In-plane Fiber Research Articles

Robustness of the wide-field imaging Mueller polarimetry for brain tissue differentiation and white matter fiber tract identification in a surgery-like environment: an ex vivo study.

During neurooncological surgery, the visual differentiation of healthy and diseased tissue is often challenging. Wide-field imaging Muller polarimetry (IMP) is a promising technique for tissue discrimination and in-plane brain fiber tracking in an interventional setup. However, the intraoperative implementation of IMP requires realizing imaging in the presence of remanent blood, and complex surface topography resulting from the use of an ultrasonic cavitation device. We report on the impact of both factors on the quality of polarimetric images of the surgical resection cavities reproduced in fresh animal cadaveric brains. The robustness of IMP is observed under adverse experimental conditions, suggesting a feasible translation of IMP for in vivo neurosurgical applications.

Thermally reduced sugarcane bagasse carbon quantum dots and in-plane flax fiber unsaturated polyester composites: surface conductivity and mechanical properties

Thermally reduced sugarcane bagasse carbon quantum dots and in-plane flax fiber unsaturated polyester composites: surface conductivity and mechanical properties

Unraveling the highly efficient synergy of adsorption and degradation for norfloxacin elimination by Mo/Fe anchored carbon fiber aerogel via peroxydisulfate activation

In peroxydisulfate (PDS) advanced oxidation processes (AOPs), the mass transfer of reactive oxygen species (ROS) and sustainability of catalysts are the rate-limiting steps for pollutant elimination. Recently, norfloxacin (NOR) has received growing concern due to its ecotoxicological potential. Here, a novel Mo2C-Fe3C anchored in-plane biomass carbon fiber aerogel (Mo/Fe-KFA) was constructed to firstly enrich NOR on a nano-surface and immediately in situ degraded from the interface via PDS activation. Mo/Fe-KFA-PDS system achieves over 99% removal of NOR within 5 min in a wide range of pH 3–11 due to NOR fast enriched on Mo/Fe interface and enhancing the mass transfer of ROS within its lifetime. The electron transport between Mo and Fe via the graphitic carbon chain (Mo-C-Fe) in Mo/Fe-KFA accelerates the Fe3+/Fe2+ cycle and largely prolongs the durability of the catalyst which the removal of NOR is over 85% after continuous operation for 96 h with a retention time of 0.5–1 s. This means that 1 g of Mo/Fe-KFA can purify ∼43.2L of NOR wastewater driven by gravity and maintain ∼85% activity. The detailed highly removal kinetics of NOR and durability of catalyst were systematically investigated associated with DFT calculations. Finally, degradation intermediates of NOR were identified by UPLC-MS and the corresponding toxicity potential was evaluated. This work develops a sustainable, high-efficiency and economical strategy for purification of water organic contaminates.

A global-to-local sub modelling approach to investigate the effect of lubrication during double diaphragm forming of multi-ply biaxial non-crimp fabric preforms

The forming behaviour of preforms constructed from multiple plies of Non-Crimp Fabric (NCF) has been investigated for manufacturing a complex double-curved geometry using Double Diaphragm Forming (DDF). An established multi-resolution finite element forming simulation has been employed to investigate the effect of the ply layup sequence on the formation of fabric wrinkles. FE simulations are shown to be in good agreement with experiments performed using the same geometry, in terms of the location and number of fabric wrinkles, for layups containing single or multi-ply orientations. Simulation results indicate that the convex double-curved features on the tool surface induce fabric over-shearing, coupled with fabric bridging, leading to wrinkles. In addition, the dissimilar inter-ply shear deformations in multi-ply preforms result in local fibre compression causing additional wrinkles. Experiments confirm the feasibility of using liquid resin as an inter-ply lubricant to mitigate out-of-plane wrinkles, but this is found to compromise the stability of the fibre architecture in local convex regions, causing additional in-plane fibre misalignment.

Manufacturing of biodegradable Flax-PLA curvatures using a unique vacuum-temperature profile

In this research, the manufacturing of completely biodegradable composites with a unique single-step sheet consolidation method was discussed. Layers of unidirectional, coarse twill, and fine twill flax; and poly lactic acid (PLA) were used as the material system to manufacture cylindrical and spherical composite half-shells. The three processing parameters were vacuum pressure, temperature and time. Thickness, mass fraction, tensile strength, shear strength, shape conformance and biodegradability of the manufactured composites were experimentally determined. The composite specimens’ cross-sections were also observed under an optical microscope, to assess, the consolidation quality of the manufactured composites, that was represented by the composite thickness, and primarily governed by the polymer viscosity, and the transverse and in-plane fibre reinforcement permeability. Biodegradable Flax-PLA composites were successfully consolidated, within 5% tolerance of the targeted mass fractions and thickness values, conforming within 8% tolerance to the shape of the mould. The highest achieved shear strength, flexural modulus, tensile strength and elastic modulus, were 22 MPa, 19.9 GPa, 179 MPa and 19.5 GPa, respectively. This research will be valuable to develop, flat and curved biodegradable composites, for one-off or small scale productions, at a relatively low capital cost.

