Adaptive vortex generators based on active hybrid composites: from idea to flight test

Nissle, Sebastian; Kaiser, Max; Hübler, Moritz; Gurka, Martin; Breuer, Ulf Paul

doi:10.1007/s13272-018-0316-1

Cited by 7 publications

(6 citation statements)

References 6 publications

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“…Thus, by embedding an SMA wire in a thin-walled FRP, a tailored shape-changing, or morphing, surface can be designed. The elimination of the need for an additional mechanical actuation makes active hybrid composites highly attractive for actuator applications in the aircraft and automotive industry as substantial savings with regard to weight, space, and cost can be achieved. − …”

Section: Introductionmentioning

confidence: 99%

“…They can provide actuation stresses up to 600 MPa accompanied by large recoverable strains up to 6%, with the only limitation being the operating frequency . Therefore, when combined with an elastic matrix, for example, FRP, which acts as a tailored antagonistic partner in cyclic actuation, new applications such as vortex generators, winglets, or wing airfoils are possible. , The bending of an active hybrid composite is induced by the contraction of an activated SMA wire positioned offset to the neutral axis of the composite . In addition to the internal stress resulting from the shape change, the hybrid composite often has to work against an external force ( e.g.…”

Section: Introductionmentioning

confidence: 99%

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Electrochemical Surface Structuring for Strong SMA Wire–Polymer Interface Adhesion

Gapeeva

Vogtmann

Zeller‐Plumhoff

et al. 2021

ACS Appl. Mater. Interfaces

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Active hybrid composites represent a novel class of smart materials used to design morphing surfaces, opening up new applications in the aircraft and automotive industries. The bending of the active hybrid composite is induced by the contraction of electrically activated shape memory alloy (SMA) wires, which are placed with an offset to the neutral axis of the composite. Therefore, the adhesion strength between the SMA wire and the surrounding polymer matrix is crucial to the load transfer and the functionality of the composite. Thus, the interface adhesion strength is of great importance for the performance and the actuation potential of active hybrid composites. In this work, the surface of a commercially available one-way effect NiTi SMA wire with a diameter of 1 mm was structured by selective electrochemical etching that preferably starts at defect sites, leaving the most thermodynamically stable surfaces of the wire intact. The created etch pits lead to an increase in the surface area of the wire and a mechanical interlocking with the polymer, resulting in a combination of adhesive and cohesive failure modes after a pull-out test. Consequently, the force of the first failure determined by an optical stress measurement was increased by more than 3 times when compared to the as-delivered SMA wire. The actuation characterization test showed that approximately the same work capacity could be retrieved from structured SMA wires. Moreover, structured SMA wires exhibited the same shape of the stress−strain curve as the as-delivered SMA wire, and the mechanical performance was not influenced by the structuring process. The austenite start A s and austenite finish A f transformation temperatures were also not found to be affected by the structuring process. The formation of etching pits with different geometries and densities was discussed with regard to the kinetics of oxide formation and dissolution.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Electrochemical Surface Structuring for Strong SMA Wire–Polymer Interface Adhesion

Gapeeva

Vogtmann

Zeller‐Plumhoff

et al. 2021

ACS Appl. Mater. Interfaces

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“…A calculation of the shear stress τ along a SMA wire during a pull-out test based on formulas (3) and (4), and assuming the materials properties for matrix and SMA from the material characterization shows for the tests at 100 °C that the maximum shear stress at the wire entrance is about 18 MPa which is the maximum shear stress, which can be transferred in the interface (see figure 18). This value can be validated by a calculation of the maximum shear stress based on the work of separation according to Antico et al [6], see formula (5), utilizing the same materials data in combination with the fracture toughness of about 0.2 N mm −1 of the matrix, derived from the technical datasheet [14].…”

Section: Discussionmentioning

confidence: 93%

“…Especially the example of active vortex generators [6] demonstrates the benefit of such hybrid structures. With standard actuators the realization of such a high number of active elements in the wing surface of an aircraft is almost impossible.…”

Section: Introductionmentioning

confidence: 99%

Characterization of active hybrid structures made of fiber reinforced composites and shape memory alloys—part A: characterization of the load transfer

Nissle¹,

Gurka²

2019

Smart Mater. Struct.

