12.1.2. Desired Failure Mode

Reference: Abbott, Richard. Analysis and Design of Composite and Metallic Flight Vehicle Structures 3 Edition, 2019

On test and in service; the desired failure mode is that the first ply (or more) should separate from the surface of the adherend.

Figure 12.1.2‑1: Single Adhesive Lap Joint Desired Failure Modes (NASA-CR-112236, 1973)

The joint geometry affects the shear and peel stress in the joint; both of which peak at the edge of the adhesive.

Figure 12.1.2‑2: Single Shear Joint Shear Stress Distribution (NASA-TN-D-7855, 1975)

Figure 12.1.2‑3: Single Shear Joint Peel Stress Distribution (NASA-TN-D-7855, 1975)