Shape-Memory Polymer Composites

Shape memory polymers (SMPs) are evolving intensively in smart materials research. SMPs can undergo large deformations, hold a temporary shape and then recover their original shape upon exposure to a particular external stimulus. The emerging development of fibre reinforced shape memory polymer composites (SMPCs) has improved SMPs’ mechanical properties to be comparable to modern fibre reinforced composites. Moreover, the inclusion of nanoparticles has enhanced the diversity in activation mechanisms and improved structural properties and durability.
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\nToday, the SMPCs are generally viewed as promising substances for engineered applications that have raised intensive interest among the scientists and engineers. Interestingly, stimulation by light enables unique and advanced shape memory effects (SMEs) in SMPCs that can fulfill the sophisticated demands of engineering. The ability to vary the light wavelength, intensity, periodicity, polarization and the irradiated position on the SMP component enables wavelength selective, reversible, sequential and multiple SMEs. Furthermore, light travel long distances in a vacuum, can be focussed onto a certain area, is safe to humans and, can be a control signal carrier and most notably, can be sent through optical fibres to extremely inaccessible areas.
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\nIncorporation of metallic, carbon and organic based photothermal fillers into a SMP matrix is a convenient proven method to prepare light activated shape memory polymer composites (LASMPCs). These photothermal fillers convert electromagnetic radiation into thermal energy that triggers the SMP matrix. The current study comprehensively reviewed the performances, mechanisms, challenges and limitations of the existing LASMPC systems and associated optical technologies. Predominantly this research was intended to develop reinforced LASMPC systems and allied optical technologies applicable for large scale structural engineering applications.
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\nIn this study, styrene and bisphenol A epoxy based thermosets and polylactic acid (PLA) based thermoplastic SMPs were used as polymer matrix materials. Carbon fibre, glass fibre, multiwalled carbon nanotube (MWCNT) and rare earth organic complexes of Nd(TTA)3Phen and Yb(TTA)3Phen were used as reinforcement and photothermal fillers. The samples were produced by means of vacuum bagging, mould casting and 4D printing. Morphological investigations were conducted to identify the microstructure and manufacturability of the LASMPCs. The samples’ mechanical and physical properties were tested by standard test methods for polymer matrix composites. Dynamic mechanical analysis was carried out to determine the thermomechanical characteristics. The photothermal effect was investigated through thermal imaging and associated shape memory behaviours were studied through shape fixing and recovery experiments. A finite element analysis was performed with ABAQUS to simulate the photothermal heating behaviour.
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\nThe current study established a material development framework for LASMPC materials and presented apt manufacturing methods for structural and large scale engineering applications. Different modes of light diffusion such as scattered low intensity light, focussed laser beams and light delivery through fibre optics were proved for structural LASMPCs. Sequential and selective wavelength activation of structural LASMPCs are presented. The FEA simulation provided additional understanding on light exposed LASMPCs’ 3-dimensional heating behaviour. Embedding a D-shaped optical fibre in an LASMPC created a single unit smart actuator, which was remotely activated by light. It was proven that flexible radiation shields can reduce the unanticipated shape recovery of LASMPCs components and protect the LASMPCs from polymer degradation due to radiation.
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\nThe improvements to their structural properties and innovative remote activation methodologies have justified LASMPCs’ aptness for space engineering applications. This study has proven its successful completion by three selected case studies of space applications. An LASMPC solar panel array model was sequentially deployed in four recovery steps. In a vacuum, a space habitat structure model was compressed to a third of its volume and then recovered its original shape. A 4D printed boom structure model was tested, proving customized LASMPC structures for sophisticated space equipment fabrication. The deployable LASMPC structures can reduce the occupied room in spacecraft. The improvements to the structural properties of LASMPCs while keeping the SME, understanding on thermomechanical and photothermal behaviours, remote actuation through optical fibres, radiation shields and the insight to space applications are the most significant novel outcomes of this study. This thesis opens up windows of opportunity for the scientific and engineering communities to provide innovative solutions to realize the sophisticated large scale engineering demands in aerospace and space applications and beyond.

