Fiber Reinforced Shape Memory Polymer Research Articles

Active vibration control effect of 3D printed cruciform honeycomb laminates based on fiber-reinforced shape memory polymer

Honeycomb structures offer the benefits of being lightweight and having high out-of-face compressive stiffness, making them a popular choice for aerostructures. The present study delineates the design and active vibration control effect for fiber-reinforced cruciform honeycomb laminates (CHLs) characterized by variable parameters. Employing a continuous fiber 3D printer, carbon fiber filament and shape memory polymers (SMPs) were utilized in the fabrication of the specimens. Differential equations of motion for CHLs were deduced from Kirchhoff plate theory. To ascertain their frequency response, these laminates were subjected to a sinusoidal swept frequency excitation. Subsequently, the classical proportional integral derivative (PID) program was employed to scrutinize the efficacy of closed-loop active vibration control on CHLs. The investigation extended to analyzing the impact of active vibration control across laminates with disparate parameters, including an examination of the convergence speed during vibration control procedures. A comparative analysis of simulated versus experimental data revealed a substantial consonance between the two, thereby corroborating the accuracy of the experimental findings. This study offers crucial insights and reference value for the utilization of CHLs in the aerospace industry.

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.

Four-Dimensionally Printed Continuous Carbon Fiber-Reinforced Shape Memory Polymer Composites with Diverse Deformation Based on an Inhomogeneous Temperature Field.

Four-dimensionally printed continuous carbon fiber-reinforced shape memory polymer composite (CFSMPC) is a smart material with the ability to bear loads and undergo deformation. The deformation of CFSMPC can be driven by the electrothermal effect of carbon fibers. In this study, the effect of temperature on the shape memory recovery performance of polylactic acid (PLA) was first studied experimentally. Continuous carbon fibers were incorporated into PLA to design CFSMPCs with thickness gradients and hand-shaped structures, respectively. The distribution strategy of the carbon fibers was determined based on simulations of the electrically driven shape recovery process of the aforementioned structures. Both the simulations and experiments demonstrated that the electrification of the CFSMPC structures resulted in an inhomogeneous temperature field, leading to distinct deformation recovery processes. Eventually, a precise unfolding was achieved for the thickness gradient structure and the five fingers in the hand-shaped structure by utilizing a safe voltage of 6 V. This demonstrates that the 4D-printed CFSMPC with diverse deformations based on an inhomogeneous temperature field has potential applications in actuators, reconfigurable devices, and other fields.

Damage behavior analysis of unidirectional fiber reinforced shape memory polymer composites

Shape memory polymer composites (SMPCs) are gradually being used in space deployable structures due to their unique shape memory properties and variable stiffness characteristics. Currently, the damage behavior of SMPC has not been systematically investigated, which affects its structural design and application. In this study, the damage behavior analysis of unidirectional fiber-reinforced SMPCs was investigated. The buckling deformation and damage modes of SMPC were analyzed theoretically. The strain energy of the matrix cracking and fiber fracture damage system was developed considering the compressive strain of the matrix. Additionally, the analytical expressions of the key parameters during bending were determined and the law of evolution was revealed. The damage mode analysis showed that decreasing fiber volume content and increasing thickness were more likely to result in matrix cracking damage. The fiber fracture would occur in the stretching region if the fiber volume content was less than a certain value. Finally, the experiment was performed to demonstrate the validity of the theoretical method. This work is significant for the design and optimization of the SMPC-based structure.

Buckling behavior and damage mechanism analysis of fiber-reinforced shape memory polymer composites

Shape memory polymer composites (SMPCs) are emerging as an attractive material for space deployable structures due to their variable stiffness, programmable deformation, high packing ratio, and controllable deployment. However, the research on the deformation behaviors and damage mechanisms of SMPC was scarce. The buckling behaviors and damage mechanisms of out-of-plane buckling and in-plane buckling of fiber-reinforced SMPC were investigated in this study. The expression and evolution law of strain energy and key parameters of fiber buckling were studied. The effects of material parameters and size parameters on damage mode and critical damage curvature were analyzed quantitatively. It was found that in-plane buckling was more likely to occur without external constraints. The damage modes of in-plane buckling are classified as delamination, matrix cracking and fiber tensile fracture. Out-of-plane buckling is more susceptible to damage and has one more fiber buckling fracture damage mode than in-plane buckling. When the fiber volume content is below a certain value, only fiber tensile fracture damage mode will appear, regardless of the thickness. Delamination is more likely to occur in cases of out-of-plane buckling, and matrix cracking is more frequent in cases of in-plane buckling. Subsequently, the correctness of the theoretical analysis was verified by the bending test. The theoretical analysis in this study provides a theoretical foundation for SMPCs-based structural design.

