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Mechanical properties are crucial in assessing the paper quality. Deformation and strength properties of paper are determined by the strength and stiffness of the interfiber and intermolecular hydrogen bonds. The contribution ratio of interfiber and intermolecular hydrogen bonds to the strength of paper can be changed by adjusting the degree of its anisotropy. The article presents the results on a study of the deformation properties of laboratory anisotropic paper samples from kraft bleached softwood pulp with a beating degree of 30 °SR. The samples had basic weight of 90 g/m2 and the degree of stiffness anisotropy TSIMD/CD of 1.75–4.08. They were made by using Techpap SAS automatic dynamic handsheet former (Grenoble, France), with varying forming parameters – diameter of the nozzle, motion speed of the forming wire, and injecting speed of pulp. Deformation properties were determined by tensile test and processing of the stress-strain dependence (σ−ε). The outcomes have shown that, an increase of the fiber orientation degree in paper structure by changing the forming parameters caused a change in the nature of the paper deformation under tension. Increasing the fiber orientation degree in the structure of paper made it possible to increase the strength by 55 %, tensile stiffness by 63 % in the machine direction, while reducing the extensibility by 10 %. In the cross direction, it was possible to decrease tensile stiffness by 33 %, strength by 55 %, and increase the extensibility by 5 %. Anisotropy of tensile strength was 1.73–6.00. The greatest effect was obtained for the elasticity modulus in the pre-failure zone E2 (2.8–38.6). It means that, fiber orientation had a key importance when large deformations in the samples took place. The established quantitative regularities allowed optimizing the values of the deformation and strength properties of paper, and their ratio in the machine direction and cross direction due to the variation of the forming parameters. For citation: Rech D., Potasheva A.N., Kazakov Ya.V. Regulating the Deformation Properties of Paper by Varying the Degree of Its Anisotropy. Lesnoy Zhurnal [Russian Forestry Journal], 2021, no. 5, pp. 174–184. DOI: 10.37482/0536-1036-2021-5-174-184

Green vehicles which employ proton-exchange membrane (PEM) fuel cells as the power source of their propulsion systems have been developed to a high stage, in the recent years. Nevertheless, additio...

Analysing the available data relative to the anisotropies of the ultra-high-energy cosmic rays (UHECR) at intermediate angular scales, we examine to what extent they can be used to constrain the origin of these particles, and what could be gained from a new generation of observatories with increased exposure. We simulate realistic UHECR sky maps for a wide range of scenarios, with the assumption that the distribution of UHECR sources follows that of matter in the Universe, also considering possible biases. We produce numerous datasets on which we apply similar analyses as those recently used by the Auger and TA collaborations. We find that: i) the investigated scenarios can easily account for the significance of the anisotropies reported by Auger and TA; ii) the direction in which the maximum flux excess is found in the Auger data differs from where it is found in most of our simulations; iii) for datasets simulated with the same astrophysical scenario, the significance with which the isotropy hypothesis is rejected through the Auger likelihood analysis can be largest either when "all galaxies" or when "starburst" galaxies are used to model the signal, depending on which GMF model is used; iv) the study of the energy evolution of the anisotropy patterns can provide new insight about the origin of UHECRs; v) the direction in which the most significant flux excess is found in the Auger dataset above 8 EeV appears to essentially disappear in the dataset above 32 EeV; vi) this appears to be very uncommon in our simulations, which could point to a failure of some generic assumption in the investigated scenarios, such as the predominance of a unique type of sources in the flux above the ankle, with essentially the same composition and spectrum; vii) a meaningful measurement of their energy evolution, from 10 EeV to the highest energies, will require a significant increase in statistics., Comment: 28 pages, 23 figures

This paper reports the effect of process orientation on the mechanical behavior and piezoelectricity of electroactive paper (EAPap) made from natural cotton pulp. EAPap is fabricated by a casting and wet drawing of cellulose film after dissolving cotton with LiCl and DMAc solvent. During the fabrication, permanent wrinkles, a possible factor for performance deterioration, were found in the films. Finite element method was introduced to identify the formation mechanism behind the wrinkles. The simulation results show that the wrinkles were caused by buckling and are inevitable under any conditions. The tensile and piezoelectric tests show that the orientation dependency of the stretched EAPap gives the anisotropic characteristics on both mechanical and piezoelectric properties. In this research, the anisotropic elastic moduli and Poisson&rsquo, s ratios are reported. The piezoelectric charge constant of EAPap in the linear elastic is calculated. The piezoelectric charge constants of EAPap are associated with the alignment angle in the order of 45&deg, &gt, 0&deg, 90&deg, due to the strong shear effect. The higher stretching ratio gives the higher piezoelectricity due to the alignment of the molecular chains and the microstructure in EAPap. The highest piezoelectric charge constant is found to be 12 pC/N at a stretching ratio of 1.6 and aligning angle of 45&deg

