Programmable and reconfigurable hygro-thermo morphing materials with multifunctional shape transformation
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Morphing
Shape-memory polymer
Smart material
Soft Robotics
Shape memory composites (SMCs) based on shape memory alloys (SMAs) and shape memory polymers (SMPs) allow many design possibilities due to their controllable temperature-dependent mechanical properties. The complementary characteristics of SMAs and SMPs can be utilized in systems with shape recovery created by the SMA and shape fixity provided by the SMP. In this research, three SMC operating regimes are identified and the behavior of SMC structures is analyzed by focusing on composite shape fixity and interfacial stresses. Analytical models show that SMPs can be used to adequately fix the shape of SMA actuators and springs. COMSOL finite element simulations are in agreement with analytical expressions for shape fixity and interfacial stresses. Analytical models are developed for an end-coupled linear SMP-SMA two-way actuator and the predicted strain is shown to be in good agreement with experimental test results.
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Substantially more attention has been given in the past to shape memory alloys and shape memory ceramics than to shape memory polymers because unreinforced shape memory polymers have much lower stiffness and recovery force potential than shape memory alloys and shape memory ceramics. However, when incorporated into a fiber-reinforced composite, both the stiffness and the recovery force of a shape memory polymer can be dramatically improved. This paper presents recent advances in characterizing the shape memory mechanics of a thermoset shape memory polymer resin for Elastic Memory Composite (EMC) materials. In particular, heretofore undocumented response behavior is characterized through a series of thermo-mechanical tests of a commercially available EMC resin, and a lumped parameter model is adapted to accurately correlate this behavior. Through application of this model, it appears that the molecular transition associated with the shape memory effect occurs at a temperature other than the glass transition temperature of the resin.
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In this paper, a newly developed polymer, shape memory polyurethane (SMP), will be introduced. The shape memory polymer possesses the same basic shape memory effect and elasticity memory effect as shape memory alloys. Shape memory polymers can change their elastic modulus up to 500 times around their glass transition temperatures. Both the shape memory effect and the elasticity memory effect of shape memory polymers make them a useful candidate for today's intelligent material systems and structures. This paper will introduce some of the basic characteristics of SMPs and the results of some initial investigation of SMP composites.
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Shape memory alloys (SMAs) have the disadvantage that cooling is difficult and the actuating speed during cooling is slow. To resolve this problem, shape memory material actuators that operate only with heating is required. SMAs are characterized by a low apparent Young's modulus below the transformation temperature and a strong shape recovery force above the reverse transformation temperature. Alternatively, shape memory polymers (SMPs) have two properties: shape fixability and shape recovery. The SMPs are hardened below the glass transition (Tg) temperature and the material is recovered to memorized shape above the Tg temperature. The other hand, 3D printer is a machine that can directly output a 3D-designed product designed by a computer in 3D, and molded materials such as polymer, resin, metal, and ceramics. In this research, we developed the SMC of SMA wire and SMP sheet using adhesive that develops actuates into two shapes only by heating.
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Morphing
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This review paper deals with the advancements of composites to shape memory alloys. The journey of smart materials from conventional composites to advance shape memory alloys and their application is described in this literature. Classification of smart materials such as smart composites, shape memory alloys, polymer composite and various other types of materials that are intelligent are explained briefly. Different manufacturing and developing techniques to manufacture smart materials and characterization of conventional composites is compared with advance modern day shape memory alloys. Shape memory effect such as one way and two-way shape memory effect are depicted. However, the most important of all the applications and extensive use of smart materials in health care sector for implants and various other uses with uses in aerospace and automotive industries are reviewed.
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Multifunctional shape memory composites composed of shape memory polymers and shape memory alloys exhibit superior shape memory properties; therefore, it is of great interest to researchers to model their thermo-mechanical behavior numerically. Although a number of constitutive models of shape memory alloys and shape memory polymers have been developed, very few models have been developed for shape memory composites and validated with experimental data. In this study, we first review separately constitutive models of shape memory alloys and shape memory polymers developed in previous studies. Both models were validated with thermo-mechanical tests conducted on a shape memory alloy fiber and shape memory polymer, respectively. A constitutive model for the shape memory composite was then developed utilizing the homogenization scheme. Shape memory composites containing 0.5% or 1% of the shape memory alloy fiber volume content embedded in the shape memory polymer matrix were fabricated. Thermo-mechanical tests were carried out on these shape memory composites to validate the proposed constitutive model. The experimental results showed that the proposed shape memory composite model was able to predict the general trend of the thermo-mechanical behavior of the shape memory composites.
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In article number 1606580, Min-Woo Han and Sung-Hoon Ahn report soft morphing structures, in which loop-linked structures made from thermally responsive fibers allow the creation of three-dimensional morphologies, including flowers. Based on the design methodology of loop patterning, the proposed morphing structures enable three-dimensional volumetric transformation as well as bending, twisting, and torsional deformation, through functional fiber actuation.
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Soft Robotics
Soft materials
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Shape memory composites (SMCs) based on shape memory alloys (SMAs) and shape memory polymers (SMPs) are interesting due to their controllable temperature-dependent mechanical properties. The complementary characteristics of SMAs and SMPs can be used to create materials or systems with shape recovery created by the SMA and shape fixity provided by the SMP. In this research, three SMC operating regimes are identified and the behavior of SMC structures is analyzed by focusing on composite fixity and interfacial stresses. Analytical models show that certain SMPs can achieve sufficient shape fixing. COMSOL Multi-Physics simulations are in agreement with analytical expressions for shape fixity and interfacial stresses. Analytical models are developed for an end-coupled linear SMP-SMA two-way actuation system.
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Abstract Shape‐morphing robotic structures can provide innovative approaches for various applications ranging from soft robotics to flexible electronics. However, the programmed deformation of direct‐3D printed polymer‐based structures cannot be separated from their subsequent conventional shape‐programming process. This work aims to simplify the fabrication process and demonstrates a rapid and adaptable approach for building stimulus‐responsive polymer‐based shape‐morphing structures of any shape. This is accomplished through mechanically assembling a set of identical self‐bending units in different patterns to form morphing structures using auxiliary hard connectors. A self‐bending unit fabricated by a 3D printing method can be actuated upon heating without the need for tethered power sources and is able to transform from a flat shape to a bending shape. This enables the assembled morphing‐structure to achieve the programmed integral shape without the need for a shape‐programming process. Differently assembled morphing structures used as independent robotic mechanisms are sequentially demonstrated with applications in biomimetic morphing structures, grasping mechanisms, and responsive electrical devices. This proposed approach based on a mechanical assembling method paves the way for rapid and simple prototyping of stimulus‐responsive polymer‐based shape‐morphing structures with arbitrary architectures for a variety of applications in deployable structures, bionic mechanisms, robotics, and flexible electronics.
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Flexible Electronics
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