Compressible Materials Research Articles

Instability analysis of Li-ion battery electrode particles induced by chemomechanical growth using incremental deformation theory

Volumetric swelling due to lithiation into active battery materials is a well-known phenomenon. A chemo-mechanical framework can suitably explain the deformations of the electrode and the generation of diffusion-induced stresses (DIS). Various experimental works have shown that the effects of DIS further cause the active material to lose its structural stability. However, relatively few frameworks exist that can investigate such phenomena in a comprehensive manner. These are mainly based on the Euler–Bernoulli beam theory and the von-Karman plate theory. In the present work we present a generalized three-dimensional instability framework incorporating the theory of incremental deformation. We use this theory on a widely used chemo-mechanical framework. Notably, similar existing instability investigations on negative electrode materials are based only on incompressible material behaviour. As opposed to it, in this work we have considered a compressible material. Also, we account for the spatial and temporal nature of growth, which is a significant departure from the existing instability frameworks. Therefore, this current work brings the investigation of structural instability of electrode material closer to physical reality. In our study, we use the compound matrix method to find the critical lithiation parameter. Then we consider three sets of problems, each with a particular combination of boundary conditions applied on the inner and outer cylindrical surfaces of hollow cylindrical anode particles. These are free-free, fixed-free, and free-fixed, where each combination represents a particular type of interaction between an electrode particle and its surroundings. Most importantly, we find that the free-free and fixed-free conditions show only a pure axial and mixed mode of instability, and do not show the pure circumferential mode. The free-fixed conditions, however, shows all three modes of instability. Additionally, the presence of mode crossover makes the instability pattern of such electrode particles significant.

The electronic structure, optical, and transport properties of novel SrScCu3M4 (M = Se, Te) semiconductors

Abstract The density functional theory is used to investigate the complex relationships between the physical properties of the novel quaternary SrScCu3M4 (M = Se, Te) semiconductors. The computed negative formation energy values of these materials demonstrate their stable nature. The distribution of ELF around chalcogens and Cu atoms shows substantial localization, indicating strong covalent bonding. The phonon dispersion curves show that they possess excellent structure stability with no negative frequencies. The s/p states of Se and s/p/d of Te play minor roles, while Cu-d orbitals possess a considerable influence on the valence band region. The calculated band gaps without SOC for SrScCu3Se4 and SrScCu3Te4 are 1.29, and 0.90, respectively. The predicted energy gap values with SOC for SrScCu3Se4 and SrScCu3Te4 are 1.35, and 0.87, respectively. SrScCu3Se4 is a harder and more compressible material than SrScCu3Te4, as confirmed by its higher bulk modulus. The ε1(ω) values decrease and ultimately become negative, which suggests these materials are reflective. SrScCu3Te4 exhibits plasmon resonance at a high energy domain compared to SrScCu3Se4, resulting in a greater loss function. The current study can establish the potential efficiency of these materials in cutting-edge optoelectronic devices.

Analysis of Processes Accompanying Cylindrical Cumulation

Flow contraction within cylindrical samples causes instability in motion, leading to the formation of circumferential compression stress. This then results in perturbations in the form of Mach three-shock configurations (protrusions) at the shock front. The area at the front of the perturbed shock wave increases due to these protrusions. Furthermore, the protrusions are amplified as a consequence of the absorption of smaller perturbations, which are continuously generated at the shock front. The shock front undergoes sharp growth at the final stage, giving rise to several large protrusions that divide it into separate sectors. These sectors undergo oscillatory movements. As the counter configurations collide, a high-pressure zone is generated, which propels some of the compressed material forward. The protrusions reach their maximum height when they become equal to the distance of the front to the axis. The near-axis region is taken up by the frontal protrusions, and the consequent rarefaction shock wave decelerates the incoming flow.

Identifying, quantifying, and mitigating background with the time-resolved x-ray diffraction platform at the National Ignition Facility.

The time-resolved x-ray diffraction platform at the National Ignition Facility (NIF) fields electronic sensors closer to the exploding laser-driven target than any other NIF diagnostic in order to directly detect diffracted x rays from highly compressed materials. We document strategies to characterize and mitigate the unacceptably high background signals observed in this geometry. We specifically assess the possible effects of electromagnetic pulse, x-ray fluorescence, hot electrons, and sensor-specific non-x-ray artifacts. Significant background reduction is achieved by strategic shielding.