This paper is concerned about an investigation of mechanical and electrical conductive properties of carbon fiber fabric reinforced shape memory polymer composite (SMPC). The shape memory polymer (SMP) is a thermoset styrene-based resin. SMP is a promising smart material, which is under intensive investigation at present. Its primary advantages over other smart materials are the high strain capacity (200% reversible strain), low density and low cost etc.. But its major drawbacks are low strength, low modulus and low recovery stress. So the fiber reinforced SMPC was naturally considered to be investigated in this paper, which may overcome the disadvantages mentioned above. The investigation was conducted with experimental methods: Dynamic Mechanical Analyzer (DMA), static and mechanical cycle loading tests, microscope observation of microstructural deformation mechanism, conductivity and shape recovery tests. Results indicated that SMPC showed higher glass transition temperature (Tg) than neat SMP and improved the storage modulus, bending modulus, strength and resistance against relaxation and creep. Both fiber microbuckling and fracture of SMPC were observed after the static 3-ponit bending test at the constant room temperature. SMPC showed favorable recovery performances during thermomechanical cycles of the bending recovery test and the fiber microbuckling was obvious. Moreover, the conductive SMPC of this study experienced low electrical resistivity and performed a good shape memory effect during numerous thermomechanical cycles.

Shape memory polymers (SMPs) have emerged as a revolutionary class of smart materials with enormous potential for applications in engineering and science. This manuscript provides a comprehensive review, examining their processing techniques, compositions, characteristics, and applications. It also looks at different shape memory polymer materials, blends, and composites in a critical way by looking at their features and improved mechanical, thermal, electrical, and other properties. It discusses all reinforcements, such as carbon nanotubes, graphene, and metal nanoparticles, used in earlier studies and their impact on various shape memory composites and their properties. Recent trends in research related to shape memory polymer composites (SMPCs) have focused on providing solutions to these problems by adding fillers or reinforcements and/or combining them with other polymers. Further, it provides major applications of SMPS in biomedical, aerospace, smart textiles, sensors, and self-healing materials. A detailed review of all these applications, along with their challenges also discussed thoroughly. This review helps in providing a bridge between existing knowledge and future directions of SMPs and composites involve developing multi-stimuli responsive materials, improving material properties using hybrid reinforcements, developing complex shape recovery mechanisms, including self-healing and functional futures in emerging areas like biomedical, soft robotics, and other applications.

Shape memory polymers (SMPs) are a new type of smart material, they perform large reversible deformation with a certain external stimulus (e.g., heat and electricity). The properties (e.g., stiffness, strength and other mechanically static or quasi-static load-bearing capacity) are primarily considered for conventional resin-based composite materials which are mainly used for structural materials. By contrast, the mechanical actuating performance with finite deformation is considered for the shape memory polymers and their composites which can be used for both structural materials and functional materials. For shape memory polymers and their composites, the performance of active deformation is expected to further promote the development in smart active deformation structures, such as deployable space structures and morphing wing aircraft. The shape memory polymer composites (SMPCs) are also one type of High Strain Composite (HSC). The space deployable structures based on carbon fiber reinforced shape memory polymer composites (SMPCs) show great prospects. Considering the problems that SMPCs are difficult to meet the practical applications in space deployable structures in the recent ten years, this paper aims to research the mechanics of deformation, and failure of SMPCs. In the overall view of the shape memory polymer material’s nonlinearity (nonlinearity and stress softening in the process of pre-deformation and recovery, relaxation in storage process, irreversible deformation), by the multiple verifications among theory, finite element and experiments, one obtains the deformation and mechanism for the process of “pre-deformation, energy storage and actuation and its non-fracture constraint domain. Then, the parameters of SMPCs will be optimized. Theoretical analysis is realized by the strain energy function, additionally considering the interaction strain energy between the fiber and the matrix. For the common resin-based or soft-material-based composites under pure bending deformation, we expect to uniformly explain the whole process of buckling occurrence, evolution and finally failure, especially for the early evolution characteristics of fiber microbuckling inside the microstructures. The research results are meaningful for the practical applications for SMPC deployable structures in space. Considering the deformation mechanisms of SMPCs, the local post-microbuckling is required for the unidirectional fiber reinforced composite materials, at the conditions of its large geometrical deflection. The cross section of SMPC is divided into three areas: non-buckling stretching area, non-buckling compressive area, and buckling compressive area. Three variables are considered: critical buckling position, and neutral plane, the fiber buckling half-wavelength. Considering the condition of the small strain and large displacement, the strain energy expression of the SMP/fiber system was derived, which contains two types, e.g., strain energy of SMP and fiber. According to the minimum energy principle, the expression for all key parameters were derived, including the critical buckling curvature, neutral plane position, the buckling half-wavelength, fiber buckling amplitude, and strain.

