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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 H can be found below.

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Terms H

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


hand lay-up
Method of moulding room temperature curing thermosetting polymers, mainly epoxies and polyesters, in association with glass, mineral, or fibre reinforcements. Catalysed resin mixtures are sprayed, brushed, or spatulated on a mould.

A precut reinforcing layer is laid on the wet resin. After the resin soaks into the reinforcement, subsequent layers are built up to the required thickness and are cured, removed from the mould and trimmed.

Some variations of hand layup techniques are bag moulding, drape moulding, vacuum moulding and spray-up moulding. Typical parts are radomes, custom auto bodies, boat hulls, and jigs and fixtures. "hand layup"


Hand
The softness of a piece of fabric, as determined by the touch (individual judgement).


handling life
The out-of-refrigeration time over which a material retains its handleability.


hardener
A substance or mixture added to a plastic composition to promote or control the curing action by taking part in it.


hardness
The resistance to surface indentation usually measured by the depth of penetration (or arbitrary units related to the depth of penetration) of a blunt point under a given load using a particular instrument according to a prescribed procedure. See also Barcol hardness, Mohs hardness, Rockwell hardness, and Shore hardness.
(("Barcol hardness") ("Mohs hardness") ("Rockwell hardness") ("Shore hardness"))


harness satin
Weaving pattern producing a satin appearance. "Eight-harness" means the warp tow crosses over seven fill tows and under the eighth (repeatedly).


heat build-up
The rise in temperature in a part resulting from the dissipation of applied strain energy as heat or from applied mould cure heat. See also hysteresis


heat cleaned
A condition in which glass or other fibres are exposed to elevated temperatures to remove preliminary sizings or binders not compatible with the resin system to be applied.


heat distortion point
The temperature at which a standard test bar deflects a specified amount under a stated load. Now called deflection temperature.
("deflection temperature under load" "deflection temperature under load")


heat resistance
The property or ability of plastics and elastomers to resist the deteriorating effects of elevated temperatures.


heat sealing
A method of joining plastic films by simultaneous application of heat and pressure to areas in contact.


heat sink
A contrivance for the absorption or transfer of heat away from a critical element or part. Bulk graphite is often used as a heat sink.


heat treating
Term used to cover annealing, hardening, tempering, and so forth.


heat-activated adhesive
A dry adhesive that is rendered tacky or fluid by application of heat, or heat and pressure, to the assembly.


heat-sealing adhesive
A thermoplastic film adhesive that is melted between the adherend surfaces by heat application to one or both of the adjacent adherend surfaces.


height-tolerance
Tolerance on the height dimension, given in inches.


Height
Measure of shortest side of a cross-sectional area, given in inches. "pultrusion size"


helical winding
In filament wound items, a winding in which a filament band advances along a helical path, not necessarily at a constant angle except in the case of a cylinder.


heterogeneous
Descriptive term for a material consisting of dissimilar constituents separately identifiable. A medium consisting of regions of unlike properties separated by internal boundaries. Note that not all nonhomogeneous materials are necessarily heterogeneous.


hexa
Shortened form of hexamethylenetetramine, a source of reactive methylene for curing novolacs.


high-frequency heating
The heating of materials by dielectric loss in a high-frequency electrostatic field. The material is exposed between electrodes and is heated quickly and uniformly by absorption of energy from the electrical field.


high-pressure laminates
Laminates moulded and cured at pressures not lower than 6.9 MPa (1.0 ksi), and more commonly in the range of 8.3 to 13.8 MPa (1.2 to 2.0 ksi).


high-pressure spot
See resin-starved area
"resin-starved area"


HIP
See hot isostatic pressing
"hot isostatic pressing"


Hollow Section
Parts with a hallow section, such as a bar or tube. "hollow section"


homogeneous
Descriptive term for a material of uniform composition throughout. A medium that has no internal physical boundaries. A material whose properties are constant at every point, that is, constant with respect to spatial co-ordinates (but not necessarily with respect to directional co-ordinates).


honeycomb
Manufactured product of resin-impregnated sheet material (paper, glass, fabric) or metal foil, formed into hexagonal-shaped cells. Used as a core material in composite sandwich construction. See sandwich construction
"sandwich constructions"


hoop stress
The circumferential stress in a material of cylindrical form subjected to internal or external pressure.


hot isostatic pressing
A process for fabricating certain metal matrix composites. A preform is consolidated under fluid pressure (usually an inert gas) at high temperature and pressure in a pressure vessel.


hot working
Any form of mechanical deformation processing carried out on a metal or alloy above its re-crystallization temperature but below its melting point.


hot-melt adhesive
An adhesive that is applied in a molten state and forms a bond after cooling to a solid state. A bonding agent that achieves a solid state and resultant strength by cooling, as contrasted with other adhesives, which achieve the solid state through evaporation of solvents or chemical cure. A thermoplastic resin that functions as an adhesive when melted between substrates and cooled.


hot-setting adhesive
An adhesive that requires a temperature at or above 100 °ree; C (212 °ree; F) to set.


hybrid
A composite laminate consisting of laminae of two or more composite material systems. A combination of two or more different fibres, such as carbon and glass or carbon and aramid, into a structure. Tapes, fabrics, and other forms may be combined; usually only the fibres differ. See also interply hybrid and intraply hybrid
"interply hybrid" "intraply hybrid"


hydraulic press
A press in which the moulding force is created by the pressure exerted by a fluid.


hydromechanical press
A press in which the moulding forces are created partly by a mechanical system and partly by an hydraulic system.


hydrophilic
Capable of absorbing water. Easily wetted by water.


hydrophobic
Capable of repelling water. Poorly wetted by water.


hygroscopic
Capable of adsorbing and retaining atmospheric moisture.


hygrothermal effect
Change in properties due to moisture absorption and temperature change.


hysteresis
The retardation or lagging of an effect behind the cause of the effect.

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