COMPOSITE MATERIALS

COMPOSITE MATERIALS

1. A material system composed of two or more physically distinct phases whose combination produces aggregate properties that are different from those of its constituents

2. DISADVANTAGES AND LIMITATIONS

   • Properties of many important composites are anisotropic
   • Many of the polymer-based composites are subject to attack by chemicals or solvents
   • Composite materials are generally expensive
   • Manufacturing methods for shaping composite materials are often slow and costly

3. Metal matrix composites (MMC’s)

   • The matrix is relatively soft and flexible
     • The reinforcement must have high strength and stiffness
       • the reinforcement-matrix bond must be strong.

4. Ceramic matrix composites (CMC’s)

   • The matrix is relatively hard and brittle
     • he reinforcement must have high tensile strength to arrest crack growth
       • the reinforcement-matrix bond must be relatively weak

5. Polymer matrix composites (PMC’s)

   • The matrix is relatively soft and flexible
     • The reinforcement must have high strength and stiffness
       • the reinforcement- matrix bond must be strong

6. Traditional composites

   • composite materials that occur in nature or have been produced by civilizations for many years

7. Synthetic composites

   • modern material systems, in which the components are first produced separately and then combined in a controlled way to achieve the desired structure, properties, and part geometry

8. MANUFACTURING PROCESS OF COMPOSITE MATERIALS

   • In function of composite constructions, those can be divided in two categories
     • Laminates
       • which have layers bonded together
     • Sandwiches
       • which are multiple-layer structural materials containing a low density core between thin faces (skins) of composite materials.
   • Hand lay-up
   • Spray lay-up
   • Automatic tape lay-up

9. composites-fiber

   • bigotes
     • graphite, SiN, SiC
   • fibers
     • polymers or ceramics
   • wires
     • steel, Mo, W

10. FUNCTIONS OF THE MATRIX MATERIAL (PRIMARY PHASE

    • Protect phases from environment
      • Transfer Stresses to phases
        • Holds the imbedded phase in place, usually enclosing and often concealing it
          • When a load is applied, the matrix shares the load with the secondary phase, in some cases deforming so that the stress is essentially born by the reinforcing agent