Nonlinear Mechanical Properties Research Articles

Temperature-dependent mechanical properties and crystal plasticity parameters for additively manufactured Haynes-214 alloy: Experiments and numerical modeling

Our experimental mechanical testing data demonstrated that the additively manufactured (AM) laser powder bed fusion (L-PBF) Haynes-214 alloy exhibits non-linear mechanical properties as the temperature rises from ambient to 870 °C. To gain a deeper insight into the microstructure–property linkages under thermomechanical loading, it is essential to use crystal plasticity (CP) simulations. This approach can reduce the need to conduct expensive high-temperature experimental mechanical testing and account for crystallographic texture and grain morphology effects, which are known to be important in many AM processed materials. However, calibrating a CP model is time-consuming because individual simulations are computationally expensive and hundreds (or more) of iterations over parameter sets may be required. To address this issue, we have designed a machine learning - differential evolution (ML-DE) CP framework that can accurately interpolate the tensile properties of AM L-PBF Haynes-214 alloy across a wide temperature range from ambient to 870 °C, with minimal reliance on experimental data. The framework uses electron backscatter diffraction (EBSD) measurements to generate statistically equivalent microstructural volume elements to serve as inputs to the CP modeling framework. Stress–strain curves were generated from 1000 CP simulations, which serve as the training data set for the three ML regression algorithms explored: linear, extra-trees, and multi-layer perceptron. These three regression models were independently evaluated to compare their efficiency and identify the most suitable algorithm for the given problem. Results revealed that the extra-trees ML regressor outperforms the other models in both qualitative and quantitative aspects with an R2 of 0.98. Subsequently, the differential evolution optimization approach is employed to calibrate the ML-based CP material parameters with experimental results obtained at various temperatures. Finally, temperature-dependent CP material parameters are formulated. The effectiveness and efficiency of the designed framework are validated through comparison with experimental results, demonstrating a high degree of agreement. These calibrated parametric constitutive equations enable further use of the CP model to study the deformation behavior of this alloy under a wide range of thermo-mechanical loading and service conditions.

Development of a Novel Transonic Fan Casing Making Use of Rapid Prototyping and Additive Manufacturing

Additive manufacturing (AM) presents significant cost savings and lead time reductions because of features inherent to the manufacturing process. The technology lends itself to rapid prototyping due to the streamlined workflow of quickly implementing design changes. Compared to traditional machining, AM techniques are simpler in execution for design engineers because they do not require detailed engineering drawings and they typically make use of the nominal geometry in computer models. A novel transonic fan casing assembly has been developed that makes use of AM inserts surrounding the rotor to provide an opportunity to cost-effectively change the corresponding flowpath. The rapid prototyping design philosophy developed from this work will allow for numerous experimental studies into the effects that different design parameters of casing geometries have on fan aerodynamic performance. A fan stage representative of a small turbofan engine was successfully tested with smooth-walled, additively manufactured inserts as a baseline case for future configurations. Before installing the 3D printed casing assembly, computational thermal stress analysis was performed to reduce the risk in implementation due to the demanding environment associated with the rotor. AM components and materials typically have nonlinear mechanical properties, adding to the complexity of the structural analysis. As part of the research, steady aerodynamic performance was measured over the entire relevant operating range of the fan.

Squid-Inspired Anti-Salt Skin-Like Elastomers With Superhigh Damage Resistance for Aquatic Soft Robots.

