Advanced Composites Office "HAMs" It Up

  • Published
  • By Heyward Burnett
  • Materials and Manufacturing
WRIGHT-PATTERSON AIR FORCE BASE, Ohio --  Air Force Research Laboratory's Air Force Advanced Composites Office (ACO), located at Hill Air Force Base, Utah, recently transitioned to Ogden Air Logistics Center a hot air module  addressing problematic elevated-temperature bonded repairs, which are especially difficult for depot crews working in field-level conditions. Cumbersome and time-consuming, bonded repairs of this nature have traditionally required large curing systems, tedious manipulation of heat lamps and blankets, and a window of time in the neighborhood of 9 hrs. Such repairs are also prone to substantial bond-line errors. The ACO's HAM solution reduces the logistical footprint (decreasing system size and also eliminating assorted peripheral equipment), cuts the lengthy cure time in half, and meanwhile resolves recognized bond quality issues.

While HAM technology is not altogether new--for example, Northrop Grumman's Portable Curing Hot Air System has been in use for years--the newly transitioned unit offers significant improvement over current capability. First and foremost, it enables depot maintainers to perform elevated-temperature bonded repairs and noncontact curing in the field. Further, it is less expensive and smaller than the non-commercially-produced PCHAS (which carries a $1 million price tag and, at several hundred pounds, is about the size of a small trailer and must be towed behind a truck). Manufactured by Jet Solutions, LLC, the ACO-developed unit's commercial availability translates to better affordability. Likewise, the HAM innovation's smaller aspect (approximately 10% the PCHAS footprint) is better suited for field use.

AFRL's strategy for implementing its updated HAM design was to make it a commercial off-the-shelfcapability. The expectation was that a COTS solution would not only facilitate as-needed purchase of units, but also push development costs to the commercial side. Leveraging an Industry Day event, AFRL supplied many potential manufacturers with a technical design package. Ultimately, it was Jet Solutions that endeavored to build a production version of the improved HAM technology, and the company has since worked closely with the ACO to ensure the resulting COTS unit's ongoing capacity to meet or exceed all requirements.

The advanced HAM technology's recent transition actually culminates efforts first begun in 2004, with Air Combat Command's initial request that AFRL's ACO assist in designing, developing, and producing a hot air generator to replace the unreliable and burdensome PCHAS units then in use. Working with industry partner KARTA, Inc., ACO materials engineers built a prototype HAM incorporating both maintainers' needs and ACC's strict notions related primarily to size and cost. Specifically, ACC levied for a new system weighing less than 45 lbs, meeting size constraints similar to those governing checked airline luggage, and providing an economical alternative to the pricey PCHAS. The engineering team responded by devising the new three-box HAM, a novel configuration that both improves portability and, with its estimated unit cost of $65,000, proffers a 94% cost savings over existing hot-air-based curing methods.

Illustrating the enhanced technology's effectiveness, depot repair crews used it to bond a machined titanium doubler (i.e., a patch used to brace a surface) to the surface of a C-130's main wing plank, with positive results. The Ti doubler repair process uses a heat-activated epoxy adhesive that requires curing at 180°F-250°F (+/- 5°F). The new HAM unit's capacity to adjust curing temperatures accordingly, with crews able to easily redirect the movement and intensity of hot air across (or directly onto) a given surface, enables a much more evenly heated--and thus greatly improved--bond-line. Having just undergone its first-ever implementation on an operational Air Force aircraft--namely, the depot repair of the C-130 wing plank--the HAM technology has proven a successful technology transition to the warfighter.