Influence of Anisotropic Consolidation on the Instability of Loose Granular Soils Under Undrained and Drained Loading

Previous studies, mostly experimental, have reported conflicting observations on the effect of the initial anisotropic consolidation stress ratio (η<sub>0</sub>) on the stress ratio at the onset of instability (η<sub>f</sub>) for drained and undrained loading that involve static liquefaction. They indicate that as η<sub>0</sub> increases, η<sub>f</sub> could decrease, increase, or remain invariant, albeit without providing potential mechanistic factors. In this study, the anisotropic critical state theory (ACST) is used to investigate potential factors, including compressibility, state, and fabric anisotropy, that can explain the influence of η<sub>0</sub> on η<sub>f</sub> under undrained and drained loading. The assessments consider numerical simulations with the ACST-based SANISAND-F model, insights from SANISAND-F based instability criteria, the instability surface concept, and available experimental observations. Our findings show that compressibility and fabric anisotropy (and its evolution) are key factors in explaining the influence of η<sub>0</sub> on η<sub>f</sub>. In particular, the results show that if fabric evolution is not substantial, an increase in η<sub>0</sub> decreases η<sub>f</sub> for materials with significant compressibility, whereas the effect of η<sub>0</sub> in low compressibility materials is minimal. On the other hand, for materials that promote fabric evolution, the results suggest that the effect of fabric changes counteract compressibility effects, potentially increasing η<sub>f</sub>.

Nonlinear analysis of spatial trusses with different strain measures and compressible solid

This paper investigates the nonlinear behavior of spatial truss elements under finite deformations, focusing on the impact of various strain measures in compressible materials. We examine both Total Lagrangian (using engineering and Green–Lagrange strains) and Eulerian formulations (using natural, Biot, and Almansi strains). The analysis assumes a linear spatial hyperelastic material where Cauchy stress is proportional to axial natural strain via Young’s modulus. For infinitesimal strains, Young’s modulus remains consistent across different stress/strain pairs. In the finite strain regime, we derive a nonlinear secant modulus based on Young’s modulus. Internal force vectors and tangent stiffness matrices are computed using the direction cosines of the truss element in its deformed state. The paper demonstrates that for infinitesimal deformations, adjusting the modulus of elasticity when using different stress/strain pairs is unnecessary. However, for finite deformations, it is essential to adjust the modulus of elasticity. Numerical simulations validate the performance of the proposed 3D truss element against established formulations. This research offers critical insights into the nonlinear response of spatial trusses, guiding the selection of appropriate strain measures for enhanced accuracy in engineering applications. These findings contribute to more reliable and efficient structural designs, especially in scenarios involving finite deformations and compressible materials.

Phenomenological constitutive laws for the dissipative behaviour of highly compressible elastomers and their finite element implementation

This paper deals with the development of constitutive equations to model the mechanical behaviour of compressible elastomers. These materials are naturally incompressible but can be made compressible by the addition of hollow microspheres, for example. Such a material is referred to as syntactic foam. The CEA (French Commission for Atomic and Alternative Energies) employs such compressible materials as seals in complex structures to reduce the internal stresses in vulnerable components and prevent their failure. The behaviour of these structures is predicted by finite element simulations. It is important to know and model the mechanical behaviour of the seals. Like elastomers, they can undergo large deformations. The microspheres enable the material to undergo large volume change unlike pure elastomer that is nearly incompressible. This compressibility also intensifies dissipative phenomena encountered in elastomers such as viscosity or plasticity. Furthermore, the Mullins stress softening effect is also intensified even for loadings that only bring about volumetric changes. To model these behaviours, a phenomenological approach was developed based on the isochoric/volumetric decomposition of the deformation gradient. The method of intermediate dissipative configurations was employed to introduce multiple phenomena, including viscosity (with several characteristic times) and viscoplasticity, for these two parts of the deformation. The constitutive equations and their flow rules were implemented in Abaqus through a UMAT subroutine and using a numerical approach to define the tangent operator. The parameters of the behaviour law were identified using a model reduction technique known as shape manifold approach. The resulting model can be compared with experimental data.

