Having these parts made with composite materials was very important to the drill owner. “If for some reason the system failed, anything that was metallic would go down and damage the drill head, which costs tens of millions of dollars. It could also capsize the rig if the drill jammed,” explains Pillay. A composite piece, even if it fell, would not have that same impact.
Pillay initially tried to design the clamps with thermosets, but they couldn’t meet the project’s cost or strength requirements. With commercially available long-fiber nylon 66 glass and a nylon 66 thermoplastic resin, he and his students used extrusion compression molding to produce 750 thermoplastic composite clamps. Through extensive testing, these clamps proved they could meet every requirement.
Meanwhile, the thermoplastic composite nuts and bolts that a private company had made to hold the clamps in place didn’t fare as well and failed testing. Fortunately, the buoyancy project team, as a favor, had tested some thermoplastic nuts and bolts designed by one of Pillay’s PhD students. The hardware designed at UAB did meet requirements, so the team asked the university to produce 2,500 hardware sets in its full-scale prototyping lab. Those sets also performed well.
Clamped into place by thermoplastic composite parts, the buoyancy system was highly successful. “In fact, it did significantly better than they had anticipated, resulting in a $5 million savings for that exploratory drill operation,” Pillay adds.
The wind industry could be another market for thermoplastic composites. Giant wind blades are currently manufactured from cost-effective thermosets, but those blades are relatively brittle and tend to erode at the edges. With a thermoplastic leading edge on the blades, the industry could improve blade durability while retaining most of the economic advantages of thermosets.
Such examples are promising, but there are several technical and cost problems that need to be ironed out before there’s a smooth path to wider adoption of thermoplastic composites. The good news for now is that the thermoplastic composites industry is still in a pre-competitive phase. As people learn about the materials’ properties, most are willing to share what they know. While this period of cooperative research may not last, the information and insights gained will help encourage continued adoption of thermoplastic composite materials in aerospace, automotive and other industries.