Aggregate is the component of a composite material used to resist compressive stress. For efficient filling, aggregate should be much smaller than the finished item, but have a wide variety of sizes. For example, the particles of stone used to make concrete typically include both sand and gravel. Composite materials (or composites for short) are engineering materials made from two or more components. ... This article is about the construction material. ... Patterns in the sand Sand is an example of a class of materials called granular matter. ... Gravel Gravel is rock that is of a certain size range. ...

Comparison to fiber

Aggregate composites tend to be much easier to fabricate, and much more predictable in their finished properties, than fiber composites. This is because fiber orientation and continuity can have an overwhelming effect, but can be difficult to control and assess. Fabrication aside, aggregate materials themselves also tend to be less expensive; the most common aggregates (mentioned above) are found in nature and can often be used with only minimal processing.

Not all composite materials include aggregate in their design. This is because aggregate particles tend to have about the same dimensions in every direction (that is, an aspect ratio of about one), so that aggregate composites do not display the level of synergy that fiber composites often do. A strong aggregate held together by a weak matrix will be weak in tension, whereas fibers can be less sensitive to matrix properties, especially if they are properly oriented and run the entire length of the part (i.e., a continuous filament). The aspect ratio of a two-dimensional shape is the ratio of its longest dimension to its shortest dimension. ... The word matrix (plural matrices) has several meanings. ... In physics, tension is a force on a body directed to produce strain (extension); it can be considered to be negative compression. ... For the meaning of fiber in nutrition, see dietary fiber. ...

Most composites are filled with particles whose aspect ratio lies somewhere between oriented filaments and spherical aggregates. A good compromise is chopped fiber, where the performance of filament or cloth is traded off in favor of more aggregate-like processing techniques. Ellipsoid and plate-shaped aggregates are also used. Definition In mathematics, an ellipsoid is a type of quadric that is a higher dimensional analogue of an ellipse. ...

Aggregate properties

In most cases, the ideal finished piece would be 100% aggregate. A given application's most desirable quality (be it high strength, low cost, high dielectric constant, or low density) is usually most prominent in the aggregate itself; all the aggregate lacks is the ability to flow on a small scale, and form attachments between particles. The matrix is specifically chosen to serve this role, but its abilities should not be abused. The word matrix (plural matrices) has several meanings. ...

Aggregate size

Experiments and mathematical models show that more of a given volume can be filled with hard spheres if it is first filled with large spheres, then the spaces between (interstices)are filled with smaller spheres, and the new interstices filled with still smaller spheres as many times as possible. For this reason, control of particle size distribution can be quite important in the choice of aggregate; appropriate simulations or experiments are necessary to determine The optimal proportions of different-sized particles.

The upper limit to particle size depends on the amount of flow required before the composite sets (the gravel in paving concrete can be fairly coarse, but fine sand must be used for tile mortar), whereas the lower limit is due to the thickness of matrix material at which its properties change (clay is not included in concrete because it would "absorb" the matrix, preventing a strong bond to other aggregate particles). Particle size distribution is also the subject of much study in the fields of ceramics and powder metallurgy. Mission, or barrel, roof tiles A tile is a small, manufactured piece of hard-wearing material such as clay or stone used for covering roofs, floors, and walls, or other objects such as tabletops. ... Mortar has several meanings: A mortar is a vessel used to contain a substance which is then ground into a powder and/or mixed with a pestle. ... The word ceramic is derived from Greek, and in its strictest sense refers to clay in all its forms. ... Powder metallurgy is a forming and fabrication technique consisting of three major processing stages. ...

Some exceptions to this rule include:

Toughened composites

Toughness is a compromise between the (often contradictory) requirements of strength and plasticity. In many cases, the aggregate will have one of these properties, and will benefit if the matrix can add what it lacks. Perhaps the most accessible examples of this are composites with an organic matrix and ceramic aggregate, such as asphalt concrete ("tarmac") and filled plastic (i.e., Nylon mixed with powdered glass), although most metal matrix composites also benefit from this effect. In this case, the correct balance of hard and soft components is necessary or the material will become either too weak or too brittle. Toughness, in material science and metallurgy, is the resistance to fracture of a material when suddenly stressed. ... Strength can mean: Physical strength of organisms means (especially the muscles of most metazoa) of locomotion and movement Strength of materials in physics, engineering and materials science Strength is a rap compilation presented by Asiatic Warriors The word strengths is one of the longest English words with one syllable. ... Plasticity has four meanings: Plasticity (physics): In physics and engineering, plasticity is the propensity of a material to undergo permanent deformation under load. ... Organic has several meanings and related topics. ... The word ceramic is derived from Greek, and in its strictest sense refers to clay in all its forms. ... Asphalt concrete is a construction material commonly used for paving roads, highways and parking lots. ... Nylon is a synthetic polymer, a plastic, invented on February 28, 1935 by Wallace Carothers at DuPont of Wilmington, Delaware, USA. The material was announced in 1938 and the first nylon products; a nylon bristle toothbrush made with nylon yarn (went on sale on February 24, 1938) and more famously... The physics definition of a glass is a uniform amorphous solid material, usually produced when a suitably viscous molten material cools very rapidly, thereby not giving enough time for a regular crystal lattice to form. ... A metal matrix composite (MMC) is a type of composite material with at least two constituent parts, one being a metal. ...

