Measurement Of Fiber Orientation Research Articles

Improved fiber orientation measurement in nonwovens with corner removal

The orientation of fibers or filaments in nonwovens is critical in determining their mechanical characteristics. Image processing techniques, prized for their minimal human intervention and rapid processing speed, are widely utilized in nonwoven fiber orientation measurement. However, these techniques often face substantial challenges, such as low accuracy in corner detection, errors in fiber segmentation, and inefficiencies in fiber orientation calculation. Addressing these concerns, this study introduces a novel, enhanced method accompanied by two innovative optimization algorithms to enhance accuracy. The first innovation involves the development of a newly developed fiber corner detection algorithm, dubbed the T-detector, specifically tailored for the unique characteristics of fiber images, enabling efficient corner point detection and removal. Subsequently, we introduce and employ a fiber length restriction algorithm to further segment the processed longer fibers into the remaining fiber fragments and utilize a skeleton projection algorithm to calculate the fiber orientation. These algorithms overcome the existing technology’s inherent shortcomings, thereby heightening measurement accuracy. The results illustrate an improvement in measurement precision over other orientation distribution measurement algorithms, with the fiber information retention (covering ratio) reaching an impressive 95%. Our proposed method not only calculates fiber orientation distribution in nonwovens with remarkable accuracy and efficiency, but its innovative approach also stands to provide a theoretical foundation for the design of three-dimensional filtering models with specific fiber orientation.

Analysis of the Influence of Fiber Orientations in Carbon Fiber Reinforced Composites on their Structural Properties Based on Eddy Current Measurements

Fiber-reinforced plastics (FRP) are a type of composite material consisting of a reinforcing structure and a plastic matrix. When compared to traditional construction materials, FRP has higher strength and stiffness due to the high mechanical properties of reinforcing fibers such as carbon or glass. However, the properties of FRP are dependent on the alignment of fibers within the composite, with deviations leading to reduced strength and stiffness. Eddy current testing is a non-destructive technique used to visualize carbon fibers in the composite and assess the impact of local fiber orientation on the structural properties of FRP. This study aims to understand the influence of local fiber orientation on tensile strength and elastic modulus by producing composites with defined fiber orientations, analyzing them with eddy current testing, and assessing their mechanical properties through tensile tests. The measured fiber orientations are then used to validate a finite element model, in which the actual, measured fiber orientation is applied to the simulation and correlated with the mechanical properties. In contrast to previous published studies measured fiber orientation is used, which as shown in this work, differs from the theoretically implemented fiber orientation.

Monitoring of multiple fabrication parameters of electrospun polymer fibers using mueller matrix analysis

Electrospun polymer fiber mats feature versatile applications in tissue engineering, drug delivery, water treatment and chemical processes. The orientation of fibers within these mats is a crucial factor that significantly influences their properties and performance. However, the analysis of fiber samples using scanning electron microscopy (SEM) has limitations such as time consumption, fixed assembly, and restricted field of vision. Therefore, a fast and reliable method for qualitative measurements of fiber orientation is required. Mueller matrix polarimetry, a well-established method for measuring orientation of chemical and biological species, was employed in this case. We investigated the effect of four important parameters of the electrospinning process, namely collector speed, applied voltage, needle-to-collector distance, and solution concentration, on fiber orientation using Mueller matrix polarimetry thus extending the range of parameters analyzed. Measurements were performed using two extreme values and a central optimized value for each fabrication parameter. Changes in matrix values were observed for each fabrication parameter, and their correlation with fiber orientation was analyzed based on the Lu-Chipman decomposition. The results were compared with SEM images, which served as the ground truth, and showed overall good agreement. In the future, the analysis of electrospun polymer fibers can be done by using Mueller matrix polarimetry as alternative to current technology and fabrication parameters, including solution concentration for the first time in this context and the production can quickly be adjusted based on the outcome of the measurements.

