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The aim of this study was to evaluate some physical and mechanical properties of the paper mill (PMS) and spruce planer shaving added cement boards. Also the effect of sludge type in consequence of waste water treatment technique on properties of wood-cement boards (WCB) was investigated. The wood/cement ratios were used as 1/3, based on the oven dry weight for the WCB manufacture. PMS was used up to 20% wt of total composite based on organic (wood) and inorganic (cement) amounts. Black sludge has shown more improvement than grey sludge on properties of WCBs, which indicates the anaerobic waste treatment technique is more effective for additive in WCB. The modulus of rupture and elasticity values of the WCBs with 5% of grey sludge, 5% and 10% of mixture of grey and black sludge were acceptable limits according to EN 634-2 standard. The mechanical strengths of all WCBs with black sludge were found above the specified EN standard. This suggests that PMS depending on sludge type may be used up to 20% wt of total composite weight for the commercial production of WCBs, which could expand the raw material base for this panel product. [ABSTRACT FROM AUTHOR]

Kirigami is the art of cutting paper to create three-dimensional figures for primarily aesthetic purposes. However, it can also modify the mechanical behavior of the resulting structure. In the literature, kirigami has been applied to modify the material's structural behavior, such as by changing its elasticity, rigidity, volume, or any other characteristic. This article examines the behavior of a pattern of rectangular kirigami cuts on a thermoplastic polyurethane soft material structure and its influence on the mechanical parameters of the macrostructure. The results demonstrate that rectangular kirigami patterns significantly affect the stiffness of the test specimens, changing from 1635 N/m to 4020 N/m. In elongation, there is a variation from 176.6% to 218% by simply altering the height of the rectangular cut. This enables the adjustment of the soft material structure's stiffness based on the geometry of the propagating kirigami cuts. [ABSTRACT FROM AUTHOR]

This paper presents a multi-scale approach to predict the effective hygro-mechanical behaviour of paper sheets based on the properties of the underlying fibrous network. Despite the vast amount of literature on paper hygro-expansion, the functional dependence of the effective material properties on the micro-structural features remains yet unclear. In this work, a micro-structural model of the paper fibrous network is first developed by random deposition of the fibres within a planar region according to an orientation probability density function. Asymptotic homogenization is used to determine its effective properties numerically. Alternatively, two much more idealized micro-structural models are considered, one based on a periodic lattice structure with a regular network of perpendicular fibres and one based on the Voigt average. Despite their simplicity, they reproduce representative micro-structural features, such as the orientation anisotropy and network level hygro-elastic properties. These alternative models can be solved analytically, providing closed-form expressions that explicitly reveal the influence of the individual micro-scale parameters on the effective hygro-mechanical response. The trend predicted by the random network model is captured reasonably well by the two idealized models. The resulting hygro-mechanical properties are finally compared with experimental data reported in the literature, revealing an adequate quantitative agreement. [ABSTRACT FROM AUTHOR]

Abstract In recent years, paper has been used as an alternative to traditional substrate materials in the development of strain sensors and accelerometers due to its flexibility, disposability due to environment low footprint and low cost. A lack of knowledge about the sources of nonlinearity in the mechanical behavior of paper makes difficult to consistently predict its performance. The characterization procedures available in the literature are based on both static and dynamic loading as a first attempt to describe the elastic behavior of paper in sensing applications. However, these procedures do not reveal the necessary information to describe the elastic behavior of paper under dynamic excitation. In this work, the nonlinear dynamic response of a harmonically excited paper-based cantilever beam is studied. A lumped model with a quadratic nonlinearity is adopted to describe the nonlinear response of paper-based cantilever beams. The obtained results show that the nonlinear resonance frequency response is dependent on the intrinsic properties of paper when discarding hygrothermal variations of paper as the main source of nonlinear behavior. It was found that the estimation of two nonlinear elastic parameters, α p (hysteresis nonlinear parameter) and E 0 (linear elastic modulus) could yield an improved description of the elastic behavior of paper subjected to vibrations. It was concluded that the existing paper characterization standards should be adapted to better predict the dynamic behavior of paper-based mechanical systems. Different types of paper materials were analyzed to study the influence of the intrinsic characteristics of paper on the nonlinear parameters. Highlights • The inherent characteristics of paper are the source of nonlinear vibration. • Paper can be modeled as a lumped parameter stiffness model with quadratic nonlinearity. • The standard T535-om96 is not suitable to characterize paper based systems. • Porosity has no apparent influence on the nonlinear parameters obtained. • Nonlinear dynamic behavior can be influenced by the filler and fiber types. [ABSTRACT FROM AUTHOR]