Mixed displacement–pressure formulations and suitable finite elements for multimaterial problems with compressible and incompressible models

Multimaterial problems in linear and nonlinear elasticity are some of the least explored using mixed finite element formulations with higher-order elements. The fundamental issue in adapting the mixed displacement–pressure formulations with linear and higher-order continuous elements for the pressure field is their inability to capture pressure and stress jumps across material interfaces. In this paper, for the first time in literature, we perform comprehensive studies of multimaterial problems in elasticity consisting of compressible and incompressible material models using the mixed displacement–pressure formulation to assess the performance of different element types in accurately resolving pressure fields within the domains and pressure jumps across material interfaces. In particular, inf–sup stable displacement–pressure combinations with element-wise discontinuous pressure for triangular and tetrahedral elements are considered and their performance is assessed along with the Q1/P0 element and Taylor–Hood elements using several numerical examples. The results show that Taylor–Hood elements fail to capture the stress jumps due to the continuity of DOFs across elements, the Crouzeix–Raviart (P2b/P1dc) element yields substantially poor pressure fields despite a significant increase in pressure degrees of freedom and that the P3/P1dc element produces superior quality results fields when compared with the P2b/P1dc element.

Ischemia-reperfusion injury after spinal cord decompressive surgery-An invivo rat model.

Although decompression surgery is the optimal treatment for patients with severe degenerative cervical myelopathy (DCM), some individuals experience no improvement or even a decline in neurological function after surgery, with spinal cord ischemia-reperfusion injury (SCII) identified as the primary cause. Spinal cord compression results in local ischemia and blood perfusion following decompression is fundamental to SCII. However, owing to inadequate perioperative blood flow monitoring, direct evidence regarding the occurrence of SCII after decompression is lacking. The objective of this study was to establish a suitable animal model for investigating the underlying mechanism of spinal cord ischemia-reperfusion injury following decompression surgery for degenerative cervical myelopathy (DCM) and to elucidate alterations in neurological function and local blood flow within the spinal cord before and after decompression. Twenty-four Sprague-Dawley rats were allocated to three groups: the DCM group (cervical compression group, with implanted compression material in the spinal canal, n = 8), the DCM-D group (cervical decompression group, with removal of compression material from the spinal canal 4 weeks after implantation, n = 8), and the SHAM group (sham operation, n = 8). Von Frey test, forepaw grip strength, and gait were assessed within 4 weeks post-implantation. Spinal cord compression was evaluated using magnetic resonance imaging. Local blood flow in the spinal cord was monitored during the perioperative decompression. The rats were sacrificed 1 week after decompression to observe morphological changes in the compressed or decompressed segments of the spinal cord. Additionally, NeuN expression and the oxidative damage marker 8-oxoG DNA were analyzed. Following spinal cord compression, abnormal mechanical pain worsened, and a decrease in forepaw grip strength was observed within 1-4 weeks. Upon decompression, the abnormal mechanical pain subsided, and forepaw grip strength was restored; however, neither reached the level of the sham operation group. Decompression leads to an increase in the local blood flow, indicating improved perfusion of the spinal cord. The number of NeuN-positive cells in the spinal cord of rats in the DCM-D group exceeded that in the DCM group but remained lower than that in the SHAM group. Notably, a higher level of 8-oxoG DNA expression was observed, suggesting oxidative stress following spinal cord decompression. This model is deemed suitable for analyzing the underlying mechanism of SCII following decompressive cervical laminectomy, as we posit that the obtained results are comparable to the clinical progression of degenerative cervical myelopathy (DCM) post-decompression and exhibit analogous neurological alterations. Notably, this model revealed ischemic reperfusion in the spinal cord after decompression, concomitant with oxidative damage, which plausibly underlies the neurological deterioration observed after decompression.

Three-dimensional continuum point cloud method for large deformation and its verification

This study presents a strong form based meshfree collocation method, which is named Continuum Point Cloud Method, to solve nonlinear field equations derived from classical mechanics for deformed bodies in three-dimensional Euclidean space. The method and its implementation are benchmarked against a nonlinear vector field using manufactured solutions. The analysis of mechanical fields firstly focuses on the study of St. Venant Kirchhoff and compressible neo-Hookean materials. Results for various initial boundary value problems are presented, including benchmark cases involving unidirectional tension and simple shear. Subsequently, the study concludes with an analysis of a displacement-controlled simulation of a compressible neo-Hookean material, specifically a bar that is pulled to 50% of its original length and rotated 90°. The pure tension case yields a 1.5% error in displacement between computed and expected values and a combined tension and torsion loading case provides further insight into material behavior under complex loading conditions. The resulting normal axial and transverse stress-strain curves are also presented. Finally, the consistency and robustness of the proposed nonlinear numerical schemes are successfully demonstrated through various numerical experiments.