Cephalopod skins evolve multiple functions in response to environmental adaptation, encompassing nonlinear mechanoreponse, damage tolerance property, and resistance to seawater. Despite tremendous progress in skin-mimicking materials, the integration of these desirable properties into a single material system remains an ongoing challenge. Here, drawing inspiration from the structure of reflectin proteins in cephalopod skins, a long-term anti-salt elastomer with skin-like nonlinear mechanical properties and extraordinary damage resistance properties is presented. Cation-π interaction is incorporated to induce the geometrically confined nanophases of hydrogen bond domains, resulting in elastomers with exceptional true tensile strength (456.5 ± 68.9MPa) and unprecedently high fracture energy (103.7 ± 45.7kJ m-2). Furthermore, the cation-π interaction effectively protects the hydrogen bond domains from corrosion by high-concentration saline solution. The utilization of the resultant skin-like elastomer has been demonstrated by aquatic soft robotics capable of grasping sharp objects. The combined advantages render the present elastomer highly promising for salt enviroment applications, particularly in addressing the challenges posed by sweat, in vivo, and harsh oceanic environments.

Non-linear stress-softening of the bacterial cell wall confers cell shape homeostasis.

The bacillus - or rod - is a pervasive cellular morphology among bacteria. Rod-shaped cells elongate without widening by reinforcing their cell wall anisotropically to prevent turgor pressure from inflating cell width. Here, we demonstrate that a constrictive force is also essential for avoiding pressure-driven widening in Gram-positive bacteria. Specifically, super-resolution measurements of the nonlinear mechanical properties of the cell wall revealed that across a range of turgor pressure cell elongation directly causes width constriction, similar to a "finger trap" toy. As predicted by theory, this property depends on cell-wall anisotropy and is precisely correlated with the cell's ability to maintain a rod shape. Furthermore, the acute non-linearities in the dependence between cell length and width deformation result in a negative-feedback mechanism that confers cell-width homeostasis. That is, the Gram-positive cell wall is a "smart material" whose exotic mechanical properties are exquisitely adapted to execute cellular morphogenesis.

Microstructure size and packing of fracture surface on the nonlinear breakage mechanical response of different marbles under cyclic loading

The microstructural properties of fracture surfaces are a remarkable reflection of the nonlinear mechanical properties of rocks, which have not been thoroughly evaluated to date. In order to understand the contributions of microstructure size and packing to the nonlinear mechanical response, both micro- (field emission scanning electron microscopy (SEM) experiments on failure specimen section) and macro-scale (unequal amplitude cycle experiment) tests were carried out on different marbles. The size and arrangement properties of microstructures on the fracture surface were determined using digital image recognition technology based on micro-scale experiments. Remarkable differences were observed among different types of marble in terms of breakage evolution, fracture combining form, and nonlinear evolution of energy. The micro-deformation of marbles is characterized by the deformation distribution and microstructure inhomogeneity in strong deformation zones of failure. The microstructures of brittle-ruptured marbles exhibit mechanical fragmentation and fracture of mineral grains. The ductile deformation of marble is characterized by the presence of solid flow traces within the mineral crystals, as well as the loose arrangement of mineral crystal grains in the strongly deformed zones. The constitutive model for marble samples with fine mineral crystals can be derived by nonlinearly separating the Helmholtz free energy during the breakage process and defining the relationship between breakage force and dissipated energy in the absence of residual strength after fracture. The obtained nonlinear breakage constitutive equation is in good agreement with the experimental results. These findings may provide basis and inspiration for engineering construction and geological disaster prevention.

Voxel Design of Grayscale DLP 3D-Printed Soft Robots.

Grayscale digital light processing (DLP) printing is a simple yet effective way to realize the variation of material properties by tuning the grayscale value. However, there is a lack of available design methods for grayscale DLP 3D-printed structures due to the complexities arising from the voxel-level grayscale distribution, nonlinear material properties, and intricate structures. Inspired by the dexterous motions of natural organisms, a design and fabrication framework for grayscale DLP-printed soft robots is developed by combining a grayscale-dependent hyperelastic constitutive model and a voxel-based finite-element model. The constitutive model establishes the relationship between the projected grayscale value and the nonlinear mechanical properties, while the voxel-based finite-element model enables fast and efficient calculation of the mechanical performances with arbitrarily distributed material properties. A multiphysics modeling and experimental method is developed to validate the homogenization assumption of the degree of conversion(DoC) variation in a single voxel. The design framework is used to design structures with reduced stress concentration and programmable multimodal motions. This work paves the way for integrated design and fabrication of functional structures using grayscale DLP 3Dprinting.

