Module 1: Introduction to Composites
  Lecture 5: Terminologies
 

 

What are the advantages of the composite materials?

The following are the advantages of composites:

  1. Specific stiffness and specific strength:

    2. The composite materials have high specific stiffness and strengths. Thus, these material offer better properties at lesser weight as compared to conventional materials. Due to this, one gets improved performance at reduced energy consumption.

  2. Tailorable design:

    3. A large set of design parameters are available to choose from. Thus, making the design procedure more versatile. The available design parameters are:

    1. Choice of materials (fiber/matrix), volume fraction of fiber and matrix, fabrication method, layer orientation, no. of layer/laminae in a given direction, thickness of individual layers, type of layers (fabric/unidirectional) stacking sequence.
    2. A component can be designed to have desired properties in specific directions.

  3. Fatigue Life:

    4.    The composites can with stand more number of fatigue cycles than that of aluminum. The critical structural components in aircraft require high fatigue life. The use of composites in fabrication of such structural components is thus justified.

  4. Dimensional Stability:

    5. Strain due to temperature can change shape, size, increase friction, wear and thermal stresses. The dimensional stability is very important in application like space antenna. For composites, with proper design it is possible to achieve almost zero coefficient of thermal expansion.

  5. Corrosion Resistance:

    6. Polymer and ceramic matrix material used to make composites have high resistance to corrosion from moisture, chemicals.

  6. Cost Effective Fabrication:

    7. The components fabricated from composite are cost effective with automated methods like filament winding, pultrusion and tape laying. There is a lesser wastage of the raw materials as the product is fabricated to the final product size unlike in metals.

  7. Conductivity:

    8. The conductivity of the composites can be achieved to make it a insulator or a highly conducting material. For example, Glass/polyesters are non conducting materials. These materials can be used in space ladders, booms etc. where one needs higher dimensional stability, whereas copper matrix material gives a high thermal conductivity.

The list of advantages of composite is quite long. One can find more on advantages of composite in reference books and open literature.

What are the disadvantages of Composites?

  1. Some fabrics are very hard on tooling.
  2. Hidden defects are difficult to locate.
  3. Inspection may require special tools and processes.
  4. Filament-wound parts may not be repairable. Repairing may introduce new problems.
  5. High cost of raw materials.
  6. High initial cost of tooling, production set-up, etc.
  7. Labour intensive.
  8. Health and safety concerns.
  9. Training of the labour is essential.
  10. Environmental issues like disposal and waste management.
  11. Reuse of the materials is difficult.
  12. Storage of frozen pre-pregs demands for additional equipments and adds to the cost of production.
  13. Extreme cleanliness required.
  14. The composites, in general, are brittle in nature and hence easily damageable.
  15. The matrix material is weak and hence the composite has low toughness.
  16. The transverse properties of lamina or laminate are, in general, weak.
  17. The analysis of the composites is difficult due to heterogeneity and orthotropy.