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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]

The current work is focused on numerical and experimental studies of woven fabric composites modified by hybridisation with biological (cellulosic) filler materials. The mechanical performance of the composites is characterized under tensile, bending and impact loads and the effect of hybridisation is observed with respect to pure and nonhybrid composites. Numerical models are developed using computational tools to predict mechanical performance under tensile loading. The computational prediction results are compared and validated with relevant experimental results. This research is aimed at understanding the mechanical performance of basalt–epoxy composites partially reinforced with micro-/nano-sized bio-fillers from cellulose and intended for various application areas. Different weave structures, e.g., plain, twill, matt, etc., were investigated with respect to the mechanical properties of the hybrid composites. The effects of hybridizing with cellulose particles and different weave patterns of the basalt fabric are studied. In general, the use of high-strength fibres such as basalt along with cellulosic fillers representing up to 3% of the total weight improves the mechanical performance of the hybrid structures. The thermomechanical performance of the hybrid composites improved significantly by using basalt fabric as well as by addition of 3% weight of cellulosic fillers. Results reveal the advantages of hybridisation and the inclusion of natural cellulosic fillers in the hybrid composite structures. The material developed is suitable for high-end applications in components for construction that demand advanced mechanical and thermomechanical performance. Furthermore, the inclusion of biodegradable fillers fulfills the objectives of sustainable and ecological construction materials. [ABSTRACT FROM AUTHOR]

Coatings with tunable refractive index and high mechanical resilience are useful in optical systems. In this work, thin films of HfO2 doped with Al2O3 were deposited on silicon at 300 °C by using plasma-enhanced atomic layer deposition (PE-ALD). The mainly amorphous 60–80 nm thick films consisted Al in the range of 2 to 26 at.%. The refractive indexes varied from 1.69 to 2.08 at the wavelength of 632 nm, and they consistently depended on the composition. The differences were higher in the UV spectral region. At the same time, the hardness of the films was from 12–15 GPa; the modulus was in the range of 160–180 GPa; and the mechanical properties did not have a good correlation with the deposited compositions. The deposition conditions, element contents, and refractive indexes at respective wavelengths were correlated. The results indicated that it is possible to tune optical properties and retain mechanical properties of atomic layer-deposited thin films of HfO2 with Al2O3 as doping oxide. Such films could be used as mechanically resilient and optically tunable coatings in, for instance, micro- or nano-electromechanical systems or transparent displays. [ABSTRACT FROM AUTHOR]

Cobalt sulphides, including CoS, CoS2, Co3S4 and Co9S8, have been studied as potential anode materials for Li- and Na-ion batteries. However, the mechanical properties of the cobalt sulphides have not been intensively investigated. In this work, density functional theory (DFT) calculation was employed to study the mechanical properties of the cobalt sulphides mentioned above. Besides, the mechanical properties of final products of lithiation/sodiation of Co9S8 have been calculated, including the bulk modulus, shear modulus, Young’s modulus and Poisson’s ratio. This work provides an insight into understanding the electrochemical performance of Co9S8 material as anode material for Li- and Na-storage during the cycling process. [ABSTRACT FROM AUTHOR]

Polymeric hydrogels have drawn considerable attention as a biomedical material for their unique mechanical and chemical properties, which are very similar to natural tissues. Among the conventional hydrogel materials, self-healing hydrogels (SHH) are showing their promise in biomedical applications in tissue engineering, wound healing, and drug delivery. Additionally, their responses can be controlled via external stimuli (e.g., pH, temperature, pressure, or radiation). Identifying a suitable combination of viscous and elastic materials, lipophilicity and biocompatibility are crucial challenges in the development of SHH. Furthermore, the trade-off relation between the healing performance and the mechanical toughness also limits their real-time applications. Additionally, short-term and long-term effects of many SHH in the in vivo model are yet to be reported. This review will discuss the mechanism of various SHH, their recent advancements, and their challenges in tissue engineering, wound healing, and drug delivery. [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]

