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Aluminium adhesive joints with

The clean appearance of an aluminium surface is very deceptive it is actually composed of a thin layer of oxidation products, invisible to the unaided eye, which forms a weak link between the true aluminium surface and the adhesive. Although the oxide films on some alloys is reasonably stable, and gives fairly robust joints with some adhesives without preparation, this must not be generally assumed but should be checked and evaluated. Failure to remove a weak oxide layer will always result in a weak joint. [Pg.83]

Figure 6 Strenglhs of lap joints in aluminium alloy bonded with a vinyl phenolic adhesive on exposure to wet air at 50°C. O Aged at 50% r.h. and 100% rJi. A aged at 100% r.h. for 5000 h, then at 50% r.h. for a further 5000 h [30]. Crown Copyright. Figure 6 Strenglhs of lap joints in aluminium alloy bonded with a vinyl phenolic adhesive on exposure to wet air at 50°C. O Aged at 50% r.h. and 100% rJi. A aged at 100% r.h. for 5000 h, then at 50% r.h. for a further 5000 h [30]. Crown Copyright.
A related issue is whether roughening a surface increases the strength of an adhesive joint. Harris and Beevers [82] found no difference in adhesion to mild steel and aluminium alloy blasted with alumina grits of different particle sizes. Shahid and Hashim [83] used a structural epoxide adhesive with mild steel adherends in cleavage joints. The surfaces had been grit-blasted or diamond-polished, and surface profiled. The results are shown in Table 15, where all differences in strength seem to be the same, within experimental scatter. [Pg.41]

An example of such a fracture envelope, in this case developed for the case of mixed-mode cracking of an adhesive joint system consisting of 7075-T6 aluminium adherends bonded with a 0.4 mm thick structural epoxy appears in... [Pg.322]

Ford Research Laboratories [15] evaluated the fatigue behaviour of aluminium alloy joints and showed the enormous benefit of using an epoxy adhesive in combination with spot welding or mechanical... [Pg.103]

As part of a US Army-sponsored programme, Martin Marietta Laboratories [17] conducted mathematical joint analysis and tested prototypes of tubular aluminium alloy joints bonded with a toughened adhesive. It is found that the tubes failed by tubular buckling at loads considerably lower than the expected limit load of the bonded joint. [Pg.104]

As discussed below, the classic example of the problem of oxide stability upon exposure of bonded joints is with aluminium and its alloys and this aspect has therefore been investigated in detail by the aerospace community. Particularly, the fundamental micro-mechanisms have been studied in order to explain observations such as those shown in Fig. 8.10, which reveals the effect of three common aerospace surface pretreatments upon the subsequent durability of the adhesive joints. The three treatments which have been studied in some detail are chromic acid etch (CAE), chromic acid anodize (CAA) and phosphoric acid anodize (PAA), and details of the processes were given in Section 4.3.4.5. [Pg.376]

It is not uncommon for composites to be bonded to metals and there are one or two important points to be brought out. Figure 58 shows the adhesive shear stress distributions for double-lap joints between aluminium and unidirectional type II CFRP adherends. If the outer adherends are aluminium and the centre adherend is CFRP, the highest shear stress occurs at the compression end of the joint where the aluminium adherends are loaded. This is because the aluminium adherends have a lower tensile stiffness than the composite adherends. However, the adhesive stress concentrations at each end of the joint are similar (Table 6). Therefore, as far as the adhesive is concerned, the joint is well conditioned. Alternatively, if the outer adherends are unidirectional CFRP and the centre adherend is aluminium, then the higher shear stress that occurs at the tension end of a joint with similar adherends is increased still further by the adherend dissimilarity. The stress concentration at the tension end of the joint is now 3 6 times the stress concentration at the compression end, with the result that the joint efficiency, in terms of the strength of the aluminium alloy adherends, is reduced from 79% to 48%. [Pg.81]

Guyott CCH, Cawley P, Adams RD (1986) The nondestructive testing of adhesively bonded structure a review. J Adhesion 20 129-159 Guyott CCH, Cawley P, Adams RD (1987) Use of the Fokker bond tester on joints with varying adhesive thickness. Proc IMechE 201(B1) 41—49 Hagemaier DJ (1985) Adhesive bonding of aluminium alloys. Marcel Dekker, New York Hart-Smith LJ, Thrall EW (1985) Adhesive bonding of aluminium alloys. Marcel Dekker, New York, pp 241—335... [Pg.1068]

Armstrong KB (1997) Long-term durability in water of aluminium alloy adhesive joints bonded with epoxy adhesives. Int J Adhes Adhes 17(2) 89-105 Bauer P, Roy A, Casari P, Choqueuse D, Davies P (2004) Structural mechanical testing of a fidl-size adhesively bonded motorboat. J Eng Marine Environ 218(M4) 259-266... [Pg.1261]

Details are given of a thermal analysis technique, referred to as micro thermal analysis, which combines the high resolution positioning of scanning probe microscopy with some of the quantitative analysis capabilities of conventional thermal analysis. The application of this technique in characterising the thermal properties of interfaces in aluminium/epoxy resin adhesive joints and in glass fibre-reinforced epoxy resin composites is described. 7 refs. [Pg.86]


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See also in sourсe #XX -- [ Pg.63 ]




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