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Anisotropy in naturally occurring or synthetic microcellular structures is an important feature for the development of materials with high specific stiffness and strength, in addition to creating materials with unique physical properties. Polymeric foams constitute a broad class of materials that are widely used for their advantages of low density, high specific mechanical properties and high insulative properties. Traditional synthetic routes are slow, energy demanding processes that employ the use of high temperature ovens, freezers, or high‐pressure equipment. Herein we present a convenient and energy efficient method to produce anisotropic high performance polymeric foams via rapid radically induced cationic frontal polymerization coupled with chemical blowing agents. The degree of pore orientation and degree of anisotropy are a result of the propagating front working in concert with the foam volume expansion. This paper presents results into FP foam formation to illustrate how changes in boundary conditions and front initiation position affect both the microcellular structure and their resulting physical and mechanical properties. Additionally, results are presented to show how changes in resin formulation, such as the addition of nanoparticles affect both properties as well as the microcellular structure and anisotropy. [ABSTRACT FROM AUTHOR]

The periodontal ligament plays a significant role in orthodontic and masticatory processes. To explicitly investigate the effects of dynamic force amplitude and frequency on the dynamic tensile properties of the periodontal ligament, in vitro tensile experiments were conducted using a dynamic mechanical analysis at various dynamic force amplitudes across a wide frequency range. Storage modulus, loss modulus, and loss factor values were measured. A Maxwell constitutive model based on modulus was established to describe the dynamic mechanical properties of the periodontal ligament. The results showed that the storage modulus ranged from 29.53 MPa to 158.24 MPa, the loss modulus ranged from 3.26 MPa to 76.16 MPa, and the loss factor values all increased with higher frequencies and higher dynamic force amplitudes. Based on the parameters obtained from the fitting results, it is evident that the short‐term response has a more pronounced impact on the elastic response of the periodontal ligament than the long‐term response. Increasing the dynamic force amplitude and its frequency amplified the viscous effects of the periodontal ligament and enhanced energy dissipation. The proposed constitutive model further demonstrated that the periodontal ligament acts as a viscoelastic biomaterial. These findings have implications for future research on the periodontal ligament. [ABSTRACT FROM AUTHOR]

As advances in heat resistant ultrahigh molecular weight polyethylene (UHMWPE) fiber via ultraviolet (UV) crosslinking, it is worth paying attention to its thermal aging behavior and heat resistance mechanism. UHMWPE fibers in different forms, the fully drawn yarn (FDY) and the UV crosslinked FDY (UVFDY), are subjected to isothermal aging at 135°C. The effects of thermal aging on their surface morphology and mechanical properties are studied and compared initially. The results demonstrate that UVFDY is a kind of a heat‐resistant fiber. Subsequently, to reveal the heat resistance mechanism of UVFDY, its crystalline and orientation structure evolution during thermal aging are further studied. It is indicated that the formation of dense‐packing crystals and disorientation behavior lead to fiber shrink, so that a number of grooves appear on the fiber surface. Since the crosslinked stucture of UVFDY hinders its molecules movement, the crystallization and disorientation behavior of UVFDY are weaker than those of FDY, resulting in UVFDY possesses slighter thermal shrinkage (Ts), fewer grooves and better mechanical properties than those of FDY. Therefore, the heat resistance of the fiber improves effectively after UV crosslinking. This work provides insights into the structure–property relationship of UVFDY during thermal aging, and offers basis data for its application in specific conditions. [ABSTRACT FROM AUTHOR]

In this work, perovskite oxide SrCeO3 was synthesized using the solution combustion method (SCM). Synthesized samples have been characterized using X‐ray diffraction (XRD), Raman, ultra violet (UV)–visible spectroscopy, and scanning electron microscopy (SEM) techniques. The XRD and Rietveld refinement has confirmed the orthorhombic structure with space group Pnma. The average grain size of this ceramic sample is 1.2 µm. The dielectric constant, dissipation factor, modulus, impedance, and alternating current (AC) and direct current (DC) conductivities were analyzed in the temperature range RT to 600°C and frequency range 20 Hz–2 MHz. Further, it was observed that the role of grain boundaries in dielectric and electrical properties is significant, at low temperatures. The origin of the dielectric relaxation and conduction process is the same. The activation energy for DC conduction (Edc) was found to be.79 eV. Electrical conduction/relaxation is assigned to the diffusion of doubly ionized oxygen (Vo··). The value of DC conductivity (1.2 × 10−3 Ω−1 cm−1 at 600°C) and activation energy of.79 eV is very close to the values reported for doped CeO2‐based oxide ion conductors for SOFCs. This study has demonstrated that SrCeO3 can be an alternative candidate for the oxide ion conductor electrolyte application and the potential to be used as a thermally stable capacitor application for microwave dielectric applications. [ABSTRACT FROM AUTHOR]

In conventional foams, anisotropy within the microcellular structure can only be achieved through confinement in one or more directions during the foaming process. Herein, we present a novel, versatile, and energy efficient method to create unique high‐performance foams where the anisotropy of the microcellular and the microcellular structure itself is not dictated by external confinement during the foaming process. To generate such foams, an initial crosslinked gel is first created where the crosslink density of the gel can be tuned by UV intensity and cure time. Next, the gel can be foamed while simultaneously creating a second network via radically induced cationic frontal polymerization (RICFP). In this case, the anisotropy in the foam is dictated by propagation front during the RICFP and the microcellular morphology and cell surface area are dictated by the crosslink density of the gel. These two unique qualities lead to rigid foams that can be generated from a gel without the need for confinement where the microcellular size and shape can be tuned by the crosslink density of the gel precursor. A one‐pot liquid system composed of miscible epoxies, acrylates, and chemical blowing agents (CBAs), allows for control over the foam physical, mechanical, and thermal properties with glass transition temperatures ranging from 74.7 to 125.8°C. Additionally, by patterning the crosslink density of the initial gel through controlled exposure of UV, complex microcellular structures can be formed that are not possible in conventional foaming processes. This positions gel frontal polymerization and foaming as an advanced technique to produce high performing anisotropic foams with a wide array of tunable physical, mechanical, and thermal properties. [ABSTRACT FROM AUTHOR]

Organic‐inorganic metal halide single crystals have attracted a lot of attention due to their flexible structural design and excellent optoelectronic applications. This study details the synthesis of copper‐based [(CH3)4N]2CuBr4 hybrid metal halide single crystals via a slow evaporation method. The crystal structure, crystal habit, chemical groups, intermolecular interactions, electrical properties of the sample were studied via single crystal x‐ray diffraction, scanning electron microscopy, Raman and Fourier transform infrared spectrometer, Hirshfeld surface analysis, impedance spectroscopy, and modulus spectroscopy, respectively. An orthorhombic crystal system with the non‐centrosymmetric space group Pna21 was identified at room temperature. The deformation in the tetrahedra was calculated by the bond angle and bond length deformation index. The Cole‐Cole plot displayed the existence of depressed semicircles, which indicated the predominant distribution of grains, further confirmed by the SEM image. The deformed semi‐circular arcs on the electric modulus curve undeniably prove that the bulk effect dominates the material's electrical properties. Significantly, the compound presents a phase transition at ~240 K and excellent thermal stability up to a temperature of 400 K. Therefore, our research sheds light on the temperature dependence of electrical responses in these hybrid crystals and gives inspiration for the development of single crystal‐based efficient energy devices. [ABSTRACT FROM AUTHOR]

