Thin sheet adherends

In the study of bond durability under impact conditions. Pre-treatment of metals prior to bonding and environmental effects have been evaluated using short diffusion path specimens derived from thin sheet adherend materials. The results (see Fig. 2) serve to emphasize the critical role of surface treatment in the formation of strong, environmentally stable adhesive bonds. 

Secondary bonding (assembly) of metals is also possible. The metal adherends are normally those with moderate to high-temperature capabilities, such as titanium alloys, either as thin sheets or honeycomb cores. Foaming versions are designed for honeycomb structural panel assembly and edge-closures. 

Fig. 7.8. Changing stress experienced by a steel lap joint as the load is progressively increased. Load (kN) A, 112 B, 100 C, 84 D, 68 E, 56 F, 44 G, 32 H, 20 I, 8 J, 4 K, 1. Joint as Fig. 7.6. Adhesive epoxide (half joint only displayed). The interpretation of computer generated data such as this does need care, for in practice the combination of the approach of the adhesive to its asymptotic (ultimate) shear stress coupled with the elastic/plastic deformation of the joint s thin sheet steel will normally cause adhesive failure of the adhesive, due to tensile forces induced by cleavage. If, in reality, adherend distortion is suppressed then the steel itself fails — not the adhesive This could be expected in the region of loads E-F. However, the computer model has been run on to illustrate the sort of load transfer, towards the inner areas of the joint, which might be anticipated for heavy steel section symmetrically loaded and not...

Due to the abrasive grains striking the adherend surfaces with high energy by means of compressed air, surface densification with ensuing development of tension may occur, entailing a deflection, especially in the case of thin adherends (sheet metal up to 2 mm thick). This phenomenon may be avoided by clamping... 

Corner joints for relatively flexible adherends such as sheet metal should be designed with reinforcements for support. With very thin adherends, angle joints offer low strengths because of high peel concentrations. A design... 

D-1876. Test Method for Peel Resistance of Adhesives (T-Peel Test). Tests resistance to peel separation in joints between two adherends which are flexible enough to deform into the T configuration (Fig. 14) without cracking or breaking (e.g., thin laminated aluminum sheets). 

The lap joint, in which two sheets are joined together with an overlay, is one of the most common joints encountered in practice. Joints of this type made from thin aluminium sheet 25 mm wide, 12 mm long (lin by 0-5 in) and 1-6 mm thick have long been used for quality control. The joint is easy to make and the results are sensitive to both adhesive quality and adherend surface preparation. 

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