Embedded Shape-Memory Alloy Wires for Improved Performance of Self-Healing Polymers

One of the main problems with a bolted joint is losing its preload. In this situation, it cannot provide the required clamping force needed to keep the joint members together or prevent fluid leakages. Although every effort is usually made at the design stage to prevent such failure, because of the numerous factors present in the problem, these efforts are not always successful. After loosening occurs, the joint should be retightened to regain its preload. However, there are circumstances where the joint is very important but it is not easily accessible and retightening cannot be done manually. The shape memory effect (SME) property can be used in such circumstances to produce the necessary preload. The shape memory alloy (SMA) element should be activated if monitoring the bolt preload through the application of strain gauges shows that the preload has fallen below a pre-determined threshold level. This paper presents a mathematical model for the SMA element and the whole joint behavior. The relation between SMA activation (corresponding to the amount of phase change in the SMA) and the resulting preload is estimated. To this end, it is assumed that the SMA element behaves in such a way that either its cross-sectional area or its volume remain constant. The analysis of this model shows the feasibility of the application of SMA for producing the required preload. Hence, if used properly, the required preload is achieved and a self-healing joint is obtained.

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Experimental assessment of self-healing nature in aluminum-based smart composites with NiTi wires and solder alloy as healing agents through Taguchi approach

Journal of Intelligent Material Systems and Structures ◽

10.1177/1045389x20942846 ◽

2020 ◽

Vol 31 (18) ◽

pp. 2101-2116 ◽

Cited By ~ 1

Author(s):

Vaibhav Srivastava ◽

Manish Gupta

Keyword(s):

Heat Treatment ◽

Shape Memory Alloy ◽

Shape Memory ◽

Solder Alloy ◽

Crack Depth ◽

Self Healing ◽

Flexural Testing ◽

The Matrix ◽

Healing Temperature ◽

Niti Wires

In this article, the healing assessment of the AA2014 matrix reinforced with NiTi wires and solder alloy as healing agents is investigated through flexural testing. The idea of a smart composite was such that it could retain its structural stability through NiTi wires reinforced, which ultimately heals the macro cracks, whereas the solder alloy binds the micro-cracks by filling through the gap after heat treatment. The objective of this work is to determine the parameters influencing self-healing assessments. Specimens with different shape memory alloy vol% (0.5%, 1.3%), specimen size (1, 2) and shape memory alloy wires diameter (0.47 mm, 0.96 mm) were fabricated for analysis. Furthermore, Taguchi orthogonal columns of L8 (4^1 2^3) array technique was implemented to study the observations from different experimental runs. Healing temperature (i.e. 600°C) was selected such that it could take advantage of the compositional healing of the matrix. The completely damaged specimens through the bend test were thermally treated at different healing durations (30, 60, 90, 120 min) in a furnace to activate healing. The results show that a maximum of 96.95% of crack depth, 100% of crack width, and 73.76% of the recovery in flexural strength was recovered after heat treatment.

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Optimal design of a bio-inspired self-healing metal matrix composite reinforced with NiTi shape memory alloy strips

Journal of Intelligent Material Systems and Structures ◽

10.1177/1045389x18803448 ◽

2018 ◽

Vol 29 (20) ◽

pp. 3972-3982 ◽

Cited By ~ 6

Author(s):

Mohammad Amin Poormir ◽

Seyed Mohammad Reza Khalili ◽

Reza Eslami-Farsani

Keyword(s):

Mechanical Properties ◽

Shape Memory Alloy ◽

Shape Memory ◽

Metal Matrix Composite ◽

Matrix Composite ◽

Smart Materials ◽

Metal Matrix ◽

Self Healing ◽

Healing Temperature ◽

Design Factors

Utilizing smart materials such as shape memory alloys as reinforcement in metal matrix composites is a novel method to bio-mimic self-healing. This study aims to investigate the influence of design factors of a self-healing metal matrix composite by employing the Taguchi method for designing of the experimental procedure. Three design factors, each in three levels, were studied simultaneously according to L-9 standard Taguchi orthogonal array to determine the optimal level of each factor in mechanical properties enhancement with a reduced number of experiments. Composite specimens were fabricated from Sn-13 wt.% Bi alloy as matrix and nickel–titanium shape memory alloy strips as reinforcement with gravity casting process. Matrix alloy was melted and casted in a preheated metallic mold in which SMA strips were installed in various quantities (one, two, or three strips) and different pre-strains (0%, 2%, or 6%). After fabrication of the specimens, a tensile test was conducted until fracture to specify mechanical properties. Then, specimens were placed in a furnace in three different temperatures (170°C, 180°C, and 190°C) to activate the shape memory effect of strips and achieve crack closure and healing. Specimens were tensile tested again after healing to calculate the amount of healed properties and healing efficiency. Results show that using three strips with 6% of pre-strain and applying 190°C healing temperature can maximize the ultimate tensile strength efficiency. Also, the existence of one strip, 0% pre-strain, and 190°C healing temperature creates the best circumstances for healing ductility.

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The Synthesis and Processing of Self-Healing Materials: A Lamellar Shape Memory Alloy in Composite Structure

Advanced Composites for Aerospace, Marine, and Land Applications II ◽

10.1002/9781119093213.ch22 ◽

2015 ◽

pp. 285-294

Author(s):

Bakr Mohamed Rabeeh ◽

Yasser Fouad

Keyword(s):

Shape Memory Alloy ◽

Shape Memory ◽

Composite Structure ◽

Self Healing ◽

Synthesis And Processing

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Flight Test of a Shape Memory Alloy Actuated Adaptive Trailing Edge Flap

Volume 1: Multifunctional Materials; Mechanics and Behavior of Active Materials; Integrated System Design and Implementation; Structural Health Monitoring ◽

10.1115/smasis2016-9141 ◽

2016 ◽

Cited By ~ 7

Author(s):

F. T. Calkins ◽

J. H. Mabe

Keyword(s):

Shape Memory Alloy ◽

Shape Memory ◽

High Speed ◽

Flight Test ◽

Federal Aviation Administration ◽

Trailing Edge ◽

Loop Control ◽

Rotary Actuator ◽

Trailing Edge Flaps ◽

Improved Performance

The Boeing Company has a goal of creating aircraft that are capable of continuous optimization for all flight conditions. Recent advances in SMA actuation and a detailed understanding of wing design were combined to design, build, and safely demonstrate small trailing edge flaps driven by SMA actuation. As part of a 2012 full-scale flight test program a lightweight and compact Shape Memory Alloy (SMA) rotary actuator was integrated into the hinge line of a small flap on the trailing edge of a commercial aircraft wing. This Adaptive Trailing Edge program was part of a Boeing and Federal Aviation Administration (FAA) collaboration. Aerodynamic studies of these small trailing edge flaps show that improved performance requires multiple flap configurations that vary with flight regime. Configurations include small angles of deployment for reduced fuel burn and emissions during high speed cruise and larger angles of deployment for increased lift and lower noise during takeoff and approach. SMA actuation is an ideal compact solution to position these small flaps and increase aircraft performance by simply and efficiently altering the wings aerodynamic characteristics for each flight segment. Closed loop control of the flap’s position, using the SMA actuator, was demonstrated at multiple flight conditions during flight tests. Results of the successful flight test on a 737–800 commercial airplane and the significantly improved performance benefits will be presented. This is the first flight test of an SMA rotary actuator system, which was matured from TRL 4 to TRL 7 during the program.

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