Backscatter tensor imaging and 3D speckle tracking for simultaneous ex vivo structure and deformation measurement of myocardium.

Biaxial mechanical testing is a common method for elucidation of mechanical properties of excised ventricular myocardium, especially in the context of structural remodeling that accompanies heart disease. Current imaging strategies in biaxial testing are based on optical camera imaging of the tissue surface, thus providing no information about the tissue microstructure and limiting strain measurements to two dimensions. Here, these limitations are overcome by replacing the camera with ultrasound imaging in order to measure both transmural fiber orientation and 3D tissue deformation during biaxial testing. Quasi-static biaxial mechanical testing is applied to four samples of excised porcine ventricular myocardium (two left- and two right-ventricular tissues). During testing, a rotational scan of an ultrasound linear array provides data for both backscatter tensor imaging and 3D speckle tracking, from which transmural fiber orientation and tissue deformation are computed, respectively. Ultrasound-derived fiber orientation and tissue strain are validated against histology and camera surface imaging, respectively. Ultrasound-derived fiber angle and tissue strain exhibit good accuracy, with root-mean-square errors of 9.9° and 1.2% strain, respectively. Further investigation into the optimization of backscatter tensor imaging is warranted. Replacing the rotational scan of a linear array with volume imaging with a matrix array will improve the technique. Ultrasound imaging can replace the optical camera measurement during biaxial mechanical testing of ventricular myocardium in order to accurately provide measurements of transmural fiber orientation and tissue strain. In situ knowledge of transmural fiber structure and tissue deformation can enhance the inverse problem used to determine tissue mechanical properties from biaxial testing.

Automated Industrial Composite Fiber Orientation Inspection Using Attention-Based Normalized Deep Hough Network

Fiber-reinforced composites (FRC) are widely used in various fields due to their excellent mechanical properties. The mechanical properties of FRC are significantly governed by the orientation of fibers in the composite. Automated visual inspection is the most promising method in measuring fiber orientation, which utilizes image processing algorithms to analyze the texture images of FRC. The deep Hough Transform (DHT) is a powerful image processing method for automated visual inspection, as the “line-like” structures of the fiber texture in FRC can be efficiently detected. However, the DHT still suffers from sensitivity to background anomalies and longline segments anomalies, which leads to degraded performance of fiber orientation measurement. To reduce the sensitivity to background anomalies and longline segments anomalies, we introduce the deep Hough normalization. It normalizes the accumulated votes in the deep Hough space by the length of the corresponding line segment, making it easier for DHT to detect short, true “line-like” structures. To reduce the sensitivity to background anomalies, we design an attention-based deep Hough network (DHN) that integrates attention network and Hough network. The network effectively eliminates background anomalies, identifies important fiber regions, and detects their orientations in FRC images. To better investigate the fiber orientation measurement methods of FRC in real-world scenarios with various types of anomalies, three datasets have been established and our proposed method has been evaluated extensively on them. The experimental results and analysis prove that the proposed methods achieve the competitive performance against the state-of-the-art in F-measure, Mean Absolute Error (MAE), Root Mean Squared Error (RMSE).

Fiber Orientation Reconstruction from SEM Images of Fiber-Reinforced Composites

The orientation of fibers in composites reinforced with short fibers can provide insight into the microstructure of the material and considerably affect its macroscopic characteristics. However, the present standard techniques for detecting fiber orientation and length based on microscopic image processing have faults in practical applications, including high effort, low efficiency, and unreliable measurement results. In this study, a method for measuring fiber orientation based on 3D reconstructions of scanning electron microscope (SEM) images is provided. The geodesic active contour (GAC) model is applied to segment the fibers in the SEM images. Matching the fiber contours with the scale-invariant feature transformation (SIFT) algorithm successfully extracts 3D orientation information from the fiber contours. The unit vector of the fiber axis is fitted from the extracted point cloud using the ordinary least squares (OLS) method. With a maximum deviation of 3.83° and an average deviation of 1.50°, the measurement findings of this method are substantially comparable to those of the image-measuring instrument. This paper offers a quantitative approach to studying the microstructure of short fiber-reinforced composites, thereby furnishing objective evidence to support the development and research of such materials.

