### 3.7.4. Drop-off and Cut-off Elements

Drop-off and cut-off elements cannot store any layered information and therefore must be associated with a homogenous material.

Drop-off elements are created when ply boundaries exist inside the part. When the plies come to an end, the solid model extrusion creates a drop-off element in the shape of a triangular prism. The drop-off elements can be modeled with either the ply (or core) material, a different material such as resin, or as a void.

Cut-off elements are created when a hexahedral element is diminished by a cut-off operation and decomposed into prism or tetrahedral elements. These elements can also be modeled with different homogenous materials.

The cut-off features offer great freedom in shaping a solid model. The trade-off when using the cut-off feature is that elements diminished by the cutting operation are decomposed into homogenous tetrahedral and prism elements. These elements cannot store any layered information and the postprocessing results for cut-off regions must be interpreted with care.

Both drop- and cut-off elements can cause steps in the structural stiffness, which may lead to stress peaks and higher IRFs. This affects the homogenous elements as well as the layered elements in their proximity.

For information on the postprocessing of stresses and strains of homogeneous elements, see Postprocessing of Drop-off and Cut-off Elements.

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