Enhancing sustainable food packaging design: A machine learning approach to predict ventilated corrugated paperboard strength

In the food packaging industry, ventilated corrugated paperboard boxes are crucial for sustainable transport of fresh products. While these boxes' ventilation holes advance air circulation, they also impact the material's compression or buckling strength. Variations in hole geometry and location affecting this strength are explored, considering the composite material, multi-layered structure. Traditional mechanical analyses, which often require simplifications, may not fully capture this complexity, leading to less accurate predictions of the paperboard's strength. To address these challenges, a machine learning (ML) approach was utilized, employing the Light Gradient Boosting Machine (LGBM) to develop a predictive model for the buckling strength of corrugated paperboard boxes with ventilation cutouts. This physics-informed ML model, trained on a compression dataset resulting from experimental tests for plates with a single cutout in three shapes and Finite Element Method (FEM) simulations for plates with various patterns of circular cutouts, provides highly accurate estimates of the plates' buckling strength. It achieved 91.7% accuracy on experimental data and 94.68% on FEM simulation data, showcasing its reliability. A new tool for predicting the buckling strength of corrugated paperboard is provided by this research, along with insights that can inform the design of more sustainable packaging solutions. Furthermore, the methodology and findings have broader applications, potentially benefiting sectors like aerospace and construction, where similar structural materials are used.

Preparation of ultra-light, highly compressible, and biodegradable chitosan porous materials for heavy metal adsorption, dye adsorption and oil-water separation

Chitosan materials are much important in adsorption, separation and water treatment due to their hydrophilicity, biodegradability and easy functionalization. However, they were difficult to form structural materials, which limited its application in engineering. In this paper, a new type of chitosan porous materials was prepared with two-step strategy involving the freezing crosslinking of chitosan with glutaraldehyde to form cryogels, and their subsequent reduction with NaBH4 to transform CN bonds into CN bonds, resulting in remarkable improvement of mechanical property. That is, the strength remained almost unchanged after 80 % deformation. The abundant -NH2 and -OH on the surface of materials, as well as the unique pore structure from cryogels, gave relatively high adsorption capacity for metals and dyes (88.73 ± 4.25 mg·g−1 for Cu(II) and 3261.05 ± 36.10 mg·g−1 for Congo red). The surface hydrophilicity of materials made it possible for selective water permeation with over 95 % separation efficiency for oil-water mixtures. In addition, simple hydrophobic modification using bromotetradecane achieved selective oil permeation with over 96 % separation efficiency for oil-water mixtures. This study not only provides a new strategy to endow chitosan materials with excellent mechanical property, large adsorption capacity and good oil-water separation performance, but also offers environmentally friendly materials for sewage treatment applications.

Superlubricity in solid lubricated sliding and rolling contacts

Superlubricity, or near zero friction is a highly desired lubrication state for a wide range of practical applications. Although such application scenarios often involve complex contact geometries, solid lubricant technologies, including previous efforts on achieving superlubricity, are almost entirely in linear sliding test conditions. This report demonstrates an experimental pathway to yield superlubricity in rolling-sliding contact conditions using solid-lubricant materials. Ti3C2X based solid lubricant was tested under complex sliding-rolling conditions at engineering-significant contact pressures. The material's compression and inter-layer shearing result in material reconstruction to pose superlubricity. High-resolution transmission electron microscopy analysis, complemented by multi-scan Raman spectroscopy showed the formation of a robust amorphous tribolayer. This demonstration is expected to not only advance the applied aspects in the development of oil-free solid lubricants but also push the boundaries of fundamental understanding of materials’ structure-property relations across physical states.

Optimized Design of Low-Carbon Mix Ratio for Non-Dominated Sorting Genetic Algorithm II Concrete Based on Genetic Algorithm-Improved Back Propagation.

