Material Stiffness Research Articles

Experimental and Simulation Study of Fiber-Reinforced and Foam-Filled Anti-Tetrachiral and Re-Entrant Structures

Negative Poisson's ratio (NPR) honeycomb structures exhibit excellent properties, including resistance to compression, impact resistance, and energy absorption. To better study NPR structures, this paper investigates two different methods to enhance the mechanical properties and energy absorption capabilities of re-entrant and anti-tetrachiral structures. Fiber reinforcement and polyurethane foam filling methods were used to address material enhancement issues, aiming to achieve structures with high specific energy absorption. Specimens were fabricated using selective laser sintering technology with three different material configurations, including nylon, carbon fiber-reinforced nylon, and glass fiber-reinforced nylon, for comparative analysis. Additionally, some specimens were filled with polyurethane foam. Quasi-static compression tests indicated that both glass fiber-reinforced nylon and foam filling significantly improved the material's stiffness, initial peak stress, and energy absorption, although the "auxetic" effect was weakened. Subsequently, finite element methods were used to simulate the deformation modes and mechanical properties of the two NPR structures, and the numerical results showed good agreement with the experimental results.

Trading Spaces: Adaptive Subspace Time Integration for Contacting Elastodynamics

We construct a subspace simulator that adaptively balances solution improvement against system size. The core components of our simulator are an adaptive subspace oracle, model, and parallel time-step solver algorithm. Our in-time-step adaptivity oracle continually assesses subspace solution quality and candidate update proposals while accounting for temporal variations in deformation and spatial variations in material. In turn our adaptivity model is subspace agnostic. It allows application across subspace representations and expresses unrestricted deformations independent of subspace choice. We couple our oracle and model with a custom-constructed parallel time-step solver for our enriched systems that exposes a pair of user tolerances which provide controllable simulation quality. As tolerances are tightened our model converges to full-space solutions (with expected cost increases). On the other hand, as tolerances are relaxed we obtain output-bound simulation costs. We demonstrate the efficacy of our approach across a wide range of challenging nonlinear materials models, material stiffnesses, heterogeneities, dynamic behaviors, and frictionally contacting conditions, obtaining scalable and efficient simulations of complex elastodynamic scenarios.

Technical note: Effects of chemical, radiational, and thermal treatment of bone tissue on material stiffness and anisotropy.

We evaluated the effects of four treatments for pathogen inactivation in bone tissue (ethanol storage, formalin fixation, gamma irradiation, and heat treatment via autoclave) on stiffness and anisotropy values in bone samples. Cortical bone samples from the humerus of 14 bovine specimens were subjected to Knoop microindentation analysis in longitudinal and transverse planes of section and four indenter orientations within each section. From each specimen, individual samples were assigned to one of five treatment conditions: 50% ethanol-saline solution, formalin immersion, gamma irradiation, autoclave, and buffered saline (controls). Each sample was microindented 100 times and the resultant stiffness data were analyzed by a resampled factorial analysis of variance. First- and second-order interactions as well as main effects of indenter orientation, treatment, and specimen were significant for both transverse and longitudinal sections, with the sole exception that indenter orientation-treatment interaction was nonsignificant for longitudinal sections. Interaction plots reveal that thermal (autoclave) and irradiation treatments depress stiffness values the most, while patterns of indentation stiffness at different orientations are relatively unaffected. Patterns of anisotropy are relatively unaffected by preservative treatments, but elastic modulus changes are consistent and unambiguous. Formalin and ethanol treatments are most comparable to controls and represent the best preservative media for mechanical testing. These options, however, are likely to be the least effective for ensuring the inactivation or sterilization of potentially contaminated samples.

An Alternative Finite Element Formulation to Predict Ductile Fracture in Highly Deformable Materials

Abstract An alternative finite element formulation to predict ductile damage and fracture in highly deformable materials is presented. For this purpose, a finite-strain elastoplastic model based on the Gurson–Tvergaard–Needleman (GTN) formulation is employed, in which the level of damage is described by the void volume fraction (or porosity). The model accounts for large strains, associative plasticity, and isotropic hardening, as well as void nucleation, coalescence, and material failure. To avoid severe damage localization, a nonlocal enrichment is adopted, resulting in a mixed finite element whose degrees-of-freedom are the current positions and nonlocal porosity at the nodes. In this work, 2D triangular elements of linear-order and plane-stress conditions are used. Two systems of equations have to be solved: the global variables system, involving the degrees-of-freedom; and the internal variables system, including the damage and plastic variables. To this end, a new numerical strategy has been developed, in which the change in material stiffness due to the evolution of internal variables is embedded in the consistent tangent operator regarding the global system. The performance of the proposed formulation is assessed by three numerical examples involving large elastoplastic strains and ductile fracture. Results confirm that the present formulation is capable of reproducing fracture initiation and evolution, as well as necking instability. Convergence analysis is also performed to evaluate the effect of mesh refinement on the mechanical response. In addition, it is demonstrated that the nonlocal parameter alleviates damage localization, providing smoother porosity fields.

