Shape Memory Polymer Composites Research Articles

Equivalent plate model of shape memory polymer composite based variable height corrugated structure

In this work, an equivalent plate model for a shape memory polymer composite based corrugation structure with varying height, for morphing application, is developed. A thermodynamically consistent constitutive relation based on temperature dependent phase transformation concept for shape memory polymer matrix is used in the composite model. The homogenization model is based on the equivalence of strain energy of a representative unit volume. Following validation, as an application, commonly used airfoil profile NACA 63210 was considered to demonstrate the model utility. Parametric studies have been undertaken to investigate the influence of corrugation parameters like thickness and number of corrugations.

Dynamic mechanical response and deformation mechanism of poly (ε-caprolactone) (PCL) / epoxy resin(EP) shape memory polymer composites

The dynamic mechanical response and deformation mechanism of poly (ε-caprolactone) (PCL) and epoxy resins shape memory polymer (SMP) composites were investigated in this paper. The SMP composites were a blend of PCL and epoxy resins by using the facile melt-mixing method. The distribution of PCL in the composites was observed by SEM, which was in from microparticle morphology to continuous morphology with the increasing PCL content. And the dynamic mechanical analyzer (DMA) tests were performed to demonstrate the viscoelastic properties and shape memory effect of the PCL/EP composites. Based on the above characterization of PCL/EP composites, the split Hopkinson pressure bar (SHPB) tests were performed to study the dynamic mechanical properties at the strain rates of 4000/s to 7000/s. The results showed that the flow stress increased with the increasing strain rate, which exhibited an obvious sensitivity to strain rate. However, the flow stress of PCL/EP decreases with the increasing PCL content due to the low strength of PCL. And PCL/EP composites failed in a typical ductile failure mode under quasi-static loading, whereas an excellent plastic deformation ability was observed at high strain rates, which was attributed to the heat generated by the plastic work during the adiabatic compression. Combining with the experimental results, the corresponding deformation mechanism was also discussed.

PLLA/(MWCNTs-ZnO)@PDA composite with NIR-light induced shape memory effect, antibacterial properties and 3D printability

PLLA based shape-memory polymer composites with multifunctions have attracted growing attention in biomedical applications. Generally, a single nanofiller has the problem of insufficient functionalization and easy aggregation. Therefore, we design and fabricate polydopamine (PDA) surface modified MWCNTs-ZnO hybrid nanostructure ((MWCNTs-ZnO)@PDA). The dispersion of (MWCNTs-ZnO)@PDA in PLLA is improved in comparison with the pristine MWCNTs or ZnO. The results indicate that the (MWCNTs-ZnO)@PDA nanosystem shows a synergistic effect on the mechanical properties and photothermal properties of the composites. Comparative analysis with neat PLLA demonstrates a remarkable 17% increase in tensile strength and a 19% increase in elongation at break for PLLA/(MWCNTs-ZnO)@PDA composite. Additionally, the composites exhibit excellent NIR light-induced shape memory effects with a shape recovery ratio reaching 100%. Moreover, PLLA/(MWCNTs-ZnO)@PDA composites show favorable antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Furthermore, the polymer composites display good 3D printability, and the 3D-printed porous scaffold possesses high compressive strength and modulus. Also, the PLLA/(MCNTs-ZnO)@PDA scaffold can be compressed into a compact size and recover its original shape under NIR light irradiation. This work provides an approach to prepare novel shape-memory polymer composites with multifunctions including high strength, light-induced shape-recovery, antibacterial properties and printability.

