Active metal-matrix composites with embedded smart materials by ultrasonic additive manufacturing

Abstract

This paper presents the development of active aluminum-matrix composites manufactured by Ultrasonic Additive Manufacturing (UAM), an emerging rapid prototyping process based on ultrasonic metal welding. Composites created through this process experience temperatures as low as 25 °C during fabrication, in contrast to current metal-matrix fabrication processes which require temperatures of 500 °C and above. UAM thus provides unprecedented opportunities to develop adaptive structures with seamlessly embedded smart materials and electronic components without degrading the properties that make these materials and components attractive. This research focuses on developing UAM composites with aluminum matrices and embedded shape memory NiTi, magnetostrictive Galfenol, and electroactive PVDF phases. The research on these composites will focus on: (i) electrical insulation between NiTi and Al phases for strain sensors, investigation and modeling of NiTi-Al composites as tunable stiffness materials and thermally invariant structures based on the shape memory effect; (ii) process development and composite testing for Galfenol-Al composites; and (iii) development of PVDF-Al composites for embedded sensing applications. We demonstrate a method to electrically insulate embedded materials from the UAM matrix, the ability create composites containing up to 22.3% NiTi, and their resulting dimensional stability and thermal actuation characteristics. Also demonstrated is Galfenol-Al composite magnetic actuation of up to 54 μ(see manuscript), and creation of a PVDF-Al composite sensor.