Aluminum (Al), poly(etheretherketone) (PEEK) thermoplastics, and their individual composites have widely been used in many industries, including aerospace and biomedical fields. However, the joining process of those composites has not been explored much to date. In this context, the friction welding process (FWP) could be used as an alternative since it has the ability to join high-strength components with minimal distortion. Therefore, the present study aimed to develop PEEK/Al nanocomposites with varying Al concentrations of 10, 20, 30, and 40 vol% using powder metallurgical technique and further joined the similar composition composites by FWP. Then, the effect of reinforced particle concentrations on the physical, morphological, structural, thermal, and micromechanical behaviors of the joined nanocomposites has been characterized by microscopy, X-ray diffraction, differential scanning calorimetry, and nanoindentation tests. The concentrations of the reinforcement were found to have a significant effect on the crystallinity, melting temperature, glass transition temperature, and thereby micromechanical properties. The results were analyzed and correlated precisely for all the welded nanocomposites systematically. The interdiffusion mechanism was found to be involved in improving the mechanical properties of the present nanocomposites. The highest elastic modulus (13.91 GPa) or nanohardness (0.31 GPa) was obtained for the rotatory part of the PEEK/Al40 nanocomposites at 80 mN load. But, the applied load of 40 mN was the best loading condition due to the uniform change in modulus and nanohardness of all the nanocomposites. Therefore, the present alternative joining method of the PEEK/Al nanocomposites might be used for aerospace components. Highlights • Development of PEEK/aluminum with 10, 20, 30 and 40 vol% Al nanocomposites. • Friction welding of similar composite material, PEEK/Al-PEEK/Al nanocomposites. • Microstructural, thermal, and nanomechanical analyses. • Effect of metal particle reinforcement on the friction welded nanocomposites. • FW PEEK/Al40 nanocomposite is found to be the best. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal (AM) fungi are ubiquitous and impactful symbionts of most land plants and can regulate essential ecological processes. AM fungi can increase the cellulose content of root cell walls and hence the root tensile strength of grass. How AM fungi can alter other essential biomechanical properties is not clear. This study aims to study the contribution of AM fungi in altering biomechanical properties by comparing mycorrhizal and non‐mycorrhizal roots. We inoculated three fungal species to vetiver grass (Chrysopogon zizanioides) for comparison. Eight root biomechanical properties (i.e., yield strain, yield stress, break strain, tensile strength, Young's modulus, plastic modulus, plastic strain, and toughness) were determined for each root using a newly developed Fortran language‐based program. Inoculating AM fungi decreased both Young's modulus and plastic modulus by 23% and 17%, respectively, versus control, although it was species‐dependent. Yield stress was not significantly affected, but tensile strength was increased by 7%–17% upon fungal symbiosis. Together with the increases in break strain by 15%–20%, mycorrhizal roots possessed a notably higher toughness than non‐mycorrhizal roots by up to 36%. Greater root cohesion of mycorrhizal roots confirmed the enhanced (1.5‐fold) factor of safety in the soil‐root system. Our findings imply that AM fungi are of significant interest in plant biomechanics and geotechnical engineering. Applying AM fungi on soil slopes has considerable potential to improve vegetation and stability of green slopes. [ABSTRACT FROM AUTHOR]

Highly efficient perovskite solar cells typically rely on spiro‐OMeTAD as a hole transporter, achieving a 25.7 % efficiency record. However, these cells are susceptible to harsh 85 °C conditions. Here, we present a peri‐xanthenoxanthene‐based semiconducting homopolymer (p‐TNI2) with matched energy levels and a high molecular weight, synthesized nearly quantitatively through facile oxidative polymerization. Compared to established materials, p‐TNI2 excels in hole mobility, morphology, modulus, and waterproofing. Implementing p‐TNI2 as the hole transport layer results in n‐i‐p perovskite solar cells with an initial average efficiency of 24.6 %, rivaling 24.4 % for the spiro‐OMeTAD control cells under identical conditions. Furthermore, the p‐TNI2‐based cells exhibit enhanced thermostability at 85 °C and operational robustness. [ABSTRACT FROM AUTHOR]

Objectives: To compare the filler weight percentage (wt%), filler and resin composition, flexural strength, modulus, and hardness of several 3D‐printed resins to direct and indirect restorative materials. Materials and Methods: Four 3D‐printed resins (C&B MFH, Ceramic Crown, OnX, and OnX Tough), one milled resin composite (Lava Ultimate), one conventional composite (Filtek Supreme), and one ceramic (IPS e.max CAD) were evaluated. Filler wt% was determined by the burned ash technique, and filler particle morphology and composition were analyzed by scanning electron microscopy and energy‐dispersive spectroscopy, respectively. Organic resin composition was analyzed by Fourier transform infrared spectroscopy. Three‐point bend flexural strength and modulus of the materials were determined by ISO 4049 or ISO 6872. Vickers microhardness was measured. Data were compared with a one‐way analysis of variance (ANOVA) and Tukey post hoc analysis. Linear regression analysis was performed for filler wt% versus flexural strength, modulus, and hardness. Results: 3D‐printed resins were composed of various sized and shaped silica fillers and various types of methacrylate resins. Significant differences were found among filler wt% with some materials around 3% (C&B MFH), others between 33% and 38% (OnX Tough and OnX), others around 50% (Ceramic Crown), and some around 72% (Filtek Supreme and Lava Ultimate). All 3D‐printed resins had significantly lower flexural strength, modulus, and hardness than the conventional and milled resin composites and ceramic material (p < 0.001). Filler wt% demonstrated a linear relationship with modulus (p = 0.013, R2 = 0.821) and hardness (p = 0.018, R2 = 0.787) but not flexural strength (p = 0.056, R2 = 0.551). Conclusions: 3D‐printed resins contain from 3% to 50% filler content. Filler wt% alone does not affect flexural strength, but strength may be affected by resin composition as well. Although the 3D‐printed resins had lower flexural strength, modulus, and hardness than milled and conventional composite and ceramic, they demonstrated nonbrittle plastic behavior. Clinical Significance: The properties of 3D‐printed resins vary based on their composition, which affects their clinical applications. [ABSTRACT FROM AUTHOR]

The axial buckling load of single carbon fiber or composite strands is typically predicted using Euler's formula, developed for isotropic materials. This study introduces anisotropy in a mechanical carbon/epoxy Z‐pin model under axial pressure. It examines the influence of compressive modulus, shear modulus, off‐axis angle, and aspect ratio on its buckling behavior. Results show that the axial instability performance of the Z‐pin decreases with lower compression, shear modulus, and aspect ratio while keeping the tensile modulus fixed. Anisotropy decreases buckling load by up to 14% compared with Euler's formula, which only considers tensile modulus. Additionally, the impact of the deflection Angle between the pressure and pin‐axis can be ignored when it is less than 3°. Highlights: Euler formula overestimates composite Z‐pin buckling force under axial pressure.Anisotropy decreases buckling load by up to 14% for carbon/epoxy.Shear modulus is more influential on Z‐pin with a small aspect ratio.For off‐axial compression angles <3°, influence can be ignored. [ABSTRACT FROM AUTHOR]

Global sensitivity analysis of complex moduli of carbon fiber reinforced polymer (CFRP) is performed by using variance‐based sensitivity analysis. Twelve material properties of matrix and fiber are selected as input arguments, including fiber volume fraction, three matrix properties, and eight carbon fiber properties. Ten thousand samples are generated with Sobol sequence. Based on the correspondence principle, six complex moduli of unidirectional CFRP, and two complex moduli of quasi‐isotropic laminate, orthogonal laminate, and symmetric laminate with different fiber angles are predicted using the generalized method of cells and classical laminate theory. The sensitivity indexes of all input arguments are calculated. The results show that the loss factors of CFRP are mainly affected by the matrix loss factor and fiber axial loss factor, and slightly affected by the fiber transverse loss factor. Highlights: Sensitivity analysis reveals key factors influencing CFRP complex moduli.Impact of fiber and matrix properties on CFRP damping revealed.Insights for high‐damping and high‐stiffness CFRP development.Enhanced understanding of energy absorption mechanisms.Uncovering the dominant role of matrix and fiber axial properties in damping. [ABSTRACT FROM AUTHOR]