Microbuckling behavior of unidirectional fiber-reinforced shape memory polymer composite undergoing compressive deformation

The microbuckling mechanics of unidirectional fiber-reinforced shape memory polymer composite (SMPC) with low fiber volume fraction were investigated, and the mechanical models were formulated considering the attenuation of shear strain in the resin matrix near the buckled fibers. We deduced the analytical expression of the attenuation function and the key parameters during the microbuckling process of SMPC, including the critical buckling wavelength and strain. The values determined by finite element analysis verified the accuracy of the above theoretical predictions. The nonlinear stress–strain relationship during the post-buckling process was also investigated. Additionally, the classical elastic–viscoelastic correspondence principle was established to determine the dynamic buckling behaviors of SMPC at different temperatures. The viscoelastic parameters of shape memory polymer (SMP) were obtained from the isothermal stress relaxation experiments, and then the variation of buckling wavelength with time at different temperatures was evaluated.

Distributed sensing based real‐time process monitoring of shape memory polymer components

AbstractShape memory polymer (SMP) materials have the capacity to undergo large deformations imposed by mechanical loading, hold a temporary shape, and then recover their original shape upon exposure to a particular external stimulus. The fiber reinforced shape memory polymer composites (SMPCs) with enhanced structural performances give a boost to breakthrough technologies for large‐scale engineering applications. This article presents a novel technique for distributed optical fiber sensor (DOFS) embedded SMPCs intended for real‐time process monitoring of large‐scale engineering applications such as deployable space structures. Herein a carbon fiber reinforced SMPC was tested under a three‐point flexural shape memory process and the DOFS data were acquired through optical backscatter reflectometry. Experiments were conducted in a temperature controlled thermal chamber coupled with a 10 kN electromechanical testing system. DOFSs offered unique advantages for spatially distributed dynamic temperature and strain measurements during the shape memory process. Compared to the standard test method dynamic mechanical analysis, larger samples can be tested effectively by using a single DOFS with large strain levels and shape complexity. The proposed technique demonstrated the ability of embedded DOFSs for in‐situ shape memory characterization such as shape fixity ratio, shape recovery ratio and recovery rate. This technique will eliminate the challenges hindering the process monitoring and performance evaluation of large SMPC components operating in their real working environments.

Accelerated Testing Method for Predicting Long-Term Properties of Carbon Fiber-Reinforced Shape Memory Polymer Composites in a Low Earth Orbit Environment.

Carbon fiber-reinforced shape memory polymer composites (CF-SMPCs) have been researched as a potential next-generation material for aerospace application, due to their lightweight and self-deployable properties. To this end, the mechanical properties of CF-SMPCs, including long-term durability, must be characterized in aerospace environments. In this study, the storage modulus of CF-SMPCs was investigated in a simulation of a low Earth orbit (LEO) environment involving three harsh conditions: high vacuum, and atomic oxygen (AO) and ultraviolet (UV) light exposure. CF-SMPCs in a LEO environment degrade over time due to temperature extremes and matrix erosion by AO. The opposite behavior was observed in our experiments, due to crosslinking induced by AO and UV light exposure in the LEO environment. The effects of the three harsh conditions on the properties of CF-SMPCs were characterized individually, using accelerated tests conducted at various temperatures in a space environment chamber, and were then combined using the time–temperature superposition principle. The long-term mechanical behavior of CF-SMPCs in the LEO environment was then predicted by the linear product of the shift factors obtained from the three accelerated tests. The results also indicated only a slight change in the shape memory performance of the CF-SMPCs.