Mechanical properties of beech wood treated with malic acid-based polyester

Abstract While chemical modification enhances wood’s resistance to deterioration and dimensional stability, it often results in alterations to the mechanical properties, limiting its engineering applications. This study focuses on the in situ esterification of beech wood using malic acid/polyol mixtures and evaluates its impact on mechanical properties. The results of the compression tests yielded limited information, characterized by a notable degree of variability as indicated by the high standard deviation. The four-point bending tests conducted here revealed an increase in the modulus of elasticity (MOE). However, this improvement in MOE was accompanied by a decrease in the modulus of rupture (MOR), indicating a trade-off between stiffness and strength. To better understand the mechanisms affecting the treated wood’s mechanical properties, we compared the experimental and theoretical glass transition (Tg) of the polymers with material stiffness. X-ray computed tomography revealed that treatment increases specimen density and creates a gradient, with higher density near the surface, potentially contributing to increased stiffness. These findings suggest a nuanced impact of the in situ esterification process using malic acid/polyol mixtures on the mechanical properties of beech wood.

Solvolysis of Nylon: A Pathway to Sustainable Recycling and Circular Economy

Polyamides (PAs) are extensively utilized across various applications, yet the accumulation of PA residues presents significant ecological and environmental challenges. Given that a substantial portion of fishing nets are composed of nylon, a type of PA, this material’s disposal raises environmental concerns impacting marine life and the global ecosystem. Therefore, to enhance sustainability, they could be collected and recycled. This study introduces a method for the chemical recycling of PA waste using hydrochloric acid (HCl). Through solvolysis, a PA was depolymerized, and the effect of various reaction conditions on the depolymerization yield was analyzed, being the best conditions established in this work (100 °C, 4 h, and an HCl/PA ratio of 11:1, wt.wt−1). Next, a novel separation methodology was employed to isolate recycled products from salts formed during neutralization. Subsequently, these recycled products were incorporated as a partial substitute (up to 10% wt.wt−1) for a conventional PA in a new material production. The results indicate that the presence of recycled products enhances material stiffness due to crystallinity differences compared to the virgin matrix. In turn, the introduction of lower-molecular-weight species increases the materials’ glass transition temperature (Tg) and their melt flow index (MFI). This research underscores a sustainable pathway for PA recycling aligned with circular economy principles, contributing positively to environmental conservation efforts.

Restoration of Corneal Stiffness in Rabbits Following Withdrawal of Travoprost.

To evaluate if the effect of travoprost on corneal material stiffness could be restored after drug withdrawal. Seventy-two rabbits were randomly allocated into three groups: medicine (M), medicine withdrawal (MW), and blank (B). Within the M and MW groups, treatment with travoprost was administered to the right eyes (MT and MWT) over a period of 12 weeks. Subsequently, the M group was killed, but the MW group underwent an additional 12-week period for treatment withdrawal. No treatment was given to the contralateral eyes (MC and MWC) in the M and MW groups. A separate blank control (BC) group remained untreated for the entire 24-week duration. In each group, corneas from 18 rabbits were tested mechanically under inflation conditions to estimate their tangent modulus (Et). The corneas of the remaining six rabbits underwent electron microscopy analysis, which focused on fibril diameter and interfibrillar spacing. Central corneal thickness (CCT) of the treated eyes (MT and MWT groups) decreased with 12 weeks of travoprost treatment (P < 0.05). The CCT in the MWT group increased after 12 weeks of withdrawal but was still lower than that in the BC group (P < 0.05). The Et of the MT group was significantly lower than that of the MC group at mean tissue stresses of 2, 4, and 6 kPa (P < 0.05). Conversely, no significant difference in Et values was observed between the MWT, MWC, and BC groups, indicating recovery after treatment cessation. Furthermore, the stromal interfibrillar spacing of the treated MT group was significantly larger (P < 0.05) than that of the control MC group, but no disparity was noted among the MWT, MWC, and BC groups following treatment withdrawal. Additionally, there were no significant differences in the mean diameter of collagen fibrils among all groups (all P > 0.05). Travoprost treatment appears to soften corneal tissue, decrease tissue thickness, and reduce the density of stromal collagen fibers by increasing the interfibrillar spacing. These changes were partially reversed after treatment cessation. Travoprost could further inhibit corneal growth, so its use in childhood and adolescence should be carefully considered. Additionally, the effect of travoprost in reducing corneal stiffness may lead to underestimations of intraocular pressure (IOP) measurement and hence overestimations in the effect of treatment in lowering IOP.