In bone tissue engineering (BTE), most of the currently developed scaffolds still lack the ability to demonstrate high porosity and high mechanical strength simultaneously or the ability to maintain bioactivity and sustained release of loaded biofactors. In this work, we constructed an anisotropic triple-pass tubular framework within a lyophilized porous GEL scaffold using FP, which was prepared by coating DEX-covered Whatman paper (WP) using the silk fibroin (SF) membrane with β-sheet conformation. This novel structural design endowed the functionalized paper frame (FPF)/scaffold implant high porosity, high mechanical strength, and sustained DEX delivery capability. Specifically, its porosity was as high as 88.2%, approximating that of human cancellous bone. The pore diameters of the implant ranged from 50 to 350 μm with an average pore diameter of 127.7 μm, indicating proper pore sizes for successful diffusion of essential nutrients/oxygen and bone tissue-ingrowth. Owing to the construction of double-network-like structure, the FPF/scaffold implant demonstrated excellent mechanical properties both in dry (174.7 MPa in elastic modulus and 14.9 MPa in compressive modulus) and wet states (59.0 MPa in elastic modulus and 3.3 MPa in compressive modulus), indicating its feasibility for in vivo implantation. Besides, the FPF/scaffold implant exhibited long-term DEX releasing behavior (over 50 days) with constant release rate in phosphate buffered saline (PBS). Murine osteoblasts MC3T3-E1 cultured in the porous FPF/scaffold implant had excellent viability. Furthermore, the cells cocultured with the FPF/scaffold implant showed positive proliferation, osteogenic differentiation, and calcium deposition. Twenty-eight days after implantation, extensive osteogenesis was observed in the rats treated with the FPF/scaffold implants. The anisotropic triple-pass tubular framework of the FPF/scaffold implant demonstrates structural similarities to the long bone. Therefore, this novel FPF/scaffold implant could be a better alternative for long bone defect repair.

Surface-Enhanced Raman Scattering (SERS) performance of filter paper (FP) loaded with gold nanoparticles (Au NPs) of three different size/shapes (spherical, triangular and star) were investigated. Spherical Au NPs were synthesized using femtosecond laser ablation of Au target in distilled water and other two anisotropic (triangular and star-shaped) Au NPs were prepared by colloidal chemical methods. COMSOL Multiphysics simulations were performed to investigate near field distributions of these Au NPs and as expected, the strongly enhanced near-field intensity at the sharp features was observed. The SERS performance [using the dye molecule Nile Blue (NB)] of star-shaped Au NPs loaded FP was superior compared to the triangle and spherical Au NPs loaded FP due to the presence of sharp tips and thus it was proved to be capable of detecting 10 pM NB concentration with an estimated enhancement factor of ∼3.7×1010.

The c-axis thermal conductivity (kc) of graphene paper (GP) is measured from 295 K to 12.3 K and extrapolation is used to identify the residual thermal reffusivity at the 0 K limit. To uncover the structural domain size based on the residual thermal reffusivity, we develop an anisotropic specific heat model to identify the phonons that sustain the heat conduction along the c-axis. This model predicts a c-mean free path (MFP) of 165 nm for graphite at room temperature (RT), very close to the value of 146 nm by molecular dynamics (MD) modeling. For widely studied normal graphite materials, this model predicts a structure domain size of 375 nm, close to the 404 nm grain size uncovered by transmission electron microscopy. Using our model, the c-MFP induced by defect in the GP is evaluated at 234 nm based on the low-momentum phonon scattering. This structural domain size significantly exceeds the graphene flake thickness (1.68–2.01 nm) in our GP, uncovering excellent c-direction atomic structure order. By subtracting the residual thermal reffusivity, the defect-free kc and c-MFP of GP are obtained. At RT, the defect-free kc is 9.67 Wm−1K−1, close to 11.6 Wm−1K−1 of graphite from the recent MD simulations.

