Post 168 ⇒ by Gautam Shah →
The constituents of a composite are ordinarily classified as Matrix and Filler. It is the nature of relationship between the filler and matrix, or the Interface that defines the composite. Fillers serve to resist stresses, mainly tension, and the Matrix serves to resist the shear, and all materials present including any aggregates, serve to resist the compression.
Matrix and Filler each are of three types: Metals, Ceramics and Polymers.
These three provide nine possible combinations.
Composite materials’ combinations: Possibilities of combinations and type-examples.
Matrix (m) + Filler(f) = Composite Type-Examples
● Metal matrix composites MMC
Metal (m)+ Metal (f) = Aluminium-Tin are non miscible metals, yet can be alloyed as a composite
Metal (m) + Ceramic (f) = Electrical semi conductors, Carbide cutting tool tips, Scissors, knives
Metal (m) + Polymer (f) = Not feasible, Metals become soft at very high temperature -unsuitable for polymer filler
● Ceramic matrix composites CMC
Ceramic (m) + Ceramic (f) = Carbon-carbon composites
Ceramic (m) + Metal (f) = Metal sprayed optic glass fiber cables
Ceramic (m) + Polymer (f) = Not feasible, Ceramics require high temperature for formation -unsuitable for polymer filler
● Polymer matrix composites PMC
Polymer (m) + Polymer (f) = Polyester or rayon fibre reinforced plastics
Polymer (m) + Metal (f) = Grinding and polishing abrasives
Polymer (m) + Ceramic (f) = Fibreglass, Fibre reinforced plastic FRP Asphalt roads, imitation granite, cultured marble sinks and counter tops
A matrix is an environment or material within which an interface is desired. A matrix surrounds the Filler material while creating a bond with it. A matrix thus creates a network within which the filler components are supported by maintaining or reinforcing their intended positions. For a matrix to be affective, it must at some stage have a lower phase than the filler material. The lower phase may occur before or while the filler material is being formed or introduced. The matrix material may turn to a higher phase by evaporation of the solvent, removal of the heat or pressure, and polymerization or action of a catalyst. Polymer matrices are most common, followed by metals and ceramics. However, paper pulp, mud, wax, etc. are some matrix materials that do not fit into any of the above-mentioned categories. Ceramic matrix composites though difficult to form, show greatest promise in material sciences.
- Portland cement, Gypsum plaster, mud (clay), and Bitumens are widely used matrix materials. Polymer matrix materials are thermosetting resins such as polymers, poly-amides, epoxies, or thermoplastic resins such as polycarbonate or polysulphones. Typically a polymer matrix composite of Epoxy and carbon fibres is of two thirds the weight of aluminium, and two and a half times as stiff.
- For metal matrices most commonly used metals are aluminium, titanium, magnesium, and copper. Composites with metal matrices generally have metal or ceramic as filler materials. Aluminium reinforced with fibres of the ceramic silicon carbide is a classic example of a metal matrix with ceramic filler. The composite material combines the strength and stiffness of a silicon carbide with the ductility of aluminium. Metal to metal composites consist of two immiscible metals (metals that do not form alloys), such as magnesium and titanium. Such metal-metal composites with bronze matrices have been in use since Bronze Age to create many useful materials.
Next article in the series -about FILLERS in COMPOSITES