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Active hybrid composites consisting of fiber reinforced polymers (FRP) and shape memory alloys (SMA) can be used for actuation purposes. With this they can provide substantial savings concerning weight, space and cost or also enable new functions. A critical point for the use of the complete actuation performance of active SMA wires for a large number of cycles is the load transfer between these wires and the FRP structure. Also the loosening of the wire from the FRP structure has to be prevented. In this paper we will have a close look to the load transfer. There solutions for the testing of this load transfer as well as its improvement still do not satisfy. We show an improved experimental set up for a pull-out test, which are used most commonly, with optical stress measurement via photo elasticity for an exact measurement of the transferred load leading to primary failure of the interface. This enables a better forecast of the transferred load of the specimen. We also compare our results with those of typical pull-out tests. From these results we estimate the shear stress at first failure and compare these to theoretical values. Furthermore, we present new experimental data and compare different possibilities to improve the load transfer.

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“…Utilizing this combination in spaceefficient lightweight actuators offers a promising solution to address current challenges related to lightweight construction and resource efficiency. [2,3] A so-called bimorph bending actuator can be realized by embedding the SMA as unidirectional SMA wires into the polymer matrix of the composite with an offset to the neutral axis, allowing them to induce a bending moment in the overall structure when activated. [4] To ensure this functionality, the interface between the SMA wire and the polymer matrix is of crucial importance, as the force transfer between the SMA wire and the polymer matrix occurs within this contact area, which is often the limiting factor for the durability and the thermomechanical strength of the resulting SMAHC.…”

Section: Introductionmentioning

confidence: 99%

Pull‐Out Testing of Electrochemically Etched NiTi Shape Memory Alloy Wires in Shape Memory Alloy Hybrid Composites

Gapeeva,

Jungbluth,

Zeller‐Plumhoff

et al. 2024

Adv Eng Mater

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This study presents an experimental characterization of the interface strength of the shape memory alloy hybrid composite (SMAHC) consisting of the two‐way effect NiTi shape memory alloy (SMA) wire structured by electrochemical etching and the surrounding thermoset matrix. Mechanically induced, in situ thermally induced, and cyclic load‐increase pull‐out tests consistently reveal that SMAHC with structured SMA wires outperforms those with as‐delivered SMA wires by a substantial factor of 2.6 to 2.7 in interfacial strength — the critical factor governing the overall performance and functionality of the composite. Analyzing the force‐displacement curves from mechanically induced pull‐out tests demonstrates that structuring the SMA wire surface leads to a significantly increased elastic energy to initiate a crack and achieve complete failure. SMA wires with structured surfaces continue transferring load even after the initial interfacial failure due to the presence of intact mechanical interlocking sites. The cyclic load‐increase pull‐out test confirms that SMA wires with structured surfaces exhibit a significantly higher load‐bearing capacity, withstanding more load levels and demonstrating greater force of the first failure. Furthermore, in thermally induced pull‐out tests with structured SMA wires, a re‐initiation of failure from the lower side follows an initial failure progression at the SMA wire entry point.This article is protected by copyright. All rights reserved.

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Adaptive vortex generators based on active hybrid composites: from idea to flight test

Cited by 7 publications

References 6 publications

Electrochemical Surface Structuring for Strong SMA Wire–Polymer Interface Adhesion

Electrochemical Surface Structuring for Strong SMA Wire–Polymer Interface Adhesion

Characterization of active hybrid structures made of fiber reinforced composites and shape memory alloys—part A: characterization of the load transfer

Pull‐Out Testing of Electrochemically Etched NiTi Shape Memory Alloy Wires in Shape Memory Alloy Hybrid Composites

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