Post 156 –by Gautam Shah
Natural and manufactured raw materials are invariably compounds, made of many materials. These raw materials are formed into products by a method of assimilation –the COMPOSITE or the raw materials are organized into a geometric form –the COMPOSITION.
Many of the raw materials are naturally compounded materials, in the form of Composites. The composite materials come into being, by putting together natural and manufactured materials in such a special way that the strength and other qualities are different from the constituents, individually and cumulatively. The term –different, is considered here as an improved quality, because man-made composites are designed and created towards specific performance requirements only.
Similarly natural and man-made materials have an inherent organization of geometric arrangements which endow unique structural behaviour capacities. Some of the simplest examples are hives of honey bees or birds’ netted nests. At a complex level a truss, bicycle frame, a hull of a boat, are all Structural Compositions or geometric arrangements.
Natural and manufactured materials, and their composites, all are further shaped, re-formed and geometrically integrated to create secondary components as well as Structural Compositions.
UNDERSTANDING THE DIFFERENCES BETWEEN COMPOSITES AND COMPOSITIONS
A composite is a natural or designed material entity with potential utility, but has no operational functionality. On the other hand, a component is a configuration of many materials into a utilitarian product. Component manufacturing involves processes that are many times similar to a composite formation. As a matter of fact for component manufacturing, the ‘composite formation’ and the ‘component creation’ both occur simultaneously. Structural compositions (trusses, bridges, buildings) are geometric-configuration of materials, often assisted by components (nuts, rivets, pins, bearings, etc.). Structural compositions use composites to form the constituent elements.
Various Definitions of Composites:
# Consisting of two or more physically distinct and conceptually separable or visually identifiable materials.
# Products that can be made by mixing separate materials, so the dispersion of one material in the other can be done in a controlled way to achieve optimum properties.
# Products with properties that are superior and possibly unique in some specific respects compared to the properties of their individual components.
Classes of Composites:
Natural composites Wood, Bamboo, Bone, Muscle and other tissues
Macro composites Galvanized steel,
Engineered products Reinforced cement concrete (beams, etc.), Helicopter blades Skis, Tennis rackets.
Microscopic composites Metallic alloys, Toughened plastic (impact polystyrene, ABS), Reinforced plastics.
Nano composites Electronics circuits, diodes, transistors
Some natural composites are easy to identify, such as: wood, bamboo, bones, muscles, etc. First man-made composites related to the bronze, as man tried to fix natural stones and ceramic pieces by hammering into the bronze. Layered wood composites have been used by Egyptians. Mud bricks reinforced with hay, hair, and rice husk have been used in prehistoric times. Cow-dung is also reinforced with granular sand particles for wall plaster. Gypsum (Plaster of Paris) has been applied on a lattice of jute, papyrus and such other fibres.
Macro, Micro and Nano Composites: Composites can be categorized in terms of the size of constituent particulate matter. Ingredients of macro composites can be distinguished by naked eye, whereas one may need an electron microscope to understand the constituents of micro composites and nano composites. Nano composites are created by introducing nano-particulate, which drastically add to the electrical, thermal, and mechanical properties of the original material.
Basic Constituents of a Composite: MATRIX and FILLERS
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.
Categories of Composites on the basis of strengthening mechanism.
Composite materials can be distinguished into three categories based on the strengthening mechanism.
These categories are:
1. Dispersion strengthened,
2 Particle reinforced
3 Fiber reinforced.
● Dispersion Strengthened Composites have a fine distribution of secondary particles (fillers) in the matrix of the material. These particles impede the mechanisms that allow a material to deform. Many Metal-matrix composites would fall into the dispersion strengthened composites’ category.
● Particle reinforced composites have a large volume of particles dispersed in the matrix. The load is shared by the particles and the matrix. Most commercial ceramics and many filled polymers are particle-reinforced composites.
● Fiber-reinforced composites have fiber as the main load-bearing component. Fiberglass and carbon fiber composites are examples of fiber-reinforced composites.