DEC 2018


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DECEMBER 2018 18 CompositesWorld WORK IN PROGRESS ThermoPulse sensors offer Industry 4.0 temperature measurement and digital cure cycle management for bonded composite repairs, laminates and more. Measuring temperature inside composites and bondlines » Having full visibility into a composite and/or adhesive bondline during cure has been an issue for decades. Current temperature sensors — thermocouples — are too large to be embedded without causing a defect in the part. us, it is now only possible to read temperature at the surface and perimeter of parts and bonded repairs. It is dicult to know the temperature of an adhesive at the bottom of a repair patch, inside a thick fuselage or wing skin laminate or between those skins and thick stringers. Yet, that temperature is crucial for proper resin •ow, wetting and cure. Currently, the composites industry compensates for this short- coming by spending months and millions of dollars testing to ensure that estimated time and temperature recipes do indeed complete cure and produce the necessary properties. Despite this, suppliers still spend many man-hours and dollars each year reviewing and certifying parts where thermocouples fail or where leading/lagging thermocouples are suciently outside of prescribed boundaries to cast doubt on properties and in-•ight performance. In an e•ort to solve this temperature-measurement problem, AvPro Inc. (Norman, OK, US) has developed the ermoPulse system, which enables wireless, remote, in-situ temperature monitoring during cure. e system comprises microwire sensors, a transmitting/receiving antenna and a reader box that collects antenna signals and uses software to convert that information into temperature data. e sensors remain embedded in the part and the system can be used with autoclave, oven, infusion or resin transfer molding (RTM). AvPro has already completed a Phase I Small Business Innovation Research (SBIR) contract with the US Air Force and is currently performing a Phase II e•ort (FA''""- •–-C-"""—), directly measuring bondline temperatures during composite repairs and composite part fabrication and verifying the accuracy of ermoPulse via round-robin testing at four independent sites. e potential for this technology is signi˜cant, o•ering real- time Industry ™." data not only for thermoset composites, but also the temperature-dependent melt and crystallinity formation of thermoplastic materials. Further, measurement is actually not the system's end goal. ermoPulse ultimately will manage cure cycles based on the composite's viscoelastic change. Cure cycles can be shortened because cure completion can be seen from real-time By Ginger Gardiner / Senior Editor Wireless, remote in-situ temperature monitoring AvPro's ThermoPulse system is being tested at Abaris Training and three other sites for statistical validation of its ability to measure temperature within a composite bondline during composite repair. Though the antenna (orange block) interrogating the microwire sensors is shown here taped to the test panel, AvPro is developing the ability for the antenna to read from overhead stations and robotic arms. Source | Abaris Training and AvPro Inc.

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