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This paper aims to present a phenomenological and quantitative model to study the constitutive relations and working mechanism for shape/temperature memory effect in polypyrrole (PPy)-based shape memory polymers (SMPs).

In this paper, the origin of relaxation law was used to theoretically predict the relationships between relaxation time and internal energy and temperature based on the thermodynamics of polymers.

A phenomenological model was proposed to quantitatively identify the factors that influence the stored mechanical energy, shape memory effect (SME) and temperature memory effect (TME) in PPy. Both structural relaxation law and Tool-Narayanaswamy (TN) model were used to couple the constitutive relations of stress and transition temperature as a function of relaxation frequency, respectively. Furthermore, the simulation of the phenomenological model was compared with experimental results reported in relevant literature for purpose of verification.

Exploration of the working mechanism underpinning the experimental (or phenomenal) results and significant enhancement of the understanding of relevant experimental features reported previously.

The outcome of this study will provide a powerful phenomenological and quantitative tool for studies on SME and TME in SMPs.

This paper aims to focus on achieving triple-shape memory effect (triple-SME) of a commercial poly (ethylene terephthalate) (PET) film with the thickness of 100 µm.

The thermal characteristics and microstructure of PET film were characterized by differential scanning calorimetry, thermogravimetric analysis and wide-angle X-ray diffraction analysis. The dual-shape memory effect (dual-SME) of the PET film was then systematically investigated, and based on that, triple-SME in thin PET film was achieved.

Investigation of the dual-SME in PET film revealed the difference between recovery temperature and programming temperature reduced with increasing programming temperature. An obvious intermediate shape shifting between the original and final programmed shape was observed during shape recovery in triple-shape memory behaviors.

Compared with dual-SME in polymer, relatively less work has been done on multi-SME in polymer, especially in thin polymer film. In this study, triple-SME in a PET film was investigated based on the results of dual-SME of the film. The main implication of the study is on how to achieve a watermark between the final programmed pattern and the original pattern, for the application of shape memory polymer in anti-counterfeiting label.

Dual- and triple-SMEs were achieved in a PET film that is only 100 µm in thickness, and the underlying mechanism for the difference between programming temperature and recovery temperature was discussed. For the novel application of triple-SME in anti-counterfeit label, the watermark during shape recovery in triple-SME can effectively prevent duplication.

This paper aims to create and to study multifunctional shape memory polymer (SMP) composites having temperature-sensing and actuating capabilities by embedding thermochromic particles within the polymer matrix.

The multifunctional materials were fabricated following a process consisting of blending (of the thermochromic particles and the SMP at various ratios), mixing, degasing, moulding and thermal curing, prepared by incorporating thermochromic particles within the polymer. The effect of the thermochromic particles on the thermomechanical properties and thermally responsive shape memory effect of the resulting multifunction SMP composites were characterised and interpreted.

It was found that exposure of the composites to temperatures above 70°C led to a pronounced change of their colour that was recorded by the thermal and electrical actuation approaches and was reproducibly reversible. It was also found that the colour of the composites was independent of the mechanical state of the SMP. Such effects enabled monitoring of the onset of the set/release temperature of the SMP matrix. Furthermore, the combination of thermochromic additive and the SMP resulted in significantly improved thermomechanical strength, absorption of infrared radiation and the temperature distribution of the SMP composites.

The temperature-sensing and actuating capabilities of the polymeric shape memory composites developed through this study will help to extend the field of potential applications of such composites to fields including sensors, actuators, security labels and information dissemination, where colour indication is an advantageous feature.

The SMP composites capable of temperature sensing and actuating are novel.

The purpose of this paper is to study the influence of calcium sulfate whiskers (CSWs) on the thermodynamic properties and shape memory properties of epoxy/cyanate ester shape memory composites.

