In fact, the stresses are highest at the ends of the strip. Here, the strip must handle three kinds of stresses when it bends, Figure 1c. In a single-skin laminate, the outside surface is in tension, the inside surface is in compression, and the middle is in shear. Tension and compression are generally easy to visualize. Shear is the tendency of the inside and outside halves of the laminate to slide against each other in opposite directions.
Shear is highest right in the middle of the laminate.
To resist all these stresses without fracturing, a single-skin laminate must be relatively thick and heavy. In a cored-skin laminate, the outside and inside skins experience the tension and compression stresses, and the core experiences the shear stress. Because of this separation of duties, the skins together can be less thick than the total thickness of its single-skin counterpart. This makes the cored-skin laminate stiffer. Most widely used throughout the world, balsa core is made with the wood grain running from skin to skin and is termed end-grain balsa.