Using mesoscopic tract-tracing data to guide the estimation of fiber orientation distributions in the mouse brain from diffusion MRI

Diffusion MRI (dMRI) tractography is the only tool for non-invasive mapping of macroscopic structural connectivity over the entire brain. Although it has been successfully used to reconstruct large white matter tracts in the human and animal brains, the sensitivity and specificity of dMRI tractography remained limited. In particular, the fiber orientation distributions (FODs) estimated from dMRI signals, key to tractography, may deviate from histologically measured fiber orientation in crossing fibers and gray matter regions. In this study, we demonstrated that a deep learning network, trained using mesoscopic tract-tracing data from the Allen Mouse Brain Connectivity Atlas, was able to improve the estimation of FODs from mouse brain dMRI data. Tractography results based on the network generated FODs showed improved specificity while maintaining sensitivity comparable to results based on FOD estimated using a conventional spherical deconvolution method. Our result is a proof-of-concept of how mesoscale tract-tracing data can guide dMRI tractography and enhance our ability to characterize brain connectivity.

A numerical strength prediction approach for wood using element-wise local fiber directions from laser scanning

Mechanical properties of wood such as stiffness and strength vary locally especially due to heterogeneities and anisotropy. Analytical models and numerical simulations of wooden boards are able to represent varying material orientation e.g. with local fiber directions from laser scanning as input for the prediction of strength. Current Finite Element Models reconstructed the grain orientation by means of computationally demanding fluid analysis around obstacles like knots; whereas the available fiber pattern, captured by means of laser scanning, was passed solely into the detection of knots, but not directly processed for the inclusion of material fiber orientation. Therefore, the goal of this paper was the development of a numerical approach to directly include locally varying measured fiber orientation with orthotropic material properties and to predict the tensile strength of boards with reduced computational effort. Therefore, the stiffness was transformed element-wise according to the measured fiber deviations and the local fiber stress components were computed for the specific tensile load case. For the virtual strength prediction, numerical maximum stress values were compared to experimental tensile strength. Good agreements were observed with reduced computational effort compared to existing approaches between numerical and experimental results.

Polarization imaging for surface fiber orientation measurements of carbon fiber sheet molding compounds

The ability to measure the fiber orientation in fiber reinforced polymers plays a vital role in process and part design. Recently, it has been discovered that carbon fibers polarize light, providing an opportunity to detect the fiber orientation in carbon fiber-reinforced polymer parts. The Fraunhofer Institute for Integrated Circuits has developed a polarization camera system capable of measuring the polarization state of light reflected from objects in real-time. In this work, the camera system is used to measure the surface fiber orientation in carbon fiber reinforced Sheet Molding Compound semi-finished products at several stages of the processing chain. First, the fiber orientation of carbon fiber-reinforced Sheet Molding Compound semi-finished product is measured during continuous production, enabling real-time quality control and complete digitization of the material's fiber orientation information. Second, the measurement system is used to characterize static flat pressed carbon fiber reinforced Sheet Molding Compound specimens. In addition, the technique is widely applicable to many other carbon fiber based raw material forms (e.g. preforms, prepregs, tapes) and even composite parts.

On the use of milled shell‐only specimens to study the effect of fiber orientation on the fatigue behavior of a short fiber‐reinforced polyamide

AbstractThe interpretation of the fiber orientation effects on the fatigue behavior of short fiber‐reinforced polymers using specimens extracted from injection‐molded plates is hampered by the typical shell‐core‐shell structure, which affects the stress distribution through the sample's thickness. In this work, local fatigue strength values are obtained using specimens machined to leave only the outer shell layers, thus having a more homogeneous fiber orientation. Results of the finite element analysis of integer and shell‐only specimens, accounting for locally measured fiber orientations, are compared. Conclusions are drawn about the role of the core layer and the limitations of milled specimens in the evaluation of the fatigue strength.