Multilayer panels that have paper cores with hexagonal cells continue to have a limited application in furniture production. In contrast, there are no sandwich honeycomb panels with cores containing rectangular cells employed in this industry. Such cores should distinguish themselves by strong orthotropic advantages, in particular, for designing shelves and partitions of cabinet furniture. Hence, the objective of this study was to determine the effect of core rectangular paper cells on the mechanical properties of three-layer furniture panels. The authors decided to ascertain relative density and elasticity constants of the designed cells. The results of empirical experiments of cell elasticity moduli were compared with the results of the analytical calculations. The impact of sample width on their mechanical properties was determined. It was demonstrated that cores with hexagonal cells in furniture panels could be replaced by cores with rectangular cells. [ABSTRACT FROM AUTHOR]

This research work presents a method for the determination of the limit of elasticity of paper considered as a variable dependent on stress and the time of its duration. For plane stress it was found that in the case of a low share of permanent strain in the total strain, we can assume that the highest value of its share appears on one of the principal axes of stress. Such an assumption allowed to use a one-dimensional rheological model to define the permanent range in a two dimensional state of stresses for paper. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to analyse altering energy demand patterns and energy factor substitution possibilities over time in the pulp and paper industry in order to increase our understanding of suitable policy options for increasing energy efficiency. The investigation employs a flexible translog cost function and an unbalanced panel data set covering 32 pulp and paper mills over the time period 1974-2005 in Sweden. Specifically, we test whether energy factor demand patterns in the industry for the period 1974-1990 differ from those during the latter period, 1991-2005. The empirical results reveal that even though the Swedish pulp and paper industry is relatively insensitive to changes in energy factor input prices in the short run, we find evidence of significant changes over time. According to the results, the own-price sensitivity of fuel has increased since the 1970s and the 1980s, thus indicating that fuel demand has become more sensitive to short-run changes in relative prices. The estimated cross-price elasticities between electricity and fuel also support the hypothesis of increased substitutability over time. However, the null hypothesis of an equal own-price elasticity of electricity demand across the two time periods cannot be rejected. [ABSTRACT FROM AUTHOR]

Within our research work we determined the Young's modulus distribution in the paper plane on the basis of results of tensile tests in selected directions. Using mathematical relationships valid for orthotropic materials, the moduli were calculated theoretically. The tensile stiffness orientation angle (TSA), and the TSO and TSI indices were also determined in order to define the deviations of the main axes of orthotrophy in the paper plane as determined by the machine and the cross directions. The calculation results were compared with measured values. They justified the conclusion that paper may be treated as an orthotropic material. [ABSTRACT FROM AUTHOR]

Copyright of Restaurator is the property of De Gruyter and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fine prediction of the elastic properties of paper materials can now be obtained using sophisticated fibre scale numerical approaches. However, there is still a need, in particular for low-density papers, for simple and compact analytical models that enable the elastic properties of these papers to be estimated from the knowledge of various structural information about their fibres and their fibrous networks. For that purpose, we pursued the analysis carried out in Marulier et al. (Cellulose 22:1517–1539, 2015. https://doi.org/10.1007/s10570-015-0610-6) with low-density papers that were fabricated with planar random and orientated fibrous microstructures and different fibre contents. The fibrous microstructures of these papers were imaged using X-ray synchrotron microtomography. The corresponding 3D images revealed highly connected fibrous networks with small fibre bond areas. Furthermore, the evolutions of their Young's moduli were non-linear and evolved as power-laws with the fibre content. Current analytical models of the literature do not capture these trends. In light of these experimental data, we developed a fibre network model for the in-plane elasticity of papers in which the main deformation mechanisms of the micromechanical model is the shear of the numerous fibre bonds and their vicinity, whereas the fibre parts far from these zones were considered as rigid bodies. The stiffness tensor of papers was then estimated both numerically using a discrete element code and analytically using additional assumptions. Both approaches nicely fit the experimental trends by adjusting a unique unknown micromechanical parameter, which is the shear stiffness of bonding zones. The estimate of this parameter is relevant in light of several recently reported experimental results. [ABSTRACT FROM AUTHOR]

Stochastic two-dimensional elastic–plastic network models are used to represent the inelastic deformation behavior of well-bonded paper. Linear kinematic hardening is employed with an initial non-zero back stress to represent anisotropic fiber yield. Network models are used to simulate simple monotonic tension and simple cyclic tension of paper materials. The performance of the models is compared to experimental results and found to perform reasonably well. The results suggest that interfiber bonding must be explicitly accounted for to adequately describe the material. Some discrepancy between the model and experimental cyclic tension results is believed to be due to time-dependent strain recovery in the material which is not represented in the network models. Experimental results are also presented which show that simple tension failure in these materials occurs along a line of localized deformation in a majority of the samples. This line is generally observed to form immediately prior to failure and is oriented at a well-defined angle with respect to the loading direction. [Copyright &y& Elsevier]