A robust flexible paper-plasmonic hybrid SERS substrate is reported by exploiting the intrinsic properties of filter paper and anisotropic Ag@SiO2 nanocubes. The fibrous structure of paper promotes the assemblage of sharp-edged nanostructures which significantly improved the SERS activity. An inexpensive sensing platform with reasonable distribution and interparticle spacing of nanocubes was obtained by filtering Ag@SiO2 through a miniaturized filter paper. The thin silica shell improved the stability and interparticle spacing of silver nanocubes in the sensing platform, rendering enhanced SERS activity through the plasmon-coupling effect as compared to a conventional rigid substrate. Assessment of the analytical performance of the substrate for melamine quantification showed a good linearity (R2 = 0.9948) up to 1 mg L−1 with a limit of detection of 0.06 mg L−1. The detection limit in liquid milk was down to 0.17 mg L−1, which is below the permissible residue limit signifying adequate sensitivity for real sample analysis with less sample treatment.

Carbon paper is commonly used to fabricate electrodes for batteries, and its morphology is crucial to the internal mass transport. In this work, geometric models of carbon paper are obtained by experimental and numerical reconstruction methods. The micromorphology of the carbon paper is obtained with a scanning electron microscope and an X-ray computed tomography scanner, and the binary slicing method is used in the experimental reconstruction method. Three different methods are used for numerical reconstruction, namely the layered 2D fibre, 3D fibre stacking and layered 3D fibre stacking methods. The structure and characteristic parameters of the carbon paper, such as pore size distribution, dimensionless specific surface area, effective diffusion coefficient and anisotropic coefficient, are statistically analysed for comparison. The dimensionless effective diffusion coefficients of Li+ in different directions in the electrolyte-filled carbon paper are obtained using lattice Boltzmann method. Results show that the internal structural features directly affect mass transport. The curves of the calculated effective diffusivity versus porosity are well fitted using a power function similar to Bruggeman equation within the porosity range of 0.66–0.86. The anisotropic coefficient is obtained from the effective diffusion coefficient in different directions.

In this paper, Ag/paper-based composites with low dielectric loss were obtained by introduce the concept of metamaterial into the fabrication process. In this kind of metacomposite, single-layer paper was used as basic block to build up a matrix with sandwich structure, in which Ag particles are embedded and silver particles are evenly distributed. The microstructure and phase composition were characterized by scanning electron microscope and X-ray diffractometer. The impedance spectrum of the composites in 20 Hz–1 MHz region was measured by using LCR Meter, which can be well fitted by equivalent circuit method. The results show that, compared to the composite in which Ag particles disorder distributed, the dielectric loss of the layer-by-layer structured metacomposite can be effectively reduced (tan θ ≤ 0.1), without negative effect on the dielectric constant. Moreover, the dielectric properties of metacomposites show obvious anisotropy in the horizontal and vertical directions, which might give a feasible way for flexible smart material in its design.

International audience; 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.

Ag triangular nanoplates have been widely used as the SERS substrate due to their anisotropic morphology and sharp corners. In this work, SERS activity of Ag triangular nanoplates on glass and paper substrates was investigated with different concentration and size. A tiny triangular nuclei based synthesis method was employed to produce Ag triangular nanoplates with different size. And the extinction coefficients of Ag triangular nanoplates with different size were quantified by inductively coupled plasma mass spectrometry (ICP-MS) and transmission electron microscopy (TEM). With definite concentration, Ag triangular nanoplates with small size showed stronger SERS intensity on glass substrate at high concentrations, while large Ag triangular nanoplates exhibited better SERS effect on paper substrate at low concentrations. The possible reasons for distinct SERS activity of Ag triangular nanoplates on glass and paper were discussed with scanning electron microscope (SEM) characterization. These results exhibited important implications for fabricating Raman substrates using Ag triangular nanoplates and could be applied to the SERS sensing with flexile substrate.

