What does "shear stress" refer to in aircraft materials?

Shear stress refers to the internal resistance of a material to forces that are applied parallel to its surface. When these parallel forces are exerted, they create an internal sliding effect between the layers or particles of the material. This is significant in aviation because aircraft structures often encounter shear forces during flight due to aerodynamic loads, landing impacts, and other operational stresses. Understanding shear stress is essential for assessing the strength and integrity of materials used in aircraft construction, ensuring they can withstand the various forces encountered in their operational environment.