Polycaprolactone (PCL) nanofibers are a promising material for biomedical applications due to their biocompatibility, slow degradation rate, and thermal stability. We electrospun PCL fibers onto a striated substrate with 12 μm wide ridges and grooves and determined their mechanical properties in an aqueous solution with a combined atomic force/inverted optical microscopy technique. Fiber diameters, D , ranged from 27 to 280 nm. The hydrated PCL fibers had an extensibility (breaking strain), ε max , of 137%. The Young's modulus, E , and tensile strength, σ T , showed a strong dependence on fiber diameter, D ; decreasing steeply with increasing diameter, following empirical equations E (D) = (4.3 ∙ 10 3 ∙ e − D 51 n m + 1.1 ∙ 10 2) MPa and σ T (D) = (2.6 ∙ 10 3 ∙ e − D 55 n m + 0.6 ∙ 10 2) MPa. Incremental stress-strain measurements were employed to investigate the viscoelastic behavior of these fibers. The fibers exhibited stress relaxation with a fast and slow relaxation time of 3.7 ± 1.2 s and 23 ± 8 s and these experiments also allowed the determination of the elastic and viscous moduli. Cyclic stress-strain curves were used to determine that the elastic limit of the fibers, ε elastic , is between 19% and 36%. These curves were also used to determine that these fibers showed small energy losses (<20%) at small strains (ε < 10%), and over 50% energy loss at large strains (ε > 50%), asymptotically approaching 61%, as E l o s s = 61 % · (1 − e − 0.04 * ε ). Our work is the first mechanical characterization of hydrated electrospun PCL nanofibers; all previous experiments were performed on dry PCL fibers, to which we will compare our data. [ABSTRACT FROM AUTHOR]

The current work is focused on numerical and experimental studies of woven fabric composites modified by hybridisation with biological (cellulosic) filler materials. The mechanical performance of the composites is characterized under tensile, bending and impact loads and the effect of hybridisation is observed with respect to pure and nonhybrid composites. Numerical models are developed using computational tools to predict mechanical performance under tensile loading. The computational prediction results are compared and validated with relevant experimental results. This research is aimed at understanding the mechanical performance of basalt–epoxy composites partially reinforced with micro-/nano-sized bio-fillers from cellulose and intended for various application areas. Different weave structures, e.g., plain, twill, matt, etc., were investigated with respect to the mechanical properties of the hybrid composites. The effects of hybridizing with cellulose particles and different weave patterns of the basalt fabric are studied. In general, the use of high-strength fibres such as basalt along with cellulosic fillers representing up to 3% of the total weight improves the mechanical performance of the hybrid structures. The thermomechanical performance of the hybrid composites improved significantly by using basalt fabric as well as by addition of 3% weight of cellulosic fillers. Results reveal the advantages of hybridisation and the inclusion of natural cellulosic fillers in the hybrid composite structures. The material developed is suitable for high-end applications in components for construction that demand advanced mechanical and thermomechanical performance. Furthermore, the inclusion of biodegradable fillers fulfills the objectives of sustainable and ecological construction materials.

The present paper describes an experimental investigation on mechanical properties of poly-lactic-acid (PLA) parts under compressive and flexural loading. The PLA parts are fabricated by fused deposition modelling (FDM) technique. In present work, effect of raster angle, raster width and infill density on strength and modulus of parts under compressive and flexural loading is studied. It is found that infill density affects compressive strength and modulus of parts significantly under compressive loading. Compressive properties increase with increase in infill density. Further, it is found that raster width and infill density significantly influence flexural strength and modulus. Flexural properties increase with increase in infill density, and decrease in decrease in raster width. Further, predictive models are developed for responses, and process parameters are optimized using genetic algorithm to maximize the responses. [ABSTRACT FROM AUTHOR]

Coatings with tunable refractive index and high mechanical resilience are useful in optical systems. In this work, thin films of HfO2 doped with Al2O3 were deposited on silicon at 300 °C by using plasma-enhanced atomic layer deposition (PE-ALD). The mainly amorphous 60–80 nm thick films consisted Al in the range of 2 to 26 at.%. The refractive indexes varied from 1.69 to 2.08 at the wavelength of 632 nm, and they consistently depended on the composition. The differences were higher in the UV spectral region. At the same time, the hardness of the films was from 12–15 GPa; the modulus was in the range of 160–180 GPa; and the mechanical properties did not have a good correlation with the deposited compositions. The deposition conditions, element contents, and refractive indexes at respective wavelengths were correlated. The results indicated that it is possible to tune optical properties and retain mechanical properties of atomic layer-deposited thin films of HfO2 with Al2O3 as doping oxide. Such films could be used as mechanically resilient and optically tunable coatings in, for instance, micro- or nano-electromechanical systems or transparent displays.