In order to achieve low-carbon optimization in the intelligent mix ratio design of concrete materials, this work first constructs a concrete mix ratio database and performs a statistical characteristics analysis. Secondly, it employs a standard back propagation (BP) and a genetic algorithm-improved BP (GA-BP) to predict the concrete mix ratio. The NSGA-II algorithm is then used to optimize the mix ratio. Finally, the method's accuracy is validated through experiments. The study's results indicate that the statistical characteristics of the concrete mix ratio data show a wide distribution range and good representativeness. Compared to the standard BP, the fitting accuracies of each GA-BP set are improved by 4.9%, 0.3%, 16.7%, and 4.6%, respectively. According to the Fast Non-Dominated Sorting Genetic Algorithm II (NSGA-II) optimization for meeting C50 concrete strength requirements, the optimal concrete mix ratio is as follows: cement 331.3 kg/m3, sand 639.4 kg/m3, stone 1039 kg/m3, fly ash 56 kg/m3, water 153 kg/m3, and water-reducing agent 0.632 kg/m3. The 28-day compressive strength, material cost, and carbon emissions show relative errors of 2.1%, 0.6%, and 2.9%, respectively. Compared with commercial concrete of the same strength grade, costs and carbon emissions are reduced by 7.2% and 15.9%, respectively. The methodology used in this study not only significantly improves the accuracy of concrete design but also considers the carbon emissions involved in the concrete preparation process, reflecting the strength, economic, and environmental impacts of material design. Practitioners are encouraged to explore integrated low-carbon research that spans from material selection to structural optimization.

A software-agnostic benchmark for DEM simulation of cohesive and non-cohesive materials

Although DEM (Discrete Element Method) was introduced >40 years ago, there are still various challenges in applying it with a certain level of confidence. To develop a realistic material model, calibration, validation, particle shape representation and scaling are well-known challenges that have been studied by various researchers over the past two decades. In addition, once a realistic DEM material model is developed and published in line with open science principles, it is unknown to what extent the calibrated values can be used across software packages. Although a benchmark between 8 open source codes was recently published, it did not cover cohesive materials, rolling friction models, realistic calibrated material behaviour, and commercial software that is widely used in industries.The aim of this study is to investigate the portability of input parameters between different codes and to identify if software independent calibration is possible. We propose a framework to assist DEM users in industry and academia to reach a software independent DEM simulation when required.To compare the results between software packages, the framework considers the following aspects: 1) identical implementation of contact models, 2) single contact modelling, 3) bulk level simulation, and 4) identical post-processing. This framework is demonstrated for two contact models (Hertz-Mindlin and Edinburgh Elasto Plastic Adhesive) with rolling friction model and two commercial software packages (EDEM and PFC) but is applicable for any other (open-source) software. Moreover, two realistic calibrated material models are included to cover a range of material characteristics, from free-flowing incompressible materials to cohesive compressible materials. This study shows that individual particle level simulations give identical results, bulk level simulations show differences for both contact models. In general, users should use parameter values from other software packages with caution, especially where critical or sensitive applications are modelled. This paper also highlights the use of novel computation techniques, such as the GPU engine, to achieve practical computation times when modelling industrial applications.

Recovery of ambulation in small, nonbrachycephalic dogs after conservative management of acute thoracolumbar disk extrusion.

Currently, low-level evidence suggests loss of ambulation associated with acute thoracolumbar disk extrusion is best treated by decompressive spinal surgery. Conservative management can be successful, but the proportion of dogs that recover and the fate of herniated material are uncertain. Determine the proportion of nonambulatory dogs with conservatively treated acute thoracolumbar disk extrusion that recover ambulation and measure the change in spinal cord compression during the first 12 weeks after presentation. Seventy-two client-owned nonambulatory dogs with acute thoracolumbar intervertebral disk extrusion. This is a prospective cohort study. Enrolled dogs underwent magnetic resonance imaging at presentation and owners were provided with conservative management recommendations. Imaging was repeated after 12 weeks. Recovery of ambulation was defined as 10 consecutive steps without falling. Spinal cord compression was determined from the cross-sectional area of the vertebral canal and extradural compressive material at the lesion epicenter. The association between recovery and change in compression over the 12-week observational period was examined. Forty-nine of fifty-one (96%; 95% confidence interval [CI], 87%-99%) of deep pain-positive and 10/21 (48%; 95% CI, 28%-68%) of deep pain-negative dogs recovered ambulation within the 12-week period. The median time to ambulation was 11 and 25 days for deep pain-positive and -negative dogs, respectively. Reduction in spinal cord compression varied among individuals from minimal to complete and apparently was unrelated to the recovery of ambulation. A high proportion of conservatively treated dogs recovered ambulation after conservative management of acute thoracolumbar disk herniation. Recovery was not dependent on the resolution of compression.