Notched tensile strength of long discontinuous glass fiber reinforced nylon composite

In this study, the hole size effect in the open hole tension (OHT) of discontinuous glass fiber-polyamide 6 organosheet composite material was studied. Organosheet used in this study is a novel long discontinuous fiber-reinforced polymer composite with long glass fiber and in-situ polymerized polyamide 6 (nylon) matrix. A progressive failure analysis (PFA) using finite-element model was proposed to predict OHT strength using measured fiber orientation distribution. The generated virtual ogranosheet samples were used to conduct OHT Monte Carlo simulations to predict variability in strength. The notch sensitivity was observed experimentally and analyzed using PFA model, which captured interactions between various failure modes. The experimental and PFA results of OHT strength were used for calibrating analytical models, Point Stress Criterion (PSC) and Modified Point Stress Criterion (MPSC). Both, experimental and modeling approaches, yielded nearly identical analytical curves, indicating that virtual testing of organosheet can be used for OHT characterization of organosheet. The results show that the notched strength of organosheet with the diameter of 2 mm was at the same level as strength of unnotched organosheet. The notch insensitivity was attributed to the increased plasticity in the matrix due to ductility in nylon.

Modeling and characterizations of mechanical behaviors of short carbon fiber and short glass fiber reinforced polyetherimide composites

As the major manufacturing methods for short fiber reinforced polymer (SFRP) composites, extrusion compounding and injection molding techniques usually lead to complex fiber length and orientation distributions in final composites for mechanical computation analysis. It is still a challenging task about how to accurately predict the comprehensive mechanical behaviors (tensile properties, damage evolutions and failure modes) of SFRPs from complicated microstructures. This work builds a new finite element model (FEM) based on the classical random sequential adsorption algorithm with genetic algorithm (GA) for high-efficiency geometrical construction for short carbon fiber and short glass fiber reinforced polyetherimide (SCF/PEI and SGF/PEI) composites. Fiber length and orientation measurements, single fiber filament and pure PEI tensile tests are carried out to support model establishment. It is found that the longer initial length would accompany with the longer final average length and the higher fiber volume fraction would bring about shorter average final length. Short carbon fibers with larger aspect ratios tend to be more preferentially aligned along mold flow direction than short glass fibers. The predicted tensile properties, damage evolutions and failure modes are in good agreement with experimental results. Finally, the effects of fiber volume fractions, orientations and lengths on the strength and modulus of SCF/PEI and SGF/PEI composites are quantitatively explored, respectively. Our proposed model can provide an efficient evaluation of the mesoscopic structure-property relationship of SFRP composites.

Homogenisation of the Local Thermal Conductivity in Injection-Moulded Short Fibre Reinforced Composites.

This paper deals with predicting the effective thermal conductivity (ETC) of injection-moulded short fibre reinforced polymers (SFRPs) using two different homogenisation schemes: a scheme based on the dielectric theory for pseudo-oriented inclusions and a two-step homogenisation model based on the mean-field homogenisation approach. In both cases, the fibre orientation tensor (FOT) obtained from Autodesk Moldflow® simulation was used. The Moldflow FOT predictions were validated via structure tensor analysis of micro-computed X-ray tomography (micro-CT) scans of the part. In the dielectric-wise approach, the orientation of fibres was originally defined by a scalar parameter, which is related to the diagonal components of the FOT. In the two-step homogenisation approach, an interpolative model based on the Mori–Tanaka theory is used in the first step for calculating the ETC for the ideal case of unidirectional fibre alignment, followed by a second step in which orientation averaging based on the FOT inside each element is applied. The ETC was calculated using both schemes for the specific case of uniform fibre orientation distribution and at three different locations with non-identical FOTs of an injection-moulded SFRP part. The results are compared with each other and evaluated against the direct numerical simulation for the uniform fibre orientation and experimental measurements for the injection-moulded SFRP. This shows that while the two-step homogenisation can predict the ETC in the full range of orientations between the perfectly aligned and uniformly distributed fibres, the dielectric-wise approach is only capable of modelling the ETC when distributions are close to the two extreme ends of the orientation spectrum.

