Interlaminar stresses near the free edges can be controlled to an extent through the choice of materials, fibre orientations, stacking sequence, layer thickness and the use of functionally graded materials. However, the interlaminar stresses in the vicinity of free edges can completely be eliminated through the use of a homogeneous material, locally. The suppression of interlaminar stresses near the free edge by the technique of reinforcement is costly. This technique provides a restraint against the delamination due to interlaminar stress, but not a complete solution. 

Notch:

Notch in the laminates acts like an external crack giving rise to high three dimensional stress state in the vicinity of the notch. Hence, the notches should be avoided in the laminated structures.

Cut-out:

Cutouts are inevitable in structures. Cutouts are made to pass electric wires; fluid passage as in the wings, doors and windows in the fuselage of an air vehicle. These are, especially in aerospace vehicles, made also to reduce the weight of the component. The cutout boundaries act like free edges leading to significant transverse stresses. This is one of the most common site for onset of delamination. A laminate with cutout is shown in Figure 6.5(d).

Ply Drop/Termination:

The optimum design of composite structures in air vehicles is important. As a result of the optimization (e.g. weight minimization) process or sometimes purely due to geometric requirements/constraints, one or more of the plies have to be terminated (also known as “ply drop”) inside the laminate. The region of ply termination acts like a region of high stresses for neighbouring laminae which can be a reason for delamination of the plies adjacent to the ply drop region. A ply drop in laminate is shown in Figure 6.5(e).