Environmentally-Preferred and Improved (Rapid) Laser Coating Removal Process for the Safe Removal of Coatings from Composite Substrates

Randy Straw | USAF Material Command

WP-201709

Objective

The objective of this proposed ESTCP project is to validate/qualify a new, commercially available nano-pulsed 1 kilowatt (kW) fiber laser system with polygon scanner on thin advanced composites coated with traditional and nontraditional military paint colors such as gloss white. The outcome of the qualification will be to implement the new qualified nano-pulsed laser system in a full production robotic laser coating removal system, funded by the Air Force for the Global Hawk and C-130 weapon systems at Warner Robins Air Logistic Complex in Georgia.

This will be an Air Force-led effort with participation of the Navy and Army. Multi-service teaming will maximize the technology transition opportunities across the services. Laser coating removal, successfully demonstrated with metallic based F-16 and C-130 aircraft, is a potential alternative to the current environmentally-burdensome coating removal methods of hand sanding, wheat starch blasting and chemical stripping from composite aircraft. These current processes generate large volumes of hazardous waste, expose workers to hazardous environments and cause severe ergonometric harm to workers all resulting in significant costs. In addition, these current processes are not capable of selectively removing topcoat and leaving the primer intact and unaffected. A significant benefit of this program is the energy savings of using a 1 kW nano-pulsed fiber laser versus a 6 kW continuous wave fiber laser. This energy savings will be documented during the Cost Benefit Analysis.

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Technology Description

Validation and qualification testing will be accomplished using an Air Force purchased commercial Ion Pulse Generator (IPG) 1 kW nano-pulse fiber laser. Pre-screening tests have already been accomplished using Global Hawk and generic composite and aluminum substrates and associated aircraft surface treatments, primers and topcoats. The nano-pulse laser effectively removed the topcoat, while leaving the primer intact and did not affect the composite substrates. One significant advantage of the nano-pulse laser is the reduced thermal effects on the substrate. This occurs because the coating removal method used by the nano-pulse laser is ablation and not thermal decomposition, which is used by continuous wave lasers. Screening tests using composite and aluminum panels validated that temperatures during processing only varied between 100°F and 140°F (peak) depending upon panel thickness, coating color and thermocouple location on the panels. In addition, the primer layer was not removed which ensures that the laser energy is never directly applied to composite fibers and resins. Primer adhesion results showed no degradation of the primer and mechanical tests showed no damage to the composite substrate. A tri-service joint test protocol will be developed for the validation and qualification testing.

A full-scale production system will be used to demonstrate and transition the technology. The system is already funded by the Air Force and the Request for Proposal (RFP) for the production system will be released in August 2016 will a planned award for January 2017. Air Force Life Cycle Management Center (AFLCMC) will develop and procure the next generation robotic laser coating removal system using the qualified 1 kW nano-pulse laser for the Global Hawk and C-130 aircraft at Robins AFB, GA. This system will incorporate the qualified nano-pulsed fiber laser from this effort. This system will incorporate advancements in laser scanners, surface mapping techniques, color sensors and control technology since the development of the first robotic laser coating removal systems for the F-16 and C-130 systems at Hill AFB, Utah. The technology used for this first robotic laser system was 2010 technology and technology advancements have been made in all critical areas including the laser, scanner, and sensors. In addition, this program will leverage the lessons learned from developing and implementing the robotic laser (continuous wave) coating removal systems at Hill AFB for full aircraft coating removal of F-16 and C-130 aircraft.

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Benefits

Laser coating removal of coatings is an environmentally-friendly process that utilizes no hazardous solvent, chemicals nor blast media. The only waste product is the minimal amount of small paint particles that are ejected as the nano-pulse laser ablates the topcoat layer, amounting in less waste that could fit in a coffee can. This process eliminates the exposure of workers to hazardous work environments, hazardous chemicals and gets the workers out of heavy and bulky personal protective suits and helmet. In fact, the F-16 work cell at Hill AFB is operated by two technicians. Cycle time reductions of 50 percent have been validated over the baseline processes. Operating costs and hazardous chemical disposal costs have also been reduced and eliminated, respectively. Operating costs have been reduced by 75 percent from the baseline PMB process for the F-16.

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Points of Contact

Principal Investigator

Randall Straw

Air Force Materiel Command

Phone: 937-255-7730

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