Flexural analysis of thermally actuated fiber reinforced shape memory polymer composite

Shape Memory Polymer Composites (SMPC) have gained popularity over the last few decades due to its flexible shape memory behaviour over wide range of strains and temperatures. In this paper, non-linear bending analysis has been carried out for SMPC beam under the application of uniformly distributed transverse load (UDL). Simplified C0 continuity Finite Element Method (FEM) based on Higher Order Shear Deformation Theory (HSDT) has been adopted for flexural analysis of SMPC. The numerical solutions are obtained by iterative Newton Raphson method. Material properties of SMPC with Shape Memory Polymer (SMP) as matrix and carbon fibre as reinforcements, have been calculated by theory of volume averaging. Effect of temperature on SMPC has been evaluated for numerous parameters for instance number of layers, aspect ratio, boundary conditions, volume fraction of carbon fiber and laminate stacking orientation. Moreover, deflection profile over unit length and behavior of stresses across thickness are also presented to elaborate the effect of glass transition temperature (Tg). Present study provides detailed explanation on effect of different parameters on the bending of SMPC beam for large strain over a broad span of temperature from 273-373K, which encompasses glass transition region of SMPC.

Modeling the laminated carbon fiber reinforced shape memory polymer composites by using a refined plate theory

Laminated carbon fiber reinforced shape memory polymer composites (CFRSMPCs) have the advantages of simple structures and flexible properties in achieving a high loading capacity and novel shape memory effects. Because the mechanical properties of the laminated CFRSMPCs decrease rapidly during the process of carbon fiber failure, it should be avoided in application. To address this issue, modeling approach for the laminated CFRSMPCs is proposed by using a refined sinusoidal shear deformation plate theory (RPT) together with the simplified constitutive model of the CFRSMPCs, for the first time. Because the carbon fiber is liable to buckle under compression in the soft SMP matrix, the buckling behavior is studied here. For comparison, the pre-buckling loading capacities of the simply supported plates with different components are simulated. Furthermore, the effect of raising fiber volume fraction or adding layers on the loading capacity is studied. Therefore, this study provides useful guidance for reasonable design of laminated CFRSMPCs.

Effect of Molding Temperature on Shape Memory Performance of SMPC

Carbon fiber reinforced shape memory polymer composite (SMPC) is a kind of smart material with shape memory characteristics, which is widely used in aerospace, biomedicine, robotics and other fields. In this paper, SMPC was prepared by heating molding process at five different molding temperatures. The effect of molding temperature on the shape memory performance of SMPC was studied. The results show that the shape memory properties of SMPC are closely related to the infiltration effect during the preparation process. When the molding temperature is 70 °C, SMPC has an optimum penetration effect and the preparation defects are effectively controlled. The shape fixing rate is 84.3%, and the shape recovery rate is 94.7%, which lays a foundation for the better application of shape memory composite.

Temperature dependence of elastic constants in unidirectional carbon fiber reinforced shape memory polymer composites

The work describes a model to predict the elastic constants of unidirectional carbon fiber reinforced shape memory polymer composites (SMPCs) with different fiber volume fractions within the temperature range of 293 K to 393 K. The model is based on a theoretical description of the phase transition of the shape memory polymer (SMP). Two glassy phase volume fraction functions are developed, one based on the Eyring equation, the other based on the normal distribution equation. The longitudinal and transverse moduli, axial and transverse shear moduli, and axial Poisson's ratio are derived by using the glassy phase volume fraction function and modified rule of mixture. The axial Poisson's ratio increases with the temperature increase, while the other four constants decrease nonlinearly with rising temperatures. An inverse identification of the elastic constants at different temperature via numerical and experimental modal analysis from a flat SMPC laminate shows that the model proposed is adequate to describe the temperature dependence of the elastic constants of the laminate.

