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Composites Terminology Database

This glossary is not an exhaustive list, however it does contain the majority of terms used in the composites industry and as part of the management of our website, it is updated on a continual basis.

The terms are accessed by clicking on the appropriate letter below, all the terms beginning with the letter M can be found below.

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Terms M

Click on a term and it will take you to the coresponding explanation.

A high beryllia (BeO2) content glass designed especially for high modulus of elasticity.
(("glass") ("C-glass") ("D-glass") ("E-glass") ("S-glass"))

To chop or shred fabric for use as a filler for a moulding resin.

In relation to composites, denotes the gross properties of a composite as a structural element but does not consider the individual properties or identity of the constituents.

The core tool around which resin impregnated paper, fabric, or fibre is wound to form pipes, tubes, or structural shell shapes.

A fibrous material for reinforced plastic consisting of randomly oriented chopped filaments, short fibres (with or without a carrier fabric), or swirled filaments loosely held together with a binder. Available in blankets of various widths, weights, and lengths. Also, a sheet formed by filament winding a single-hoop ply of fibre on a mandrel, cutting across its width and laying out a flat sheet.

matched metal moulding
A reinforced plastics manufacturing process in which matching male and female metal moulds are used (similar to compression moulding) to form the part, with time, pressure, and heat.

The essentially homogeneous resin or polymer material in which the fibre system of a composite is imbedded. Both thermoplastic and thermoset resins may be used, as well as metals, ceramics, and glasses.

max diameter
Maximum diameter, given in mm/inches.

max wall thickness
Maximum thickness of any wall, given in mm/inches"pultrusion size"

mechanical adhesion
Adhesion between surfaces in which the adhesive holds the parts together by interlocking action.

mechanical properties
The properties of a material, such as compressive and tensile strengths, and modulus, that are associated with elastic and inelastic reaction when force is applied. The individual relationship between stress and strain.

A charge of molten metal. See also liquid metal infiltration
"liquid metal infiltration"

The repeating structural unit of any polymer.

An intermediate phase in the formation of carbon from a pitch precursor. This is a liquid crystal phase in the form of microspheres, which upon prolonged heating.(above 400 degree C) coalesce, solidify, and form regions of extended order. Heating to above 2000 degree C (3630 degree F) leads to the formation of graphite structure.

metallic fibre
Manufactured fibre composed of metal, plastic-coated metal, metal-coated plastic, or a core completely covered by metal.

Metric Type
A descriptor of the class of the Metric. Currently metrics can be BOOLEAN, Numeric, or Qualitative.

In relation to composites, denotes the properties of the constituents, that is, matrix, reinforcement, and interface only, and their effects on the composite properties.

Cracks formed in composites when thermal stresses locally exceed the strength of the matrix. Since most microcracks do not penetrate the reinforcing fibres, microcracks in a cross-plied tape laminate or in a laminate made from cloth prepreg are usually limited to the thickness of a single ply.

A structure with heterogeneities that can be seen through a microscope. For advanced composites, the most important characteristics of microstructure are fibre volume fraction, fibre length, and fibre orientation.

The unit used in measuring the diameter of glass fibre strands, wire, and so forth ( 1 mil = 0.001 in.).

milled fibre
Continuous glass strands hammer milled into very short glass fibres. Useful as inexpensive filler or anticrazing reinforcing fillers for adhesives.

min inside radius
In the pultrusion process, it is good practice to radius mat-reinforced profiles by a minimum of 1.5mm/1/16 inches, and all axially reinforced rods and bars by a minimum of 0.8mm/1/32 inch. "min inside radius"

min toll wall thickness
"Tightest" tolerance on any wall thickness dimension, given in mm/inches.

min toll wall thickness
"Tightest" tolerance on any wall thickness dimension, given in mm/inches.

min toll wall thickness
"Tightest" tolerance on any wall thickness, given in mm/inches.

min wall thickness
Minimum wall thickness specified, given in mm/inches. "pultrusion size"

modulus of elasticity
The ratio of the stress or load applied to the strain or deformation produced in a material that is elastically deformed. If a tensile strength of 13.8 MPa (2.0 ksi) results in an elongation of 1%, the modulus of elasticity is 13.8 MPa (2.0 ksi) divided by 0.01, or 1380 MPa (200 ksi). Also called Young's modulus. See also offset modulus and secant modulus
"Young's modulus" "offset modulus" "offset modulus"

modulus of resilience
The energy that can be absorbed per unit volume without creating a permanent distortion. Calculated by integrating the stress-strain curve from zero to the elastic limit and dividing by the original volume of the specimen.

