Advantages of Bonding

	The bond is continuous. On loading, there is a more uniform distribution of stresses over the bonded area. The local concentrations of stresses present in sewed joints are avoided. Bonded structures can consequently offer a longer life under load. The bonded joint being continuous produces a stronger structure. Alternatively, if increased resistance is not needed, the weight of the structure can be decreased while maintaining the required load resistance.

			Adhesive bonding can simplify assembly procedures by replacing several patches, Assembling Tape (6) or Dacron-tape reinforcement (7) with a single bond. Adhesives form a continuous bond between the joint surfaces. yarns (5) and holes pin the surfaces together only at localized points (4) . Bonded structures are consequently much resistant and loading may be increased (by up to 30-100%). Adhesive bonding may be used in combination with sewed seams, without Assembling Tape (6) or Dacron-tape reinforcement (7) in order to improve the performance of the completed structure.

	The sewed seam (1) on the top and right is highly stressed (9) in the vicinity of each yarn (5). Failure tends to initiate in these areas of peak stress(4). A similar distribution of stress occurs with cracky adhesive or too hardness glue.

	Adhesive bonding gives a smooth appearance to designs: there are no fasteners such as yarns and holes.
	The bonded structure on the left is a safer structure because, owing to the fewer and less severe concentrations of stresses (11), fatigue cracks are less likely to occur. The continuous adhesive bond forms a seal (12). The joint is consequently leak proof and less prone to humidity entrance and wet weight increasing. Light or complex assemblies that cannot be joined together without reinforcements (dacron-tape) in sewing technology are feasible with adhesives. (Composite sandwich structures are a typical example). All these advantages may be translated into economic advantages: improved design, more simple assembly, lighter weight, longer life in service. The bond is continuous. The local concentrations of stresses present in sewed seams are avoided. Bonded structures can consequently offer a longer life under load. The bonded joint being continuous produces a stronger structure. Alternatively, if increased resistance is not needed, the weight of the structure can be decreased while maintaining the required load strength.

	Limitations Adhesives are drawn from the class of materials which we know as polymers', `plastics' or 'synthetic resins'. They have the limitations of that class. They are not as strong as High Modulus Fiber. (The difference is offset by the increased surface contact area provided by the bonded joints.) With increasing temperature the bond strength decreases, and the strain properties of the adhesive move from elastic to plastic. This transition is usually in the temperature range 70-180'C: the transition temperature depends on the particular adhesive. The resistance of bonded joints to the in service environment is dependent on the properties of the polymer from which the adhesive is made. Possible exposure of the bonded structure to oxidizing agents,solvents, etc., must be bone in mind when selecting the adhesive type to use. With most adhesives maximum bond strength is not produced instantly as it is with mechanical fastening or with welding. The assembled joint must be supported for at least part of the time during which the strength of the bond is building up. The quality of the bond may be adversely affected if, in the bonding process, the surfaces are not easily wetted by the adhesive.To ensure consistently good results may necessitate the setting up of serious quality control and confirmed users. A badly made joint is often more difficult to correct. Bonded structures are usually less easily dismantled than Sewed seams, an heat action is usually needed.

ADVANTAGES of ADHESIVE BONDING