4D printed electro-induced continuous carbon fiber reinforced shape memory polymer composites with excellent bending resistance

Four-dimensional (4D) printing technology of continuous carbon fiber reinforced shape memory polymer composites is a potential manufacturing process for lightweight and high-strength intelligent composite structures. In this study, a 3D printer with dual feed channels based on the fused deposition modeling (FDM) was designed to fabricate continuous carbon fiber reinforced shape memory poly(lactic acid)-based composites (CFRSMPC). The impact of various printing parameters on the bending strength and flexural modulus of 4D printed CFRSMPC was evaluated by the three-point bending test. Meanwhile, mathematical prediction models of bending strength and modulus based on the existing experimental data were established. The electro-induced shape memory effect of 4D printed CFRSMPC was investigated by the electric heating shape recovery test. The shape recovery rate of the specimens was more than 95%, indicating that the resistance heating method is stable and feasible. The quantitative effect of bending angle and temperature on the resistance of CFRSMPC during the programming and recovery process was further investigated. The results demonstrated that the real-time deformation of the CFRSMPC could be monitored by the resistance measurement method. It can be concluded that the CFRSMPC fabricated using the 4D printing method can serve as potential building blocks for electrically activated and deployable structures.

Modeling the thermomechanical behavior of carbon fiber–reinforced shape memory polymer composites under the finite deformation

In this article, a thermoviscoelastic constitutive model is introduced to describe the unidirectional continuous elastic fiber–reinforced shape memory polymer composites under the finite deformation. Although the shape memory polymers can be used in finite deformations, only a small strain can be applied on the carbon fiber for its small failure tensile strain (about 2%). Using the model, the effective strain of the carbon fiber for the unidirectional continuous carbon fiber–reinforced shape memory polymer composites can be derived. It is found that the carbon fiber–reinforced shape memory polymer composites with the fiber inclination angle in a typical range can be used in the finite deformation, without failure of the carbon fiber. Besides, a simplified buckling model is proposed to predict the fiber buckling under axial compression. It is calculated that the buckling critical stress is rather small. Therefore, it should be avoided in application. As for carbon fiber–reinforced shape memory polymer composites, the bending driving capacity is the crucial property in their applications. Hence, the shape memory effect of the carbon fiber–reinforced shape memory polymer composite beam under the finite deformation is also studied here. The findings can be used to provide guidance for the design and application of the carbon fiber–reinforced shape memory polymer composites and their structures.

Ultra-light release device integrated with screen-printed heaters for CubeSat’s deployable solar arrays

Deployable solar arrays can improve the potential utilization of CubeSats by generating sustainable energy. This paper presents an ultra-light release device integrated with screen-printed heaters to latch and release CubeSat’s solar arrays in the sequence of structure and material design, fabrication, and experimental verification. Finite element analysis of interference fit gives the locking force and maximum Von Mises stress variation with the interference and thickness, which provides the selection basis for geometrical parameters of the release device. Tensile and fracture toughness tests have been conducted to verify improved toughness for spandex fiber reinforced shape memory polymer composites (SMPCs). And the fine denier fiber shows a better toughness improvement performance. DMA tests have been performed to give the temperature sensitivity of the materials. Besides, locking forces obtained from finite element analysis and experiments show good consistency. Moreover, recovery tests confirm the release device with good shape recovery properties and excellent adaptability to energizing conditions. Finally, experiments on a CubeSat prototype qualify the release device with good feasibility, reliable locking performance and satisfactory reusability. This work is expected to provide an effective miniaturized hold-release mechanism for deployable structures.

Modeling the thermomechanical behaviors of short fiber reinforced shape memory polymer composites

Short fiber reinforced shape memory polymer composites (SF-SMPCs) possess better mechanical properties compared to pure shape memory polymers, and in the meantime, keep the high deformability and the good shape memory properties. In the paper, a thermoviscoelastic finite deformation constitutive model is developed for thermally activated SF-SMPCs. The key of the model is the modified temperature-dependent laminate analogy theory for the prediction of the thermal-dependent effective elastic properties of the composites of different fiber volume fractions. The constitutive theory is based on a generalized three-element model consisting of a hyperelastic branch and a viscoelastic branch, in which the volume fraction dependent yielding properties are described by a modified Eying model. The developed constitutive model is then implemented into Mathematica to simulate the thermomechanical behaviors of the materials under different loadings, and the simulation results show great agreements with the experimental data. Finally, the shape memory effects of the SF-SMPCs are studied by a typical free-recovery thermomechanical cycle. The shape fixity and shape recovery speed are slightly influenced by the reinforcements, and the shape recovery ratios are almost 100% for all SF-SMPCs. The paper offers an efficient method to theoretically describe and predict the thermomechanical behaviors of SF-SMPCs.

