separated by a layer of less-dense material, or core, which has lower stiffness and lower strength. The faces bear most of the in plane loading, and also any transverse bending stresses.
  • Typical face materials include aluminum alloys, fiber-reinforced plastics, titanium, steel, and plywood. 27 Functions of the Core
  • It separates the faces and resists deformations perpendicular to the face plane.
  • It provides a certain degree of shear rigidity along planes that are perpendicular to the faces. 28
  • Another popular core consists of a ‘‘honeycomb’’ structure—thin foils that have been formed into interlocking hexagonal cells, with axes oriented perpendicular to the face planes. The material of which the honeycomb is made may be similar to the face material. 29 30 Schematic diagram showing the construction of a honeycomb core sandwich panel.