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]

Robotic Automated Fiber Placement (R-AFP) technology was developed to manufacture composite laminates by placing carbon fiber thermoset towpregs, obtained by impregnating 12 K high-strength grade carbon fibers in an epoxy resin system. In order to avoid placement induced defects, a thermographic scanning technique was implemented for on-line quality monitoring of the R-AFP process. The thermal analysis proved to be an effective and quick approach for the real-time detection of deposition defects generated during. The R-AFP process was performed by applying a constant pressure through the compaction roller; different pressure values were investigated. The effect of the resin weight fraction and compaction pressure on the mechanical properties applied by the deposition head during R-AFP of cross-ply laminates was studied. The reduction of the tensile strength and the increase of the elastic modulus with decreasing pressure of the compaction roller was observed. Furthermore, the values of ultimate tensile strength and elastic modulus decrease as the resin content increases. Finally, the three-dimensional topography of surface fracture of tensile samples was investigated by means of the optical and scanning electron microscopy. [ABSTRACT FROM AUTHOR]

Natural fibers such as banana, sisal, snake grass, coir, hemp, jute and so on are armed with enormous advantages like less weight, reliability, recyclability and environmental friendly nature. Such fibers may enhance the system’s performance by acting as additives with the thermoplastics in different perspectives. Besides the natural composites, hybrid composites facilitate the design of material with specific property matched to an application. In the present work an attempt has been made to manufacture and test the banana and snake grass short fiber reinforced hybrid polyester composites in random orientation and random lay-up. Methyl Ethyl Ketone Peroxide was used as the coupling agent and Cobalt Naphthalene as the catalyst. Hand layup technique was used to manufacture the composites. Relative volume fraction of the fibers was varied between 2.5-12.5% in the ratio 1:1. Properties like tensile strength and modulus, flexural strength and modulus are measured for the composites by conducting the appropriate tests according to ASTM standards.

Polymeric hydrogels have drawn considerable attention as a biomedical material for their unique mechanical and chemical properties, which are very similar to natural tissues. Among the conventional hydrogel materials, self-healing hydrogels (SHH) are showing their promise in biomedical applications in tissue engineering, wound healing, and drug delivery. Additionally, their responses can be controlled via external stimuli (e.g., pH, temperature, pressure, or radiation). Identifying a suitable combination of viscous and elastic materials, lipophilicity and biocompatibility are crucial challenges in the development of SHH. Furthermore, the trade-off relation between the healing performance and the mechanical toughness also limits their real-time applications. Additionally, short-term and long-term effects of many SHH in the in vivo model are yet to be reported. This review will discuss the mechanism of various SHH, their recent advancements, and their challenges in tissue engineering, wound healing, and drug delivery.

Research on the vitreous humor and development of hydrogel vitreous substitutes have gained a rapid increase in interest within the past two decades. However, the properties of the vitreous humor and vitreous substitutes have yet to be consolidated. In this paper, the mechanical properties of the vitreous humor and hydrogel vitreous substitutes were systematically reviewed. The number of publications on the vitreous humor and vitreous substitutes over the years, as well as their respective testing conditions and testing techniques were analyzed. The mechanical properties of the human vitreous were found to be most similar to the vitreous of pigs and rabbits. The storage and loss moduli of the hydrogel vitreous substitutes developed were found to be orders of magnitude higher in comparison to the native human vitreous. However, the reported modulus for human vitreous, which was most commonly tested in vitro, has been hypothesized to be different in vivo. Future studies should focus on testing the mechanical properties of the vitreous in situ or in vivo. In addition to its mechanical properties, the vitreous humor has other biotransport mechanisms and biochemical functions that establish a redox balance and maintain an oxygen gradient inside the vitreous chamber to protect intraocular tissues from oxidative damage. Biomimetic hydrogel vitreous substitutes have the potential to provide ophthalmologists with additional avenues for treating and controlling vitreoretinal diseases while preventing complications after vitrectomy. Due to the proximity and interconnectedness of the vitreous humor to other ocular tissues, particularly the lens and the retina, more interest has been placed on understanding the properties of the vitreous humor in recent years. A better understanding of the properties of the vitreous humor will aid in improving the design of biomimetic vitreous substitutes and enhancing intravitreal biotransport. [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]

