Joining Carbon Fiber and Aluminum with Ultrasonic Additive Manufacturing
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Due to increasing emphasis on vehicle lightweighting to increase fuel efficiency, integration of carbon fiber composites with metal structures is necessary. Current adhesive and mechanical fastening methods used for joining carbon fiber composites to metals are not ideal due to cost, corrosion issues, stress concentrations, poor peel strength, and composite delamination. Consequently, new joining techniques are needed for increasing the use of carbon fiber composites. In this research project a novel method of creating joints between carbon fiber and 6061-T6 aluminum was explored by using ultrasonic additive manufacturing (UAM). The UAM process was used to embed dry carbon fibers within an aluminum matrix, creating a mechanical joint between the two materials. The joints were then wet with epoxy and tested in tension. The epoxy acted as a load distributing agent by bonding the embedded fibers to each other. Pullout strength results suggest that the UAM joining process can be used to create joints with strength exceeding that of the carbon fiber being joined. Further developments showed that full bidirectional carbon fiber fabric can be embedded within an aluminum matrix. SEM and optical imaging of joint cross sections showed that the joint strength comes from a mechanical interlocking between the carbon fibers and the aluminum. UAM joining of carbon fiber to aluminum shows promise and with further development may prove superior to current industry standard joining techniques.