Shape memory property and mechanism of the knitting-fabric reinforced epoxy composites subjected to tensile loading

Thermomechanical constitutive modeling of fiber reinforced shape memory polymer composites based on thermodynamics with internal state variables

Shape memory polymers (SMPs) is a type of smart polymers. Shape-memory polymers (SMPs) allow for the development of stimuli-responsive polymer-based materials that can undergo substantial recoverable deformation in response to an external stimulus. Shape-memory effects (SMEs) of these SMP-based materials for task-specific applications are picking the interest of academic and industrial researchers. Significant progress has been gained in the field of shape memory polymers (SMPs) in recent years, with the discovery of new compositions for property tweaking, the discovery of new processes for shape fixing and recovery, and the initiation of phenomenological modelling. The current review will provide a brief account of the history of SMPs, their qualities, their structure and mechanism, classification, biodegradable SMPs and use of SMPs in various fields. Recent advancements in shape memory polymer composites (SMPCs) and shape-memory polymer blends (SMPBs) are also emphasized. This review explains distinct classification criteria of SMPs with a view of polymer type and structure and external stimulation.

Shape memory polymers (SMPs) have drawn wide attention of many researchers for its potential applications to shipping industry, aerospace, bionics engineering and mechanical engineering. Shape memory polymers composites (SMPCs) have ability to improve the properties and obtain attain new functions of shape memory polymers. In this paper, trans-1, 4-polyisoprene reinforced by carbon fiber is developed to improve the mechanical weakness of trans-1, 4-polyisoprene bulk. Composites with carbon fiber weight fraction of 5%, 10%, and 15% are fabricated by casting samples with an average length of 2 mm. The mechanical property of the trans-1, 4-polyisoprene reinforced by short carbon fiber is evaluated and the effects of short carbon fiber on shape memory behavior are investigated. The results indicate that there is an optimum fiber weight fraction between 5 and 15 wt% where exists an extremely low recovery ratio, re-crystallizing temperatures (Tc) and an extremely high tensile stress.

Precise stimulation of near-infrared light responsive shape-memory polymer composites using upconversion particles with photothermal capability

Thermomechanical and fire performance of DGEBA based shape memory polymer composites for constructions

Shape memory polymers are temperature-controlled variable stiffness materials, which have potential for use as morphing skins. Shape memory polymer skins undergo large strain in their flexible, rubbery state and resist aerodynamic loads in their stiff, glassy state. However, pure shape memory polymers are brittle in their glassy state, and in their rubbery state, they tear rapidly along micro-cracks formed under tension. Due to these disadvantages, the shape memory polymers are not safe and reliable enough for application. In this article, elastic fibers were mixed into pure shape memory polymers to solve these problems. The mechanical properties of the shape memory polymer composites were investigated. The strength and Young’s modulus of pure shape memory polymers at high temperature were improved by elastic fibers, and the toughness of pure shape memory polymers at room temperature (glassy state) was enhanced with acceptable reduction in Young’s modulus. The tear strength of shape memory polymers was significantly improved by elastic fibers, especially at high temperature. Recovery properties and thermal performance were also discussed. Finally, shape memory polymer composite skins were used in a variable camber wing structure to demonstrate their application.

