Search results for "kuidut"

Predicting stiffness and strength of birch pulp:Polylactic acid composites

2016

This paper studies failure of birch pulp–polylactic acid composites. Stiffness and strength are calculated using the theory of short fibre composites and the results are compared to experimental data. The results differed from the experimental values by 0–6%. With less aligned fibres the short fibre theory is not feasible. The performance of the 40 wt% birch pulp – polylactic acid composite is predicted with X-ray microtomography based finite element modelling, and the results are compared with experiments. Stiffness results differed from experiments by 1–17% . By adding into the models a third material phase representing the interface between the fibres and the matrix, the stress–strain c…

Effective elastic properties of biocomposites using 3D computational homogenization and X-ray microcomputed tomography

2021

A 3D computational homogenization method based on X-ray microcomputed tomography (μCT) was proposed and implemented to investigate how the fiber weight fraction, orthotropy and orientation distribution affect the effective elastic properties of regenerated cellulose fiber-polylactic acid (PLA) biocomposites. Three-dimensional microstructures reconstructed by means of the X-ray μCT were used as the representative volume elements (RVEs) and incorporated into the finite element solver within the computational homogenization framework. The present method used Euclidean bipartite matching technique so as to eliminate the generation of artificial periodic boundaries and use the in-situ solution d…

Kuituverkostojen yksityiskohtainen analysointi korkean resoluution kolmiulotteisista kuvista

2009

Nanoscale probing of the supramolecular assembly in a two‐component gel by near‐field infrared spectroscopy

2023

The design of soft biomaterials requires a deep understanding of molecular self-assembly. We introduce here a nanoscale infrared (IR) spectroscopy study of a two-component supramolecular gel to assess the system´s heterogeneity and supramolecular assembly. In contrast to far-field IR spectroscopy, near-field IR spectroscopy revealed differences in the secondary structures of the gelator molecules and non-covalent interactions at three distinct nano-locations of the gel network. A β-sheet arrangement is dominant in single and parallel fibres with a small proportion of an α-helix present, while the molecular assembly derives from strong hydrogen bonding. However, at the crossing point of two …

Determination of Fibre Orientation Distribution from Images of Fibre Networks

2003

We recall two categories of algorithms for estimating fibre orientation distribution from an image of a spatial fibre system. In the first algorithm, the estimate is a magnitude-weighted distribution from angles perpendicular to the directions of the gradients in the image. The second algorithm is based on the scaled variogram of grey values scanned along a sampling line and its relation to the fibre orientation distribution. Using lines in several directions and assuming a parametric model for the orientation distribution, the orientation parameters are estimated numerically from a least-squares type procedure. Two versions of variogram-based methods are used in this work. We compare the p…

Puukuitususpension putkivirtauksen virtausprofiilin symmetrisyys ja sen turbulenttisen alueen mallintaminen

2007

Determining the number of fibre-fibre contacts in cardboard samples using tomographic imaging

2011

The fibrous network of cardboard samples was studied with the aid of tomographic imaging. For analysing the samples a method of determing the number of contacts between fibres in a planar fibrous network was introduced. The model is based on the fact that deposited paper-like structures tend to have predominantly planar fibre orientation. With this assumption an expression of the mean segment length was derived in terms of the average shortest path along fibres through the sample in the out-of-plane direction. The density profiles of cardboard samples were analysed by determing four quantitative features, the solids content, standard deviation of the solids content, slope and curvature. All…

Permeability properties of paper materials

2013

Characterization of micro-fibrillated cellulose fiber suspension flow using multi scale velocity profile measurements

2017

Rheological properties and boundary layer flow behavior of Micro Fibrillated Cellulose (MFC) suspended in water was studied using a novel velocity profiling rheometric technique. The method is based on measuring stationary velocity profiles of fluid flow in a straight tube simultaneously by Doppler Optical Coherence Tomography (DOCT) and by Ultrasound Velocity Profiling (UVP). The high resolution DOCT provides velocity profiles near the transparent tube wall, while UVP yields corresponding information in the interior parts of the flow. The data from the two instruments is combined into a comprehensive velocity profile including both the thin boundary layer near the wall and the interior par…

Online measurement of floc size, viscosity, and consistency of cellulose microfibril suspensions with optical coherence tomography

2021

AbstractIn this study, cellulose microfibril (CMF) suspensions were imaged during pipe flow at consistencies of 0.4%, 1.0%, and 1.6% with optical coherence tomography (OCT) to obtain images of the structure and the local velocity of the suspension. The viscosities obtained by combining pressure loss measurement with the OCT velocity data showed typical shear thinning behavior and were in excellent agreement with viscosities obtained with ultrasound velocity profiling. The structural OCT images were used to calculate the radial and the axial floc sizes of the suspension. A fit of power law to the geometrical floc size–shear stress data gave the same power law index for all consistencies, sug…