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Ultrasonic Process for Curing Adhesives

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Interim rept. Jun 1992-Feb 1993

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The objective of this program was to demonstrate in the laboratory the feasibility of using ultrasonic energy to cure a structural adhesive used to bond two pieces of 2024-T3 aluminum. A process was developed that demonstrated that American Cyanamid FM-73 adhesive could be cured using ultrasonic energy at a power level of less than 25 wattssq. inch of adhesive area. The bonds produced using ultrasonic energy were just as strong as the bonds produced using a thermal process. A styrene butadiene rubber was found to be an excellent material to couple the ultrasonic energy to the adhesive through the aluminum substrate. The required coupling pressure ranged from 10 to 15 psi. Ultrasonic energy is absorbed by the adhesive and is converted to heat. Fine thermocouples embedded in the adhesive showed that the temperature of the adhesive increased from room temperature 70 deg F to 250 deg F in less than 10 minutes. The method currently used to cure the epoxy adhesive bonding a composite repair patch to an aircraft structure employs a heating blanket over the patch and the surrounding aircraft structure. This method is inefficient and requires the area surrounding a patch to be heated to the same temperature required to cure the adhesive. Since ultrasonic energy is absorbed directly by the adhesive, very little energy is wasted heating up the area surrounding the patch. Thus, an ultrasonic heating process is more efficient than the heating blanket method. The ultrasonic process has the potential to be used for repairing aging aircraft structures with bonded composite patches. Ultrasonic curing, Composite patches, Adhesive curing, Aging aircraft, Structural adhesives, Ultrasonic activation of adhesives

Subject Categories:

  • Adhesives, Seals and Binders
  • Metallurgy and Metallography
  • Elastomers and Rubber
  • Acoustics

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