The Interior Contact-Aided Rolling Element

Abstract This work introduces an interior contact-aided rolling element (I-CORE) compliant mechanism that draws upon the concepts used for the contact-aided rolling element, cross-axis flexural pivot, and pre-curved flexible beam. The I-CORE incorporates a bilinear compressive stiffness response with an initial tailorable stiffness governed by the flexural geometry, followed by a stiffness curve governed by the material stiffness at the contact point. The I-CORE mechanism can achieve one or two degrees of rotational freedom as well as a single degree of translational freedom. The purpose of the present work was to introduce the I-CORE mechanism, as well as a pseudo-rigid-body replacement model (PRBM) of the I-CORE mechanism which was subsequently validated using both finite element analysis and benchtop mechanical testing. A pseudo-rigid body model was created for the I-CORE to simplify the rapid adaptation of this mechanism to different design applications. This model was validated using both finite element analysis and benchtop mechanical testing under both compression and rotation loading conditions. Additionally, multiple configurations of the device were created and evaluated in order to test its sensitivity to certain design features including the flexure width, flexure thickness, and the radius of the rounded contact surfaces. It was found that the model is sensitive to the thickness of the flexures and that despite some limitations, the pseudo-rigid body model is sufficiently accurate for initial design work. Some possible applications of the mechanism are proposed.

Tendon‐Driven Stiffness‐Tunable Soft Actuator via Thermoelectric‐based Bidirectional Temperature Control

AbstractSoft robots have excellent spatial adaptability and high flexibility, but they are limited by the low stiffness of their constituent materials when faced with high‐load tasks. In recent years, there have been many works on the development of stiffness‐tunable soft actuators by introducing variable stiffness materials into soft actuators, but the existing solutions usually suffer from the problems of slow response, complex structure, and the need of many auxiliary devices to support the completion of the stiffness tuning cycle. This paper proposes a tendon‐driven stiffness‐tunable soft actuator that addresses these issues. Benefiting from the bidirectional temperature control of thermoelectric modules and the excellent in‐plane thermal conductivity of graphene, the actuator is capable of achieving the heating and cooling process by transferring the heat flow through the graphene structure into and out of the shape‐memory polymer (SMP) layer of the tendon‐driven actuator. This enables stiffness tuning via a single device, reducing the dependence on complex external cooling systems. The use of tendon‐driven actuators further eliminates the complex bellow structure of conventional pneumatic actuators and dramatically reduces the size and manufacturing difficulty of individual actuators. Finally, the high load capacity and shape adaptability of the actuator are demonstrated by a gripper equipped with three actuators, which successfully grips objects of various shapes and weights, ranging from less than 10 g to up to 1.6 kg.

Investigating the influence of bending stiffness and processing parameters on single-leg bending geometries of additively manufactured composites

In less than a decade, additive manufacturing technologies have been developed so successfully that they already produce small and medium-sized lot sizes of prototypes or customised components in the industry. With its new possibilities such as combining materials and technologies, the benefits of different technologies can be merged and broaden future application fields. One way is to print with one technology on a part produced by another. Thus, a thermally bonded part composed of, e.g., selectively sintered and material-extruded components can be created. This combination of technologies was considered in this study to investigate the bonding strength of extrusion-based layers on selectively sintered surfaces and the impact of nozzle temperature, orientation, and thickness of imprinted materials. The extrusion-based layers covered stiff (fibre-reinforced polyamide) and soft (thermoplastic polyurethane) material properties with pre-cracked single-leg bending (SLB) specimens to study their effect on delamination tendencies. This combination of materials and additive manufacturing technologies has not yet been studied for the SLB testing method. The scope of this study is to obtain more information on how relatively hard-hard and hard-soft combinations behave for this special testing method. The results of this testing method were evaluated using two different fracture mechanical approaches to determine the energy release rate. A clear trend towards an improved bonding, thus, higher values, was found for higher nozzle temperatures. Furthermore, a limitation regarding the required bending stiffness of the composites was found. Overall, the single-leg bending testing method enables a relative ranking for material combinations with a certain bending stiffness.