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]

Abstract This paper presents results of studies characterizing the mechanical properties of irradiated U 10Mo fuel in support of low-enriched fuel conversion of several United States high-performance research reactors (USHPRR), specifically the monolithic base fuel qualification. Specimens were tested from ten test fuel plates irradiated at the Advanced Test Reactor (ATR) from the RERTR-12 and AFIP-6 Mk. II irradiation campaigns. Tests were conducted at Idaho National Laboratory (INL) in the Hot Fuel Examination Facility (HFEF) inert atmosphere Main Cell. The monolithic fuel plates consist of a U 10Mo fuel foil meat covered with a Zr diffusion barrier layer fabricated by co-rolling, and clad in 6061 Al using a hot isostatic press (HIP) bonding process. Initial unirradiated specimens exhibited nominal (fresh) fuel meat thickness ranging from 0.25 mm to 0.64 mm, and irradiated (as tested) fuel plate average burnup ranged from approximately 0.36 × 1021 to 6.2 × 1021 fissions/cm3. After sectioning individual specimens from the fuel plates, the 6061 Al cladding was removed by dissolution in concentrated NaOH. Pre-dissolution measurement of width and post-dissolution measurement of thickness were conducted on test specimens to facilitate accurate analysis of bend test results. The final thickness values varied from 0.3 to 0.8 mm. Four-point bend testing was conducted on the HFEF Remote Load Frame (RLF) using custom-designed test fixtures and calibrated force and displacement sensors. All specimens exhibited dominantly elastic behavior and failed in a brittle manner. Analysis of test results showed decreasing elastic modulus and bending failure strength with increasing fission density. The trend of modulus decrease intersected with unirradiated modulus at zero fission density. The trend of decreasing bending strength with increased fission density is apparent, but has significantly higher uncertainty levels than the modulus results over the fission density range evaluated. A linear trend fit of the calculated bend strengths versus fission density does not coincide with unirradiated tensile strength, which is significantly higher. Porosities measured on the test specimen material are used with several model equations to predict irradiated modulus values. Over the range of available porosity information, comparison to the experimental modulus values are favorable. Other factors and their potential influence on modulus and strength calculations are discussed. [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]

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The ability of a tissue-engineered scaffold to regenerate functional tissues depends on its mechanical and biochemical properties. Though the commonly used collagen scaffolds have good biochemical properties, they fail due to their poor mechanical and physical properties. We have reinforced the collagen matrix with elastin-like polypeptide (ELP) to improve the mechanical and physical properties and optimized the composite composition using a novel statistical method of response surface methodology (RSM). RSM used a central composite design to correlate the 2 input factor variables (collagen and ELP concentrations) and 3 output objectives (tensile strength, elastic modulus, and toughness) using a second order polynomial equation. Upon uniaxial tensile testing and subsequent RSM optimization, a composite prepared using 6 mg/mL collagen and 18 mg/mL ELP was identified as having an optimal combination of all the three tensile properties. Physical properties of the 6:18 mg/mL composite versus the 6:0 mg/mL collagen-only hydrogel characterized by swelling ratio, differential scanning calorimetry, and FTIR spectroscopy revealed that the addition of ELP reduced the residual water content in the composites and provided evidence of the presence of collagen-ELP interactions. Scanning electron microscopy images of the collagen-only hydrogel showed porous fibrillar and dense afibrillar collagenous microstructure, but the collagen-ELP composite showed a dense collagenous microstructure with characteristic ELP aggregates. We surmise that because of the low water content and dense microstructure, the 6:18 mg/mL collagen-ELP composite had improved mechanical properties. Taken together, the composites prepared in this research can form good quality, rigid porous structures required for tissue engineering applications. [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]