An important material property in the paper industry is the anisotropic stiffness distribution due to the fibrous microstructure of paper and to processing procedures. Ultrasonic methods offer a means of determining the stiffness of sheets of paper from the anisotropic propagation characteristics of elastic Lamb waves along the machine direction and the cross direction. That is, along and perpendicular to the direction of paper production. Currently, piezoelectric ultrasonic methods are employed in the industry to measure the elastic polar diagram of paper through multiple contacting measurements made in all directions. This paper describes a new approach utilizing the INEEL Laser Ultrasonic Camera to provide a complete image of the elastic waves traveling in all directions in the plane of the paper sheet. This approach is based on optical dynamic holographic methods that record the out of plane ultrasonic motion over the entire paper surface simultaneously without scanning. The full-field imaging technique offers great potential for increasing the speed of the measurement and it ultimately provides a substantial amount of information concerning local property variations and flaws in the paper. This report shows the success of the method and the manner in which it yields the elastic polar diagram for the paper from the dispersive flexural or antisymmetric Lamb wave. [Copyright &y& Elsevier]

Abstract: Nanopaper was prepared using ground cellulose nanofibers (GC) from canola straw and bacterial cellulose nanofibers (BC). The characteristics of GC and BC nanopapers were investigated and compared. Micropaper was also prepared from as-bleached cellulose microfibers of canola straw, used as a control sample to evaluate the effect of grinding on the properties of cellulose nanofibers and nanopaper. The average diameters for the microfiber, GC and BC were 26μm, 32nm and 45nm, respectively. Micropaper had crystallinity and crystallite size of 69% and 5.5nm, respectively. As the result of grinding, the crystallinity and crystallite size of GC nanopaper dropped to 62% and 5.1nm, respectively. BC nanopaper showed the highest values, with 80% and 6.2nm, respectively. GC nanopaper had a lower onset temperature (270°C) and thermal stability than that of both micropaper (275°C) and BC nanopaper (320°C). Micropaper was permeable to air while GC and BC nanopapers showed very high barrier property. Grinding had a drastic positive effect on mechanical properties: the tensile strength and Young''s modulus of GC nanopaper increased 11 times on average over those of micropaper, reaching 114MPa and 13.6GPa, respectively. BC nanopaper had the highest tensile strength and Young''s modulus, with 185MPa and 17.3GPa, respectively. GC and BC nanopapers are regarded as highly tough, fully bio-based, fully biodegradable and multi-performance materials. [Copyright &y& Elsevier]

2D materials < such > as planar fibrous networks exhibit several mechanical peculiarities, which we here decipher through a 3D-to-2D transition in the framework of continuum micromechanics or random mean-field homogenization theory. Network-to-fiber concentration (or "downscaling") tensors are derived from Eshelby–Laws matrix-inclusion problems, specified for infinitely long, infinitely flat fibers, and for infinitely flat spheroidal pores of vanishing stiffness. Overall material failure is associated with microscopic shear failure orthogonal to the fiber direction. Corresponding structure–property relations between porosity on the one hand, and in-plane stiffness as well as strength on the other hand, appear as linear. This is in good agreement with mechanical experiments carried out on pulp fibers, on pulp fiber-to-pulp fiber bonds, and on corresponding paper sheets. • A theoretical model has been developed that is able to predict the macroscopic mechanical behavior of planar transversely isotropic fiber networks out of the properties of fibers and fiber-to-fiber bonds leading to their formation. • An explicit, closed-form expression for the Hill morphology tensor of an infinitely thin oblate spheroidal inclusion embedded into a transversely isotropic, as well as an innovative numerical approach to treat associated singularities, have been used. • The model is computationally highly efficient and effective, being capable of quickly predicting the mechanical properties of virtually any planar transversely isotropic fiber network. • Theoretically predicted data for the case of wood-based paper sheets, computed from experimentally determined properties of pulp fibers and pulp fiber-to-pulp fiber bonds leading to their formation, are shown to be in good agreement with experimentally determined mechanical data for the very same paper sheets. [ABSTRACT FROM AUTHOR]

The reutilization of paper mill sludge as filler/reinforcement of polypropylene composites has been evaluated. The results show that the increasing content of sludge in composites resulted in materials with higher Young's modulus, although with lower tensile strength and deformation at break. Thus, in composites submitted to tensile stress paper mill sludge behaved mainly as filler. On the contrary, when materials were submitted to flexural stresses sludge worked partially as reinforcement. The addition of a coupling agent enhanced the fiber-matrix interface. As a result, composite materials with improved mechanical properties, either to tensile, flexural and impact tests were obtained. Considering the mechanical properties of the materials obtained, the substitution of traditional mineral fillers by paper mill sludge is a feasible alternative for composites used in low mechanical demand applications. [ABSTRACT FROM AUTHOR]