Optimization of energy storage performance in dielectric ceramics has been a focus in recent decades due to the benefits of high energy storage density, efficiency, and exceptional temperature stability. In this work, we report huge dielectric constant in La0.55Li0.35TiO3‐δ and sharp decrease in its value with the substitution of Sr and Cu at Ti position. These samples La0.55Li0.35TiO3‐δ (LLTO), La0.55Li0.35Ti0.9Cu0.1O3‐δ (LLTCO) and La0.55Li0.35Sr0.1Ti0.9O3‐δ (LLSTO) were prepared by solid state reaction method. The interfacial polarization of lithium ion aggregation close to the grain boundaries and the dipoles of Li ions in the sample are suggested to be the source of the enormous dielectric values. Parent composition (LLTO) shows highest dielectric constant value (6.29 × 105 at frequency 10 Hz, 7.30×104 at 1 kHz) recorded at room temperature while the lowest dielectric loss value (0.124) was observed for LLSTO at frequency 1 kHz. Structural characterization has been done using X‐ray diffraction (XRD) technique to investigate the crystal structure of the prepared compositions. The XRD patterns show the similar crystal structure for all the compositions with the parent composition LLTO. The optical band gap is calculated by Kulbeka Munk function and Tauc plot using UV–visible diffuse reflectance spectroscopy technique. The maximum band gap value (3.32 eV) is obtained for parent composition while doping of Cu and Sr at Ti site in La0.55Li0.35TiO3‐δ decreases the band gap value. Optical microscopy shows the micron size grains in these samples. Doping of Sr and Cu in perovskite structure of LLTO brings tunability in dielectric and optical properties. [ABSTRACT FROM AUTHOR]

Optimization of energy storage performance in dielectric ceramics has been a focus in recent decades due to the benefits of high energy storage density, efficiency, and exceptional temperature stability. In this work, we report huge dielectric constant in La0.55Li0.35TiO3‐δ and sharp decrease in its value with the substitution of Sr and Cu at Ti position. These samples La0.55Li0.35TiO3‐δ (LLTO), La0.55Li0.35Ti0.9Cu0.1O3‐δ (LLTCO) and La0.55Li0.35Sr0.1Ti0.9O3‐δ (LLSTO) were prepared by solid state reaction method. The interfacial polarization of lithium ion aggregation close to the grain boundaries and the dipoles of Li ions in the sample are suggested to be the source of the enormous dielectric values. Parent composition (LLTO) shows highest dielectric constant value (6.29 × 105 at frequency 10 Hz, 7.30×104 at 1 kHz) recorded at room temperature while the lowest dielectric loss value (0.124) was observed for LLSTO at frequency 1 kHz. Structural characterization has been done using X‐ray diffraction (XRD) technique to investigate the crystal structure of the prepared compositions. The XRD patterns show the similar crystal structure for all the compositions with the parent composition LLTO. The optical band gap is calculated by Kulbeka Munk function and Tauc plot using UV–visible diffuse reflectance spectroscopy technique. The maximum band gap value (3.32 eV) is obtained for parent composition while doping of Cu and Sr at Ti site in La0.55Li0.35TiO3‐δ decreases the band gap value. Optical microscopy shows the micron size grains in these samples. Doping of Sr and Cu in perovskite structure of LLTO brings tunability in dielectric and optical properties. [ABSTRACT FROM AUTHOR]

In this study, the formation of clay nanolayer clusters inside the high‐density polyethylene (HDPE) matrix was evaluated using a specific strategy based on energy equilibrium in the melt mixing stage. Furthermore, the formed interphase region around nanoparticle domains was precisely evaluated considering the molecular structure of the matrix and linear variation of the physical/mechanical characteristics. The obtained results were used in a developed analytical model to predict the tensile modulus of the nanocomposite system containing randomly oriented nanoparticle domains. The domains consisted of exfoliated, intercalated, or aggregated/agglomerated nanolayers placed in different excluded volumes as the components of an equivalent box model. Different comparative studies were performed using the obtained data from different tests, applied to the prepared HDPE/clay nanocomposite samples, and other data from the literature. It was found that the confrontation between the exerted dispersion energy, by the mixer, and interparticle cohesion energy defined the thickness and physical/mechanical characteristics of the final aggregates/agglomerates in a nanocomposite. Though, the size and content of aggregates/agglomerates increased with the content of initially added nanoparticles. Consequently, the random orientation of each nanoparticle domain and formation of the polymer/particle interphase were proved to have determinative impacts on the mechanical properties of the system. [ABSTRACT FROM AUTHOR]

A novel fitting method of obtaining the anisotropic complex moduli of fibers based on the complex moduli of matrix and composites is presented. The complex longitudinal, transverse and in‐plane shear moduli of the unidirectional T700 carbon fiber reinforced epoxy resin composite and the complex modulus of its matrix are measured using dynamic mechanical analysis. The predicted properties of the composite are calculated using the generalized method of cells (GMC). The complex axial, transverse and axial shear moduli of the carbon fibers are obtained by minimizing the sum of the squares of the modules of the difference between the test properties and predicted properties. Finally, the results of the experiment, finite element analysis, and GMC are compared. The results show that the complex axial and transverse moduli of the carbon fibers can be accurately evaluated, while the complex axial shear modulus cannot be accurately determined. [ABSTRACT FROM AUTHOR]

During cataract surgery, diseased lenses in the eye are surgically removed and replaced with polymeric artificial intraocular lenses (IOLs). Patients can experience a complication called posterior capsular opacification (PCO) that is corrected through the removal of part of the posterior capsule using a neodymium: yttrium‐aluminum‐garnet (Nd‐YAG) laser to restore the optical path. These interventions have increased costs and can damage the retina and the IOL. PCO develops when lens epithelial cells (LECs) proliferate, migrate, and undergo epithelial‐to‐mesenchymal transition. Neutrophils involved in the immune response triggered during implantation impact LEC behavior and produce damaging neutrophil extracellular traps (NETs). In this research, poly(2‐hydroxyethyl methacrylate) (PHEMA) ‐based disks were synthesized with varying amounts of comonomer (HEMA with 0, 2, and 12 mol% MMA) and functionalized with carboxyl and amine groups, yielding nine different hydrogels. Material and chemical properties of the disks were characterized, and neutrophil‐like HL60 cells and B3 LECs were incubated with the disks. HL60 cell behavior was more strongly influenced by chemical functionalization than by mechanical properties with increases in adherence and NET accumulation. Conversely, the behavior and viability of B3 LECs were more strongly influenced by mechanical properties with increases in cell adhesion and α‐SMA expression with increasing compressive moduli. Interestingly, B3 LECs had decreased viability and increased α‐SMA expression when cultured on PHEMA2 disks pretreated with isolated NETs. Critical to the understanding of PCO and its prevention are both surface chemistry and mechanics as well as the inflammatory response. [ABSTRACT FROM AUTHOR]

