Tag Archives: woven

-“Dark-on-dark”: a machine vision approach for dry carbon fiber inspection

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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.

APODIUS VISION SYSTEM

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.

Apodius inspection head

Apodius´ inspection head

PROFACTOR FSCAN

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.

Profactor´s high constract carbon fiber images

Profactor´s high constrast carbon fiber images

EDIXIA

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.

Edixia features

Edixia´s features

SURAGUS

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.

Suragus´ Eddy Current Inspection system

Suragus´ Eddy Current Inspection system

 

 

-Advancements in dry reinforcements for aerospace infusion process

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While in some previous posts we focused on talking about different automated processes for dry material deposition (ADMP, Pick-and-place and DAFP), this post deals with information about dry reinforcements aimed at aerospace infusion process and automation.

  • Why dry reinforcements?

Dry reinforcements offer significant advantages versus prepreg materials that have been traditionally used in the aerospace sector. They present several benefits, thanks to their low prices, their long shelf life, reduction in inventory costs, potential to increase parts integration and  potential to avoid the costly autoclave curing process.

The growth of the resin infusion process in the aerospace industry (as  can bee seen in the image above and our -Aerospace Looking to Dry Fiber/Infused Composites post) is increasing the need to adapt dry materials to the aerospace and new technologies requirements.

Infused Aerospace parts

Infused Aerospace parts  in Boeing 787, A380, A400, Bombardier C-Series and IRKUT MS-21

  • What is driving innovation in dry reinforcements?

Although there is still much to do in the area, material suppliers offer more and more products oriented to automated dry material deposition processes. Focusing our attention on dry reinforcements, the main research and developments in the area are aimed at:

Binders which are compatible with the resin to be infused and ease the manageability of the fiber during the material deposition.

Thin layers of thermoplastic veils to facilitate the flow of resin infusion and provide the final part with a greater toughness.

Dry carbon fibers that provide the strength and stiffness in a unique or multiple directions (unidirectional or multiaxial reinforcements). Different forms of dry carbon fabrics can be used to this end. NCF (Non crimp fabrics) are the most used fabrics nowadays, whereas the woven fabrics have also improved their properties in order to ensure the achievement of the required qualities.

The combination of the dry reinforcements with the proper resin is essential in order to manufacture a good quality part. Great developments are being carried out in this area.

  • Unidirectional tapes or Non Crimp Fabrics: Different choices for automation.

Unidirectional tapes up to 1″ offer high flexibility in terms of the geometries they can achieve. Automated process, such as the Dry Automated Fiber Placement (DAFP), use these tapes to produce preforms that will be infused during further stages. The productivity they can reach is low so far.

Wider Non Crimp Fabrics (NCF) can be used with the automated process such as ADMP and Pick-and-Place. The improvements in these materials and related automated deposition technologies could revolutionize the composites sector because of the great production rates they can accomplish.

You can have an overview of these different automated process in our post Making a Preform – How Can I Count the Ways?

  • What are the most common dry material forms used by the latest aerospace programmes?

It is known that the Saertex group supplies high-performance multiaxial and unidirectional NCFs for the manufacturing of the Bombardier´s C-Series and Learjet 85´s major primary structures.

Meanwhile, AeroComposit has qualified Hexcel´s OoA Hi-Tape material to produce Irkut Ms-21´s wings and wingboxes, whereas Spirit AeroSystems has also used the same material to form a skin of an engine nacelle outer fan cowl. Aircraft structures made with HiTape are reported to demonstrate mechanical properties as high as those found in parts  made with the latest generation primary structure prepregs.

Hexcel´s OoA HiTape

Hexcel´s OoA dry HiTape

Finally, it is worth mentioning that Cytec offers a material with equivalent properties, being applied also in the Irkut  MS-21. Both tapes (Hexcel´s and Cytec´s) will be used to manufacture the aircraft structures automatically within a DAFP machine.