Reference object for traceability establishment in X-ray computed tomography measurements of fiber length in fiber-reinforced polymeric materials

X-ray computed tomography (CT) is an advanced non-destructive measuring technique that enables holistic three-dimensional measurements of outer as well as inner geometries and micro-scale features. In the field of fiber-reinforced polymeric (FRP) materials, CT can overcome the limitations of conventional methods typically based on time-consuming and destructive operations used for the measurement of fiber orientation and length, which are two characteristics that have a great impact on physical and mechanical properties of FRP parts. This work specifically addresses the CT measurement of fiber length, which is particularly complex because – differently from the fiber orientation analysis – it requires the individual fibers to be properly identified and segmented. Moreover, the traceability of such measurement has not been achieved yet. This work investigates an experimental methodology for traceability establishment and measurement uncertainty determination, based on the substitution approach. In particular, a task-specific reference object, including a selection of fibers with different lengths and configurations, was designed, manufactured and calibrated for the purpose.

Non-Destructive Multi-Method Assessment of Steel Fiber Orientation in Concrete

Integration of fiber reinforcement in high-performance cementitious materials has become widely applied in many fields of construction. One of the most investigated advantages of steel fiber reinforced concrete (SFRC) is the deceleration of crack growth and hence its improved sustainability. Additional benefits are associated with its structural properties, as fibers can significantly increase the ductility and the tensile strength of concrete. In some applications it is even possible to entirely replace the conventional reinforcement, leading to significant logistical and environmental benefits. Fiber reinforcement can, however, have critical disadvantages and even hinder the performance of concrete, since it can induce an anisotropic material behavior of the mixture if the fibers are not appropriately oriented. For a safe use of SFRC in the future, reliable non-destructive testing (NDT) methods need to be identified to assess the fibers’ orientation in hardened concrete. In this study, ultrasonic material testing, electrical impedance testing, and X-ray computed tomography have been investigated for this purpose using specially produced samples with biased or random fiber orientations. We demonstrate the capabilities of each of these NDT techniques for fiber orientation measurements and draw conclusions based on these results about the most promising areas for future research and development.

Precision Fibre Angle Inspection for Carbon Fibre Composite Structures Using Polarisation Vision

This paper evaluates the precision of polarisation imaging technology for the inspection of carbon fibre composite components. Specifically, it assesses the feasibility of the technology for fibre orientation measurements based on the premise that light is polarised by reflection from such anisotropically conductive surfaces. A recently commercialised Sony IMX250MZR sensor is used for data capture by using various lighting conditions. The paper shows that it is possible to obtain sub-degree accuracy for cured and dry woven and unidirectional materials in ideal conditions, which comprised dark field illumination. Indeed, in ideal conditions, the average relative angles can be measured to an accuracy of 0.1–0.2°. The results also demonstrate a precision of the order 1° for more general illumination, such as dome illumination and ambient lighting, for certain material type/lens combinations. However, it is also shown that the precision varies considerably depending on illumination, lens choice and material type, with some results having errors above 2°. Finally, a feasibility study into the inspection of three-dimensional components suggests that only limited application is possible for non-planar regions without further research. Nevertheless, the observed phenomena for such components are, at least, qualitatively understood based on physics theory.