The ability of the bacteria Gluconacetobacter sucrofermentans to produce high-quality cellulose is well known. This bacterial cellulose has unique properties, as the result of an ultrathin crosslinked structure. It is almost chemically pure (until 98% cellulose), has a high crystallinity, mechanical strength, elasticity and durability. It is compatible with plant cellulose and could be grown on a vegetal fibrous network what makes bacterial cellulose an excellent candidate to reinforce damaged papers. The objective of this work is to promote the production of bacterial cellulose on the surface of a variety of papers by the direct application of a culture of G. sucrofermentans and to test if this procedure could be an economic and feasible possibility in reinforcing papers or cellulosic surfaces. After 7 days of cultivation, G. sucrofermentans deposits a thin layer (ca. 10 µm) of bacterial cellulose on the papers surfaces. Microscopic observations have shown a heterogeneous covering of the surfaces, while the modified papers maintain their thickness and their basic weight. The treatment has not increased the papers mechanical properties, but maintains them after artificial aging. The changes in optical properties of the reinforced papers, such as opacity and colorimetric coordinates, are minor even after further aging. Air permeance is the paper characteristic that experiences more variations because the layers of bacterial cellulose inhibit the airflow through the papers. The changes in the static and dynamic contact angles suggest that the bacterial cellulose structure is more compact and make the surface more hydrophobic than the original paper surface. [ABSTRACT FROM AUTHOR]

The free-banking history of Switzerland is subdivided into periods with unfettered competition (1826–1881), and strict banknote regulation (1881–1907). This paper suggests that the Federal Banknote Act of 1881 was introduced to remedy the fragmentation of the unfettered-competition period, during which private note-issuing banks were unable to issue standardised paper money. Although the corresponding minimum-reserve and mutual-acceptance rules led to a standardisation, they created new problems. For example, these regulatory interventions reduced the flexibility (or "elasticity") of the paper-money supply. It turned out that a central note-issuing bank is needed to supply adequate amounts of standardised banknotes. [ABSTRACT FROM AUTHOR]

Fruit quality is a crucial factor in affecting shelf-life and purchase choice for customers. Protecting the quality of cantaloupe fruits in the chain from harvest to marketing is a very important process. The objective of this study was to investigate the dynamic characteristics of cantaloupe fruit during excitation, to investigate the effect of vibration strength on the mechanical characteristics of cantaloupe fruit, and to show the effects of this strength on the mechanical damage of cantaloupe. Experiments were performed to measure the dynamic behavior of cantaloupe fruit during transportation and to evaluate the dynamic behavior of the packaging and the damage to the cantaloupes due to transient vibration during transportation. The results show that using the paper pulp tray packing method reduces cantaloupe damage and improves their quality during harvest and post-harvest processes. The range of resonance frequencies is important for the transporting of cantaloupes; a higher starting resonance is an indication of a stiffer cantaloupe bottom, and the paper pulp tray shifts the resonance frequency when compared to volume packing methods. Another interesting observation in this study is that a fruit with a high internal damping capacity is not as injured by exciting vibrations as a fruit with a low damping capacity, even if its natural frequency falls within the range of excitation. [ABSTRACT FROM AUTHOR]

This work is concerned with the determination of the adhesion strength between a paper web and an adhesive surface. Edvards- son et al. [Edvardsson, S., Gradin, P., and Isaksson, P., "On Dissipative Effects of Paper Web Adhesion Strength," Int. J. Solids Struct., Vol. 48(1), 2011, pp. 24-30] suggested recently a model that takes into account the energy dissipation caused by elastic-plastic deformation in the bent structure of a paper specimen. This model is fial'ther developed and investigated in the present work. A linear relation in plastic dissipation is discovered facilitating a novel analysis of the peeling tension and a more convenient determination of the proper adhesion strength. Industrial relevant examples are made with wet newsprint and kraft stock. A straightforward experimental procedure for determining the consistent adhesion strength is suggested. It is found that the agreement between the model and the experimental observations is good. [ABSTRACT FROM AUTHOR]

We study the mechanical response, and tearing features of crêpe paper, a two-dimensional, very anisotropic material, with one direction much less stiff than the other one. Depending on how the soft direction has been pre-stretched or not, the apparent Young modulus of the material can be varied over a broad range, while its fracture energy remains unaltered. The classical tearing concertina problem shows that a macroscopic measurement (the shape of the teared region) provides a direct access to the fracture properties of the material (effective Young's modulus, and fracture energy). The overall discussion is conducted in the frame of Griffith's theory of fracture. [ABSTRACT FROM AUTHOR]

Copyright of Studies in Conservation is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract  In this paper it is shown that the well known special orthotropy of paper, explained by micromechanical models of complex bodies, actually corresponds to a special case of orthotropy of a plane elastic body. The existence of this special orthotropy was predicted by the author in a previous work. [ABSTRACT FROM AUTHOR]

