Innovators at NASA Langley developed a calibration system for automated fiber placement (AFP) machines. AFP is a composites manufacturing method offering speed, repeatability, and waste-minimization benefits over traditional layup techniques. Used to make aerospace parts and wind turbine blades, AFP employs a robotic arm to apply strips of carbon fiber prepreg (aka composite tape or tows) to build up a composite part layer by layer.
While advantageous, any imperfectly placed (or slipped) tows generate lap-and-gap defects relative to adjacent tows, which can degrade structural integrity by as much as 30 percent. Currently, manual visual inspection is used to identify and fix such defects before curing, which is highly labor-intensive. In-situ inspection systems are emerging but no method exists to create accurate “defect standards” to facilitate active system calibration. The new calibration system will enable the next generation of AFP in-situ inspection technologies.
The system creates defects within the course of layup with known sizes, geometries, and locations. Using this defect creation technique, one can accurately quantify the ability to detect defects on inspection systems, perform accurate risk assessments, and calibrate in-situ inspection equipment to specific materials. The equipment that makes the defects can be efficiently and inexpensively 3D-printed. This technique is currently being used to successfully calibrate NASA’s in-situ inspection system for their AFP equipment.
AFP is experiencing increasing adoption in aerospace, automotive, and other industries that leverage large-scale advanced composite components. The AFP calibration system could be very useful to companies that develop and manufacture AFP machines or AFP machine inspection equipment to improve the quality of their products in a provable manner. Users of AFP machines may find value in the tool for creating their own calibration standards.