Ultrasound measurement of fiber orientation and tissue strain in excised myocardium under biaxial tension

Biaxial mechanical testing is a useful tool for determining the mechanical properties of myocardium tissues, which are anisotropic due to their layered and fibrous microstructure. Mechanical properties of the tissue are largely determined by those of the laminar myofiber sheets, whose orientations vary in a helix throughout the tissue thickness. Fiber architecture of tested tissues is usually determined post hoc by destructive histological sectioning, and the contribution of fiber kinematics to tissue-level mechanical behavior is accomplished by assuming a continuum model for the myocardium. In this work is presented simultaneous ultrasound-based measurement of fiber orientation and tissue strain in excised myocardium under biaxial tension. Two-protocol (1:1 and 1:6) testing is employed in order to probe tissue anisotropy and fiber kinematics. An ultrasound linear array (15 MHz) is scanned by rotation about the imaging axis to obtain three-dimensional backscatter data from the tissue during quasi-static biaxial deformation, from which transmural fiber orientation and tissue strain are determined by backscatter tensor imaging and 3D speckle tracking, respectively. Results illustrate feasibility of the simultaneous measurement and future utility for studying fiber mechanics in diseased tissues. Fiber rotation and elongation measured directly from ultrasound is compared to that calculated under the continuum assumption.

New Perspectives for LVL Manufacturing from Wood of Heterogeneous Quality—Part. 1: Veneer Mechanical Grading Based on Online Local Wood Fiber Orientation Measurement

The grading of wood veneers according to their true mechanical potential is an important issue in the peeling industry. Unlike in the sawmilling industry, this activity does not currently estimate the local properties of production. The potential of the tracheid effect, which enables local fiber orientation measurement, has been widely documented for sawn products. A measuring instrument exploiting this technology and implemented on a peeling line was developed, enabling us to obtain the fiber orientation locally which, together with global density, allowed us to model the local elastic properties of each veneer. A sorting method using this data was developed and is presented here. It was applied to 286 veneers from several logs of French Douglas fir, and was compared to a widely used sorting method based on veneer appearance defects. The effectiveness of both grading approaches was quantified according to mechanical criteria. This study shows that the sorting method used (based on local fiber orientation and average density) allows for better theorical quality discrimination according to the mechanical potential. This article is the first in a series, with the overall aim of enhancing the use of heterogeneous wood veneers in the manufacturing of maximized-performance LVL by veneer grading and optimized positioning as well as material mechanical property modelization.

Sensitivity of fiber orientation dependent to temperature and post mortem interval.

imaging of brain white matter is well known for being sensitive to the orientation of nerve fibers with respect to the B0 field of the MRI scanner. The goal of this study was to evaluate whether and to which extent fiber orientation dependent differs between in vivo and post mortem in situ examinations, and to investigate the influence of varying temperatures and post mortem intervals (PMI). Post mortem in situ and in vivo MRI scans were conducted at 3T. was acquired with a multi-echo gradient-echo sequence, and the orientation of white matter fibers was computed using diffusion tensor imaging (DTI). Fitting of the measured fiber orientation dependent was performed using three different formulations of a previously proposed model. increased with increasing fiber angle for in vivo and post mortem in situ examinations, whereby the orientation dependency was lower post mortem. The different formulations of the fiber orientation model resulted in an identical fit, but showed large variations of the estimated parameters. The higher order orientation dependent components significantly decreased with decreasing temperature, while the orientation independent components showed no significant correlation with either temperature or PMI. Although the mean diffusivity is strongly reduced post mortem, we could successfully estimate the fiber angle using DTI. Due to the strong correlation of the higher order orientation dependent components with temperature, the decreased fiber orientation dependency post mortem in situ might primarily be attributed to the lower brain temperature.

Ultrasound measurement of transmural fiber orientation and 3D tissue strain in excised myocardium under uniaxial loading

The noninvasive measurement with ultrasound of myofiber orientation and 3D tissue strain through the tissue thickness during the application of uniaxial tension is demonstrated on porcine myocardium. Complex tissue deformation, including rotation of myofiber sheets, during the application of stretch is observed.