The tensile response of dense fiber-based materials like paper or paperboard is mainly dependent of the properties of the fibers, which store most of the elastic energy. In this paper, we investigate the influence of geometrical and material parameters on the mechanical response of the pulp fibers used in paper manufacturing. We developed a three-dimensional finite element model of the fiber, which accounts for microfibril orientation of cellulose fibril, and the presence of lignin in the secondary cell wall. The results showed that the change in the microfibril orientation upon axial straining is mainly a geometrical effect, and is independent of the material properties of the fiber, as long as the deformations are elastic. Plastic strain accelerates the change in microfibril orientation and thus makes it material-dependent. The results also showed that the elastic modulus of the fiber has a non-linear dependency on microfibril angle, with elastic modulus being more sensitive to the change of microfibril angle around small initial values of microfibril angles. Based on numerical results acquired from a 3D fiber model supported by available experimental evidence, we propose an anisotropic-kinematic hardening plasticity model for a fiber within a beam framework. The proposed fiber model is capable of reproducing the main features of the cyclic tensile response of a pulp fiber, such as stiffening due to changing microfibril angle. The constitutive model of the fiber was implemented in a finite-element model of the fiber network. By using the fiber network model, we estimated the level of strain that fiber segments accumulate before the typical failure strain of the entire network is reached. [ABSTRACT FROM AUTHOR]

Many factors affectthe characteristics of stickies and their removalfrom deinked paper pulp. Because most papers have a specific servicelifetime and because there is often a time lag between collectionand processing for paper recycling, the adhesives on the collectedpapers can age. This study investigates the effects of the aging ofpressure-sensitive adhesives on stickies properties and their removalefficiency during paper recycling. Adhesives coated on the surfaceof label paper were subjected to accelerated aging with specializedequipment and introduced into paper as the origin of stickies. Theresults showed that adhesive aging deteriorated the adhesion performance,surface physicochemical characteristics, and elasticity of the stickiesparticles. The aging had a direct effect on particle size during recyclingunit operations. The removal efficiencies of adhesive contaminantsduring screening and flotation were reduced as a result of adhesiveaging. Heterogeneity in the aging composition of stickies mixturesalso had a negative effect on their removal behavior. [ABSTRACT FROM AUTHOR]

Abstract: In order to understand the influence of the thicknesses of Kraft paper honeycomb core and medium density fiberboard skins on the stiffness of the sandwich panel, the corresponding finite element models for the resulting sandwich panels were developed. The material properties for the core and skin components of these finite element models were determined using the published data and specifications. It was found that a decrease in the thickness ratio of the core to skin layer (shelling ratio) resulted in an increase in the modulus of elasticity and shear modulus of the sandwich panels. The increase was significant when the shelling ratio was smaller than six. Cell size only affected the modulus of elasticity of the sandwich panels under the flat-wise compression and panel’s inter-laminar shear modulus. Regression equations relating the stiffness of the sandwich panels to the shelling ratio and core cell size were obtained using the finite element model simulated results and were found to compare well with the existing models for layered wood composites. [Copyright &y& Elsevier]

Significant dimensional variations may occur in paper-based materials when subjected to changes in moisture content. Moisture induced deformations are governed by the swelling of individual fibres, which is transferred through inter-fibre bonds to the entire fibrous network. Complex interactions between mechanical and hygro-expansive properties take place in the bonding areas, affecting the overall material response. In most network models, the role of these inter-fibre bonds is not explicitly incorporated. This work presents a periodic meso-structural model for the discrete fibrous network, which considers the free-standing fibre segments and inter-fibre bonds. Despite its simplicity, the reference unit-cell enables the incorporation of relevant micro- and meso-structural features such as network structure, fibres and bond geometry and hygro-elastic properties. The proposed model is solved analytically through a proper homogenization strategy, allowing to recover the paper’s anisotropic hygro-mechanical response in terms of effective elastic constants and effective hygro-expansive coefficients, exploiting the coupling at the meso-structural level between hygroscopic and mechanical behavior. A comparison with experimental results obtained from the literature shows that the presented approach is quite accurate in predicting the overall paper response, thereby revealing the influence of several meso-scale parameters (e.g. fibre orientation, dimensions, mechanical strength). [ABSTRACT FROM AUTHOR]

In this study, we focus on processing and characterizing composite material structures made of carbon nanotubes (CNTs) and reproducibly engineering macro-pores inside their structure. Highly porous bucky-papers were fabricated from pure carbon nanotubes by dispersing and stabilizing large 1 μm polystyrene beads within a carbon nanotube suspension. The polystyrene beads, homogeneously dispersed across the thickness of the bucky-papers, were then either dissolved or carbonized to generate macro cavities of different shape and properties. The impact of adding these macro cavities on the porosity, specific surface area and Young's modulus was investigated and some benefits of the macro cavities will be demonstrated. [ABSTRACT FROM AUTHOR]

