Industry Glossary - H

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

The process of placing (and working) successive plies of reinforcing material or resin-impregnated reinforcement in position on a mold by hand. Method of molding room temperature curing thermosetting polymers, mainly epoxies and polyesters, in association with glass, mineral, or fiber reinforcements. Catalyzed resin mixtures are sprayed, brushed, or spatulated on a mold. 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 mold and trimmed. Some variations of hand lay-up techniques are bag molding, drape molding, vacuum molding and spray-up molding. Typical parts are custom auto bodies and boat hulls.

A roving product that is not very soluble in acetone or styrene which results in the tendency of the individual bundles to retain their integrity (hardness) and not filamentize in the matrix resin. Hard glass is often stiff and brashy. The size is generally less than 40% soluble in acetone.

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

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.

Batch and continuous processes in which organic yarn binder is removed from glass fabrics.

Temperature at which the strength of a material begins to degrade. Now called deflection temperature.

This is a measurement of the temperature which will cause the material to bend under a give load. It was developed for thermoplastic materials which soften considerably when heated. It has relatively little value as a design figure for thermosetting reinforced plastics. During this test a load is applied in bending to cause 264 psi stress in the material. The temperature of the material is then raised until the material bends one tenth of an inch at the center. Units – degrees Fahrenheit (�F)- degrees Centigrade (�C). Higher numbers mean that the material can be heated to a higher temperature before it deflects one tenth of an inch under this arbitrary load of 264 psi.

The property or ability of plastics and elastomers to resist the deteriorating effect of elevated temperatures.

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.

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.

Polyester resin with exceptional fire qualities.

Laminates molded and cured at pressures not lower than 6.9 MP (1.0 ksi), and more commonly in the range of 8.3 to 13.9 Mpa (1.2 to 2.0 ksi).

Descriptive term for a material of uniform composition throughout.

A compound produced by polymerization.

Manufactured product of resin-impregnated sheet material (paper, glass, fabric, and so on) or metal foil, formed into hexagonal-shaped cells. Used as a core material in sandwich construction.

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

A composite laminate consisting of laminate of two or more composite material systems. A combination of two or more different fibers, such as carbon and glass or carbon and arimid, into a structure.

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

Material that absorbs moisture from the air.

The energy absorbed in a complete cycle of loading and unloading. This energy in converted from mechanical to friction energy (heat).