Dynamic Viscoelastic Properties of Kenaf Fiber Reinforced Shape Memory Polymer Composites

This paper comprehensively investigates the dynamic viscoelastic behavior of shape memory polymer composites (SMPCs) reinforced with different weight percentages of kenaf fiber (KF) ranging from 0%, 5%, 10%, 15%, 20%, 30% and 40%. The dynamic mechanical behavior of these composites was characterized using dynamic mechanical analysis (DMA) over a range of temperatures. The objective was to determine the optimal fiber content of KF as reinforcement in SMPCs, specifically on viscoelastic response, storage modulus, loss modulus, damping and glass transition behaviour. The results revealed a clear correlation between the KF contents and the dynamic mechanical properties of SMPCs. The storage modulus significantly improves at higher KF content, particularly at elevated temperatures. Additionally, a quantitative assessment of coefficient C demonstrates strong interfacial bonding between fibers and the matrix in samples 30KF and 40KF. These samples also exhibit higher loss modulus and lower tan delta values, providing evidence for the efficacy of KF in enhancing composite properties. Moreover, higher KF contents induce a shift in the glass transition temperature, signifying enhanced in fiber-matrix interaction and thermal stability. The Cole-cole further demonstrates that at higher KF content, the sample surpasses Neat SMPU, presenting compelling evidence of improved matrix-fiber bonding. Statistical analysis through one-way analysis of variance (ANOVA) substantiates the statistical significance of the dynamic mechanical properties across the different weight percentages of KF-SMPCs. Based on these findings, 30KF is the optimal fiber content, balancing mechanical enhancement and feasible fabrication. This decision is grounded in challenges encountered at 40KF, where ensuring composite homogeneity becomes complex. This study contributes to the growing body of knowledge on utilization of natural fibers in development of advanced polymer composites while maintaining eco-sustainability.

4D printed continuous fiber reinforced shape memory polymer composites with enhanced mechanical properties and shape memory effects

Multi-material four-dimensional (4D) printing has gathered significant interest among researchers as an emerging manufacturing technique. In this study, continuous carbon fibers are integrated into shape memory polymers (SMPs) using multi-material co-extrusion 4D printing. This process results in the creation of shape memory polymer composites (SMPCs) characterized by high load-bearing capacity and stimulus responsiveness. Micro-CT scanning is employed to evaluate the internal porosity of SMPCs, based on which the three-dimensional (3D) reconstruction images are generated. Meanwhile, various mechanical tests are implemented, including tensile, three-point bending, and compression tests, to explore the mechanical properties and fracture modes of the 4D printed SMPCs. In addition, the shape memory effect of the 4D printed SMPCs is verified by experiments and finite element simulations. The results demonstrate shape recovery rates higher than 96%. This study offers valuable insights into the fabrication and testing of smart composites with compatible deformation and high load-bearing capacity.

Shape memory polymer composite fabrics with high recovery force and excellent electrothermal drive deformability

AbstractFabric‐reinforced shape memory polymer composites are lightweight, strong, formable, controllable, and suitable for various engineering and innovative applications. This study aims to fabricate and characterize electrothermal dual drive shape memory polymer composite fabrics (SMPCFs) of different densities with three‐dimensional (3D) angle‐interlock structures. The tensile properties, electrothermal properties, recovery forces (both tensile and bending), and shape recovery properties of SMPCFs were evaluated. The SMPCFs exhibited a tensile elongation of over 20% at the transition temperature. SMPCFs can reach transition temperatures when loaded with 2 V. The recovery forces are up to 225 N in tensile recovery force and 3.6 N in bending recovery force. In the shape recovery test, the recovery ratio exceeded 97%. Finally, the demonstration of recovery properties can stimulate the possibilities of SMPCFs in innovation and applications.Highlights Core‐shell structured composite filaments were prepared. 3D angle‐interlock composite fabrics: high strength, electrothermal drive. Tensile recovery force of composite fabrics can be up to 225 N. Elongation at transition temperatures was up to 20%.

Self-Unfolding Properties of Smart Grid-Reinforced Membrane Origami

Origami-based membrane structures have shown great potential to revolutionize the construction of deployable and lightweight space structures in the future. However, the efficient unfolding mechanism puts forward major challenges to the practical realization of space-deployable structures. Here, a smart grid-reinforced membrane origami (SGRMO) is presented. The unfolding action hinges upon the application of forces facilitated by shape memory polymer composites (SMPCs). Subsequent locking action ensues through the restoration of the initial rigidity, accomplished via cooling mechanisms. This novel structure achieves the required lightweight and functionality by employing the grid design concept and effectively reduces the decline in unfolding extent caused by irreversible plastic deformation at the crease. Its recovery properties, including unfolding angle, distance, and surface precision, are experimentally and analytically investigated under different conditions. The results indicate that the structure can be reliably unfolded into the predefined shapes. In the case of Miura-SGRMO, the optimal surface precision is attained when the angle-ψ registers at 30°. The results of this study are expected to serve as the design of ultra-large flexible solar arrays and deployable antenna structures.

