What are the four most common stress modes of structural adhesives?

Tensile - Pull perpendicular to the plane and away from the adhesive bond Force is distributed equally across the entire bond area. (Compression stress is in the opposite direction, where the substrates are pushed together perpendicular to the bond plane.) Shear - Pull directed across the adhesive forcing the substrates to slide past one another. Here the force is in the same plane as the bond and distributed across the entire area. Cleavage - Concentrated at one edge of the joint exerting a prying force on the bond as the substrates separate. While that end of the adhesive join is experiencing concentrated stress, the other edge of the joint is theoretically under zero stress. Cleavage occurs between the two rigid substrates. Peel - Concentrated at one edge of the joint. At least one of the substrates is flexible resulting in even more concentration at the leading edge tthan with cleavage stress.