Mechanical, thermal, and microstructure analysis of 3D printed polyolefin elastomer-acrylonitrile butadiene styrene blends for tunable mechanical properties

Fused Deposition Modeling (FDM) has emerged as a cost-effective and user-friendly technique that has garnered significant attention in recent years. However, challenges persist when printing soft materials using FDM technology. This study proposes a solution by blending a soft polyolefin elastomer (POE) with a stiffer material, acrylonitrile butadiene styrene (ABS). A comprehensive experimental investigation utilizing a direct pellet printing method was conducted to 3D print POE-ABS blends in various ratios (10%, 30%, and 50% ABS content). The study encompassed material preparation, 3D printing, SEM (Scanning Electron Microscopy) analysis, Dynamic Mechanical Thermal Analysis (DMTA), uniaxial tensile testing, and compression testing to assess the mechanical properties and energy absorption capabilities of the 3D printed blends. The results of the DMTA showed that the blends with a higher amount of ABS have a larger area under the Tan δ curve, indicating their ability to absorb more energy. The SEM images revealed that as the proportion of ABS increases, the gaps between layers and beads become smaller. The mechanical properties of the pure printed POE, such as its elongation at break and tensile strength, were 2138% and 2.83 MPa, respectively. However, as the ABS content increased, the samples exhibited more rigid behavior, with a final transition to 50/50 ratio resulting in 9.4 MPa tensile strength and 160% elongation at break. The energy absorption test demonstrated that the sample with 30% ABS content has the highest energy absorption capability among all the tested samples. This research underscores the potential of blending soft and stiff materials to tailor properties for additive manufacturing applications, emphasizing the significance of material composition in achieving desired mechanical performance, printability, and functionality in printed objects.

Variation of Secant Young’s Modulus in an Unsaturated Gap-Graded Granular Fill

It is of great significance to understand the variation of stiffness in unsaturated granular materials for predicting performance of earth structures. Variation of secant Young’s modulus in an unsaturated gap-graded granular fill was investigated using unsaturated triaxial tests with local strain measurements in this work. Unlike the insignificant suction impact on shear strength in coarse-grained granular material, it seems that suction has greater effect on stiffness of the tested soil at small strain. Young’s modulus enhances as suction and net confining pressure rise since average skeleton stress increases and soil skeleton gets more stable by meniscus water. In addition, specimen at larger suction possesses greater degradation speed than that at lower ones. One equation was adopted to estimate Young’s modulus of soil. It shows that this equation may capture the variations of secant Young’s modulus of soil under different suctions and net confining pressures.

A multiscale Gaussian expansion method for low-frequency multimodal damping analysis of variable stiffness acoustic black hole beams

To address the issues of slow convergence and poor accuracy in existing dynamics methods caused by non-uniform variable cross-sections and layered material stiffness variations in variable stiffness acoustic black hole structure (VSABH). A multiscale Gaussian expansion method (MSGEM) is proposed in this paper. The structural dimensions are taken into account, and the structural parameters of multiple shape functions are adaptively selected based on stiffness and cross-sectional variation parameters. This results in the formation of shape function groups of various scales, which in turn creates the matrix of multi-scale Gaussian function groups. The feature information of the displacement field is realized to be extracted from multiple scales, and the fitting error of MSGEM to the displacement field of VSABH beam is within 2.02 %. The missing solution of eigenfrequency of Gaussian expansion method is avoided, and the modal vibration patterns are basically matched, which verifies the validity of MSGEM. Meanwhile, the advantages of low-frequency multimodal vibration reduction of VSABH beams are highlighted from several aspects, and the trend of the adjustment of the vibration reduction characteristics of VSABH beams by different parameters is clarified, which provides valuable design guidance for ABH metamaterials oriented to low-frequency vibration reduction.