Information on mechanical properties of human enamel and dentin and effect of load on their deformation and damage tolerance is very important in the development of successful dental materials. In this study, the hardness, indentation modulus and deformation characteristics of tooth have been investigated across the lingual–buccal enamel and dentin cross‐section by instrumented indentation up to 1500‐nm indentation depth. We realized and examined the distribution of hardness and modulus at different areas of enamel and dentin with the aim to understand deformation behaviour at these different locations. Scanning electron microscopy was used for the microstructure characterization of the enamel and dentin and their deformation behaviour. Raman spectroscopy analyses were carried out for determination of the enamel and dentin composition as well. The average values of hardness and modulus for enamel in the occlusal area are 5.35 ± 0.19 and 98.1 ± 1.5 GPa, in the inner area 3.68 ± 0.5 and 81.8 ± 5 GPa and in the area close to the dentin–enamel junction 2.83 ± 0.27 and 71.4 ± 4.1 GPa, respectively. The average values of hardness and modulus of dentin in the area close to the dentin–enamel junction are 0.71 ± 0.05 and 21.27 ± 0.76 GPa and in the inner area 0.65 ± 0.06 and 19.79 ± 0.93 GPa, respectively. The effect of the indentation location on deformation and mechanical properties was clarified. [ABSTRACT FROM AUTHOR]

Polyacrylamide nanospheres are a kind of polymer material that can improve the development effect of oilfield water flooding and realize reservoir stimulation. However, due to its good water absorption, the strength cannot well meet the needs of practical production, and is forced to be limited to application on oil displacement. Therefore, in this paper, SiO2/PAM composite nanospheres were synthesized by the inverse microemulsion method to meet the needs of profile control and water shutoff in oilfields. The structure, oil displacement effect and rheological properties of polyacrylamide nanospheres and SiO2/PAM composite nanospheres were comparatively studied. The results show that both nanospheres are viscoelastic nanospheres. Since the elastic response is greater than the viscous response in SiO2/PAM composite nanospheres, and the polymer nanospheres do the opposite, there are significant differences in various rheological properties, such as variation of apparent viscosity with shear rate, creep recovery characteristics, viscoelasticity etc. This work provides a basis for the practical application of SiO2/PAM composite nanospheres in oilfields. [ABSTRACT FROM AUTHOR]

Colorless polyimide (CPI) films showed great potential for flexible display applications due to their unique combination of excellent optical transparency, and outstanding thermal and mechanical properties. Herein, a series of colorless poly(amide‐imide)s were prepared via a conventional two‐step method, using 1,2,3,4‐cyclobutanetetracarboxylic dianhydride (CBDA), 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 2,2′‐bis(trifluoromethyl)benzidine (TFMB), and 4,4′‐diaminobenzanilide (DABA) as the monomers. The thermal, mechanical, and optical properties of these copolymers were optimized by adjusting the molar ratios of these monomers. The amide linkages significantly improved the mechanical properties and dimensional stability of the resultant CPI films due to strong hydrogen bonding interactions. In particular, CPI‐f films with monomer compositions of TFMB (50 mol%), DABA (50 mol%), 6FDA (50 mol%), and CBDA (50 mol%) exhibited tensile strength of 177 MPa, modulus of 5.5 GPa, coefficient of thermal expansion value of 18 ppm K−1, and glass transition temperature of 394°C. Furthermore, the optical properties of these copolymers were well balanced due to the adoption of CBDA, which can suppress the formation of charge transfer complexes. Specifically, these CPI films displayed transmittance at 550 nm of >88%, b* values of <5.5, haze values of <1%. The aforementioned results revealed that copolymerization is an effective strategy to achieve CPIs with excellent comprehensive properties. [ABSTRACT FROM AUTHOR]

The present paper describes an experimental study on mechanical properties of additively manufactured anti‐tetrachiral auxetic structures under shear and flexural loading. Specimens of ABS material are fabricated using material extrusion technique of additive manufacturing. Experiments are planned using central composite design method. Three process factors, namely, slice thickness, print speed, and contour width, are considered to study their influence on modulus, strength, and specific energy absorption (SEA) of fabricated structures. To perform shear testing on specimen, a novel fixture is designed and fabricated. Flexural properties are measured using three‐point bending test on universal testing machine. It is found that all three process factors significantly affect modulus, strength, and SEA of the structure under shear and flexural loading. Mechanical properties improve with increase in slice thickness, print speed, and contour width. Regression models are developed to predict the response characteristics. In addition, optimized values of process factors are determined to maximize the mechanical properties of the structure. [ABSTRACT FROM AUTHOR]

Purpose: Osteoporosis is a bone disease associated with enhanced bone loss, microstructural degeneration, and fracture‐risk. Finite element (FE) modeling is used to estimate trabecular bone (Tb) modulus from high‐resolution three‐dimensional (3‐D) imaging modalities including micro‐computed tomography (CT), magnetic resonance imaging (MRI), and high‐resolution peripheral quantitative CT (HR‐pQCT). This paper validates an application of voxel‐based continuum finite element analysis (FEA) to predict Tb modulus from clinical CT imaging under a condition similar to in vivo imaging by comparing with measures derived by micro‐CT and experimental approaches. Method: Voxel‐based continuum FEA methods for CT imaging were implemented using linear and nonlinear models and applied on distal tibial scans under a condition similar to in vivo imaging. First, tibial axis in a CT scan was aligned with the coordinate z‐axis at 150 μm isotropic voxels. FEA was applied on an upright cylindrical volume of interests (VOI) with its axis coinciding with the tibial bone axis. Voxel volume, edge, and vertex elements and their connectivity were defined as per the isotropic image grid. A calibration phantom was used to calibrate CT numbers in Hounsfield unit to bone mineral density (BMD) values, which was then converted into calcium hydroxyapatite (CHA) density. Mechanical properties at each voxel volume element was defined using its ash‐density defined on CT‐derived CHA density. For FEA, the bottom surface of the cylindrical VOI was fixed and a constant displacement was applied along the z‐direction at each vertex element on the top surface to simulate a physical axial compressive loading condition. Finally, a Poisson's ratio of 0.3 was applied, and Tb modulus (MPa) was computed as the ratio of average von Mises stress (MPa) of volume elements on the top surface and the applied displacement. FEA parameters including mesh element size, substep number, and different tolerance values were optimized. Results: CT‐derived Tb modulus values using continuum FEA showed high linear correlation with the micro‐CT‐derived reference values (r ∈ [0.87 0.90]) as well as experimentally measured values (r ∈ [0.80 0.87]). Linear correlation of computed modulus with their reference values using continuum FEA with linear modeling was comparable with that obtained by nonlinear modeling. Nonlinear continuum FEA‐based modulus values (mean of 1087.2 MPa) showed greater difference from their reference values (mean of 1498.9 MPa using micro‐CT‐based FEA) as compared with linear continuum methods. High repeat CT scan reproducibility (intra‐class correlation [ICC] = 0.98) was observed for computed modulus values using both linear and nonlinear continuum FEA. It was observed that high stress regions coincide with Tb microstructure as fuzzily characterized by BMD values. Distributions of von Mises stress over Tb microstructure and marrow regions were significantly different (p < 10–8). Conclusion: Voxel‐based continuum FEA offers surrogate measures of Tb modulus from CT imaging under a condition similar to in vivo imaging that alleviates the need for segmentation of Tb and marrow regions, while accounting for bone distribution at the microstructural level. This relaxation of binary segmentation will extend the scope of FEA application to assess mechanical properties of bone microstructure at relatively low‐resolution imaging. [ABSTRACT FROM AUTHOR]

This study aimed at searching the predictive values of testicular shear wave elastic modulus in testicular functions for varicocele patients. This was a prospective case–control study. We divided the participants into two groups: varicocele group and control group, the latter recruited men with normal physical examination, testicular ultrasound, semen and endocrine results. A total of 97 participants were enrolled: 67 patients in varicocele group, 30 participants in control group. There were statistical differences in left testicular shear wave elastic modulus, left testicular volume, testicular atrophy index, total sperm count, sperm concentration, sperm viability and testosterone between the two groups, between different grades in varicocele group, between different periods in varicocele group. Left testicular shear wave elastic modulus was inversely correlated with total sperm count, sperm concentration, sperm viability and testosterone. Left testicular shear wave elastic modulus cut‐off was calculated as 5.235, 5.130, 4.640 and 5.310 Kpa using ROC curve according to the abnormalities of total sperm count, sperm concentration, sperm viability and testosterone. When the left testicular shear wave elastic modulus was higher than these values, the corresponding parameter was more likely to be abnormal. Testicular shear wave elastic modulus has predictive values in testicular functions for varicocele patients. [ABSTRACT FROM AUTHOR]