To seek dentine analogue materials that could reliably replace human dentine in ceramic crown fatigue test. Two dentine analogue materials, woven glass fibre-filled epoxy (NEMA grade G10, International Paper, Hampton, SC, USA; G10) and glass fiber-reinforced polyamide-nylon (30% glass fiber reinforced polyamide-nylon 6,6, Goodfellow Cambridge Limited, Huntingdon, England; RPN), were used as substrates and compared with human extracted teeth (HD). Beam-shaped specimens were prepared and tested with three-point bending test in anti-plane longitudinal direction to determine the flexural strength and elastic modulus (n=10). Nanohardness (n=3) was tested on the beam specimens. Abutment-shaped substrates were prepared and restored with monolithic lithium disilicate crowns (n=10) and then subjected to wet cyclic loading in a step-stress manner (500 N initial load, 100 N step size, 100,000 cycles per step) with a 20 Hz frequency. Mechanical and fatigue test data were statistically analyzed using Kruskal-Wallis one-way ANOVA and post-hoc comparisons (α=0.05). Survival probability estimation was performed by Mantel-Cox Log-Rank test with 95% confidence intervals (CI). For the fatigue failure load (FFL) and the number of cycles until failure (NCF), Weibull modulus (m), characteristic strength (η), and load for 10% failure probability (B10) with 90% CI were calculated using the median-rank regression method. Finite Element Models of the fatigue test were established for stress distribution analysis and lifetime prediction. Fractographic observations were qualitatively analyzed. The flexural strength in descending order was HD (164.27±14.24 MPa), G10 (116.48±5.93 MPa), and RPN (86.73±3.56 MPa), which showed significant difference (p<0.001). No significant difference was observed in the flexural moduli of three materials (p=0.377) and the nanohardness between HD and RPN (p=0.749). G10 and RPN presented comparable mean FFL and NCF with human dentine (p=0.237 and 0.294, respectively). The Mantel-Cox Log-Rank test revealed similar survival probabilities of crowns restored with three substrate materials (p=0.055). However, the Weibull modulus (m) of RPN (13.57 for FFL, 9.46 for NCF) was significantly higher than those of G10 (2.87 for FFL, 1.91 for NCF), i.e. RPN is a more reliable dentine analogue material than G10. FEA analysis presented a correlation with the experimental results, such that RPN showed a closer stress distribution to dentine. Dentine analogue materials with similar elastic properties and fatigue performance to human dentine can reliably replace human dentine as substrate in ceramic crown fatigue test. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper proposes a meso-structural model for the discrete fibrous network of paper, which is able to upscale the irreversible phenomena from the underlying hygro-mechanics towards the effective behaviour at the macro-scale. The swelling of individual fibres, induced by moisture content variations, is transmitted to the network through inter-fibre bonds and governs the resulting effective material response. The present approach is based on a recently developed discrete meso-structural model for the reversible part of the response, which distinguishes between the influence on the hygroscopic behaviour of free-standing fibre segments and inter-fibre bonds. The network structure, fibre and bond geometries and hygro-elastic properties are explicitly incorporated. The major novelty of this contribution is the extended fibre constitutive model, enabling to describe some typical irreversible mechanisms and instability effects related to the history of the manufacturing. This extension strongly affects the effective material behaviour beyond the elastic range. Despite the valuable work in the literature, no papers can be found dedicated to meso-structural models including these phenomena. Using an appropriate homogenization strategy, the unit-cell is solved analytically, capturing irreversible shrinkage in restrained dried paper and the occurrence of local buckling within the bond for freely dried material. The proposed scale transition offers a deeper insight into the complex relation between the events occurring at the different length scales. The potential of the proposed methodology is demonstrated through the convincing agreement with experimental data obtained from the literature. [ABSTRACT FROM AUTHOR]