Experimental Investigation of Low-Cost Bamboo Composite (LCBC) Slender Structural Columns in Compression

This paper experimentally investigates the behavior of innovative sustainable Low-Cost Bamboo Composite (LCBC) structural columns under compressive loading. The LCBC columns are manufactured from bamboo culms in combination with bio-based resins to form composite structural columns. Different LCBC cross-sectional configurations are investigated in this study, including the Russian doll (RD), Big Russian doll (BRD), Hawser (HAW), and Scrimber (SCR). Two bio-based resins, including one bio-epoxies and one furan-based resin, in addition to a soft bio-based filler and a synthetic epoxy resin, are applied. The bamboo species used as the cast-in-place giant bamboo for all configurations include Moso, Guadua, and Tali. Slender LCBC columns showed maximum stress equal to 60 MPa at failure. The study found that the samples with bio-epoxy resin (BE2) exhibited enhanced material stiffness when compared to synthetic epoxy (EPX) and furan-based resin (PF1), while PF1 specimens demonstrated increased ductility. Among the specimens with Moso bamboo and BE2 resin, those with SCR and HAW configurations achieved the highest compressive strengths.

Tensile and Bending Strength of Birch and Beech Lamellas Finger Jointed with Conventional and Newly Developed Finger-Joint Profiles.

In this study, the tensile and bending strength of birch and beech lamellas finger jointed with conventional (Standard) and newly developed finger-joint profiles (New) are presented. Polyurethane (PUR), Melamine-Urea-Formaldehyde (MUF) and Phenol-Resorcinol-Formaldehyde (PRF) adhesive systems were used to bond the finger joints. The objective of the New profiles was to reduce the stress concentrations within the finger joint by cutting the cross-grooved fingers perpendicular to the main orientation of the finger-joint profile. In the first trials of the development, larger cross-grooved fingers were cut with the aim to improve the stress distribution and to reinforce the finger joint by filling gaps in the finger joint with adhesive. As the study progressed, initial optimisations of the New profile were made. Smaller cross-grooved fingers were cut as it was assumed that they are beneficial for the manufacturing and integrity of the New profile. In combination with the MUF adhesive system, the New profile achieved the highest increase in the bending and tensile strengths compared to the Standard profile. In addition to the increased strength, other advantages such as reduced cracking in the finger joint were observed when using the New profile. The high strength and stiffness of hardwoods or other high-performance materials used in timber construction can probably be better exploited in combination with the New profile. Further tests will be carried out by considering different configurations of the New profile and different materials.

A novel approach for improving material stiffness using a direct method in below-knee prosthetic sockets

The conventional techniques for producing a socket are time-consuming disproportionate to the significant population afflicted by limb amputations. Although the new manufacturing direct method, the modular socket system (MSS) method, involves reduced labor time, the technique produces sockets with high stiffness that cause discomfort for those with lower limb amputations during walking. This study investigated the tensile characteristics of numerous materials in below-knee prosthetic sockets. Initially, a vacuum molding approach was used to produce the sockets, which involved various polymers and composite materials to improve the prosthesis socket properties. An F-socket device was also employed to ensure efficient production and optimized pressure distribution at the interface between the socket and the residual limb. A SOLIDWORKS® software was then applied to determine the numerical analysis (stress distribution and the maximum internal pressure). The samples from Group E involved utilizing a novel mixture compared to the direct and traditional methods of various materials. This study presents a novel prosthetic limb socket made from a mixture of four carbon fiber layers, utilizing 20% polyurethane resin and 80% acrylic as the matrix. The resulting material demonstrated acceptable stiffness, extended socket life, and reduced curing time. During the patient's gait cycle, peak pressure of 300 KPa was recorded using the F-socket, while SOLIDWORKS® software indicated an internal pressure of 343 KPa, aligning closely with F-socket measurements. The new direct-fit socket design prioritizes comfort and flexibility using materials with reduced stiffness.

Shear-Wave-Velocity Profiling of a Test Embankment for a High-Speed Rail Project using the Spectral-Analysis-of-Surface-Waves (SASW) Method

Nondestructive seismic testing was conducted at 24 locations on and around the embankment to evaluate the compaction effort and lateral variabilities at the site. This embankment was being constructed as a test embankment for a high-speed railroad section in the U.S.A. Different compaction techniques were used in different embankment areas, and nuclear-gauge density measurements were performed to evaluate the compaction quality in all areas. Additionally, Spectral-Analysis-of-Surface-Waves (SASW) testing was performed to determine the Vs profiles at numerous locations on and around the embankment. The Vs values determined from the SASW testing were used to compare and evaluate areas where different compaction methods were used, as well as to help understand the overall site. The embankment was divided into three zones. In each zone, five shorter and one longer SASW arrays on top of the embankment were used to determine the Vs profiles. Also, in each zone, Vs profiles in the natural soil were determined using two additional long SASW arrays on the natural ground, one array on each longitudinal side of the embankment. These 24 Vs profiles on and around the embankment were used to evaluate lateral variability in the shear stiffnesses of the geotechnical materials at the site.