Multiscale modeling for the impact behavior of 3D angle-interlock woven composites

In this paper, a multiscale modeling framework predicting the impact response of three-dimensional angle-interlock woven composites (3DAWCs) is presented. Multiscale modeling is performed sequentially at the mirco, meso, and macroscales. A microscopic representative volume element (RVE) model is established to characterize the yarn's nonlinear mechanical properties and damage behavior at different strain rates. At the mesoscale, a novel subcell-based discretization scheme is proposed to discretize 3DAWCs, and developing six representative subcells (RSCs) that bridge the microscale and macroscale effective properties. Based on it, a ballistic impact model involving six kinds of homogeneous material bricks is established. Furthermore, elastic-viscoplastic damage constitutive models are developed for the epoxy matrix and the yarn, respectively, to enhance the predicted accuracy of the multiscale model. Ballistic impact tests of 3DAWCs are conducted, and X-ray micro-computed tomography is employed to evaluate the internal damage of the 3DAWC target after impact. Validation work is conducted by comparing the experimental and numerical results of the ballistic impact of the 3DAWC target, which indicates the effectiveness and efficiency of the developed multiscale framework in the impact damage prediction of 3DAWCs.

Bilinear stiffness and bimodular Poisson's ratio in cylindrical sinusoidal lattices through topology morphing

Bilinear elastic behaviour allows structural designs to respond in either a stiff or compliant manner depending on the load. Here a cylindrical sinusoidal lattice structure is described that stiffens beyond a certain load. When subjected to axial compression, the lattice can undergo a topological transformation by forming contact connections. This topology change involves a transition from rectangular-like unit cells to kagome-like unit cells, associated with an approximately fourfold increase in stiffness. The lattice exhibits negative Poisson's ratio with a step-change from ≈−0.66 to ≈−0.23 prior to and during contact formation, respectively. After contact formation, it displays a nonlinear Poisson's ratio behaviour. The mechanics underpinning these behaviours are analysed using a combination of experiments and numerical modelling. A comparison with similar planar lattices reveals the effect of the global topology of the lattice (e.g. planar, cylindrical) on the unit cell-level topology morphing. The proposed topology-morphing cylindrical sinusoidal lattice introduces new design possibilities in the application-rich context of tubular structures with nonlinear mechanical properties.

Micro-tensile rheology of fibrous gels quantifies strain-dependent anisotropy

Semiflexible fiber gels such as collagen and fibrin have unique nonlinear mechanical properties that play an important role in tissue morphogenesis, wound healing, and cancer metastasis. Optical tweezers microrheology has greatly contributed to the understanding of the mechanics of fibrous gels at the microscale, including its heterogeneity and anisotropy. However, the explicit relationship between micromechanical properties and gel deformation has been largely overlooked. We introduce a unique gel-stretching apparatus and employ it to study the relationship between microscale strain and stiffening in fibrin and collagen gels, focusing on the development of anisotropy in the gel. We find that gels stretched by as much as 15 % stiffen significantly both in parallel and perpendicular to the stretching axis, and that the parallel axis is 2–3 times stiffer than the transverse axis. We also measure the stiffening and anisotropy along bands of aligned fibers created by aggregates of cancer cells, and find similar effects as in gels stretched with the tensile apparatus. Our results illustrate that the extracellular microenvironment is highly sensitive to deformation, with implications for tissue homeostasis and pathology. Statement of significanceThe inherent fibrous architecture of the extracellular matrix (ECM) gives rise to unique strain-stiffening mechanics. The micromechanics of fibrous networks has been studied extensively, but the deformations involved in its stiffening at the microscale were not quantified. Here we introduce an apparatus that enables measuring the deformations in the gel as it is being stretched while simultaneously using optical tweezers to measure its microscale anisotropic stiffness. We reveal that fibrin and collagen both stiffen dramatically already at ∼10 % deformation, accompanied by the emergence of significant, yet moderate anisotropy. We measure similar stiffening and anisotropy in the matrix remodeled by the tensile apparatus to those found between cancer cell aggregates. Our results emphasize that small strains are enough to introduce substantial stiffening and anisotropy. These have been shown to result in directional cell migration and enhanced force propagation, and possibly control processes like morphogenesis and cancer metastasis.

