As automation of dry carbon fiber manufacturing gains more and more momentum across the board, inspection systems become a crucial factor when it comes to assuring the quality of final products and the efficient use of available resources. Due to their ability to detect mistakes and faults at an early stage, it is straightforward to infer the great impact inspection systems can have when suitably integrated in a production line.
The systems presented in this entry are focused mainly in machine vision technology and cover inspection for both dry composite fabrics and post-infusion manufactured pieces. One of the main drawbacks they will need to overcome is the fact that carbon fabric absorbs a wide spectrum of light and presents a black color. Therefore, the design of an adequate lighting system will play a critical role at the task of detecting faults on the material (holes, fuzzballs, foreign-object-debris,etc.) and at providing good performance in the so called “dark-on-dark” scenario where vision systems tend to struggle.
The Apodius Vision System (AVS) is designed to measure the fiber orientation of composite fabrics and, based on the irregularities of the obtained pattern, also detect gaps or impurities that dry composite plies may exhibit. Specifically, it can take orientation angle measurements of 0.1º precision for every 50×50 mm² of both woven and non-woven fabrics thanks to its diffuse lighting technology that minimizes reflections on the fabric’s surface. Also, it is attachable to a robotic arm and, combined with an intuitive software interface the AVS, enables an easy integration of fabric inspection inside a production system.
Another product worth mentioning and highly related to quality control of composite parts is the FScan, designed by the Austrian applied research company Profactor. Instead of using the above mentioned diffuse lighting technique, their machine vision system exploits the reflection model of carbon fiber material and allows to produce high-contrast images. The sensor has a field of view of 60×60 mm² and its capable of scanning a surface with a speed of 1 m/s while detecting in real time all sorts of defects suchs as gaps, inclusions or missing rovings.
This French company with worldwide presence has a very strong background on automation of processes in several industries and is now expanding into the composite market. Their vast experience with different technologies allows them not only to look for defects in several kinds of fabrics, but also to inspect cracks, surface roughness and even fiber orientation of manufactured pieces, after the infusion process is completed. Contrary to 2D systems that infer the presence of defects from irregularities in the observed patterns, Edixia also makes use of 3D technologies which allows them to take direct measurements of the height of a wrinkle, depth irregularities or the 3D location of a cut edge.
Finally, although they do not integrate cameras in their solution, a very original alternative is provided by Suragus. Taking advantage of the conductive properties of carbon fiber, Suragus takes an eddy current approach for this problem, allowing them to successfully leap over the challenging “dark-on-dark” scenario of vision systems. Furthermore, since eddy currents have some penetration in the material, the obtained measurements are not limited to the properties of the surface but also cover a few layers below it. This enables fast inspection for mulitple-layer fabrics (up to 5-7) that otherwise could not be inspected with standard vision systems. Their current products are able to inspect a square surface of up to 600×600 mm² with a resolution up to 100-200 microns.