What patch shape provides the best strength for repairing smooth skin?

What patch shape provides the best strength for repairing smooth skin?

• A. Circular patch
• B. Rectangular patch
• C. Elongated octagonal patch
• D. Square patch

Answer: (C)

In repairing smooth skin, how the patch distributes load and how quickly stress concentrates at the edge are the key factors. Shapes with sharp corners create points where stress can pile up, and patches that don’t extend far enough in the direction of the main loads won’t carry as much bending or shear. An elongated octagonal patch hits a sweet spot: it preserves smooth, rounded corners to reduce local stress concentrations, while its longer, multi-edge outline gives more surface area for fasteners and better distribution of the load along the patch boundary. This combination improves fatigue resistance and strength compared with a square or rectangular patch, which have sharper corners, or a circular patch, which doesn’t span as much area in the load direction.

In repairing smooth skin, how the patch distributes load and how quickly stress concentrates at the edge are the key factors. Shapes with sharp corners create points where stress can pile up, and patches that don’t extend far enough in the direction of the main loads won’t carry as much bending or shear.

An elongated octagonal patch hits a sweet spot: it preserves smooth, rounded corners to reduce local stress concentrations, while its longer, multi-edge outline gives more surface area for fasteners and better distribution of the load along the patch boundary. This combination improves fatigue resistance and strength compared with a square or rectangular patch, which have sharper corners, or a circular patch, which doesn’t span as much area in the load direction.