In a series of papers which are either published [Hadjesfandiari, A., Dargush, G. F., 2011a. Couple stress theory for solids. Int. J. Solids Struct. 48 (18), 2496–2510; Hadjesfandiari, A., Dargush, G. F., 2013. Fundamental solutions for isotropic size-dependent couple stress elasticity. Int. J. Solids Struct. 50 (9), 1253–1265.] or available as preprints [Hadjesfandiari, A., Dargush, G. F., 2010. Polar continuum mechanics. Preprint arXiv:1009.3252; Hadjesfandiari, A. R., Dargush, G. F., 2011b. Couple stress theory for solids. Int. J. Solids Struct. 48, 2496–2510; Hadjesfandiari, A. R., 2013. On the skew-symmetric character of the couple-stress tensor. Preprint arXiv:1303.3569; Hadjesfandiari, A. R., Dargush, G. F., 2015a. Evolution of generalized couple-stress continuum theories: a critical analysis. Preprint arXiv:1501.03112; Hadjesfandiari, A. R., Dargush, G. F., 2015b. Foundations of consistent couple stress theory. Preprint arXiv:1509.06299] Hadjesfandiari and Dargush have reconsidered the linear indeterminate couple stress model. They are postulating a certain physically plausible split in the virtual work principle. Based on this postulate they claim that the second-order couple stress tensor must always be skew-symmetric. Since they do not consider that the set of boundary conditions intervening in the virtual work principle is not unique, their statement is not tenable and leads to some misunderstandings in the indeterminate couple stress model. This is shown by specifying their development to the isotropic case. However, their choice of constitutive parameters is mathematically possible and we show that it still yields a well-posed boundary value problem. [ABSTRACT FROM AUTHOR]

Free-standing paper-like or foil-like materials are an integral part of our technological society. Their uses include protective layers, chemical filters, components of electrical batteries or supercapacitors, adhesive layers, electronic or optoelectronic components, and molecular storage. Inorganic ‘paper-like’ materials based on nanoscale components such as exfoliated vermiculite or mica platelets have been intensively studied and commercialized as protective coatings, high-temperature binders, dielectric barriers and gas-impermeable membranes4,5. Carbon-based flexible graphite foils composed of stacked platelets of expanded graphite have long been used in packing and gasketing applications because of their chemical resistivity against most media, superior sealability over a wide temperature range, and impermeability to fluids. The discovery of carbon nanotubes brought about bucky paper, which displays excellent mechanical and electrical properties that make it potentially suitable for fuel cell and structural composite applications. Here we report the preparation and characterization of graphene oxide paper, a free-standing carbon-based membrane material made by flow-directed assembly of individual graphene oxide sheets. This new material outperforms many other paper-like materials in stiffness and strength. Its combination of macroscopic flexibility and stiffness is a result of a unique interlocking-tile arrangement of the nanoscale graphene oxide sheets. [ABSTRACT FROM AUTHOR]

In my article (Featonby 2018 Phys. Educ. 53 047002) we asked what happens when a semi inflated Japanese kamifusen, or paper balloon, is bounced in the hand or passed from one person to another. [ABSTRACT FROM AUTHOR]

A discussion on the paper by Mousavi et al. (2018) is presented. The paper is focused on the estimation of elastic modulus (E) and uniaxial compressive strength (UCS) of sandstone using indentation test. The authors concluded that the thickness effect of samples on the indentation indices (critical transition force (CTF) and indentation modulus (IM)) was negligible. They proposed a dimensionless surface parameter (S) to eliminate the size effect on the E and UCS. On the basis of the test results and analysis method presented in the paper by Mousavi et al. (2018), three aspects of indentation test need to be clarified: the methods to prevent the movement of rock specimens, the results obtained from indentation test and the effect of specimen sizes on the CTF and IM. Meanwhile, the present discussion paper proposed some references for the methods to prevent the movement of rock specimens and the methods to eliminate the size effect in indentation test. • Methods to prevent the movement of rock specimens are proposed. • The influences of the specimen size/indenter diameter on the indentation indices are studied. • Methods to eliminate the size effect on the indentation test are recommended. [ABSTRACT FROM AUTHOR]

We report the fabrication of a sticky superhydrophobic paper surface with extremely high contact angle hysteresis: advancing contact angle ∼150° (superhydrophobic) and receding contact angle ∼10° (superhydrophilic). In addition, we report the controlled tunability of the contact angle hysteresis from 149.8 ± 5.8° to 3.5 ± 1.1°, while maintaining superhydrophobicity, as defined through an advancing contact angle above 150°. The hysteresis was tuned through the controlled fabrication of nano-scale features on the paper fibers via selective plasma etching. The variations in contact angle hysteresis are attributed to a transition of the liquid–surface interaction from a Wenzel state to a Cassie state on the nano-scale, while maintaining a Cassie state on the micro-scale. Superhydrophobic cellulosic surfaces with tunable stickiness or adhesion have potential applications in the control of aqueous drop mobility and the transfer of drops on inexpensive, renewable substrates. [ABSTRACT FROM AUTHOR]

