Metal honeycomb bonding

During the temperature ramp period, pressure is applied. How much pressure is applied depends on the adhesive and the type of assembly. Honeycomb assemblies are limited by the compression strength of the honeycomb core, so cure pressure is typically limited to 50 psi for aluminum core of standard density. Metal to metal assemblies can withstand higher pressures and usually have fewer bondline voids when cured at higher pressures. Metal-to-metal assemblies bonded with standard modified epoxies are cured at 90 psi. 

FM 94 Cytec Engineered Materials 60-90 min at 121°C Modified epoxy provides metal-to-metal and metal-to-honeycomb bonds... 

The high cost of replacement parts made from adhesively bonded metal, metal/honeycomb, composite/honeycomb or monolithic composite laminates ensures that the interest in... 

Epoxy- phenolic Two-part paste, supported film Heat and pressure Uaod properties at moderate cures volatiles released during cure retains 50% of bond strength at 500 F limited shelf life low peel strength and shock resistance Metals, honeycomb core, plastic laminates, ceramics Med... 

Typical Use Suitable for metal, composite and honeycomb bonding with continuous exposure up to 175 C. 

Nitrile phenolic Bonding metal honeycombs and skins for high-temperature situations... 

Also metal to honeycomb bonds need to be tested in tensile load. The aircraft industry uses EN 2243-4 or the American MIL A 25463 and MIL 401B for this test (Fig. 33). 

In aircraft construction, sandwich panels made of metal facings bonded onto honeycomb are usually peeled with the climbing drum peel test, according to EN 2243-3 (Fig. 36) or ASTM D 1781 or MIL A 83376. 

Abstract. This chapter is concerned with an in-depth examination of the adherend surface pretreatments used prior to structural adhesive bonding. It encompasses the various substrates encountered, particularly but not exclusively, in the aerospace industry. It compares and contrasts mechanical, chemical and electrochemical methods used for substrates comprising aluminium alloys, titanium, stainless steel, thermoplastic and thermoset fibre reinforced composites and non-metallic honeycomb. Scanning and transmission electron microscope techniques are used to analyse and characterise many of the pretreated surfaces so produced. 

The supporting medium may be glass or nylon cloth. Neoprene-phenolic adhesive may be used to bond a variety of substrates such as aluminum, magnesium, stainless steel, metal honeycombs and facings, plastic laminates, glass, and ceramics. Wood-to-metal bonds are often primed with neoprene-phenolic adhesives. 

These structural adhesives are used in bonding metal to metal in aircraft assemblies, metal honeycomb panels, and wood-to-metal sandwich construction. Other applications include bonding cyclized rubber and, in some cases, vulcanized and unvulcanized rubbers and copper foil to plastic laminates for printed circuits. They are also applied as a primer for metal-to-wood bonding... 

Infrared patterns can lead to detection of lack of bonding between surface platings, between coatings and base metal, or within bra2ed honeycombs and other composite materials where bonding is vital. Mote recent developments involve infrared television or image tubes similar to the types used for night vision in military and other appHcations. 

The ceramic oxide carrier is bonded to the monolith by both chemical and physical means. The bonding differs for a ceramic monolith and a metallic monolith. Attrition is a physical loss of the carrier from the monolith from the surface shear effects caused by the exhaust gas, a sudden start-up or shutdown causing a thermal shock as a result of different coefficients of thermal expansion at the boundary between the carrier and the monolith, physical vibration of the cataly2ed honeycomb, or abrasion from particulates in the exhaust air (21) (see Fig. 6d). 

Quite often, NBR adhesives are used to bond various kinds of gasketing (cork, fibre, foam, rubber, metal) to rigid superstructures, such as aircraft. Films cast from solution are often used to fabricate honeycomb structures for aircraft. 

Adhesive bonding is an integral part of virtually all composite structure. Early composite matrix resins could in some cases act as an adhesive, such as with self-filleting systems used for honeycomb sandwich fabrication. As composite systems became more optimized for minimum resin content and limited flow, supplementary adhesives became more common. Modern-day composite structure relies on adhesives almost as much as bonded metallic structure. 

Table 1 contains the metal-to-metal engineering property requirements for Boeing Material Specification (BMS) 5-101, a structural film adhesive for metal to metal and honeycomb sandwich use in areas with normal temperature exposure. The requirements are dominated by shear strength tests. Shear strength is the most critical engineering property for structural adhesives, at least for the simplistic joint analysis that is commonly used for metal-to-metal secondary structure on commercial aircraft. Adhesive Joints are purposefully loaded primarily in shear as opposed to tension or peel modes as adhesives are typically stronger in shear than in Mode I (load normal to the plane of the bond) loading. 

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