Modeling the shape memory and strength properties of fiber-reinforced shape memory polymer composite laminates

Shape memory polymer composites (SMPCs) are one of the promising material candidates applied in the fields of aerospace and biomedicine. The shape memory and strength properties of SMPCs are very important in engineering structures based on the material. In the paper, an efficient generalized Maxwell model is developed to describe the constitutive relations of the pure shape memory polymers under small deformation at first, and then extended to predict the thermomechanical properties of the SMPCs based on the bridge micromechanics model. The simulation results show that the SMPCs possess remarkable shape memory performance and enhanced mechanical properties. Thereafter, the strength properties of the matrix and the composites, as well as the effects of fiber contents, temperatures and loading angles, are studied in detail based on the polymer strength theory, the composite bridge model and the Tsai-Hill criterion. The present micromechanical model provides an efficient method for designing and optimizing SMPCs.

Study on 3D printing process of continuous carbon fiber reinforced shape memory polymer composites

In this paper, shape memory polymer (SMP) and continuous carbon fibers (CCF) were utilized as raw materials to manufacture composites by means of 3D printing based on FDM. Various process parameters were systematically studied by the orthogonal experiment to find out the optimal process combination where interfaces and mechanical properties of printed composites specimens were treated as research objectives. The influence of each factor on the performance of the specimen was discussed. The results indicated that the mechanical properties were preferable when the printing temperature was 200°C, the printing speed was 4.5mm/s, the scanning pitch was 1.1 mm, and the ply stacking sequence was 0°. Furthermore, the fiber content had little effect on the shape memory performance of the polymer matrix. The rapid manufacture of shape memory carbon fiber composites has potential use in the field of aerospace.

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

Shape memory polymer composites (SMPCs) can be used to improve the mechanical properties of the shape memory polymers (SMPs). They also have the potential to enhance or enable new stimulus approaches and novel shape memory effects (SMEs). In this paper, a thermoviscoelastic finite deformation constitutive model is developed for thermally activated unidirectional continuous elastic fiber reinforced SMPCs. Since the structural relaxation and viscous flow mainly exist in the SMP matrix, an internal state variable modeling approach is used to describe the thermomechanical behavior of the SMPCs. Recent works mainly focus on the thermomechanical behavior of carbon fiber reinforced SMPCs in the small strain range, for the tensile tolerant strain of carbon fiber is small. The model that is developed here shows that the unidirectional continuous carbon fiber reinforced SMPCs with proper fiber inclination angle and volume fraction can also be used in finite deformation range for the first time. The finite deformation thermomechanical response of unidirectional continuous carbon fiber reinforced SMPCs with different inclination angles and volume fractions is addressed here. Therefore, this study provides useful guidance for reasonable design of unidirectional continuous elastic fiber reinforced SMPCs.

Constitutive modelling of carbon fiber-reinforced shape memory polymer composites

Shape memory polymer (SMP) is one of smart polymers which exhibit shape memory effect upon external stimuli such as heat, moisture, electricity etc. To overcome low mechanical properties of SMP, a woven carbon fiber-reinforced shape memory polymer composite (SMPC) has been proposed. However, the prediction of the mechanical behavior of woven carbon fiber-reinforced SMPC is not routine due to anisotropy and multidimensional deformation during bending or unfolding. In this study, a 3D constitutive model of woven carbon fiber reinforced SMPC was developed based on phenomenological three elements in parallel; rubbery and glassy phases and anisotropic fiber part. To treat the anisotropic behavior of woven fabric reinforcement such as high stiffness with slight nonlinearity in the warp and weft directions and nonlinear shear behavior, an anisotropic hyperplastic constitutive model was used that decompose total strain energy into warp and weft stretching and fabric shearing energies. Finally, 3D constitutive equation was obtained by summing the stresses resulting from rubbery and glassy phases and fiber part considering interface effect between matrix and fiber. The developed equation was implemented into COMSOL software. Finally, shape memory bending and anisotropic behavior of woven carbon fiber-reinforced SMPCs was simulated.