Abstract: A mechanical model of the elastic, viscous and creep behavior of a cellulose-based Electro-Active Paper (EAPap), including C1, C2, and C6 along three material axes is developed and verified. The model consists of a spring-dashpot system that predicts the response under cyclic loading as a function of temperature. The modeling system providing the most consistent results consists of a spring and dashpot in parallel with each other, both in series with another dashpot. While the spring and dashpot in parallel represents both elastic and viscous response delay, the series dashpot accounts for the higher creep rates associated with elevated temperatures. The three parameters of this model are determined by fitting experimental data to the mathematical solution under cyclic loading conditions through a nonlinear least-squares method. There are a number of complex nonlinear load displacement mechanisms involved in the initial load cycle, thus to minimize modeling errors, most of the simulation modeling was developed to predict the mature portion of the load deflection curve through failure. The results presented in these studies strongly suggest that this three-parameter accurately describes the response of the three electroactive papers studied. The material creeps at elevated temperature, but there is insignificant creep at room temperature. The elastic behavior varies inversely with temperature and with the bias angle tested; however, the overall viscous behavior of the three types of EAPap tested is relatively complex. [Copyright &y& Elsevier]

This paper presents results of a comprehensive study from first principles into the properties of Ni, Pd, Rh, and Ir crystals under pressure. We calculated elastic constants, phonon spectra, isotherms, Hugoniots, sound velocities, relative structural stability, and phase diagrams. It is shown that in nickel and palladium under high pressures (>0.14 TPa) and temperatures (>4 kK), the body-centered cubic structure is thermodynamically most stable than of the face-centered cubic one. Calculated results suggest that nickel under Earth-core conditions (P ∼ 0.3 TPa, T ∼ 6 kK) have a bcc structure. No structural changes were found to occur in Rh and Ir under pressures to 1 TPa at least. This paper also provides estimations for the pressure and temperature at which the metals of interest begin to melt under shock compression. [ABSTRACT FROM AUTHOR]

The Scott bond test method has been used extensively in the paper industry over the years as a means to assess the bond strength of paper. The method has been a subject of some controversy lately since it does not always correlate to the sensitivity of the material to fracture by delamination. To gain some further insight into which parameters govern the fracture process in a Scott bond test a simplified approach has been chosen in order to formulate an analytical mathematical/mechanical model of the test. The model is dynamic in the sense that inertia effects are included. The material model utilised is a simple cohesive theory that assumes a linear behaviour between stress and crack opening when the material has started to degrade. This choice of material model makes the mathematical model very nonlinear. In fact, a system of three coupled nonlinear second order partial differential equations have to be solved and adjusted to the correct initial conditions. The material parameters needed for the model are the elastic modulus in the thickness direction, the transverse shear (elastic) modulus, the tensile strength (in the thickness direction) and the fracture work (per unit area) for a delamination crack. To investigate the ability of the model, a Scott bond testing apparatus have been equipped with a piezoelectric load sensor. The load cell was mounted on the apparatus’ pendulum so that the load acting on the sample holder could be recorded during the whole impact stage. This was done for a number of different initial velocities of the pendulum and it is found that the model gives a fair prediction of the contact load. [ABSTRACT FROM AUTHOR]

Crumpling a sheet of paper leads to the formation of complex folding patterns over several length scales. This can be understood on the basis of the interplay of a nonconvex elastic energy, which favors locally isometric deformations, and a small singular perturbation, which penalizes high curvature. Based on three-dimensional nonlinear elasticity and by using a combination of explicit constructions and general results from differential geometry, we prove that, in agreement with previous heuristic results in the physics literature, the total energy per unit thickness of such folding patterns scales at most as the thickness of the sheet to the power 5/3. For the case of a single fold we also obtain a corresponding lower bound. [ABSTRACT FROM AUTHOR]

An elastic–plastic material model for the out-of-plane mechanical behaviour of paper is presented. This model enables simulation the elastic–plastic behaviour under high compressive loads in the through-thickness direction (ZD). Paper does not exhibit a sharp transition from elastic to elastic–plastic behaviour. This makes it advantageous to define critical stress states based on failure stresses rather than yield stresses. Moreover, the failure stress in out-of-plane shear is strongly affected by previous plastic through-thickness compression. To cover these two features, a model based on the idea of a bounding surface that grows in size with plastic compression is proposed. Here, both the bounding and the yield surfaces are suggested as parabolas in stress space. While the bounding surface is open for compressive loads, the yield surface is bordered by the maximum applied through-thickness compression. [Copyright &y& Elsevier]

Paper and paperboard generally exhibit anisotropic and non-linear mechanical material behaviour. In this work, the development of an orthotropic elastic–plastic constitutive model, suitable for modelling of the material behaviour of paper is presented. The anisotropic material behaviour is introduced into the model by orthotropic elasticity and an isotropic plasticity equivalent transformation tensor. A parabolic stress–strain relation is adopted to describe the hardening of the material. The experimental and numerical procedures for evaluation of the required material parameters for the model are described. Uniaxial tensile testing in three different inplane material directions provides the calibration of the material parameters under plane stress conditions. The numerical implementation of the material model is presented and the model is shown to perform well in agreement with experimentally observed mechanical behaviour of paper. [Copyright &y& Elsevier]