modulus of rigidity
The ratio of stress to strain within the elastic region for shear or torsional stress. Also called shear modulus or torsional modulus.
"shear modulus" "torsional modulus"

modulus of rupture, in bending
The maximum tensile or compressive stress value (whichever causes failure) in the extreme fibre of a beam loaded to failure in bending.

modulus of rupture, in torsion
The maximum shear stress in the extreme fibre of a member of circular cross section loaded to failure in torsion.

modulus, initial
See initial modulus
"initial modulus"

modulus, offset
See offset modulus
"offset modulus"

modulus, secant
See secant modulus
"secant modulus"

modulus, tangent
See tangent modulus
"tangent modulus"

Mohs hardness
A measure of the scratch resistance of a material. The higher the number, the greater the scratch resistance (No. 10 being termed diamond).

moisture absorption
The pickup of water vapour from air by a material. It relates only to vapour withdrawn from the air by a material and must be distinguished from water absorption, which is the gain in weight due to the take-up of water by immersion.

moisture content
The amount of moisture in a material determined under prescribed conditions and expressed as a percentage of the mass of the moist specimen, that is, the mass of the dry substance plus the moisture present.

moisture equilibrium
The condition reached by a sample when it no longer takes up moisture from, or gives up moisture to, the surrounding environment.

moisture vapour transmission
A rate at which water vapour passes through a material at a specified temperature and relative humidity (g/mil/24 h/100 in.).

mould shrinkage
The immediate shrinkage that a moulded part undergoes when it is removed from a mould and cooled to room temperature. The difference in dimensions, expressed in inches per inch, between a moulding and the mould cavity in which it was moulded (at normal-temperature measurement).

The incremental difference between the dimensions of the moulding and the mould from which it was made, expressed as a percentage of the mould dimensions.

mould surface
The side of a laminate that faced the mould (tool) during cure in an autoclave or hydroclave.

mould-release agent
A lubricant, liquid or powder (often silicone oils and waxes), used to prevent sticking of moulded articles in the cavity.

The cavity or matrix into or on which the plastic composition is placed and from which it takes form. To shape plastic parts or finished articles by heat and pressure. The assembly of all the parts that function collectively in the moulding process.

moulded edge
An edge that is not physically altered after moulding for use in final form, and particularly one that does not have fibre ends along its length.

moulded in holes
Holes that are made during the composite main processing procedure; as opposed to holes that are cut in subsequent operations.

moulded net
Description of a moulded part that requires no additional processing to meet dimensional requirements.

moulding cycle
The period of time required for the complete sequence of operations on a moulding press to produce one set of mouldings. The operations necessary to produce a set of mouldings without reference to the total time taken.

moulding powder or compound
Plastic material in varying stages of pellets or granulation, and consisting of resin, filler, pigments, reinforcements, plasticises, and other ingredients ready for use in the moulding operation.

moulding pressure
The pressure applied to the ram of an injection machine or compression or transfer press to force the softened plastic to fill the mould cavities completely.

The forming of a polymer or composite into a solid mass of prescribed shape and size by the application of pressure and heat for given times. Sometimes used to denote the finished part.

molecular weight
The sum of the atomic weights of all the atoms in a molecule. A measure of the chain length for the molecules that make up the polymer.

A single fibre or filament of indefinite length, strong enough to function as a yam in commercial textile operations.

The basic laminate unit from which cross-plied or other laminate types are constructed. Also, a "single" layer of atoms or molecules adsorbed on or applied to a surface.

A single molecule that can react with like or unlike molecules to form a polymer. The smallest repeating structure of a polymer (mer). For additional polymers, this represents the original un-polymerised compound.

The overall form of a polymer structure, that is, crystallinity, branching, molecular weight, and so on.

multi-curved panel
Panel, frequently of the sandwich type, with more than one curve in the plane.

multicircuit winding
In filament winding, a winding that requires more than one circuit before the band repeats by laying adjacent to the first band.

multifilament yarn
A large number (500 to 2000) of fine, continuous filaments (often 5 to 100 individual filaments) usually with some twist in the yarn to facilitate handling.

"moisture vapour transmission"

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