In the present work, an experimental investigation is performed to study the influence of process parameters on mechanical properties of tetra‐anti‐chiral auxetic structures manufactured by material extrusion (ME) technique of additive manufacturing (AM). Process parameters namely layer height, print speed, and print temperature are considered, while responses are compressive strength (σ), modulus (E), and specific energy absorption (SEA). Specimens of acrylonitrile‐butadiene‐styrene (ABS) polymer are fabricated and then tested under compressive loading. From the experimental results, it is observed that all process parameters significantly influence the mechanical properties of the structure. Scanning electron microscope (SEM) is used to study microstructural defects of the tested specimen. To maximize the responses, optimization of process parameter is performed using desirability function approach. Regressive models are developed to predict the mechanical properties. [ABSTRACT FROM AUTHOR]

In the current article, Kolarik model is progressed for the tensile modulus of a polymeric system containing dispersed halloysite nanotubes (HNT) and adjacent interphase section. The progressive model correlates the nanocomposite's modulus to HNT concentration (volume fraction and weight percentage), the extents of HNT and nearby interphase section in addition to the densities of polymer medium and HNT. The productions of the progressive model are linked to the tentative results and the influences of all variables on the modulus of system are justified. The modulus of system reduces as HNT radius increases, but HNT weight percentage directly controls the nanocomposite's modulus. The modulus of samples maximizes by 47% by the deepest interphase section of 20 nm establishing a straight link among nanocomposite's modulus and interphase thickness. The increment of polymer matrix density improves the modulus of samples, but there is an opposite relation between the modulus of system and HNT density. Furthermore, the calculations exactly match to the experimental facts of numerous examples representing the accurateness of the progressed model. [ABSTRACT FROM AUTHOR]

Colloidal probes have been increasingly demanded for the characterization of cellular modulus in atomic force microscope because of their well‐defined geometry and large contact area with cell. In this work, submicron colloidal probes are prepared by scanning electron microscope/focused ion beam and compared with sharp tip and micron colloidal probe, in conjunction with loading velocity and indentation depth on the apparent elastic modulus. NIM and cartilage cells are used as specimens. The results show that modulus value measured by sharp tip changes significantly with loading velocity while remains almost stable by colloidal probes. Also, submicron colloidal probe is superior in characterizing the modulus with increasing indentation depth, which could help reveal the mechanical details of cellular membrane and the modulus of the whole cell. To test the submicron colloidal probe further, the modulus distribution map of cell is scanned with submicron colloidal probe of 50 nm radius during small and large indentation depths with high spatial resolution. The outcome of this work will provide the effective submicron colloidal probe according to the effect of loading velocity and indentation depth, characterizing the mechanical properties of the cells. [ABSTRACT FROM AUTHOR]

Native and carbonized freeze‐cast bacterial cellulose‐alginate (BC‐ALG) foams possess an ice‐templated honeycomb‐like architecture with remarkable properties. Their unique pore morphology consists of two levels of porosity: 20–50 µm diameter pores between, and 0.01–10 µm diameter pores within the cell‐walls. The mechanical properties of the BC‐ALG foams, a Young's modulus of up to 646.2 ± 90.4 kPa and a compressive yield strength of up to 37.1 ± 7.9 kPa, are high for their density and scale as predicted by the Gibson–Ashby model for cellular materials. Carbonizing the BC‐ALG foams in an inert atmosphere at 1000–1200 °C in a second processing step, both pore morphology and mechanical properties of the BC‐ALG remain well preserved with specific mechanical properties that are higher than those reported in the literature for similar foams. Also the electrical conductivity of the BC‐ALG foams is high at 1.68 ± 0.04 S cm−1 at a density of only 0.055 g cm−3, and is found to increase with density as predicted, and as a function of the degree of carbonization determined by both carbonization temperature and atmosphere. The property profile makes freeze‐cast BC‐ALG foams and their carbonized foams attractive for energy applications and as a sorbent. [ABSTRACT FROM AUTHOR]

The present work reports formation of polyurethane (PUR) and carboxylic functionalized graphene (COOH‐fG) nanocomposites via solution mixing method and static and dynamic mechanical characterization with dynamic mechanical analysis (DMA), nano indentation, and tensile and compressive testing. Magnetic stirring of the solutions of PUR in N,N dimethylformamide (DMF) and COOH‐fG in DMF was performed for different compositions of filler, 1%, 3%, 5%, 7%, and 10%, which were heated to obtain nanocomposite films followed by injection molding to cast into samples. Uniform dispersion and good intercalation were observed upon characterization by field emission scanning electron microscopy and X‐ray diffraction techniques. DMA showed that the storage modulus improved with increasing frequency of loading, and a linear decrement in the damping factor with an increase in the concentration of filler was observed. The maximum depth of indent in nano‐indentation test showed a decreasing trend, indicating improvement in nanohardness and elastic modulus with an optimum obtained at 5 wt% composition. An improvement in tensile modulus, tensile strength, and toughness, which were more substantial at lower compositions of filler, was observed. An optimum compressive modulus was obtained for 10 wt% of filler due to more resistance provided by graphene plates to compression as compared to PUR. [ABSTRACT FROM AUTHOR]

Aluminium matrix hybrid composites have been consolidated effectively by spark plasma sintering with new combinations of reinforcement and high volume percentage of ceramic particulates to maximize specific hardness and specific modulus through the powder metallurgy route. The aforementioned techno‐scientific accomplishment with regard to metal matrix composite aims to meet a continuous increase in the global demand for a material with minimum structural weight and high‐modulus for structural (automotive and aerospace) applications. The new aluminium based hybrid composite developed by incorporating ceramic particulate reinforcements (12.5 wt.% silicon carbide and 12.5 wt.% titanium carbide) along with 22.5 wt.% copper as the metallic reinforcement attains significantly high specific hardness (85 HV/gcm−3), specific Young's modulus (33.56 GPa/g cm−3), specific bulk modulus (27.97 GPa/g cm−3) when compared with the reported range of specific hardness (13 HV/g cm−3–89 HV/g cm−3), specific Young's modulus (24 GPa/g cm−3–27 GPa/g cm−3) and specific bulk modulus (20 GPa/g cm−3–22 GPa/g cm−3) possessed by structural steels. This is accredited to the genesis of a novel microstructure that consists of fine copper, silicon carbide and titanium carbide particulates together with a nominal in‐situ originated aluminium‐copper equilibrium phases distributed in a highly substructured aluminium based matrix with a significant dislocation density (7.56 ⋅ 1014 m‐2). [ABSTRACT FROM AUTHOR]

This work attempts to estimate the effect of the reinforcement percentage on Young's modulus for membranes of polymer‐clay nanocomposites (PCNs). Models tried to simulate different contents of the reinforcement for experimentally obtained PCNs with nanometric montmorillonite clays (MMT) incorporated into a polynorbornene dicarboximide matrix. The analyses were carried out modeling through discrete element method (DEM) and finite element analysis (FEA) volume fractions from 0.01 to 0.025 of elliptical MMT nano‐platelets with aspect ratios = 0.2 (1000 × 500 nm) and thicknesses of 1 nm. These models were generated using as starting point the morphology and distribution of the reinforcements observed in scanning electron microscopy for experimental PCNs. Estimations were compared to predictions obtained by Rule of Mixtures and other mathematical models. Results showed that the elastic modulus of the nanocomposites significantly rises as MMT volume fraction increases. Besides, the use of DEM‐FEA generated the predictions closest to the experimental values, with relative errors lower than 10%. For the other models, the errors were significantly high, even reaching 100%. This shows the importance of DEM‐FEA to obtain a more accurate model of a real composite and a better estimation of its mechanical behavior. [ABSTRACT FROM AUTHOR]