Nanocomposites

Many materials properties change radically at small length scales (see nanotechnology. In the case where this change is desirable, a certain range of aggregate size is necessary to ensure good performance. This naturally sets a lower limit to the amount of matrix material used. A mite next to a gear chain produced using nanotechnology Nanotechnology as a collective term refers to technological developments on the nanometer scale, usually 0. ...

Unless some practical method is implemented to orient the particles in micro- or nano-composites, their small size and (usually) high strength relative to the particle-matrix bond allows any macroscopic object made from them to be treated as an aggregate composite in many respects.

While bulk synthesis of such nanoparticles as carbon nanotubes is currently too expensive for widespread use, some less extreme nanostructured materials can be synthesized by traditional methods, including electrospinning and spray pyrolysis. One important aggregate made by spray pyrolysis is glass microspheres. Often called microballoons, they consist of a hollow shell several tens of nanometers thick and approximately one micrometer in diameter. Casting them in a polymer matrix yields syntactic foam, with extremely high compressive strength for its low density. An electronic device known as a diode can be formed by joining two nanoscale carbon tubes with different electronic properties. ... This page is a candidate to be moved to Wiktionary. ... Pyrolysis is the chemical decomposition of organic materials by heating in the absence of oxygen and water. ... A nanometre (American spelling: nanometer) is 1. ... A micrometer is a widely used device in mechanical engineering for precisely measuring thickness of blocks, outer and inner diameters of shafts and depths of slots. ... A polymer is a long, repeating chain of atoms, formed through the linkage of many molecules called monomers. ...

Many traditional nanocomposites escape the problem of aggregate synthesis in one of two ways:

Natural aggregates: By far the most widely-used aggregates for nano-composites are naturally occurring. Usually these are ceramic materials whose crystalline structure is extremely directional, allowing it to be easily separated into flakes or fibers. The nanotechnology touted by General Motors for automotive use is in the former category: a fine-grained clay with a laminar structure suspended in a thermoplastic olefin (a class which includes many common plastics like polyethylene and polypropylene). The latter category includes fibrous asbestos composites (popular in the mid-20th century), often with matrix materials such as linoleum and Portland cement. Quartz crystal A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. ... GM redirects here. ... For the town in the United States, see Clay, New York. ... A thermoplastic is a plastic that softens when heated and hardens again when cooled. ... An olefin is an alkene hydrocarbon. ... Polyethylene or polyethene is one of the simplest and most inexpensive polymers. ... Polypropylene is a thermoplastic polymer, used in a wide variety of applications, including Australian banknotes. ... Asbestos (Greek a-, not; sbestos, extinguishable) is a group of fibrous metamorphic minerals. ... (19th century - 20th century - 21st century - more centuries) Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s As a means of recording the passage of time, the 20th century was that century which lasted from 1901–2000 in the sense of the Gregorian calendar (1900–1999 in the... Linoleum floor - a cheaper variety printed to appear to be wood Linoleum is a floor covering made from solidified linseed oil (linoxyn) in combination with wood flour or cork dust over a burlap or canvas backing. ... Sampling fast set Portland cement Portland cement is the most common type of cement in general usage, as it is a basic ingredient of concrete and mortar. ...

In-situ aggregate formation: Many micro-composites form their aggregate particles by a process of self-assembly. For example, in high impact polystyrene, two immiscible phases of polymer (including brittle polystyrene and rubbery polybutadiene) are mixed together. Special molecules (graft copolymers) include separate portions which are soluble in each phase, and so are only stable at the interface between them, in the manner of a detergent. Since the number of this type of molecule determines the interfacial area, and since spheres naturally form to minimize surface tension, synthetic chemists can control the size of polybutediene droplets in the molten mix, which harden to form rubbery aggregates in a hard matrix. Dispersion strengthening is a similar example from the field of metallurgy. Polystyrene is a polymer made from the monomer styrene, a liquid hydrocarbon that is commercially manufactured from petroleum. ... A solvent is a liquid that dissolves a solid, liquid, or gaseous solute, resulting in a solution. ... A polymer is a long, repeating chain of atoms, formed through the linkage of many molecules called monomers. ... Andrew sucks ... A detergent is a compound, or a mixture of compounds, intended to assist cleaning. ... In physics, surface tension is an effect within the surface layer of a liquid that causes the layer to behave as an elastic sheet. ... Metallurgy is a domain of materials science and of materials engineering that studies the physical and chemical behavior of metallic elements and their mixtures, which are called alloys. ...