This paper addresses the development of active metal-matrix composites manufactured by Ultrasonic Additive
Manufacturing (UAM), an emerging manufacturing process that allows the embedding of materials into seemingly
solid metal components. In the UAM process, successive layers of metal tapes are ultrasonically bonded together
at low temperatures to form a metal-matrix. Being a low-temperature process, UAM offers unprecedented
opportunities to create metal components with embedded thermally-sensitive materials, such as shape memory
alloys. In this study UAM is used to create composites with aluminum matrices and embedded NiTi ribbons.
These composites exhibit tunability of both the coefficient of thermal expansion and natural frequencies. These
effects are due to the phase-dependent modulus and transformation stresses developed by the prestrained NiTi
phase. Since the embedded NiTi ribbons are constrained by the matrix, thermally-induced transformation from
detwinned martensite to austenite will be accompanied by the generation of transformation stresses. The effect
of transformation stress and changing phase of NiTi on thermally-induced strain is observed and modeled by
combining strain matching algorithms with thermodynamic-based constitutive models. The composite model
accurately describes effects due to changing NiTi modulus and strain recovery due to initial stress-induced
martensitic volume fractions including a 200 με contraction with increasing temperature. The observed dynamic
behaviors include up to a 16.6% increase in natural frequency at 100°C as compared to room temperature tests.
No substantial increase in damping ratio was observed relative to solid aluminum.
This paper presents the development and characterization of active aluminum-matrix composites manufactured
by Ultrasonic Additive Manufacturing (UAM), an emerging rapid prototyping process based on ultrasonic metal
welding. The primary benefit of UAM over other metal-matrix fabrication processes is the low process temperatures,
as low as 25 °C. 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. The objective of this research is to develop UAM composites with
aluminum matrices and embedded shape memory NiTi, magnetostrictive Galfenol (FeGa), and polyvinylidene
fluoride (PVDF) phases. The paper is focused on the thermally induced strain response and stiffness behavior of
NiTi-Al composites, the actuation properties of FeGa-Al composites, and the embedded sensing capabilities of
PVDF-Al composites. We observe up to a 10% increase over room temperature stiffness for NiTi-Al composites
and a magnetomechanical response in the FeGa-Al composite up to 52.4 με. The response of the PVDF-Al
composite to harmonic loads is observed over a frequency range of 10 to 1000 Hz.
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.
[Smart Vehicle Workshop] 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 UAM experience process temperatures as low as 20°C, in contrast to current metal-matrix
fabrication processes which require fusion of materials and hence reach temperatures of 500°C and above. UAM thus
creates unprecedented opportunities to develop adaptive structures with seamlessly embedded smart materials and
electronic components without degrading the properties that make embedding these materials and components attractive.
This research focuses on three aspects of developing UAM Ni-Ti/Al composites which have not been accomplished
before: (i) Characterization of the mechanical properties of the composite matrix; (ii) Investigation of Ni-Ti/Al
composites as tunable stiffness materials and as strain sensors based on the shape memory effect; and (iii) Development
of constitutive models for UAM Ni-Ti/Al composites. The mechanical characterization shows an increase in tensile
strength of aluminum UAM builds over the parent material (Al 3003-H18), likely due to grain refinement caused by the
UAM process. We demonstrate the ability to embed Ni-Ti wires up to 203 μm in diameter in an aluminum matrix,
compared with only 100 μm in previous studies. The resulting Ni-Ti/Al UAM composites have cross sectional area ratios
of up to 13.4% Ni-Ti. These composites exhibit a change in stiffness of 6% and a resistivity change of -3% when the Ni-
Ti wires undergo martensite to austenite transformation. The Ni-Ti area ratios and associated strength of the shape
memory effect are expected to increase as the UAM process becomes better understood and is perfected. The Brinson
constitutive model for shape memory transformations is used to describe the stiffness and the strain sensing of Ni-Ti/Al
composites in response to temperature changes.
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