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  • August 11th, 2012

    The use of carbon fibre composite materials is spreading wider than its traditional motoring base, to aerospace and beyond. As a result, new, powerful methods of non-destructive inspection (NDI) or non-destructive testing (NDT) are required to ensure that materials have the necessary strength to perform effectively in their expanding roles. Applied Computing & Engineering Ltd (AC&E) is at the forefront of new developments in robot simulation software that ensure composite materials are safe.

    Carbon fibre composite is an effective high strength, low weight material. It has been used in smaller
    aircraft for years but never larger passenger planes. The drive to reduce the cost of air travel, meet
    environmental responsibilities and cope with the rising cost of fuel has led the aircraft industry to
    demand lighter passenger aircraft with improved performance.
    Carbon fibre composite is the obvious material of choice, but ensuring the production process
    eliminates manufacturing defects in the material is a challenge – and not one that can be overcome
    by conventional techniques.

    The porosity problem

    The process of manufacturing carbon fibre composite (baking many layers of carbon fibre coated
    tape in an autoclave) hardens the material, but can lead to gaps or bubbles opening up between
    the tape layers leaving the structure vulnerable. Such imperfections determine the porosity of the
    material and can affect mechanical performance, which is why porosity values must typically be
    lower than 2.5%. Spotting bubbles and cracks in a black, opaque material, however, isn’t easy.

    Scanning at the limits

    Ultrasound scanning, of the sort used in pre-natal care, is traditionally used to determine porosity
    in carbon fibre materials. Yet the size and shape of, for example, an aircraft panel demands new
    capabilities of the scanning software.
    Additionally, ultrasound scanning requires the use of water as a sound conducting medium meaning
    inspection of the part has to be fast, but at a suitably high resolution to pick up any flaws or
    anomalies.

    Manually operated devices can’t deliver the required speed and accuracy, and the traditional choice
    of a Cartesian axes machine no longer offers the accuracy required for scanning more complex
    shapes like engine nacelles and structural stiffeners.

    Computer simulation based off-line programming (OLP) methods for robots have been available for
    some time but early OLP techniques were developed predominantly for the automotive industry and
    are not suitable for programming NDI robots.

    AC&E

    Simulation software specialist AC&E has a reputation for delivering more from scanning robots. Its
    experts are enhancing robot off-line programming software and the results it delivers, in order to
    make NDI faster and more accurate than has previously been possible.
    These developments are a natural progression for a company long experienced in tailoring its
    simulation software to clients’ robot systems.

    From its base at Sci-Tech Daresbury in North West England, AC&E works with leaders in robot
    manufacturing such as Fanuc, Motoman, Kuka, ABB and Natchi, to apply its technology to
    organisations across Europe. Nissan uses AC&E software in its painting and spot welding and AC&E
    has been helping EADS develop an NDI robot programming methodology for its factories in France
    and Spain.

    Now its new software is helping manufacturers working with carbon fibre composite achieve the
    greater scanning accuracy they need.

    New software, new standards

    To create simulation software suitable for passenger aircraft AC&E knew the resolution of the scan
    would need to increase dramatically. At the same time the speed of the scan would need to increase
    to meet throughput requirements.

    And since the scanned components are irregular shapes, AC&E knew that advanced collision
    anticipation and avoidance also had to be a key part of the software. The solution was to avoid
    contact with the subject of the scan.

    AC&E Technical Director, Yash Khandhia explains: “Typically, in robot programming, you ‘teach’ the
    robot to operate in simple plains. Where there is an obstacle there can be a collision causing costly
    damage to both robot and component. In contrast, AC&E’s software automatically programmes the
    robot to scan the structure without making contact with it. This allows complex structures, as well as
    flat panels, to be scanned without risk.”

    This new generation of automated scanning software does more than avoid collisions. It achieves
    the faster scan times at greater resolutions that the new carbon fibre composite applications
    require.

    Yash Khandhia: “AC&E encounters different NDI requirements and procedures depending on who
    we are working with. Currently the basic minimum sizes of scanning for defects in composites are
    equivalent to 6mm x 6mm or a flat bottom hole with a 6mm diameter. However we are beginning to
    see projects where a 3mm diameter test is required. When this happens the number of points to be
    checked in areas such as aircraft wings will number in the hundreds of thousands. Our customized
    software automatically programmes a robot for this level of inspection in a way that is unique in the
    industry.”

    Aerospace and beyond

    AC&E expects its new software system to find applications far beyond its current uses in automotive
    and aerospace manufacturing. “We expect this form of NDI software will appeal to the shipbuilding
    industry, particularly pleasure boats,” says Yash Khandhia. “We also expect it to play a pioneering
    role in defence related manufacturing, for example in the construction of unmanned drones, which
    are extensively carbon fibre composite.”

    Faster. Deeper. Smarter

    What began as a challenge to meet the evolving requirements of manufacturing became something
    far more involved. AC&E has applied its expertise in NDI programming to ensure the carbon
    composite materials used in tomorrow’s aircraft, boats and defence projects have the strength to
    perform safely and effectively.

    In doing so they have transformed NDI with software that scans faster, without collisions, at higher
    resolutions than ever before.