Pick up a drill, and instinctively, as the bit grinds through a board, wall plaster or aluminum, the urge to saw the bit back and forth to neaten the hole seems the right thing to do.
Do it with a composite, though, and those finishing touches are likely to ruin the project, an instructor in aerospace manufacturing explains to his students.
Richard Whitaker teaches the manufacturing courses for Texas-based Amarillo College in a program that was designed as part of the incentives to bring Bell Helicopter Textron’s V-22 Osprey assembly operations to Amarillo in 1998.
After Bell Helicopter chose Amarillo over other large cities in Texas for the plant that now employs 1,200 in the assembly of the Osprey and modification work on Cobra and Huey helicopters for the military, its engineers met with AC and West Texas A&M University instructors to develop courses for the initial 200 employees.
Initially, new hires took continuing education level courses; the certificate programs in mechanical and electrical assembly expanded on those courses when they were established in 2001. Today, students can choose between the 24-credit hour certificate program and the 61-credit hour associates degree, which includes an advanced course in composites repair.
And though 11 years have passed since the initial training push was put into place, Bell and Amarillo College remain partners in the program, with Bell serving on an industrial advisory board that is part of the program’s accreditation process, and providing tools and materials.
The school worked together to obtain a grant for an autoclave so students could learn the fabrication process, which requires controlled high temperatures to bake the materials in a laminate. And in Whitaker’s classroom now, two helicopter doors improperly shipped are stacked on a table. Bell donated the doors because of damage to their edges.
Whitaker’s beginning students are learning how to assemble panels and to handle composite materials without damaging them.
He shows a laminate square from scrap materials donated by Bell where students learn how to use the carbide bits, also provided by Bell, to properly drill the holes that typically would be for fasteners in assembly work. The squares have a row of holes—some drilled properly with smooth edges and the layers intact all around the edges, and some improperly with egg-shaped holes or holes where the layers have peeled away from the holes.
In another exercise, students assemble a panel with honeycomb between the Kevlar layer and the composite panel held together by adhesives. To simulate the type of damage that can occur to an aircraft made from composites, Whitaker swings a ball peen hammer against the outer edge, leaving the kind of ding from a hail stone that can lead to severe damage if it were left unattended.