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Direct long-fibre technology makes inroads in the sky – and on the water

News International-French

19 Feb 2011

For the first time in aviation history, compression-moulded thermoplastic composite parts made by PlastiComp LLC are replacing traditional aluminium materials in a non-structural application for Wipaire, Inc., the largest aircraft float manufacturer in the world.








The parts – inspection hatch covers – provide access to watertight compartments in seaplane floats for Wipaire’s Wipline 7000 floats as installed on the amphibious version of the Quest Kodiak, a single-engine turboprop, ten-seat, backcountry utility aircraft manufactured in Sand Point, Idaho. The float-equipped Kodiak is scheduled to be certified for service in the spring of 2010. The new long-glass-reinforced thermoplastic hatch covers were a joint development: PlastiComp provided technical guidance on materials and processes, plus the actual part moulding; Wipaire designed the part and made the mould in their in-house machine shop. The project took just under 120 days to complete.


PlastiComp people saw this project with Wipaire as a particularly good partnership with a well-established aviation manufacturer. It spotlights the company’s ability to help develop a custom-designed metal replacement part which, despite its low-volume, still represents an important breakthrough in the aviation field for the Pushtrusion® D-GMT® (Direct Glass Mat Thermoplastic) process. The hatch cover is approximately 35 x 40 cm. The exposed, upper surface is largely smooth, with a channel for a sealing gasket and thicker sections on the perimeter for threaded fasteners.


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PlastiComp’s business focuses on long-fibre-reinforced thermoplastic composite technology: both LFT (long-fibre-reinforced thermoplastic pellets) and D-LFT (direct long-fibre-reinforced thermoplastic), and DGMT (direct glass mat thermoplastic) direct in-line compounding technologies.


Complēt® composite pellets, produced with LFT technology, are made for the injection moulding market in standard and custom formulations. PlastiComp manufactures and installs Pushtrusion machinery for direct in-line compounding as a D-LFT technology for injection moulding, as well as a D-GMT® technology for compression moulding.


There is also a perimeter wall with ribs radiating out from a central boss where a standard, snap-in-place inspection port is installed. The hatch itself is moulded in a self-coloured, black pigmented, UV-stabilized, long-glassfibre- reinforced thermoplastic composite material which is then painted with a black non-skid coating on its exposed surface to match the upper, walked-on deck surface of the float. Foot traffic dictated sufficient load bearing stiffness as a primary criterion in the design. The new hatch cover replaces earlier machined aluminium versions. The aluminium parts were too heavy, while these new ones weigh less than 900 g. They were also subject to dents and bending, and they cost too much – approximately five times the cost of the composite parts. The composite hatch covers have good corrosion resistance and can be easily replaced, which was another benefit Wipaire was seeking. Wipaire also considered a thermoset sheet moulding compound (SMC) with long fibres but the high material and development costs for that approach made PlastiComp a more logical choice.



This project was also an opportunity to demonstrate PlastiComp’s part moulding capabilities, an area of business that the company is currently expanding. In addition, the proprietary Pushtrusion technology, which has been installed in the technical development centre in Winona, means the company can rely on small volume production, preproduction or prototype manufacturing for selected customers.


Since 2006, PlastiComp has been producing parts for customers who neither want nor need full-scale Pushtrusion technology in-house, but do want to benefit from parts produced with this advanced technology. This contract moulding was initially limited to injection moulding with Pushtrusion Direct In-line Compounding, but it is now offered with Pushtrusion D-GMT for compression moulding, the technology used to produce the hatch covers for Wipaire.


Since 1960, Wipaire has developed a full line of floats for all sizes of aircraft, from the Piper Cub to the de Havilland Twin Otter, as well as over 100 Supplemental Type Certificates for a variety of useful aircraft modifications.


The D-GMT system produces hot charges of customized, precisely metered, long-fibre-reinforced compound that are transferred to a compression press and immediately pressed into finished parts, eliminating the typical glass mat technology (GMT) sheet used for compression moulding. Pushtrusion units are custom-sized to the job and can be used with a wide variety of polymers (PP, PA, TPU, PBT, etc.) and fibres (E-glass, S-glass and carbon). The process gives processors the flexibility to customize their specific formula by fibre loading, polymer type and colour. They are not limited to standard GMT sheet offerings.


Once the material has been selected, customers for D-GMT parts have several options: the part can be purchased directly from PlastiComp, or a part-sized preform can be purchased for moulding, or a Pushtrusion system can be used to mould parts in their own facility. In the case of the hatch covers, the team partnered with Wipaire from the start and is very pleased with both the results and the future potential. “You might say the sky is not the limit; it’s just the beginning.”