Gas-Spring Quasi-Zero Stiffness Air Damping Isolator for Vertical Vibration Control of Indoor Substation Excited by Metro Loads

To mitigate the metro-induced vertical vibration of the indoor substation structure, this study proposes a gas-spring quasi-zero stiffness air damping isolator (AD-QZSI) with excellent low dynamic stiffness and high-static stiffness characteristics. The working principle and mechanical properties of the AD-QZSI are introduced and studied through theoretical and numerical methods. A model for substation considering soil–structure–equipment interaction is established using the software ABAQUS, its accuracy is validated based on a series of measured data from actual projects, and the AD-QZSI’s simulation method and parameter design method are described in detail. The air damper’s stiffness [Formula: see text] is integrated into the isolator’s mechanical model, theoretically and numerically achieving an accurate simulation of AD-QZSI’s nonlinear mechanical properties. The numerical results have an error of less than 5% with the measured data, indicating that the model is able to better capture the actual structure’s dynamic characteristics and is reasonable to be employed for subsequent analysis. Numerical results show that AD-QZSI can significantly reduce the structural vertical vibration, and its control effect is better in the whole frequency band, in particular, the effect is also visible in the low-frequency band, indicating that its vibration isolation frequency band is wider than that of traditional QZS isolator. With the vibration source distance increasing, the control effect of AD-QZSI presents a tendency to decrease and then level off, and its vibration isolation gain is weakened by the continuous increase of the damping ratio greater than 0.01. Moreover, the equipment’s dynamic amplification factor of the isolated structure decreases significantly. Finally, the proposed AD-QZSI can obtain ideal quasi-zero stiffness characteristics by adjusting the air pressure, and the adopted air damper belongs to the green low-carbon components, featuring great practical value and application prospects.

Bioinspired multilayer braided structure with controllable nonlinear mechanical properties for artificial ligaments

Inspired by “crimped” collagen fiber, which induce a low-level load region within the hierarchical structures of ligaments and tendons, this study introduces a braiding technology aiming at characterizing nonlinear mechanical behavior. Samples of the developed artificial ligament with a multilayer braided structure were fabricated and tested. Alterations in the number of braiding layers, wales, and courses significantly affect the mechanical properties of the artificial ligaments. Specifically, the toe length exhibited an increase of up to 104.58 %, while the linear stiffness exhibited variations concomitant with changes in these parameters. Additionally, a mathematical model to describe the relationship between the toe length and linear stiffness was developed based on the braiding parameters and material properties of the fibers. Alternative fibers were employed and tested to demonstrate a consistency with the mathematical model. The correlation coefficients were calculated as 0.9644 for the toe length and 0.9203 for the linear stiffness. Lastly, this study mimics the mechanical behavior of the human medial collateral ligament (MCL) by integrating the artificial ligament into a bio-fidelity knee model with a joint stiffness of 1.77 Nm/deg, resulting in a high degree of similarity with human knee in valgus-varus, further affirming the utility and applicability of this study.

