CompositesWorld

SEP 2018

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NEWS 55 CompositesWorld.com Welding Thermoplastics crossover between the plies, they are just layered. us, you need more power to induce current compared to fabric laminates." However, adding more power does not make managing the welding process easier. Balancing electrical power and tempera- ture at the weldline is not straightforward because the induction welding process not only changes with stacking sequence but also with laminate thickness and part geometry. "So we look at the process parameters and how heat is generated in the materials," says Sebastiaan Wijskamp, TPRC's technical director. "We want to have guidelines and design tools to predict weld performance ahead of time. If you want to switch from fabric to UD, how can you do this quickly without having to go through a trial-and- error process? Ideally, simulations based on the electrical and thermal conductivity properties of fibers and polymers, even for a certain layup, and also factoring in part geometry, would allow you to design your welding process per part. We are performing collaborative research with KVE and Michel van Tooren at the McNair Center to develop the fundamental under- standing for these guidelines and tools." "We're quantifying all of these factors — UD vs. fabric, stacking sequence, areas of more resin and less resin — and estab- lishing their relationship, then we add this back into the general welding model," explains Labordus (Fig. 3, pg. 54). Areas with high resin content act as an isolator, retarding heat, while areas where resin content is lower (and fiber content is higher) facilitate heating. "At first, we were 40% off our welding predictions with UD, but now we are within 10% and are getting close to our high-accuracy levels for CF fabric/PPS," Labordus adds. Van Tooren also is close to being able to predict induction welding performance for UD laminates. "By the end of 2018, we will have a simulation tool that works for relatively simple geometries, helping to identify the necessary coil shape, power, robot speed and heating profile for a given application." is prediction capability is being developed in parallel with physical testing to support the use of welded TPC components in larger primary structures for future aircraft. Van Tooren's lab is a research partner with KVE and one of four sites — along with KVE's facility in e Hague, the Netherlands Aerospace Centre (NLR, Amsterdam) and er- moPlastic composites Research Center A Strong Grip on Performance COR-Grip ® Adhesives and Compounds Whether your composite needs are for structural bonding, general fairing, gap filling or surface finishing, the COR-Grip line of products provide exceptional adhesion for a firm bond. COR-Grip also provides the flexural, tensile and compression properties you need – all at an economical cost. Our line of adhesives and compounds feature the superior strength, excellent bonding, low shrinkage and corrosion resistance that your applications require. They are designed for various markets including marine, transportation, corrosion and wind energy. The full line of products includes vinyl ester, isophthalic, fire retardant, and specialty putties and adhesives. For more information, call 1.800.736.5497 or visit www.interplastic.com . (TPRC, Enschede, e Netherlands) — that has installed a stan- dardized induction welding setup developed by KVE (Fig. 4, p. 57) to support process qualification at OEMs and Tier 1 suppliers (see Learn More, p. 63). Bespoke induction coils An alternative induction welding approach has been used by Composite Integrity (Porcelette, France) to develop the "dynamic induction welding" process used to join CF/PEKK UD tape stringers and fuselage skins in the STELIA Aerospace (Toulouse,

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