Highly compressive aerogel-elastomer hybrid porous material with redistributed strain for high-sensitive soft pressure sensors

Owing to the good sensitivity and simple fabrication process, flexible piezoresistive pressure sensors based on aerogels shows great applications in soft robotics, bioelectronics and so on. However, the poor compressibility and stability of the aerogel is still challenging the development of aerogel based flexible piezoresistive pressure sensors, simultaneously, it is urgent to pave a way to enhance the sensitivity of these sensors. Here, for the first time, we propose a universal strategy to prepare aerogel skeleton-elastomer shell hybrid porous material with enhanced compressibility for high-sensitive and stable flexible pressure sensors. We found that the elastomer shell disperses the strain in the aerogel skeleton and enhances the compressibility of the aerogel, which improve the stability of the sensor (10000 cycles of compression). More importantly, there are elastomer micro-blocks formed in the hybrid material, these micro-blocks redistribute the strain in the material which contributes to the high sensitivity (10.25 kPa−1) of the sensors. Furthermore, the sensors are successful in monitoring both of the large joint bending and subtle skin vibration, as well as remote controlling toy car and artificial hand. This work provides an effective and universal strategy to enhance the sensitivity and stability of the aerogel based flexible pressure sensors and promotes their development towards practical applications.

Experimental investigation and soft bond modelling analysis on mechanical behaviours of foamed polyurethane solidified ballast

Polyurethane solidified ballasted track (PSBT) offers a novel solution to the frequent maintenance requirements of ballasted track, delivering a high-quality track infrastructure. In this study, laboratory tests were carried out on polyurethane solidified ballast (PSB) specimens under compression, tensile and shear conditions to obtain stress-strain curves and deformation characteristics. The numerical model of the PSB specimens was developed based on the discrete element method (DEM). The effects of the parameters related to the bond elongation on the tensile and compressive properties of the PSB specimens were analysed, and the parameters were calibrated by the test results. The results showed that the compressive, tensile and shear strengths of the specimens increased with increasing polyurethane foam density. During uniaxial and split loading, the stress-strain curves of the PSB specimens gradually entered the stress softening stage after an elastic phase. The compressive-tensile strength ratio of the specimens was around 1.55. From the perspective of deformation, the PSB specimen is primarily strained by the highly compressible polyurethane materials, and the specimen generates a considerable residual strain at the initial stage of cyclic loading. Thus, it is necessary to pre-compress the PSB to achieve an optimal load-bearing condition. DEM simulations show that there is a strong correlation between the mesoscale bond elongation of particles and the macroscopic tensile and compressive strengths of the specimens. It is therefore possible to utilise a high value of bond elongation to simulate bonded granular materials with low compressive-tensile strength ratios. The results obtained from the simulation of the numerical method used in this study are in high agreement with the test, which provides a new idea for revealing the meso- and macro- mechanical properties of PSB and its application in PSBT.

Evaluation of the mechanical properties and chemical components of naturally aged glued laminated bamboo

This study experimentally investigated the mechanical properties of aged GLB. The material under investigation was obtained from an outdoor-exposed GLB frame that had been subjected to outdoor exposure for a period of ten years. In-depth discussions were conducted on the mechanical properties and failure modes of the material in tension, compression, and bending. The failure modes were identified as fiber fracture under tension, fiber buckling accompanied by delamination in compression, and a combination of tension failure and transverse shear failure in bending. In comparison to new materials, the tensile strength, compressive strength, and bending strength of aged GLB exhibited a reduction of 5.19–41.2 %, 11.5–26.9 %, and 6.6–40.1 %, respectively. The reduction in strength exhibited considerable variability across the various positions within the aged GLB component cross-section. The greatest reduction in strength was observed in materials located on the upper surface of the component, which were directly subjected to UV radiation and rainwater erosion. Furthermore, Fourier transform infrared (FT-IR) spectroscopy analysis was conducted. The FT-IR spectra demonstrate that the chemical components of bamboo, including cellulose, hemicellulose and lignin, have experienced severe degradation.

Finite Elastic Deformations of Initially Flat Thin Rubber-Like Materials

This contribution aims to derive a nonlinear FE formulation for large elastic deformation of hyperelastic thin rubber-like elastomeric materials. The formulation accounts for isotropic as well as transversely isotropic rubber-like materials. Besides, with the developed formulation, deformation of incompressible as well as compressible materials can be investigated. The formulation is applicable for in-plane and out-of-plane deformation of thin membranes. Several problems are inspected including uniaxial and equibiaxial extension of rubber, axisymmetric deformation of annular sheet, stretching a perforated rubber, extension of an anisotropic rubber, and inflation of an initially-flat circular and a square membrane. The results show very good agreement compared with those reported in the literature. Moreover, this model is able to model the inflation of initially flat membranes which is not possible to be done by commercial software.