Our previous study presented a shape memory polymer composite (SMPC) hinge and successfully tested it at a low temperature of −10°C using commercial polyimide-film heating elements and a one-heating element design. The employment of the one-heating element design, however, revealed an unexpected drawback which influenced the deployment performance of the SMPC hinge. In this study, our goal was to define and address the drawback, and then to improve the performance. The result was to create a three-heating element design of the SMPC hinge along with a Proportional Integral Derivative temperature control. The superiority of the three-heating element design was proved by an increased number of bending-deployment cycles at −10°C. Nonetheless, the use of commercial heating . In this sense, we proposed and fabricated in-house polyimide-film heating elements, which consisted of an Fe-Chrome heating element wire No. 2 and two insulating polyimide films placed up and down, with different smaller sizes. Deployment tests with handmade heating elements at room temperature were conducted to determine the optimum heating element size, for which the successful deployment of the SMPC hinge was retained.

Shape memory polymers (SMPs) are employed in a wide range of fields because to their appealing properties, which include low density, low production costs, and ease of processing. In the present work, SMP composites were developed using ultrasonic mixing of carbon fiber (CF) and amorphous epoxy to enhance the properties of epoxy and shape memory effect. The prepared composites were tested for mechanical and shape memory properties. Flexural strength and tensile strength of pristine epoxy enhanced after dispersing 1% CF which are about 12.7% and 16.2%, respectively, higher than pristine epoxy. Fracture toughness of epoxy improves after adding 1% CF which is about 94.05% higher compared to pristine epoxy. UV–vis-NIR showed reduction in energy bandgap. Shape fixity and shape recovery ratios for pristine epoxy was 98.49% and 93.40%, respectively. These ratios decrease to 90.52% and 87.86%, respectively with addition of 1.5 wt.% CF. However, recovery time improves from 57 s to 33 s with addition of 1.5 wt.% CF in epoxy. Shape recovery rate enhances with CF reinforcement in epoxy composite.

Shape memory polymers (SMPs) possess the remarkable ability to recover their original shape after being severely deformed, triggered by the right stimulus. This chapter reviews recent progress in shape memory materials, focusing on traditional types like shape memory alloys (SMAs) and SMPs, as well as emerging shape memory hybrids, which enable customizable properties for specific applications in a “do-it-yourself” manner. SMPs, in particular, show great promise for morphing aircraft applications due to their temperature- and time-dependent mechanical properties. Tests on SMPs under monotonic loading in high shear demonstrate their ability to recover original shapes while resisting large loads. Advances in SMP composites (SMPCs), which incorporate functional materials and nanostructures, further enhance their deformation recovery, mechanical properties, and controllable actuation. SMPs have broad applications across aerospace, biomedical devices, flexible electronics, and more. This chapter also provides an in-depth analysis of the shape recovery mechanisms, multifunctionality, and potential future directions for SMP development.

Shape memory polymer composites (SMPCs) have the potential for many applications in aerospace, spanning from self-repairing of structures to self-deploying of antennas, solar sails, or functional devices (e.g. for grabbing small space debris). In all these cases, it may be essential to have information about their configuration at different stages of shape recovery. In this study, the strain history of a prepreg carbon fibre system, cured with a shape memory polymer (SMP) interlayer, is monitored through a Fibre Bragg Grating (FBG), a fibre optic sensor device. SMPC has been manufactured by using traditional technologies for aerospace. After manufacturing cylindrical shape samples, an external fibre optic system is added to the composite structure; this system is especially suited for high temperatures which are necessary for SMP recovery and composite softening. Sensor functionality is checked before and after each strain history path. Optic fibre arrangement is optimized to avoid unwanted breakings whereas strains are limited by fibre collapsing, i.e. within nominal 2% of deformation. Dynamic information about shape recovery gives fundamental insights about strain evolution during time as well as its spatial distribution.