Honeycomb sandwich construction

TSB 124, Bonded Honeycomb Sandwich Construction, Hexcel Corp., Dublin CA. (Also in Advanced Composites March/April 1993.)... 

One application is honeycomb sandwich construction that consists of thin high strength prepreg skins bonded to a thicker honeycomb, foam, or balsa core. The advantages are very low weight, high stiffness, durable, design freedom, and reduced production costs. 

Shiratori. M., Qiang. Y.. Takahashi. Y.. and Ogasawara, N. (1994). Application of infrared thermography to detection of flaws in honeycomb sandwich constructions. JSME International Journal. Series A, 37, 4.. 396 402. 

Nitrile rubber/phenolic resin produces one of the most durable and toughest elastomeric materials developed in the adhesive industry. Further, its resistance to water as to organic solvents is excellent. For these reasons, the nitrile rubber/phenolic resin laminates are used in printed circuit board manufacturing, to bond metallic substrates between themselves (aluminium, steel) and to bond rubber to magnesium. Films of nitrile rubber/phenolic blends have also been used in the aircraft industry for bonding metal-to-metal surfaces in both plain and honeycomb sandwich constructions. 

A modified epoxy, foaming adhesive in sheet form which during the 120 C curing expands to fill gaps and adhere strongly to all parts of the typically honeycomb sandwich construction. Designed for use in conjunction with Araldite 312, 312/5 or 609, where the operating temperature can be between -55 C and +100 C. 

A flame retardant two component, low density epoxy filler paste for room temperature cure and specially formulated for use as an edge filler in honeycomb sandwich constructions where the fire properties of the filled panel edges may affect the fire retardancy rating of the component. 

A one-part, microballoon filled pottable epoxy for use in insert manufacture or the edge filling of honeycomb sandwich constructions. 

However, the majority of sandwich panels now utilise a honeycomb core rather than either balsa wood or plastic foam the adhesive can be based on either thermosetting or thermoplastic chemistries. The three basic components used in honeycomb sandwich construction are discussed below. 

The three basic components used in honeycomb sandwich construction are discussed later. 

Fig. 3-18 Example of a sandwich construction with a honeycomb core.

Since the stiffness of a laminate varies as a cubic relationship with the thickness, there are alternate methods employed to achieve thickness - and hence stiffness - than by using multiple layers of fiberglass and resin. Lightweight core materials, such as end-grained balsa wood, high-density polyurethane foam, PVC foam, and honeycombed materials, are available. These materials are sandwiched in between layers of unsaturated polyester resin to achieve increased laminate stiffness. The common terminology used for this technique is sandwich construction . 

A similar specimen design uses a sandwich construction with a dissimilar material bonded between the two cylindrical halves of the button specimen. This design is commonly used to measure the tensile strength of adhesives between dissimilar materials or if the adherend does not have the strength or characteristics to be machined into the shape of the button specimen. With some modifications in the dimensions, the button tensile test has also been adapted for testing adherence of honeycomb-cover sheets to the core (ASTM C 297). 

This aluminum honeycomb material is made by bonding aluminum foil sheets to form hexagonal cells. It is used to make sandwich construction panels that have a very high strength-to-weight ratio. 

The following review relates to the performance of sandwich constructions such as those with RP skins and honeycomb core. For an isotropic material with a modulus of elasticity (E), the bending stiffness factor (El) of a rectangular beam 6 wide and 11 deep is ... 

Two-sided films can be prepared for use in lightweight sandwich constructions. The honeycomb side will provide good filleting, while the skin side wiU provide high peel strength. 

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