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Accelerated ageing test: Short-term test designed to simulate the effects of longer-term service conditions.
Adherend: Body that is or intended to be held to another body by an adhesive.
Adherend failure: Failure of a joint in the body of the adherend.
Adhesion: State in which two surfaces are held together by interfacial bonds.
Adhesive: Non-metallic substance capable of joining materials by surface bonding (adhesion), the bonding possessing adequate internal strength (cohesion).
Adhesive failure: Failure of an adhesive bond, such that separation appears to be at the adhesive/adherend interface.
ASTM: American Society for Testing and Materials.
Bond: The union of materials by adhesives.
Bond-line: The layer of adhesive, which attaches two adherends.
Bond strength: The unit of load applied to tension, compression, flexure, peel, impact, cleavage, or shear, required to break an adhesive assembly with failure occurring in or near the plane of the bond.
BSI: British Standards Institute
Butt joint: Joint in which the plane of the bond is at right angles to a major axis of the adherends.
Bulk adhesive: The adhesive unaltered by the adherend.
Cleavage: Mode of application of a force to a joint between rigid adherends, which is not uniform over the whole area, but results in a stress concentrated at one edge.
Cohesion: The ability of the adhesive to resist splitting or rupture.
Cohesive failure: Failure within the body of the adhesive (i.e. not at the interface).
Creep: The time-dependent increase in strain resulting from a sustained load.
Cure: To set or harden by means of a chemical reaction.
Cure time: Time required to induce cure at a given temperature.
Double lap joint: Joint made by placing one or two adherends partly over one or two other adherends and bonding together the overlapped portions.
Durability: The endurance of joint strength relative to the required service conditions.
Environmental test: Test to assess the performance of an assembly under service conditions.
Exothermic: A chemical reaction that emits heat.
Fatigue life: Number of cycles necessary to bring an adhesive bond to the point of failure when the bond is subjected to repeated cyclic stressing under specified conditions.
Fatigue strength: Force that a joint will withstand when the force is applied repeatedly for an infinite number of cycles.
Fillet: Portion of an adhesive that bridges the adherends outside the bond-line.
Gel: A semi-solid system consisting of a network of solid aggregates in which liquid is held.
Gelation: Formation of a gel.
Glass transition: A reversible change in an amorphous polymer or in amorphous regions of a partially crystalline polymer from (or to) a viscous or rubbery condition to (or from) a hard and relatively brittle one.
Hygroscopic: Material capable of absorbing and retaining environmental moisture.
ISO: International Standards Organisation.
Lap joint: Joint made by placing one adherend partly over another and bonding together the overlapped portions.
Open time: Time interval from when an adhesive is applied to when the material becomes unworkable.
Peel: Mode of application of a force to a joint in which one or both of the adherends is flexible and which the stress is concentrated at a boundary.
Peel ply: A layer of resin free material used to protect a laminate for later secondary bonding.
Plasticisation: Increase in softness, flexibility, and extensibility of an adhesive.
Post-cure: Further treatment by time and/or temperature of an adhesive to obtain the required properties by curing.
Porosity: A condition of trapped pockets of air, gas or vacuum within a solid material.
Primer: A coating applied to a surface, prior to the application of an adhesive, to improve the performance of the bond.
Scarf joint: Joint made by cutting identical angular segments at an angle less than 45° to the major axis of two adherends and bonding the adherends with the cut areas fitted together to be coplanar.
Service life (N): Number of stress cycles applied to a specimen until it has reached the chosen end of the test.
Shear: Mode of application of a force to a joint that acts in the plane of the bond.
Shelf life: The period for which the components of the adhesive may be stored, under the conditions specified by the manufacturer, without being degraded.
Strain: Unit change due to force in size of body relative to its original size.
Stress: Force exerted per unit area at a point within a plane.
Stress-cycles (SN) curve: Curve, allowing the resistance of the material to be seen, which indicates the relationship observed experimentally between the service life N and maximum stress.
Stress-strain diagram (or curve): A diagram in which corresponding values of stress and strain are plotted against each other.
Structural bond: A bond, which is capable of sustaining in a structure a specified strength level under a combination of stresses for a specified time.
Substrate: An adherend, a material upon which an adhesive is applied.
Surface preparation (or treatment): Physical and/or chemical treatments applied to adherends to render them suitable or more suitable for adhesive bonding.
Tack: The property of an adhesive that enables it to form a bond of measurable strength immediately after adhesive and adherend are brought into contact under low pressure.
Tension: Mode of application of a tensile force normal to the plane of a joint between rigid adherends and uniformly distributed over the whole area of the bond-line.
Thermoset: A resin that is substantially infusible and insoluble after being cured.
Thermoplastic: A material that can be repeatedly softened by heating.
Traveller: A test specimen used for example to measure moisture content as a result of conditioning.
Viscosity: Resistance of a liquid material to flow.
Wet strength: Strength of an adhesive bond determined immediately after removal from a liquid in which it has immersed under specified conditions.
Wetting: A surface is considered completely wet by a liquid if the contact angle is zero, and incompletely wet if the contact angle has a finite value.
Yield stress: The stress (either normal or shear) at which a marked increase in deformation occurs without an increase in load.
Yield strain: The strain, below which a material acts in an elastic manner, and above which it begins to exhibit permanent deformation.
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