Propagation of solitary waves in origami-inspired metamaterials

We propose a design strategy for creating origami-like mechanical metamaterials with diverse non-linear mechanical properties and capable of remote actuation. The proposed triangulated cylindrical origami (TCO)-inspired metamaterials enable the highly desirable strain-softening/hardening and snap-through behaviors via a multi-material and highly deformable hinge design. Moreover, we couple these novel non-linear mechanical properties of the TCO origami-inspired metamaterials with the transformative ability of hard-magnetic active materials, allowing for untethered shape- and property-actuation in the developed metamaterials. We develop a mathematical modeling framework for the proposed TCO origami-inspired metamaterials, building on approximating the highly deformable hinges as a combination of longitudinal and rotational springs. We validate the accuracy of the developed mathematical modeling approach by comparing the analytically predicted compressive response of a unit cell structure with the corresponding numerical and experimental results. Using the developed mathematical modeling framework, we investigate the magnetic field-induced large deformation and superimposed solitary wave propagation in the TCO origami-inspired metamaterial system. We show that the proposed metamaterial allows us to tune the key characteristics of the enabled non-linear solitary waves, including their characteristic width and amplitude. The proposed design strategy for readily manufacturable origami-inspired metamaterial systems paves a novel path for practical engineering applications. Our studies also underscore the potential of magneto-mechanical interaction in the design of reconfigurable metamaterial systems with superior non-linear mechanical and elastic wave properties.

Nonlinear dynamic analysis of opto-electro-thermo-elastic perovskite plates

AbstractPhotostrictive materials have attracted tremendous interest as the new generation of smart materials that can achieve a direct conversion from optical energy to mechanical energy. Understanding their nonlinear mechanical properties under light illumination is of paramount significance for their realistic optomechanical applications. This article proposes a novel opto-electro-thermo-elastic constitutive model that can consider the effects of photostriction, photothermal temperature, and electrostriction for metal halide perovskite crystals and investigates the nonlinear static and dynamic responses of the perovskite plates. The nonlinear governing equations are established based on the first-order shear deformation theory and von Kármán nonlinearity and are numerically solved by the differential quadrature method. A detailed parametric investigation is performed to analyze the effects of light and electricity on the nonlinear mechanical behaviors of perovskite plates. It is concluded that light illumination leads to the presence of optical stress and thermal stress in the perovskite plates, giving rise to increased static and dynamic deformations and stresses, as well as reduced postbuckling and free vibration characteristics. The research findings pave the way for the optomechanical applications of perovskite-based smart materials and structures.

An Equivalent Linear Method to Predict Nonlinear Bending Mechanics of Dredging Floating Hose String

Dredging hoses are flexible and are particularly suitable for slurry transportations for mud or sand in dredging projects. To achieve sufficient bending stiffness and to prevent the pipe body from collapsing, this type of hose segment is a composite structure that is embedded with several cord reinforcement layers and steel wires in its rubber layer. To quickly evaluate the nonlinear bending mechanical properties of rubber hoses, this study proposes the equivalent stiffness method of linear superposition, which is verified by test data and numerical results. The results show that the equivalent bending stiffness method proposed in this study is in good agreement with numerical and experimental results. Then, by comparing the calculation results of the hose string, it was demonstrated that the linear stiffness superposition method proposed in this study can also accurately predict the bending mechanical behavior characteristics of string hose, and provide reliable guidance for hose design in practice.

Interfacial failure behavior of longitudinally coupled slab tracks restored by interface adhesives

Longitudinally coupled slab tracks (LCSTs), one of the most popular slab track types, have experienced severe damage like interfacial debonding and gapping over the past few years. Although adhesives have been used to restore the separated interfaces of LCSTs, the high-temperature environment still poses a great challenge to the repaired tracks. Therefore, this paper presents a numerical investigation on the interfacial failure behavior of LCSTs restored by interface adhesives under high-temperature load. Firstly, the constitutive relationships and the damage behavior of the original and the restored interfaces between the track slabs and mortar layers was modelled based on the cohesive zone theory. Secondly, a finite element model of the LCST was established in which the nonlinear mechanical properties of the interfaces and the materials, as well as the nonlinear distribution of track temperature were considered. Last but not least, damage evolution law of interfaces restored by adhesives, the effects of adhesive-use area, and the performance of adhesives on interfacial debonding and gapping under high-temperature loads were studied. The following conclusions are drawn: (1) After adopting the adhesive, the maximum vertical displacement of track slabs can be reduced by 35.2%. (2) An adhesive-use depth above 500 mm on both sides of the lateral path is recommended to lower the height of interfacial gaps to below 1 mm. (3) In addition to using adhesives, keeping the T-shaped joints in a good condition also plays a crucial role in mitigating interfacial gapping. (4) The distribution of the interfacial damage index D on the lateral path of the track shows a significant asymmetry when adhesives are only used on one side of the lateral path.