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]

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]

Purpose: This review summarises the way in which mechanical property measurements combined with clinical perception have influenced the last half century of materials evolution in contact lens development.Methods: Literature concerning the use of in-vitro testing in assessment of the mechanical behaviour of contact lenses, and the mutual deformation of the lens material and ocular tissue was examined. Tensile measurements of historic and available hydrogel lenses have been collected, in addition to manufacturer-generated figures for the moduli of commercial silicone hydrogel lenses.Results: The three conventional modes of mechanical property testing; compression, tension and shear each represent different perspective in understanding the mutual interaction of the cornea and the contact lens. Tensile testing provides a measure of modulus, together with tensile strength and elongation to break, which all relate to handling and durability. Studies under compression also measure modulus and in particular indicate elastic response to eyelid load. Studies under shear conditions enable dynamic mechanical behaviour of the material to be assessed and the elastic and viscous components of modulus to be determined. These different methods of measurement have contributed to the interpretation of lens behaviour in the ocular environment. An amalgamated frequency distribution of tensile moduli for historic and currently available contact lens materials reveals the modal range to be 0.3-0.6MPa.Conclusion: Mechanical property measurements of lens materials have enabled calibration of an important aspect of their ocular interaction. This together with clinical feedback has influenced development of new lens materials and assisted clinical rationalisation of in-eye behaviour of different lenses. [ABSTRACT FROM AUTHOR]

Numerous tests have been used to elucidate mechanical properties of tissues and implants including tensile, compressive, shear, hydrostatic compression, and three-point bending in one or more axial directions. The development of a nondestructive test that could be applied to tissues and materials in vivo would promote the analysis of tissue pathology as well as the design of implant materials. The purpose of this article is to present the results of preliminary studies demonstrating nondestructive in vitro testing of a tissue model, decellularized human dermis, and a model implant, silicone rubber, using a combination of optical coherence tomography (OCT), and vibrational analysis. The results presented suggest that nondestructive vibrational testing of tissues and materials can be used to determine the modulus of polymeric materials and the results are similar to those found using tensile stress-strain measurements. The advantage of this method is that the modulus can be obtained from vibrational methods without having to approximate the tangent to the stress−strain curve, which is difficult for nonlinear materials that have a rapidly changing slope. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 15-22, 2017. [ABSTRACT FROM AUTHOR]

ABSTRACT Design and application of mechanically extraordinary nanofibers requires their full comprehension, based on conclusive testing methods. Electrospun polymer nanofibers, for instance, show a progressive and pronounced increase in their Young's moduli when diameters decrease below the µm scale. Measurement of mechanical properties in this diameter range is challenging and in the vast majority of reports, two classes of methods are commonly used: highly sensitive tensile testing and atomic force microscopy three-point deformation testing. Despite the methods' inherent dissimilarity, we resolve their conformity for the first time, with respect to the determination of Young's moduli. Here, we benchmark them against each other for electrospun polyvinyl-alcohol nanofibers, a well-defined model system. Our results provide an experimental basis for a comprehensive understanding of nanofiber structures and its implications on their mechanical properties. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 2418-2424 [ABSTRACT FROM AUTHOR]

In this work, TEMPO-oxidized cellulose nanofibers (TOCNs) were investigated as a green additive to the waterborne polyurethane (WPU) based coating, for improving its mechanical properties. The structure, morphology, mechanical properties and performances of the WPU/TOCNs coating were determined. Results showed that TOCNs had good compatibility to the WPU coating, and significantly enhanced the mechanical properties of the coating. The Halpin-Tsai and Ouali models were used to fit for the Young’s modulus of the resulting coating, and good agreements were found between the Ouali model and experimental results when the TOCNs content exceeded the critical percolation threshold (0.7 vol% or 1.0 wt%). It was also found that the pencil hardness of the coating was improved with the addition of TOCNs. However, AFM and pull-off test revealed the negative effects of the TOCNs addition on the surface roughness and adhesion strength of the coating to the wood surface. [ABSTRACT FROM AUTHOR]