Impact of CoFe2O4 Magnetic Nanoparticles on the Physical and Mechanical Properties and Shape Memory Effect of Polylactide

The acceleration in advancements of smart materials and non-contact controlled devices in the field of 4D printing is facilitated by the use of magnetically responsive shape memory polymer (SMP) composites. This study is dedicated to the development of promising shape memory materials based on polylactic acid (PLA) and cobalt ferrite (CoFe2O4) nanoparticles. The activation of the shape memory effect (SME) in magnetic nanoparticle composites was achieved by applying a high-frequency alternating magnetic field (HFAMF). The PLA/CoFe2O4 composites exhibited a remarkable shape recovery ratio (>84%) and underwent rapid heating when exposed to HFAMF. The interaction of these composites with mouse adipose-derived mesenchymal stem cells demonstrated adequate cytocompatibility. The rapid magnetosensitive behavior and high shape recovery characteristics of PLA/CoFe2O4 composites make them promising candidates for biomedical applications.

Development of a laser induced graphene (LIG) and polylactic acid (PLA) shape memory polymer composite with simultaneous multi-stimuli response and deformation self-sensing characteristics.

This study presents the integration of laser-induced graphene (LIG) on a polylactic acid (PLA) substrate to create a novel shape memory polymer composite (SMPC) with multi-stimuli response and deformation self-sensing characteristics. The LIG was initially engraved on a commercial polyimide film and subsequently transferred to the PLA substrate through hot compression. Raman spectra analysis confirmed the successful engraving of the LIG, exhibiting the typical characteristic peaks. Durability tests revealed that the transferred LIG adhered well to the PLA substrate. Additionally, the transferred LIG demonstrated a sheet resistance of 40.3 Ω sq-1, which facilitated the electrical actuation of the LIG/PLA composite through Joule heating, allowing precise temperature control by manipulating the applied electrical power. An optimum electrical power of 0.95 W was identified to rapidly reach the actuation temperature without exceeding 80 °C. The study also demonstrated the LIG/PLA composite's responsiveness to infrared (IR) light, attributed to photothermal conversion behavior of LIG. An optimum IR intensity of 85 mW cm-2 was established for reaching the actuation temperature without surpassing 80 °C. This multi-stimulus functionality was achieved alongside real-time monitoring of the shape recovery ratio, enabled by the piezoresistive properties of LIG, which allowed for recording electrical resistance changes during recovery. This approach eliminates the need for external components and offers a straightforward fabrication process. The ability to actuate and sense deformation using a single, integrated LIG pattern opens new opportunities for developing advanced, multi-responsive, and self-sensing shape memory polymer composites.

Selective near-infrared laser programming for shape-memory polymer–carbon nanotube composite material 4D printing

Abstract Light stimulation can realise the remote control of the deformation of the specific position of 4D printing structure. Shape-memory polymer–carbon nanotube (CNT) composite materials, with outstanding near-infrared photothermal conversion rate and shape-memory ability, is one type of the most popular light responsive smart materials. However, current studies focused on the photothermal effect and shape-memory applications of light-responsive shape-memory polymer composite (SMPC) sheet structures, and there is no research on the photothermal effect in the depth direction of light-responsive SMPC three-dimensional structures. Here, we prepared a UV curable, mechanically robust, and highly deformable shape-memory polymer (IBBA) as the matrix of light responsive SMPC. CNTs were added as photothermal conversion materials. We explore the photothermal effect of near-infrared laser on the surface and depth of IBBA–CNT composites cube. Shape-memory experiments show that different folded shapes can be obtained by selective near-infrared laser programming. Selective near-infrared laser programming three-dimensional movable type plate shows a programming application in depth direction of three-dimensional light-responsive intelligent structure. This research extends the application of near-infrared laser in 4D printing to the depth direction of intelligent structures, which will bring more complex and interesting 4D printing structures in the future.