Mechanical Characterization of the Male Lower Urinary Tract: Comparison among Soft Tissues from the Same Human Case Study

Background: Nowadays, a challenging task concerns the biomechanical study of the human lower urinary tract (LUT) due to the variety of its tissues and the low availability of samples. Methods: This work attempted to further extend the knowledge through a comprehensive mechanical characterization of the male LUT by considering numerous tissues harvested from the same cadaver, including some never studied before. Samples of the bladder, urethra, prostate, Buck’s fascia and tunica albuginea related to corpora cavernosa were considered and distinguished according to testing direction, specimen conformation and anatomical region. Uniaxial tensile and indentation tests were performed and ad hoc protocols were developed. Results: The tissues showed a non-linear and viscoelastic response but different mechanical properties due to their specific functionality and microstructural configuration. Tunica albuginea longitudinally displayed the highest stiffness (12.77 MPa), while the prostate transversally had the lowest one (0.66 MPa). The minimum stress relaxation degree (65.74%) was reached by the tunica albuginea and the maximum (88.55%) by the bladder. The prostate elastic modulus was shown to vary according to the presence of pathological changes at the microstructure. Conclusions: This is the first experimental work that considers the mechanical evaluation of the LUT tissues in relation to the same subject, setting the basis for future developments by expanding the sample population and for the development of effective in silico models to improve the solutions for most LUT pathologies.

Mechanical performance of CRTS II slab tracks in reinforced-unreinforced transition zone in extreme heat events

Anchors have been widely utilized to reinforce the CRTS II slab tracks. The mechanical performance of the tracks in the reinforced-unreinforced transition zone exposed to extreme heat waves can be very complex due to the difference in mechanical properties between the two kinds of track segments. This paper investigates the damage behavior of the tracks in the reinforced-unreinforced transition zone in extreme heat events. A finite element model of the CRTS II slab track in the transition zone has been established and validated, in which the nonlinear mechanical properties of track materials and interfaces are considered by applying the Concrete Damaged Plasticity model and the Cohesive Zone Model respectively. The nonlinear temperature field in the track structure in extreme heat events is applied to the model. Structural damage of the track, including slab-end arching and interfacial failure, in the transition zone under extreme heat is thoroughly investigated. In particular, the effects of joint use of post-installed reinforcement anchors and other track maintenance measures like interface adhesives and concrete joint restoration are studied. The following conclusions are drawn: (1) The more reinforced track-slabs in the transition zone, the milder the track diseases including slab-end arching and interfacial gapping. (2) Joint use of anchor installation and other maintenance measures such as interface adhesives and concrete joint restoration shows a better effect on mitigating track damage than using post-installed reinforcement anchors solely. (3) Concrete joint restoration overweighs interface adhesives in terms of reducing slab-end arching and interfacial damage when they are jointly used with post-installed reinforcement anchors. (4) In the transition zone, track damage surges when the air temperature increases from 42 ℃ to 47 ℃, which is the temperature range for an extreme heat wave. Monitoring of track state in the transition zones is necessary during extreme heat waves. The novel findings are expected to provide some insights into the mechanical performance of slab tracks and help to prevent potential damage to the tracks in the transition zone, which is a common and practical issue in railway engineering.