Background: The modulus and resonant frequency of cancer cells and extracellular matrix are increased in both basal cell and squamous cell carcinomas, and in addition, the collagen stiffness is increased. The organization of the extracellular matrix surrounding cancer cells is clearly different than the extracellular matrix that is seen in normal skin. Materials and Methods: We have used vibrational optical coherence tomography (VOCT) to measure the resonant frequency and stiffness of collagen, vascular, and reorganized fibrous extracellular matrix components. Measurements of vessels and fibrotic collagen content made on basal cell carcinomas (BCCs) are compared to similar measurements made on normal skin from different anatomical locations. Results: Lesions with basal cell carcinomas exhibit characteristic resonant frequencies and moduli of reorganized extracellular matrix characteristic of fibrotic tissue. Cancerous lesions are characterized by dermal collagen (100 Hz), vascular (150 Hz), and fibrotic peaks (200‐230 Hz). The fibrotic peak is not found in areas of normal skin. Conclusions: Based on this pilot study, it is hypothesized inflammation may promote precancerous lesion formation in the surrounding extracellular matrix. Measurement of the increases in vaculature and fibrotic content may be useful in early detection of BCCs. [ABSTRACT FROM AUTHOR]

High‐load bearing bone replacement composite was produced from poly(lactic acid) (PLA), surface modified hydroxyapatite (HA) and glass fiber (GF). Composition dependence and other salient properties of the composites were investigated with respect to the mechanical and dynamic mechanical performance of the composites. Incorporation of modified HA facilitates dispersion, improves bonding, as well as induce heterogeneous nucleation in the PLA matrix. On the other hand, GF greatly influenced the mechanical properties of the composite. The effectiveness coefficient, C, and adhesion factor, A, showed that incorporation of hybrid HA/GF filler helps to improve interfacial interaction due to increased bonding among the components, which produced remarkable enhancement in mechanical performance. For instance, tensile and flexural modulus of the PLA‐HA‐GF composite was raised by 86% and 82%, respectively. In addition, whereas incorporation of HA alone resulted in decreased impact strength (IS) of PLA, the IS of the PLA‐HA‐GF composite improved by 42%. Furthermore, damping of the ternary composite was reduced by 34% whereas the storage modulus is 1273 MPa higher than neat PLA. Therefore, hybrid HA/GF reinforced PLA offers alternative possibility for the fabrication of composites suitable for use in bone replacement and other orthopedic applications requiring high‐load bearing materials. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to evaluate the flexural strength (FS), flexural modulus (FM), and fatigue limit (FL) of 3D-printed resin-based polymers and composites and compare them to 3D-printed composites., Materials and Methods: A bar-shaped specimen (25 × 2 × 2 mm) was CAD designed according to ISO 4049:2019, and 60 duplicates of the 3D model were nested at a 45-degree angle with the printing platform and 3D-printed with three materials: denture teeth resin (Denture Teeth, Formlabs), temporary crown and bridge resin (Temporary CB, Formlabs), and composite (Flexcera Smile Ultra+, Desktop Health). The 3D model was also imported into a dental CAM software, duplicated 60 times, nested, and milled from a 3D-milled composite puck (Ivotion Denture Teeth, Ivoclar). All specimens were post-processed following the manufacturer's recommendation. The specimens were then subjected to a three-point bending test until failure using a Universal Testing Machine at a crosshead speed of 0.75 mm/min, and FS and FM were calculated. The remaining thirty specimens were tested for Fatigue Limit using the staircase approach starting at 50% FS maximum up to 1.2 M cycles at 10 Hz. The data were analyzed using one-way ANOVA and the Weibull distribution (α = 0.05)., Results: The results showed that Ivotion and Flexcera had higher FS (110.3 ± 7.1 MPa and 107.6 ± 6.4 MPa, respectively) and FM (3.3 ± 0.1 GPa and 3.0 ± 0.2 GPa, respectively) compared to the 3D-printed Denture Teeth (FS = 66.4 ± 18.5 MPa and FM = 1.8 ± 0.1 GPa) and Temporary CB (FS = 79.6 ± 12.1 MPa and FM = 2.7 ± 0.4 GPa). Weibull analysis showed that the Ivotion and Flexcera had a more uniform and narrower spatial distribution of defects (m: 27.98 and 29.19) than the printed materials, which had m values of 8.17 and 4.11 for Temporary CB and Denture Teeth, respectively. Although no differences were found in the static properties (FS and FM) between Ivotion and Flexcera, Ivotion presented a higher endurance limit than Flexcera (51.43 vs. 40.95 MPa). The Temporary CB presented 21.08 MPa and Denture Teeth presented 17.80 MPa of endurance limit., Conclusions: 3D-milled (Ivotion Denture Teeth) and 3D-printed (Flexcera Smile Ultra+) composites outperformed 3D-printed resins (Formlabs Denture Teeth and Temporary Crown & Bridge) in terms of flexural properties and fatigue resistance. 3D-milled (Ivotion) and 3D-printed (Flexcera) composites exhibited similar flexural properties, but 3D-milled composites showed a 25% higher fatigue endurance limit, suggesting improved clinical longevity., (© 2024 by the American College of Prosthodontists.)

This work aims to develop smart stimuli responsive composites utilizing hydrogenated nitrile rubber (HNBR), fly ash (FA), and slag (SG) with white cement (WC). HNBR has been chosen by capitalizing its unique attributes of high temperature performance and high oil resistance as the matrix and coining the synergistic setting characteristics of FA and SG as industrial wastes with WC. The composites displayed synergism in mechanical and thermal properties. The calcium‐rich phases of FA and SG, entice the postpolymerization modification of the rubber matrix in conjunction with cement serving as reactive fillers. The changes of modulus (~50 MPa), mass (~7%), volume (~8%), and hardness were observed upon repeated wet‐dry cycles. These are attributed to the ionic interactions between the modified polymer matrix and cementitious phases as a result of postpolymerization conversion. These smart composite materials could be used for sealing and microfluidic valves for the downhole applications in oil field industries. [ABSTRACT FROM AUTHOR]

In this work, we studied the effects of storage moduli on thermal healing of poly(styrene‐co‐methacrylate) and poly(styrene‐co‐itaconate) ionomers. It was found that as the ion content and neutralization degree of the ionomers increased, the healing efficiencies decreased. This was due to the fact that the ionic aggregates, acting as physical cross‐links, and the clustered regions of the ionomers, reducing polymer chain mobility, interrupted the relaxation of the polymer chains near the damaged site, slowing the recovery. The most important finding in this work was that, to heal the ionomer without severe sample deformation, the optimal healing temperature should be the temperature where the storage modulus of the ionomer was similar to 106.6 Pa. Obviously, the healing rate and healing efficiency were mainly influenced by the healing temperature, related directly to the storage modulus of the polymer, and the maximum healing efficiency was strongly affected by healing time. [ABSTRACT FROM AUTHOR]

Rheology is a powerful and versatile analytical tool for providing information about changes in the composition, structure, and interactions of food emulsions. Moreover, an understanding of emulsion rheology is essential for designing efficient food processing operations and emulsion‐based foods with the desired physicochemical, sensory, and nutritional attributes, such as appearance, texture, flavor, shelf life, and bioavailability. This article provides a brief overview of the current understanding of food emulsions, with a focus on how their viscosity is related to the properties of the emulsion droplets present. [ABSTRACT FROM AUTHOR]