Effect of kenaf fiber loading on mechanical and morphological properties of polyurethane shape memory polymer composites

Shape memory polymers (SMPs) have captivated researchers and engineers with their unique ability to recover their original shape after deformation. Among SMPs, shape memory polyurethane (SMPU) is promising due to its easy processing, cost-effectiveness, and biocompatibility. Despite its potential, SMPU faces limitations in strength and modulus, hindering structural applications. This study investigates the sustainable improvement of shape memory polymer composites (SMPCs) by integrating kenaf fibers (KF) as a reinforcing material at different percentages, specifically 5%, 10%, 15%, 20%, 30%, and 40% of the composite’s weight. A combination of hand lay-up technique and compression moulding technique was employed for the fabrication process to achieve the desired shape. The results reveal a clear correlation between the KF content and the mechanical properties. Tensile testing reveals improved strength and strain up to 20% KF, peaking at this level but declining at 30% and 40% due to fiber agglomeration and void formation. Scanning electron microscope (SEM) analysis highlights favourable fiber-matrix adhesion at optimal level. By shedding light on the mechanical behaviour of SMPC with KF reinforcements, this study paves the way for developing high-performance composites tailored for shape memory applications.

4D printed biocompatible magnetic nanocomposites toward deployable constructs

Herein, an alternating magnetic field-triggered shape memory polymer composite has been 3D printed as a tissue scaffold that can be remotely deployed at physiological temperatures and can be extended to soft robotics.

Recent Advances in Shape Memory Polymers: Multifunctional Materials, Multiscale Structures, and Applications

AbstractShape memory polymers (SMPs) are one of the primary directions in the development of modern high‐tech new materials, which are integrated with sensing, actuation, information processing, and autonomous deformation. Here, multifunctional shape memory polymers are focused and a detailed introduction to the characteristics of self‐deformation, self‐sensing, self‐healing, and self‐learning is provided. Integrating with other functional materials to form shape memory polymer composites (SMPC), designing and controlling the material structure and organization at the microscale, thereby achieving more precise and controllable shape memory effects and expanding the potential of material applications. Ultimately, it is shown that SMPs and their composites have a wide range of fascinating applications in the fields of robotics, smart clothing, smart textiles, biomedical devices, and wearable technology. SMPs will thus continue to play a significant role in future deeper exploration.

Axial and radial reversibility and energy absorption behaviors of braided shape memory composite thin-walled tubes

Braided shape memory polymer composites (SMPCs), which integrate braided structures with shape memory polymers, are well-known for their superior mechanical properties, reversible deformation, and recovery capabilities. This study focused on exploring the reusable energy absorption capacity of intelligent braided SMPC tubes. The effects of braiding structure on compression modes, mechanical properties, energy absorption, shape memory performance, and repeatability under axial and radial compression have been comprehensively investigated. The results show that SMPC tubes have a shape recovery ratio exceeding 94 % after four cycles. As the number of compressions increased, both the mechanical and energy absorption properties decreased, particularly during the first compression. Higher energy absorption capacity has been observed in SMPC tubes with larger braiding angles, up to 32.51 J, 2.3 times that of pure TPU tubes. These findings offer potential approaches for the development of high-performance reusable protective devices and lightweight intelligent structures.