Design and performance evaluation of embedded micro stiffness sensor for On-Orbit service tools

On-orbit service of the space station is a vital mission. The space station will be in orbit for many years, and parts would break down and instruments could fail in tight space. This research focuses on the needs of on-orbit maintenance operations in tight space and designs an end tool with embedded micro-sensors. The pressure & deformation sensing module is designed based on the principle of polyurethane flexible plate and metal strain film. The sensor module uses alloy as the housing to form a stiffness sensor, built into the end tool to achieve a single sensor envelope size in the range of 15*15*13 mm3. Calibration results indicate that the overall stiffness of this sensing unit is approximately 12000 N/mm, capable of sensing material stiffness within the range of 50 N/mm ∼ 12000 N/mm. Through multiple measurements and root mean square error (RMSE) analysis, it is shown that the uncertainty of different sensors is within the acceptable range compared with the standard data. The results of the fatigue test and simulated temperature test in the space station show that the performance of the stiffness sensor can meet the normal operation requirements in the space station environment. Comparisons with geometric dimensions, accuracy, sensitivity, and measurement precision show that the uncertainty between different position sensors, metal strain film sensors, and standard sensors does not exceed 1.8 %. The research results confirm the potential of this stiffness-sensing unit in future space missions and dexterous operations applications.

Failure resistance of single-implant crowns assembled from polyetheretherketone and lithium disilicate abutments and different crown materials after artificial aging.

The objective of the present study was to investigate the effect of using different materials for the fabrication of implant abutments and crowns on the mechanical behavior of implant-supported single crowns after artificial aging. The materials were tested in different combinations to reveal whether using stiff or resilient materials as an abutment or a crown material might influence the fracture strength of the whole structure. A total of 40 implants (blueSKY) were restored with identical custom-made CAD/CAM abutments milled out of lithium disilicate or ceramic-reinforced polyetheretherketone (PEEK) and divided into five test groups (n &#61; 8). Forty crowns made of three different materials (zirconia, lithium disilicate, and ceramic-reinforced PEEK) were used to restore the abutments. Specimens were subjected to mechanical loading up to 1,200,000 cycles in a chewing simulator (Kausimulator) with additional thermal cycling. The surviving specimens were subjected to quasi-static loading using a universal testing machine (Z010). The PEEK abutments with zirconia crowns showed the highest median failure load (3890.5 N) while the PEEK abutments with lithium disilicate crowns exhibited the lowest (1920 N). Fracture and deformation occurred in both the crowns and abutments. The failure load of the restorations was influenced by the material of the abutment and crown. Restoring PEEK abutments with zirconia crowns showed a high failure load and no screw loosening.

Cellular solids and prestressed affine networks as models of the elastic behavior of soft biological structures.

We reviewed two microstructural models, cellular solid models and prestressed affine network models, that have been used previously in studies of elastic behavior of soft biological materials. These models provide simple and mathematically transparent equations that can be used to interpret experimental data and to obtain quantitative predictions of the elastic properties of biological structures. In both models, volumetric density and elastic properties of the microstructure are key determinants of the macroscopic elastic properties. In the prestressed network model, geometrical rearrangement of the microstructure (kinematic stiffness) is also important. As examples of application of these models, we considered the shear behavior of the cytoskeleton of adherent cells, of the collagen network of articular cartilage, and of the lung parenchymal network since their ability to resist shear is important for their normal biological and physiological functions. All three networks carry a pre-existing stress (prestress). We predicted their shear moduli using the microstructural models and compared those predictions with existing experimental data. Prestressed network models of the cytoskeleton and of the lung parenchyma provided a better correspondence to experimental data than cellular solid models. Both cellular solid and prestressed network models of the cartilage collagen network provided reasonable agreements with experimental values. These findings suggested that the kinematic stiffness and material stiffness of microstructural elements were both important determinants of the shear modulus of the cytoskeleton and of the lung parenchyma, whereas elasticity of collagen fibrils had a predominant role in the cartilage shear behavior.