Accurate evaluation of the reliability of photovoltaic (PV) packaging materials is critically important for the long‐term safe operation of modules. However, the complexity of the laminated systems due to their multilayered and multicomponent structures and diverse aging mechanisms makes a thorough system evaluation very challenging, especially when the degradation is non‐uniform through the thickness. In such a case, neither surface nor bulk measurements can present a clear picture of the degradation profile. In this study, fluorescence imaging was developed to visualize the degradation depth‐profiles of an aged laminated PV system. A glass/ethylene vinyl acetate (EVA) encapsulant/poly(ethylene terephthalate) (PET)‐PET‐EVA (PPE) backsheet laminate was weathered with the glass‐side facing an ultraviolet (UV) light source for 3840 h. Cross‐sectional fluorescence images revealed a non‐uniform distribution of degradation species across the thickness of the EVA encapsulant, providing greater insight into the mechanisms of degradation, which are unavailable by traditional bulk‐based methods. In addition, strong fluorescence emissions were observed from the two thin adhesive layers of the aged backsheet, indicating severe degradation of the adhesives and a potential for interlayer delamination. This method is further confirmed with other microscale characterization techniques. The changes in optical (yellowness index), chemical (oxidation, UV absorber concentration), mechanical (Derjaguin‐Muller‐Toporov modulus), and thermal (melting enthalpy) properties of the EVA encapsulant were found to be related to fluorescence profiles, following the attenuation of UV light. This study highlights that fluorescence imaging is a spatially‐resolved and sensitive method for rapid failure assessment and in‐depth mechanism study for complex PV‐laminated system. [ABSTRACT FROM AUTHOR]

The technology is able to provide good intermediate performance from liquid and tape. Thermo reversible material is able to follow large step, make wide range modulus, and make good uniformity after slit die coating. In addition, the technology keep good optical performance. [ABSTRACT FROM AUTHOR]

Background: Increased tissue stiffness (also termed modulus) has been shown to be a characteristic of potential tumor metastasis. Measured values of the stiffness of tumors and cancer cells are reported in the literature to increase compared to neighboring normal tissues. Yet the relationship between the mechanical properties of cells and the extracellular matrix has yet to be correlated with the histopathology of cancerous lesions. Materials and Methods: We have developed a technique to do virtual biopsies of skin lesions by combining images made using optical coherence tomography with stiffness measurements made simultaneously using vibrational analysis. The technique is termed vibrational optical coherence tomography (VOCT). Results: In this paper, we report that precancerous and cancerous lesions are characterized by changes in both the morphology and stiffness of the cellular components of the skin. The ratio of the peak heights that correspond to the epidermal (40‐60Hz) and dermal (140‐160 Hz) resonant frequencies appear to be different for benign and cancerous or precancerous lesions compared with normal skin and scar. Conclusions: Cell‐to‐cell and epidermal‐to‐dermal interactions may be very important in evaluating the potential of skin lesions to become malignant. These interactions can be evaluated using VOCT, a new technique for performing "virtual biopsies" of skin lesions. [ABSTRACT FROM AUTHOR]

A gel forming method with sections with different elastic modulus is developed. Gels with hardness distribution are formed from one base gel material by adjusting the crosslinking density of the polymer network using a 3D gel printer. It is confirmed that hardness is arranged as designed by using mixing rules of composite materials. Furthermore, as a prototype of a practical gel application, a gel finger model having a soft-fleshy part and a hard-bony part is printed. 3D printing of an organ model that reproduces a realistic feel that takes not only the shape of the organ but also the distribution of hardness into consideration may become possible. [ABSTRACT FROM AUTHOR]

Background: The need to quantitatively identify the composition and organization of the macromolecular components of skin, skin lesions, scars, tumors, extracellular matrices (ECMs), and wound tissue has been a goal of researchers for many decades. A variety of studies have been recently reported applying optical coherence tomography (OCT) to image skin and cutaneous lesions. Materials and Methods: This article describes the use of vibrational OCT to image and noninvasively characterize the macromolecular components of the ECM of skin. Results: We report that the major macromolecular components of skin and scar can be identified noninvasively by their characteristic moduli calculated from measurements of the resonant frequency and tissue thickness. Moduli for fat (0.03 MPa), elastic tissue (0.8 MPa), skin (2 MPa), and scar (7 MPa) can be differentiated using images and measurements of the resonant frequency and the sample thickness obtained from OCT. Conclusions: Using vibrational OCT, it is possible to identify and map the location of the macromolecular components in skin and skin lesions. [ABSTRACT FROM AUTHOR]

Maintaining buoyancy with gas‐filled floats (pneumatocysts) is essential for some subtidal kelps to achieve an upright stature and compete for light . However, as these kelps grow up through the water column, pneumatocysts are exposed to substantial changes in hydrostatic pressure, which could cause complications as internal gases may expand or contract, potentially causing them to rupture, flood, and lose buoyancy. In this study, we investigate how pneumatocysts of Nereocystis luetkeana resist biomechanical stress and maintain buoyancy as they develop across a hydrostatic gradient. We measured internal pressure, material properties, and pneumatocyst geometry across a range of thallus sizes and collection depths to identify strategies used to resist pressure‐induced mechanical failure. Contrary to expectations, all pneumatocysts had internal pressures less than atmospheric pressure, ensuring that thalli are always exposed to a positive pressure gradient and compressional loads, indicating that they are more likely to buckle than rupture at all depths. Small pneumatocysts collected from depths between 1 and 9 m (inner radius = 0.4–1.0 cm) were demonstrated to have elevated wall stresses under high compressive loads and are at greatest risk of buckling. Although small kelps do not adjust pneumatocyst material properties or geometry to reduce wall stress as they grow, they are ~3.4 times stronger than they need to be to resist hydrostatic buckling. When tested, pneumatocysts buckled around 35 m depth, which agrees with previous measures of lower limits due to light attenuation, suggesting that hydrostatic pressure may also define the lower limit of Nereocystis in the field. [ABSTRACT FROM AUTHOR]

Abstract: Measurement of the mechanical properties of skin in vivo has been complicated by the lack of methods that can accurately measure the viscoelastic properties without assuming values of Poisson's ratio and tissue density. In this paper, we present the results of preliminary studies comparing the mechanical properties of skin and scar tissue measured using a technique involving optical cohesion tomography (OCT) and vibrational analysis. This technique has been reported to give values of the modulus that correlate with those obtained from tensile measurements made on decellularized dermis (Shah et al., Skin Res Technol 2016;23:399–406; Shah et al., J Biomed Mater Res Part 2017;105:15–22). The high correlation between moduli measured using vibrational studies and uniaxial tensile tests suggest that the modulus can be determined by measuring the natural frequency that occurs when a tissue is vibrated in tension. The results of studies on glutaric anhydride treated decellularized dermis suggest that vibrational analysis is a useful technique to look at changes in the properties of skin that occur after cosmetic and surgical treatments are used. Preliminary results suggest that the resonant frequency of scar tissue is much higher than that of adjacent normal skin reflecting the higher collagen content of scar. OCT in concert with vibrational analysis appears to be a useful tool to evaluate processes that alter skin properties in animals and humans as well to study the onset and pathogenesis of skin diseases such as cancer. This technique may be useful to evaluate the extent of wound healing in skin diabetic ulcers and other chronic skin conditions, scar tissue formation in response to implants, and other therapeutic treatments that alter skin properties. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1421–1427, 2018. [ABSTRACT FROM AUTHOR]