4D printing of shape memory polymer with continuous carbon fiber

Shape memory polymer composites (SMPCs) have gained attention for their shape memory effects and wide-ranging applications. Understanding the bending shape recovery characteristics of 3D printed SMPCs is crucial for optimizing their performance. This study focuses on investigating the influence of different fiber orientations of continuous carbon fiber (CCF) in thermally stimulated SMPC. By controlling printing parameters and fiber orientation during the 3D printing process, we fabricate tailor-made rectangular composite test specimens. These specimens are subjected to controlled bending above the glass transition temperature of the polymer, inducing temporary deformation. The subsequent shape recovery process is carefully captured through high-speed video. Precise measurements of the bending curvature over time are obtained using the row-by-row image processing technique and analyzed. The shape recovery rate, shape recovery ratio, and shape fixity ratio of the test specimens were evaluated as a function of three CCF layout arrangements as well as fiber infill density embedded in Shape Memory Polymer (SMP) test specimens. The results revealed that the addition of CCF in the polymer matrix has a significant impact on shape memory behavior. Vertically aligned CCF in the SMP matrix improves the shape recovery ratio (92.97% compared to 78.77% of the pure SMP sample), while horizontal alignment of CCF ensures maximum shape fixity ratio (91.78% compared to 66.22% of the pure SMP sample). The cross-aligned CCF sample provides good recovery as well as fixity values. Further, it was observed that the horizontal alignment of CCF yields the fastest recovery performance. The outcome confirms that optimizing the fiber orientation enhances shape memory performance. Also, 40% of fiber infill density had greater shape fixity and overall recovery performance when compared to 30% and 50%. These findings have implications for tailored and high-performance SMPCs in biomedical devices, aerospace components, and robotics. Understanding temporal curvature behavior enables optimizing the design of materials with precise control over shape recovery. This research contributes to the design and optimization of SMPCs for diverse applications.

Design and Optimization of 4D Printed Carbon Fiber Reinforced Poly Lactic Acid Parts Using Fused Deposition Modeling for Shape Memory Applications: A Taguchi Approach

The manufacturing industry has witnessed substantial interest in the advancement of 4D printing technology in recent years. This technology has enabled the production of complex structures with enhanced functionality and adaptability. Fused Deposition Modeling (FDM) has become a preferred technique for 4D printing due to its ease of use, affordability, and versatile nature. To achieve efficient and effective 4D printing, the process parameters must be optimised to ensure the desired shape recovery behaviour of the printed parts. The main objective of this study is to optimize the process parameters for the production of 4D printed components using FDM technology and Carbon Fiber reinforced Poly Lactic Acid (CF/PLA) Shape Memory Polymer Composites (SMPCs). This study examines the shape recovery properties of the printed components by modifying the process parameters, including Infill Density (ID), Geometrical Thickness (GT), and Bending Angle (BA), through the implementation of Design of Experiments (DOE) L9 Orthogonal Array (OA). Utilizing Analysis of Variance (ANOVA) to determine the significant factors and their optimum levels, the process parameters are statistically analysed. The results indicate that ID and GT are the statistically significant parameters, and the optimum levels for parameters includes 20% ID, 1.5mm GT, and 300 BA led to faster shape recovery. This study demonstrates the effectiveness of the Taguchi approach in the design and optimization of the process parameters for 4D printed parts using FDM.

A three-dimensional constitutive equation for shape memory polymer composites considering energy dissipation under single loading–unloading condition

Shape memory polymer composites (SMPCs), composed of shape memory polymers (SMPs) and fabrics, can recover their deformed shapes to initial configurations by changing temperature. The shape recovery energy of the SMPs and the elastic energy of the fabrics are regarded as key points to predict the restored configuration of the SMPCs. In this research, a three-dimensional constitutive equation for SMPCs is newly developed, considering the energy dissipation of fabrics under a single loading–unloading condition. The constitutive equation is derived from Mooney–Rivlin, viscoelastic, and stored strain energy models for SMPs, as well as polynomial functions for fabrics. The Mooney–Rivlin and viscoelastic models describe the time- and temperature-dependent hyperelastic properties, and the stored strain energy model can explain the shape recovery. The polynomial functions are newly proposed to take into account the dissipated energy of fabrics, such as residual deformation and hysteresis effect. Because the elastic energy of fabrics considerably influences the shape recovery of SMPCs, the proposed constitutive equation can accurately predict the recovered configuration. Analyses of SMPCs are conducted using the finite element method and validated by comparing them with the results obtained from experiments. The constitutive equation is used to analyze the shape recovery behaviors of an SMPC skin. The skin can be largely stretched, and the deformed shape can be restored to its initial shape by applying electricity. The SMPC skin is applied to a morphing flap, and its shape-changing behaviors are demonstrated experimentally.

