AIRCRAFT BONDED TYPE CONSTRUCTION

BONDED TYPE CONSTRUCTION

A bonded structure is a construction that is produced by chemical bonding of two or more layers of material with the application of a bonding agent (e.g thermosetting resin) between the layers.

Aircraft bonded structure is a form of LAMINATED CONSTRUCTION or a SANDWICH CONSTRUCTION.

A LAMINATED CONSTRUCTION is defined as a construction composed of laminations or layers of material firmly united by bonding.

A SANDWICH CONSTRUCTION is a laminated construction of three laminations: two facing sheets and a core sandwiched between the facing sheets.

Examples of bonded structure:

a)     A cricket bat or a wooden propeller: Laminated wood structure made of plank of    wood ( e.g birch)

b)     A honeycomb panel in a modern airplane: Sandwich structure with a cellular core (like honey cell) sandwiched between two facing sheets by bonding.

Varieties of bonded structures: There are wide variations of bonded structure, such as:

a)                 Laminated wood structure

b)                 Laminated metal structure or Metal bonded structure

c)                  Laminated fiberglass structure

d)                 Metal bonded honeycomb structure (sandwich construction)

e)                 Fiberglass honeycomb structure and so on.

Honeycomb sandwich structure in modern aircraft: Introduction of bonded structure, specially the sandwich construction (honeycomb)  in airframe design came as a major breakthrough in the search for a more efficient type of structure because bonded honeycomb structures are manufactured and used to perform their jobs in a manner different from the conventional structures.

Compared to the conventional structures, bonded structure has many excellent combinations of advantages like:

a)                 Much higher strength/weight ratio

b)                 Rigidity/Pliability as desired

c)                  Metallic or non-metallic or combination

d)                 Less or absolutely no corrosion problem

e)                 Better surface finish and aerodynamic smoothness

f)                   May be manufactured in a variety of shapes and sizes

Sandwiched constructed assemblies are used for such areas as bulkheads, control surfaces, fuselage panels, wing panels, and empennage skins, radomes or shear webs.

Figure 2.12 illustrates a section of bonded honeycomb. The honeycomb stands on end and separates facings, which are bonded to the core by means of an adhesive or resin. This type of construction as a superior strength/weight ratio over that of conventional structure. Also it is better able to withstand sonic vibration, as relatively low cost when compared with fastener cost and installation of conventional structures reduces the number of parts needed and greatly reduces sealing problems while increasing aerodynamic smoothness.

Special applications of metal bonded honeycomb may employ Stainless Steel, Titanium, Magnesium, and Plywood, Resin-impregnated paper, Glass, Nylon or Cotton cloth in various combinations.

Figure 2.12: Bonded honeycomb structure