Study and Evaluation a New Predictive Control Method for Speed and Stator Current Control of Induction Motor

It is clear that modern industries rely heavily on electric motors, especially induction motors. These motors convert electrical energy into mechanical energy. The distinction in the performance of the induction motor lies in that it is powerful when exposed to various operational and environmental variables, and it is also inexpensive. However, there are many traditional disadvantages that appear during the operation of the induction motor in its non-linear mechanical properties in addition to the difficulty in regulating the speed of the motor. In this paper , we present a new control method for controlling the stator current and speed of induction motor based on current control with speed control technique. The present model is based on conventional predictive controller development with a structure which is similar to rotor control and the direct torque control .It has double loops and both loops will use the prediction power. The inner loop controls the stator current based on Finite Control Set - Model Predictive Control (FCS-MPC) and the outer loop controls the speed to maximize the dynamic response of the loop. The MATLAB software has been used to implement the controller circuit. The obtained simulation results indicates that the presented control method has comparable performance to conventional controllers with some reduction in the overshoot and fast response interval.

Nanocolloidal hydrogel mimics the structure and nonlinear mechanical properties of biological fibrous networks.

Fibrous networks formed by biological polymers such as collagen or fibrin exhibit nonlinear mechanical behavior. They undergo strong stiffening in response to weak shear and elongational strains, but soften under compressional strain, in striking difference with the response to the deformation of flexible-strand networks formed by molecules. The nonlinear properties of fibrous networks are attributed to the mechanical asymmetry of the constituent filaments, for which a stretching modulus is significantly larger than the bending modulus. Studies of the nonlinear mechanical behavior are generally performed on hydrogels formed by biological polymers, which offers limited control over network architecture. Here, we report an engineered covalently cross-linked nanofibrillar hydrogel derived from cellulose nanocrystals and gelatin. The variation in hydrogel composition provided a broad-range change in its shear modulus. The hydrogel exhibited both shear-stiffening and compression-induced softening, in agreement with the predictions of the affine model. The threshold nonlinear stress and strain were universal for the hydrogels with different compositions, which suggested that nonlinear mechanical properties are general for networks formed by rigid filaments. The experimental results were in agreement with an affine model describing deformation of the network formed by rigid filaments. Our results lend insight into the structural features that govern the nonlinear biomechanics of fibrous networks and provide a platform for future studies of the biological impact of nonlinear mechanical properties.

Nonlinear behaviour of epoxy and epoxy-based nanocomposites: an integrated experimental and computational analysis

The focus of this study is on the nonlinear mechanical properties of epoxy and epoxy-based nanocomposites, exploring frequency and strain amplitude dependency. Nanocomposite samples of epoxy are reinforced with fumed silica (FS), halloysite nanotubes (HNT) and Albipox 1000 rubber (Evonik) nanoparticles. Considering these particles have different geometries and stiffnesses, they are expected to have significantly different influences on the mechanics of the resulting composite. To enhance the reliability of the results and to reveal the impact of nanofillers on the mechanics of the material more distinctly, the manufacturing process is designed to be the same for all the specimens within the same material groups to eliminate the effects of the manufacturing process. The comprehensive characterization process consists of Fourier-Transform InfraRed Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Dynamic Mechanical Analysis (DMA). The DMA tests are designed so that the material properties are measured depending on the vibration frequency and strain amplitude. Finally, the characterized nonlinear dynamic properties of these nanocomposites are used as the input material properties into a numerical model. In this simulation, a cantilever beam with representative nonlinear material properties, for these nanocomposites, is created, as example and its forced response is plotted under the same levels of excitation in the frequency domain. Key effects of the different nanofillers are identified using the resonance behavior, primarily focusing on the stiffness and damping of the epoxy-based nanocomposites. These experimental and numerical procedures followed show the significant impact of the nanoparticle reinforcements on the nonlinear nature of these epoxy-based composites.