4D printed and multi-stimulus responsive shape memory polymer nanocomposites developed on hydrogen bonding–metal-phenolic sacrificial network: Application for hazardous chemical operations soft robots

Designing 4D printed shape memory polymers (SMPs) with mechanical robust and multi-stimulus responses applied in soft robot holds vast promise. While significant progress has been made in this area, implementing SMP composites with multi-stimulus response capabilities for fused filament fabrication (FFF) 4D printing typically sacrifices the inherent mechanical properties of the materials, limiting the requirements for robust and tough applications of SMP in soft robotics. In this work, Fe3O4 nanoparticles are employed as functional particles, and the "hydrogen bonding–metal-phenolic" sacrificial network in the nanoparticles and polymer is designed to achieve NIR light and magnetic stimulation response without sacrificing the maximum strength and toughness of the 4D printable SMP. The SMP nanocomposite developed from the sacrificial network has a tensile strength of 18.98 MPa and an elongation at break of 897 %, a 40 % increase in strength and 196 % increase in elongation at break compared to SMP nanocomposites with direct Fe3O4 addition. In addition, the shape-programmable soft robot with NIR light and magnetic stimulation response is developed based on 4D printing. The remote precision control and drugs release demonstrates the potential application of 4D printed soft robots in hazardous chemical operations.

Smart Composite Booms for Solar Sails

Composite booms for solar sails have been prototyped by using innovative smart materials. Shape memory polymer composites (SMPCs) have been manufactured by interposing SMP layers between carbon-fiber-reinforced (CFR) plies. A polyimide membrane has been embedded into the CFR-SMPC frame of the sail during lamination. The sail’s size has been limited to 250 × 250 mm2 to allow its testing on Earth. The feasibility of large sail deployments has been shown by prototyping small CFR-SMPC elements to insert only in the folding zones. Numerical simulation by finite element modeling allowed for predicting the presence of wrinkles close to the frame’s vertexes in the cases of large sails under solar radiation pressures. Nevertheless, the frame’s configuration, with SMPC booms at all the edges of the sail membrane, seems to be suitable for drag sails instead of propulsion. On-Earth recovery tests have been performed on 180° folded sails by using flexible heaters. After an initial induction time, the maximum rate was reached with a following drop. In the case of two heaters per folding zone, the angular recovery rate reached the maximum value of about 30 deg/s at the power of 34 W, and full recovery was made in 20 s.

Effect of curing temperature on shape memory properties of graphene oxide‐carbon fiber hybrid‐reinforced shape memory polymer composites

AbstractIn order to study the effect of curing temperature on the shape memory properties (SMPs) of GO‐CF hybrid‐reinforced SMPCs, eight sets of composites were prepared at different curing temperatures (60, 70, 80, 90, 100, 110, 120, and 130°C). The rheological and curing properties of the matrix, and the apparent density, porosity, microstructure, and SMPs of the composite were measured and analyzed, respectively. The results showed that at 100°C, the composite has the highest apparent density (1.52 g/cm3), the lowest porosity (0.47%), the best SMPs, the shape fixed rate of 99.13%, the shape recovery rate of 96.54%, and the maximum shape recovery force (5.15 N). The shape recovery speed and rate of shape recovery are also the fastest. This is because when the curing temperature is 100°C, the viscosity of the matrix can be kept at a low level, and the curing reaction rate is appropriate. This not only ensures that the matrix can be fully infiltrated into the fiber space but also obtains the matrix with appropriate crosslinking degree. Therefore, the microstructure of the prepared composite is ideal, which makes the matrix has a strong ability to restrain the expansion force of the fiber and a high efficiency of the transfer force and heat. Finally, in the test of SMPs, the composite showed higher SMPs. It was concluded that the SMPs of the composites were mainly affected by the infiltration effect of the matrix in the fiber.Highlights The microstructure of the composite was more ideal at 100 °C. The composite with the lowest porosity has the best shape memory properties. The high porosity weakens the heat and force transfer ability of the matrix. The shape memory properties of composites are the best prepared at 100 °C.