NASA’s new ISAAC project moves laboratory research into the real world.
With its shiny black and white surface and wide range of motion, the new 7-ton robot at NASA’s Langley Research Center in Virginia has something of a Star Wars feel to it. That’s appropriate, since researchers will use the machine to produce stronger, more efficient composite parts and prototypes for the agency’s aeronautics and space exploration programs. But the robot, currently equipped with an automatic fiber placement (AFP) end effector, has another role as well, one that is particularly important to the composites industry. It will enable NASA to conduct research that bridges the gap between the laboratory and real world applications, speeding the adoption of new techniques and new materials for composites manufacturing in the aerospace industry.
Built by Electroimpact of Mukilteo, Wash., NASA’s robot is an adaptation of commercial systems currently used by two private companies (Orbital/ATK and Boeing) for the manufacture of advanced composites. It is part of the ISAAC project – the Integrated Structural Assembly of Advanced Composites. Although the press sometimes refers to the robot itself as ISAAC, the acronym actually refers to the entire composites manufacturing capability, encompassing all of the upstream and downstream activities involved in fiber layup, from design and 3-D modeling to curing and final production stages.
New Directions for AFP
The 21-foot-high ISAAC robot, in operation since January, moves back and forth on a 40-foot-long track. The robot’s AFP end effector holds up to 16 spools that carry ¼-inch wide tows of fibers. A CNC system dictates the movement and spin of the robot’s huge arm as it lays the carbon fibers and epoxy resins over complex forms and molds. The robot can build a composite part as large as 35 feet long, 10 feet wide and 12 feet high. Repositioning the mold allows for construction of larger parts as well.
One of the first projects that ISAAC researchers will undertake is an exploration of how the directionality of fibers in tow-steered composites can affect the strength of parts. Composite manufacturers currently lay fibers at angles of 0, 45 and 90 degrees to each other; the strength and stiffness of the composite structure varies with the number of plies of each angle used.
“We’ve gotten to a point now where we can, depending on the load case, reliably design composite structures that are about 20 percent more efficient than metallic structures,” says Chauncey Wu, ISAAC project manager, who wrote his doctoral dissertation on tow-steered composites. “But if you look at the stiffness- and strength-to-weight [ratios] of metals versus composites, there’s untapped potential there. There are more savings to be gained if we do something different, and one way we can do something different is to exploit the directionality of the tow steering.”
The industry has used tow steering to place fiber on doubly-curved surfaces, Wu says. “But what we haven’t been doing is aggressively tailoring the fiber angles over the surface. Within a given ply we can actually steer the fibers to shift loads around.” With ISAAC, NASA researchers will be looking at ways to tailor the fiber angles and the strength and the stiffness of a composite to better match the load paths.