HOW TO IMPROVE BENDING PROPERTY OF MDF AND PLYWOOD?

Plywood is a material manufactured from thin layers or “plies” of wood veneer that are glued together with adjacent layers having their wood grain rotated up to 90 degrees to one another.

All plywoods bind resin and wood fiber sheets (cellulose cells are long, strong and thin) to form a composite material. A typical plywood panel has face veneers of a higher grade than the core veneers. The principal function of the core layers is to increase the separation between the outer layers where the bending stresses are highest, thus increasing the panel’s resistance to bending. As a result, thicker panels can span greater distances under the same loads. In bending, the maximum stress occurs in the outermost layers, one in tension, the other in compression. Bending stress decreases from the maximum at the face layers to nearly zero at the central layer. Shear stress, by contrast, is higher in the center of the panel, and at the outer fibers.

Kerfing helps in reducing the panels resistance to bending based on the kerfing pattern applied, thickness of the ply and material removed during subtractive manufacturing. As the majority of the tension occurs in the outermost layers, the method explored by us makes the material bendable by increasing the number of edges. Since the material is not homogeneous in one direction it is less susceptible to shear. The goal of this research is to explore the possibility of applying these principles to achieve a double-curved wooden panel.

Based on our tests the graph illustrates that of the thicknesses we selected 0.8 mm, 1.5 mm, 3 mm and 5 mm. Only the 0.8mm and 1.5 mm could easily be bent with kerfing.