The Second World War Impetus

One man’s vision for the possibilities of new synthetic adhesives had a powerful impact on history. Before World War II, Geoffrey de Havilland had designed the recordbreaking Comet racer and Albatross airliner, both
made of wood.[670] Delivering a speech at the Royal Aeronautical Society in London in April 1935, however, de Havilland seemed to have already written off wooden construction. "Few will doubt, however,” he said, "that metal or possibly synthetic material will eventually be used universally, because it is in this direction we must look for lighter construction.”[671] Yet de Havilland would introduce 6 years later the immortal D. H. 98 Mosquito, a lightweight, speedy, multirole aircraft mass-produced for the Royal Air Force (RAF).

De Havilland’s decision to offer the RAF an essentially all-wooden aircraft might seem to be based more on logistical pragmatism than aerodynamic performance. After all, the British Empire’s metal stocks were already committed to building the heavy Lancaster bombers and Spitfire fighters. Wooden materials were all that were left, not to men­tion the thousands of untapped and experienced woodworkers.[672] But the Mosquito, designed as a lightweight bomber, became a success because it could outperform opposing fighters. Lacking guns for self-defense, the Merlin-powered Mosquito survived by outracing its all-metal opponents.[673] Unlike metal airplanes, which obtain rigidity by using stringers to con­nect a series of bulkheads,[674] the Mosquito employed a plywood fuselage that was built in two halves and glued together.[675] De Havilland used a new resin called Aerolite as the glue, replacing the casein-type resins that had proved so susceptible to corrosion.[676] The Mosquito’s construction technique anticipated the simplicity and strength of one-piece fuselage structures, not seen again until the first flight of Lockheed’s X-55 ACCA, nearly six decades later.

For most of the 1940s, both the Government and industry focused on keeping up with wartime demand for vast fleets of all-metal aircraft. Howard Hughes pushed the boundaries of conventional flight at the
time with the first—and ultimately singular—flight of the Spruce Goose, which adopted a fuselage structure developed from the same Haskelite material pioneered by Clark in the late 1930s.

Pioneering work on plastic structures continued, with research­ers focusing on the basic foundations of the processes that would later gain wide application. For example, the NACA funded a study by the Laboratory for Insulation Research at the Massachusetts Institute of Technology (MIT) that would explore problems later solved by auto­claves. The goal of the MIT researchers was to address a difficulty in the curing process for thermoset plastics based on heating a wood-resin composite between hot plates. Because wood and resin were poor heat conductors, it would take several hours to raise the center of the mate­rial to the curing temperature. In the process, temperatures at the sur­face could rise above desired levels, potentially damaging the material even as it was being cured. The NACA-funded study looked for new ways to rapidly heat the material uniformly on the surface and at the cen­ter. The particular method involved inserting the material into a high- frequency electrical field, attempting to heat the material from the inside using the "dielectric loss of the material.”[677] This was an ambitious objec­tive, anticipating and appropriating the same principles used in micro­wave ovens for building aircraft structures. Not surprisingly, the study’s authors hoped to manage expectations. As they were not attempting to arrive at a final solution, the authors of the final report said their contribution was to "lay the groundwork for further development.” Their final conclusion: "The problem of treating complicated shapes remains to be solved.”[678]

Meanwhile, a Douglas Aircraft engineer hired shortly before World War II began would soon have a profound impact on the plastic com­posite industry. Brandt Goldsworthy served as a plastics engineer at Douglas during the war, where he was among the first to combine fiber­glass and phenolic resin to produce laminated tooling.[679] The invention did not spark radical progress in the aviation industry, although the
material was used to design ammunition chutes used to channel machine gun cartridges from storage boxes and into aircraft machine guns.[680] More noteworthy, after leaving Douglas in 1945 to start his own com­pany, Goldsworthy would pioneer the automation of the manufactur­ing process for composite materials. Goldsworthy’s invention of the pultrusion process in the 1950s would make durable and high-strength composites affordable for a range of applications, from cars to aircraft parts to fishing rods.[681]

As plastic composites continued to mature, the U. S. Army Air Corps began an ambitious series of experiments in the early 1940s on new com­posite material made from fiberglass-polyester blends. In the next two decades, the material would prove useful on aircraft as nose radomes and as both helicopter and propeller blades.[682] The combination of fiber­glass and polyester also proved tempting to the military as a potential new load-bearing structural material for aircraft. In 1943, researchers at Wright-Patterson Air Force Base fabricated an aft fuselage for the Vultee BT-15 basic trainer using fiberglass and a polyester material called Plaskon, with balsa used as a sandwich core material.[683] The Wright Field experiments also included the development of an outer wing panel made of cloth and cellulose acetate for a North American AT-6C.[684] The BT-15 experiment proved unsuccessful, but the plastic wing of the AT-6C was more promising, showing only minor wing cracks after 245 flight hours.[685]