Theoretical Analysis of Stresses and Strains

Most theoretical analyses have been carried out on single or double lap joints, which are the primary types of joints used for determining the strength of adhesives. Properly designed joints stress the adhesive in shear. Adhesives are especially weak in peel, and are also weak under tensile loads applied normal to the plane of the joint. The earliest theoretical lap-joint work involved simplifying assumptions that (1) the joint was a 

Recent theoretical studies have become much more complex. New computer-assisted techniques permit the use of finite-element matrix-theory type approaches. The effects of important variables are being determined by parametric studies. More complex joints are also being studied. New adherend materials, including advanced filamentary composites, are also being evaluated. The elastic, low-deflection, constant temperature behavior of scarf and stepped-lap joints has been replaced by elastic-plastic, large-deflection behavior, combined with thermal expansion differences, or curing shrinkage-induced residual stresses. 

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