Duramold is a composite material process developed by Virginius E. Clark. Birch plies are impregnated with phenolic resin, such as Haskelite and laminated together in a mould under heat (280°F) and pressure for use as a lightweight structural material.[1] Similar to plywood, Duramold and other lightweight composite materials were considered critical during periods of material shortage in World War II, replacing scarce materials like aluminum alloys and steel.[2]
The material has some advantages over metal in strength, construction technique, and weight. A cylinder made of duramold is 80% stronger than a cylinder made of aluminum.[3] There are over 17 varieties of Duramold, using various quantities of birch or poplar wood, with as many as seven plies.[4] The Duramold process has also been used to make radomes for aircraft as well as missile bodies.[5]
The Fairchild Aircraft Corporation patented the process, designing and constructing the AT-21, (NX/NC19131) as the first aircraft made using the Duramold process.[6] Several aircraft used Duramold in parts of their structure but the largest aircraft manufactured with the process is the Hughes H-4 Hercules, which was almost completely built with Duramold in very large sections. Hughes purchased rights to the process for this use.