Understanding heat transfer in corrugated fibreboard is important to the design of more effective packaging for industries which involve the freezing and chilling of food. In this work the thermal conductivity of papers which compose corrugated fibreboard were measured and used to validate finite element models of heat transfer in fibreboard. The results showed paper to be highly anisotropic, with thermal conductivity in the machine and cross machine directions being almost an order of magnitude larger than in the thickness direction. The finite element models showed good agreement with experimental results and demonstrated that the majority of heat transfer in corrugated fibreboard is though the fluted medium. Based on the finite element models, simple models for the prediction of the thermal performance of corrugated board were evaluated and shown to be very effective in reproducing the results of the more complex finite element methods. These simple methods can be used to perform corrugated fibreboard design calculations, and the models with and without radiation can be used to provide estimates of the lower and upper bounds of the thermal resistance for a given board design.

The effects of fibre orientation and laminate stacking sequence on the mechanical anisotropy of paper-based all-cellulose composites produced via a partial dissolution route is examined. As part of this work, the fibre architecture and microstructure of the paper precursor is controlled and characterised in order to follow the anisotropy of the materials through from precursor to final composite material. The fibre orientation of the precursor was found to strongly influence the mechanical anisotropy of the final composite material. The ultimate tensile strength and Young’s modulus of the paper-based all-cellulose composite laminates was 191 MPa and 17.5 GPa in the fibre direction, respectively, compared with 104 MPa and 10.4 GPa in the transverse direction, respectively. The ACC crystal structure was assessed with powder and transmission mode Wide-angle X-ray diffraction (WAXD) to measure the changes in crystallinity and crystal orientation due to the dissolution process. The mechanical response of multi-axial all-cellulose composite laminates was also determined experimentally and compared with analytical predictions by Classical Lamination Theory, demonstrating the utility of CLT for the prediction of the elastic properties of ACC laminates.

In narrow senses, flexible devices consist of soft upholders and functional materials/devices. Such hybrid devices with elastic deformations are promising for broad applications ranging from displays to sensors/detectors and micro/nano mechanical systems (MEMS). In contrast, plastic deformations are typically avoided, because of the common belief that the functionalities of the flexible devices degrade due to irreversible deformations. In this letter, we show that, for exploiting the competition between macro-elastic and local-plastic deformations, on common binding papers, the direction of magnetization in Permalloy thin films realizes a 90 ∘ rotation. A positive magnetic anisotropic constant starts at the center of sample, approaches zero after leaving from the center, and then increases its strength gradually with a negative sign until the sample edge, following an approximately linear relationship. In addition, the magnetic stability of the samples improved owing to the residual stress of the local-plastic deformations, as well as diversification of functionality and transfer are easy to be implemented by the composite substrate.

1 The aim of the present work is to assess similarities between papers used in a collection of 215 lithographs by Henri Matisse. It combines the use of an anisotropic multiscale analysis built upon the hyperbolic wavelet transform to compute distances between textures, with the fact that four textures of the same print were digitized, corresponding to four different (recto/verso and top/side) views. A permutation algorithm is devised showing the importance of reordering the four views to achieve a meaningful comparison across the papers, thus suggesting possibly different artistic intentions in some prints.

The response of paper to humidity variations is a complex, inherently multi-scale problem. The hygroscopic swelling of individual fibres and their interactions within the fibrous network govern the macroscopic, sheet-level response. At this scale, moisture induced instabilities and out-of-plane deformations may occur, which are critical for a number of industrial applications. This work specifically focuses on several aspects of this important issue. A macroscopic phenomenological hygro-mechanical model is first proposed, which aims at predicting moisture induced out-of-plane deformations in paper sheets. The constitutive model is based on the relation between these deformations and typical irreversible phenomena associated to the history of paper manufacturing, i.e. the release of dried-in strains. The model is used to describe bending induced by moisture gradients through the thickness of the sheet as well as buckling due to moisture variation in the presence of mechanical constraints. The results of the model show that the anisotropic sheet-level hygro-expansion has a strong influence on the instability phenomena. Moreover, a comparison with experiments provides adequate semi-quantitative estimates. An additional step is made towards the multi-scale understanding of paper hygro-mechanics. The fundamental physical mechanisms governing the macroscopic moisture induced response are investigated on the basis of the underlying fibrous network. To this aim, a meso-structural model is developed which consists of a network of fibres randomly positioned in a planar region according to an orientation probability density function. A series of network simulations reveals that upon moisture content variations the expansion of the inter-fibre bonding regions essentially drives the overall deformation. Particularly in the case of anisotropic fibre orientation, this explains the origin of the macro-scale anisotropic hygro-expansion, which is essential for the observed sheet-level instability phenomena.