2 Raw Materials

Giant Quarry. This is where raw materials come from.

2.1 Matrix
2.2 Reinforcement
2.3 Prepregs
2.4 Some other Materials

The relative role of the matrix and reinforcement generally fall into the following categories :

~ The reinforcement has high strength and stiffness, and the matrix serves to transfer stress
    from one fiber to the next and to produce a fully dense structure.

~ The matrix has many desirable, intrinsic physical, chemical, or processing characteristics,
   and the reinforcement serves to improve certain other important engineering properties,
   such as tensile strength, creep resistance, or tear resistance.

~ Emphasis is placed on enhancing the economic attractiveness of the matrix, e.g., by mixing
   or diluting it with materials that will improve its appearance, process, or cost advantage while
   maintaining adequate performance.

2.1 Matrix 

Role of Matrix.

The word " Matrix " is about mother, matri --  such as Matriarch : a woman who rules or
dominates a family, a group, or state. From the meaning of the Matrix, basically you can
understand the function of the matrix.

~ To maintain alignment of the filaments and increase structural stiffness and stability.
~ To provide adequate transverse properties perpendicular to the reinforcement,
~ To act as a load transfer medium for discontinuous of broken filaments.
~ To protect the filaments from damage, mutual abrasion and environmental degradation.

Matrix Types :

Organic Materials, Metals, Ceramics.
The polymeric matrices are the lowest in density, yielding the lightest composites.

Thermosets
Thermoplastics
Polyster
Epoxy
....

2.2 Reinforcement

Role of Reinforcement

To impart the stiffness and strength characteristics of the filament by being able to carry a
major part of the load in the direction of the filaments. For discontinuous (or broken) filaments,
the load is transferred by a relatively low shear stress generated on the matrix.

Carbon

Carbon is a very versatile element.  Carbon fiber are fabricated by controlled pyrolysis of an
organic fiber precursor.

2.3 Prepregs

Commercial prepregs are reinforcements impregnated with predetermined amounts of
uniformly distributed resin and are processed to attain optimum handling characteristics and
reproducible cured laminate properties. The impregnating resins include epoxy, polyester,
phenolic, silicone, polyimide, and thermoplastics such as polysulfone. Resin systems are
applied as liquid, hot melt, and solvent diluted compositions, as well as unpolymerized monomeric reactants.

Prepreg

Ready to mold material in sheet form, which may be cloth, mat or paper impregnated with
resin and stored for use. The resin is partially cured to a B-stage and supplied to the
fabricator, who lays up the finished shape and completes the cure with heat and pressure.

B-Stage

An intermediate stage in the reaction of a thermosetting resin in which the material softens
when heated and swells when in contact with certain solvents, but does not entirely fuse or
dissolve. Materials are usually precured to this stage to facilitate handing and lay-up prior to
final cure.

2.4 Some Other Materials

Core Material

The core material may be solid (Balsa), cellular (PU or PVC foam), honeycomb, or any other
other configuration. It must transmit the loads from one facing to the other. There is little penalty
in the performance when a solid core is replaced with less-dense materials.

Balsa wood was used as the core between thin layers of plywood in the sandwich construction
of the all-wood Mosquito aircraft of World War II.

Manufacture of Honeycomb.

The physical and mechanical properties of the honeycomb are dependent on the basic
composition, cell size, and cell geometry. All honeycombs are anisotropic. large cells or
over-expansion on the honeycomb pattern will lower density and change the strength level of
the core-to-face attachment. If cell walls are too thin, the bend and shear strengths of the
sandwich will be lower.    

Fillers

Fillers are small organic and inorganic particulate materials mixed with  plastics to modify
their properties, extend resins in short supply, and reduce cost.

a. Physical Properties Modification

Lower coefficient of thermal expansion; increased electrical resistivity or conductivity;
better electromagnetic shielding;

b. Mechanical Properties Modification

Increased strength (requires good bonding to resin ); increased creep resistance; ...