To improve the mechanical properties of shape memory cyanate ester (CE)/epoxy polymer (EP) resin, high performance CSWs were used to reinforce the thermo-induced shape memory CE/EP composites and the shape memory CSW/CE/EP composites were prepared by molding. The effect of CSW on the mechanical properties and shape memory behavior of shape memory CE/EP composites was investigated.

After CSW filled the shape memory CE/EP composites, the bending strength of the composites is greatly improved. When the content of CSW is 5 Wt.%, the bending strength of the composite is 107 MPa and the bending strength is increased by 29 per cent compared with bulk CE/EP resin. The glass transition temperature and storage modulus of the composites were improved in CE/EP resin curing system. However, when the content of CSW is more than 10 Wt.%, clusters are easily formed between whiskers and the voids between whiskers and matrix increase, which will lead to the decrease of mechanical properties of composites. The results of shape memory test show that the shape memory recovery time of the composites decreases with the decrease of CSW content at the same temperature. In addition, the shape recovery ratio of the composites decreased slightly with the increase of the number of thermo-induced shape memory cycles.

A simple way for fabricating thermo-activated SMP composites has been developed by using CSW.

The outcome of this study will help to fabricate the SMP composites with high mechanical properties and the shape memory CSW/CE/EP composites are expected to be used in space deployable structures.

Shape memory polymers (SMPs) respond with a change in their shape against a specific stimulus by memorizing their original shape and are reformed after deformation most often by changing the temperature of the surrounding without additional mechanical efforts. In the coming years, these polymers indeed will be in limelight to manufacture textile materials which will retain their shape even after prolonged use under disturbed conditions. This study aims at defining shape memory materials and polymers as well as their technological characteristics and also highlights application in various fields of textiles.

The methodology used to explain these SMPs have been carried out starting with the discussion on their properties, their physical nature, types, viz., shape memory alloys (SMAs), shape memory ceramics, shape memory hybrid, magnetic shape memory alloy, shape memory composites, shape memory gels and SMP along with properties of each type. Other related details of these polymers, such as their advantages, structure and mechanism, shape memory functionality, thermally responsive SMPs and applications, have been detailed.

It has been observed that the SMPs are very important in the fields of wet and melt-spun fibers to offer novel and functional properties, cotton and wool fabric finishing, to produce SMP films, foams and laminated textiles, water vapor permeable and breathable SMP films, etc.

The field of SMPs is new, and very limited information is available to enable their smooth production and handling.

The purpose of this paper is to demonstrate the feasibility of using shape memory polymer (SMP) for developing vascular stent. In particular, the expansion performance is analyzed through extensive modeling and simulation.

Firstly, the authors construct the model geometry and propose a constitutive model to describe the deformation of the stent due to the expansion process. The authors then simulate the expansion process under varying conditions, including different heating rates and recovery temperatures. Finally, the authors analyze the radial strength of the SMP stent.

A less invasive and stable expansion performance of the SMP stent is confirmed by the simulation method. A fitting function of the expansion process is proposed based on the characteristics of the SMP.

The effects of dynamic blood flow on the SMP stent is ignored. A fluid-structure interaction analysis may need to be considered to give a more accurate description of the behaviour of the SMP stent.

The findings will provide guidance for the rational design and application of SMP stents.

The work will provide guidance for the new generation stent design.

This is the first time that the expansion performance of a SMP stent has been analyzed both qualitatively and quantitatively through modelling and simulation.

This paper aims to present a review on utilizing shape memory technology (SMT) for active assembly/disassembly, i.e. assembly/disassembly without physically touching.

The fundamentals behind the shape memory effect (SME) in materials, in particular shape memory alloys (SMAs) and polymers, which are the cornerstones of SMT, are introduced, together with the possible approaches to implement this effect in active assembly/disassembly. Example applications for not only active assembly/ disassembly, but also programmed active disassembly are presented.

The advantages of utilizing SMT over conventional assembly/disassembly techniques are identified.