Chiral metastructures consisting of ring (polygonal or cubic) nodes and elastic bending ligaments exhibit excellent design flexibility for compliant structures. In this paper, based on rigid cubic node rotation and the kinematic geometrical relations of a three‐dimensional (3D) isotropic anti‐tetrachiral structure, an analytical expression for the modulus of the 3D isotropic anti‐tetrachiral structure is derived from strain energy analysis. The nylon powder Selected Laser Sintering (SLS) additive manufacturing technique is employed for fabricating two types of 3D isotropic anti‐tetrachiral specimens with different geometrical parameters; then comparison between experiments, finite element analysis (FEA), and theoretical studies is performed for verifying the analytical formula. The mechanical properties of 3D isotropic anti‐tetrachiral structures can be tuned with two independent dimensionless geometrical parameters. The proposed 3D anti‐tetrachiral structures can be employed for designing advanced structures against impact damages, realizing flexibility of industrial components, and optimizing the vibration attenuation abilities of engineering structures. [ABSTRACT FROM AUTHOR]

ABSTRACT We have investigated the effect of antiplasticization on the stress-optical behavior of polycarbonate (PC) containing terphenyls (tPh) and di(2-ethylhexyl)adipate (DEHA). Addition of the three tPhs ( p-, o-, and m-tPh) and DEHA at contents of 5-10 wt % increases the tensile storage modulus ( E') of PC owing to the antiplasticization effect. In particular, p-tPh increases E' more than the other additives, suggesting that the rod-like shape matches the free volume of PC in the glassy state. The three tPh isomers improve the glassy birefringence of PC while DEHA does not change the glassy birefringence, which corresponds to the polarizability anisotropy. The stress-optical coefficient, a ratio of stress and birefringence, of PC decreases with increasing additive content in order of p-tPh ≫ o-tPh > m-tPh = DEHA. This result is agreement with a restricted rotational motion of additive molecule in PC, which is observed in dynamic mechanical and birefringence data. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1837-1842 [ABSTRACT FROM AUTHOR]

The study focuses on the development and characterization of poly(lactic acid) (PLA)/montmorillonite (clay) nanocomposite films. Samples of 0%, 1%, 3%, and 6% (by weight) clay were shear-mixed, melt-blended, and blown-film processed. Afterward, the effects of clay on the kinetics of cold-crystallization, mechanical properties, and the oxygen barriers are investigated using differential scanning calorimetry, dynamic mechanical analyzer, and permeation tester, respectively. Through the traditional Avrami analysis, clay is found to accelerate the crystallization process with a higher crystallization rate constant. The Avrami exponent obtained for composites is higher than the neat PLA although all samples show a decreased Avrami exponent with increase of the crystallization temperature. At the same time, the clay exhibits reinforcement effects on the glassy modulus of the composites and influences the cold-crystallization event, similar to the calorimetric results. In addition, the oxygen permeation slightly decreases on adding the clay. With 3% clay concentration, the permeation coefficient is reduced by 24%. The implication of the results is discussed in the article. [ABSTRACT FROM AUTHOR]

Several new methods have been used to non-destructively evaluate the mechanical properties of materials and tissues including magnetic resonance elastography, ultrasound elastography, optical coherence elastography, and various forms of vibrational analysis. One of the limitations of using these methods is the need to establish a relationship between the modulus measured using each new technique and moduli measured using well-established techniques such as constant rate-of-strain and incremental stress-strain curves. In addition, there are no available methods for analyzing the mechanical properties of the individual components of multi-component materials. In this article, we present data showing that there is a strong correlation (correlation coefficient >0.9) between the modulus measured using classical uniaxial tensile incremental stress-strain tests and those made using a combination of optical coherence tomography and vibrational analysis. Beyond this, we demonstrate that the moduli of the major structural components of pig skin can be measured using this technique. These results suggest that optical coherence tomography in concert with vibrational analysis can be used to measure the moduli of biological and implant materials without having to determine Poisson's ratio. In addition, each of the moduli of the major fibrous components of pig skin can be measured concurrently using this technique. These results may be useful in the characterization of synthetic implants and tissue derived materials without requiring removal of one or more components that are to be characterized. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1666-1671, 2017. [ABSTRACT FROM AUTHOR]

Elastic-plastic fracture behavior of a structural adhesive in the bulk and bonded forms is discussed. The model adhesive chosen with and without scrim carrier cloth (neat resin) solid film adhesives exhibit a relatively brittle material behavior to justify the use of Linear Elastic Fracture Mechanics (LEFM) methods. The solid film adhesives are first cast in the form of tensile coupons to determine the bulk fracture properties with the use of single-edge-cracked specimen geometry. KIC evaluation is done using the procedure suggested by the ASTM standard. A K-calibration method based on application of boundary collocation procedure to the William's stress function is utilized to relate the measured critical loads to the KIC values. The yield stresses (σY) and elastic moduli (E) values in the bulk tensile mode are also evaluated. The availability of KIC, σY, E and ν (Poisson's ratio) values makes the calculation of crack tip plastic zone radii (rYC) and fracture energy (GIC) values possible on the basis of Irwin's theory. The bulk casting procedure is done under different cure (temperature, time and cool-down) conditions to determine optimum properties. We found that the most suitable model that would fit the stress-strain response of the model adhesives with prediction of the stress whitening stress level, σ*, under material damage surrounding flaws and crack tips was a modified version of Ramberg-Osgood equation. A bilinear behavior is obtained when log(ϵp) is plotted against log(σ - Θ). The plastic strain ϵp is assumed to be a function of the over-stress above the elastic limit stress, Θ, and the stress levels defining the intersection point for the bilinear behavior are found to occur slightly below the stress whitening stress values. [ABSTRACT FROM AUTHOR]

Calix[4]arenes namely, 5,11,17,23 tetra tert butyl calix[4]arene and 5,11,17,23 tetra chlorosulfonyl calix[4]arene were synthesized to produce octakis (hydroxyl ethyl) sulfonamide calix[4]arene which was used in polyurethane-calixarene rigid foam composite formulation. The effect of calixarene ratio on mechanical properties of synthesized composites was studied at three calixarene ratios including 1.5, 2, and 3 % (w/w). The obtained data indicate that the tensile strength and modulus are increased as the calixarene ratio increases while the fracture strain is decreased. Quantitatively, addition of 3% (w/w) of calixarene to the polyurethane resulted in 30.99% and 30.01% improvements in modulus and tensile strength, respectively. Contrarily, a decrease of about 13.1% was observed in fracture strain when compared to the properties of the pristine polyurethane rigid foam. The effect of Calixarene on thermal stability of Calixarene- polyurethane composite indicating that Calixarene component strictly enhances the thermal stability of composite. [ABSTRACT FROM AUTHOR]

ABSTRACT 1-Ethyl-3-methylimidazolium triflate ionic liquid (IL) was incorporated in Pebax® MV 3000 copolymer through solvent cast (SC) or melt blending (MB) for composition from 0 to 30 wt % IL. The morphology was investigated by small angle neutron scattering, transmission electron microscopy, and differential scanning calorimetry. The SC copolymer film exhibited a lower mean correlation distance ( D = 87 Å) and smoother transition between the rigid and soft phases in comparison with the MB film ( D = 103 Å). By dissolving in the copolymer soft phase, IL acted as a plasticizer, impeded soft segments crystallization and led to linear increase of D. The differences observed in morphology as a function of the film process impacted the mechanical and gas transport properties: below 20 wt % IL, all SC films sustained thermomechanical properties up to 120 °C and exhibited lower permeability than MB films. IL adding made permeability decrease up to 60%, depending on the gas nature and IL amount. Hydration of the films was investigated by sorption and SANS analyses. The impact of water uptake on swelling was similar for all membranes whereas water diffusion depended on the film morphologies and IL amount. Interesting mechanical and transport properties were obtained for IL content up to 20 wt %. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 778-788 [ABSTRACT FROM AUTHOR]