The paper introduces the fundamentals behind the SME and the basic approaches to implement the SMT in not only active assembly/disassembly, but also programmed active assembly.

The purpose of this paper is to provide a review of recent systematic and comprehensive advancement in electrospun polymer fiber and their composites with shape memory property.

The nanofiber manufacture technique is initially reviewed. Then, the influence of electrospinning parameters and actuation method has been discussed. Finally, the study concludes with a brief review of recent development in potential applications.

Shape memory polymer (SMP) nanofibers are a type of smart materials which can change shape under external stimuli (e.g. temperature, electricity, magnetism, solvent). In general, such SMP nanofibers could be easily fabricated by mature electrospinning technique. The nanofiber morphology is mainly affected by the electrospinning parameters, including applied voltage, tip-to-collector distance, viscosity of solution, humidity and molecular weight. For actuation method, most SMP nanofibers and their composites can change their shapes in response to heat, magnetic field or solvent, while few can be driven by electricity. Compared with the block SMPs, electrospun SMP nanofibers’ mat with porosity and low mechanical property have a wide potential application field including tissue engineering, drug delivery, filtration, catalysis.

This paper provides a detailed review of shape memory nanofibers: fabrication, actuation and potential application, in the near future.

The purpose of this paper is to prepare novel electroactive shape memory nanocomposites based on graphene and study the thermomechanical property and shape memory behavior of nanocomposites.

Graphene was dispersed in N,N-dimethylformamide, and the mixture was spooned into epoxy-cyanate ester mixtures to form graphene/epoxy-cyanate ester nanocomposites. The nanocomposites were deformed under 150°C, and shape recovery test was conducted under an electric voltage of 20-100 V.

Graphene is used to improve the shape recovery behavior and performance of shape-memory polymers (SMPs) for enhanced electrical actuation effectiveness. With increment of graphene content, the shape recovery speed of nanocomposites increases significantly.

A simple way for fabricating electro-activated SMP nanocomposites has been developed by using graphene.

The outcome of this study will help to fabricate the SMP nanocomposites with high electrical actuation effectiveness and improve the shape recovery speed of the nanocomposites.

A review on additive manufacturing (AM) of shape memory polymer composites (SMPCs) is put forward to highlight the progress made up to date, conduct a critical review and show the limitations and possible improvements in the different research areas within the different AM techniques. The purpose of this study is to identify academic and industrial opportunities.

This paper introduces the reader to three-dimensional (3 D) and four-dimensional printing of shape memory polymers (SMPs). Specifically, this review centres on manufacturing technologies based on material extrusion, photopolymerization, powder-based and lamination manufacturing processes. AM of SMPC was classified according to the nature of the filler material: particle dispersed, i.e. carbon, metallic and ceramic and long fibre reinforced materials, i.e. carbon fibres. This paper makes a distinction for multi-material printing with SMPs, as multi-functionality and exciting applications can be proposed through this method. Manufacturing strategies and technologies for SMPC are addressed in this review and opportunities in the research are highlighted.

This paper denotes the existing limitations in the current AM technologies and proposes several directions that will contribute to better use and improvements in the production of additive manufactured SMPC. With advances in AM technologies, gradient changes in material properties can open diverse applications of SMPC. Because of multi-material printing, co-manufacturing sensors to 3D printed smart structures can bring this technology a step closer to obtain full control of the shape memory effect and its characteristics. This paper discusses the novel developments in device and functional part design using SMPC, which should be aided with simple first stage design models followed by complex simulations for iterative and optimized design. A change in paradigm for designing complex structures is still to be made from engineers to exploit the full potential of additive manufactured SMPC structures.

Advances in AM have opened the gateway to the potential design and fabrication of functional parts with SMPs and their composites. There have been many publications and reviews conducted in this area; yet, many mainly focus on SMPs and reserve a small section to SMPC. This paper presents a comprehensive review directed solely on the AM of SMPC while highlighting the research opportunities.