Fast characterization of in-plane fiber orientation at the surface of paper sheets through image analysis

The in-plane fiber orientation distribution has a decisive impact on paper mechanical and dimensional properties (e.g., tensile stiffness, hygroexpansion). It is usually estimated offline through relatively expensive bench instrumentation such as diffusion-based optical methods and ultrasonic devices. In this work we present an alternative methodology that is fast, portable, inexpensive and able to provide the complete surface polar fiber orientation profile. The proposed technology combines an image acquisition setup, consisting of a digital camera with a low angle illumination system, with the gradient-segmentation method (GSM), a robust image analysis algorithm. This camera-GSM methodology presented high internal consistency, accurately identifying the angles of samples subjected to known rotations at the imaging step. The methodology also produced comparable results to the TSO (tensile stiffness orientation) technique, used as reference. The methodology is easily transferable to plant operation, including for the online assessment of fiber orientation.

Distribution of In-plane Physical Properties of Handmade Xuan Paper: Revealing the Effects of the Sheet Forming Process and the Folded State on Handmade Xuan Paper

ABSTRACT Xuan paper is one of the most famous handmade papers in China and is an important paper for conservation. However, the evenness of Xuan paper has not yet received much attention. In this study, the distribution of the in-plane grammage and mechanical properties of Xuan paper are measured. It is found that the distribution of the in-plane grammage and mechanical properties of Xuan paper is uneven. In the handmade direction, the grammage and mechanical properties of Xuan paper are overall largest in the lower area, followed by the upper and middle areas. The sheet forming process of Xuan paper has an important effect on the distribution of in-plane grammage, mechanical properties, and fiber orientation of Xuan paper. The folded state has a negative effect on the mechanical properties of the folded area of Xuan paper. This study will help raise awareness of the unevenness in physical properties of Xuan paper, which is important in both conservation and research applications.

Identification of defects in composite laminates by comparison of mode shapes from electronic speckle pattern interferometry

A novel technique for identifying defects in carbon fibre reinforced plates has been developed. Firstly, modal analysis by impact excitation was performed to obtain the first five resonant frequencies for three defect-free and three defective specimens with in-plane fibre waviness. Then amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) was used to obtain the mode shapes at these frequencies. The contours of the nodal regions visible in the mode shapes were extracted using a specially-developed algorithm employing density-based spatial clustering of applications with noise (DBSCAN). Fourier descriptors, that are invariant to rotations, translations, and scaling, were used to decompose the contours to reduce data dimensionality and make comparisons. The differences in contours between the two sets of specimens showed that the 4th and 5th mode shapes can be used for identifying the presence of the waviness defects. This technique for nodal region comparison was found to greatly simplify the comparison of fringe patterns for the purpose of damage assessment and could potentially be used as part of validation procedures.

Prediction of Residual Strains Due to In-Plane Fibre Waviness in Defective Carbon-Fibre Reinforced Polymers Using Ultrasound Data

Residual strains affect the properties and performance of composite components, therefore measuring and predicting them are important. The prediction of residual strains from a model can be achieved by two steps: the generation of a geometric ply map and the modelling based on that to predict 3D residual strains. A novel method for identifying the most effective algorithm for characterising fibre orientation for the geometric ply map using ultrasound C-scan data has been developed. Finite element models were generated based on the fibre-orientation data from three different algorithms: the Radon transform, 2D fast Fourier transform, and Sobel filter. The models were used to predict residual strains due to three different severities of in-plane fibre waviness induced in a set of 18 specimens. Stratified leave-one-out cross validation was applied to obtain optimum parameters for the three characterisation algorithms and to update the values of the coefficient of thermal expansion for the material. Residual strains on the surface of the specimens were obtained from calculations based on the out-of-plane displacements measured using a digital image correlation system. The predicted and measured residual strain maps were decomposed into feature vectors using orthogonal polynomials to reduce data dimensionality and make quantitative comparisons. The measured residual strains and the predictions based on models using optimised parameters showed good agreement. The differences in performance were quantified based on the accuracy of the predicted residual strains, which showed that the Radon transform performed best.

Polymer/carbon pin through thickness reinforcement

ABSTRACT This work discusses the development and refinement of a polymer/fibre through thickness reinforcement method. Similar in initial concept to the traditional metalworking process of riveting this allows the manufacture of through thickness reinforced 2-D preforms. Pins are placed with deliberate excess length using a veterinary needle to part in-plane fibres. A lay-up with an array of pins is then subjected to a hot-press process flattening the pin ends resulting in a consolidated preform. This preform exhibits useful characteristics such as the ability to be cut and reformed to a new topology, with the through thickness reinforcement also conforming to the new shape. Refinements to the process introduce a multi-stage press process aimed at improving pin orientation with both original and refined processes evaluated using ASTM D5528 to determine the effect on interlaminar fracture toughness.

Algorithm to determine orientation distribution function from microscopic images of fibrous networks: Validation with X-ray microtomography

Quantitative analysis of fibre orientation in a random fibrous network (RFN) is important to understand their microstructure, properties and performance. 2D fibre orientation distribution presents an in-plane fibre orientation without any information on fibre orientation in thickness direction. This research introduces a fully parametric algorithm for computing 3D fibre orientation as thickness is important for high-density or thick fibrous networks. The algorithm is tested for 3 major classes of nonwoven fabrics called low- (L), medium- (M) and high-density (H) ones. H fabric density is 6–8 times larger than the L fabric density. M fabric density (traditional intermediate fabric density) is 3–4 times larger than the L fabric density. Voxel models of experimental nonwoven webs were generated by an X-ray micro-CT (µCT) system and evaluated with the algorithm. Statistical results showed that a fraction of fibres orientated along the thickness direction increases as fibre density grows. To validate the accuracy of findings, deterministic voxelated virtual fibrous structures, created using mathematical functions were used. This novel algorithm is able to produce a 3D orientation distribution function (ODF) for any RFN including, models of nonwovens produced with various manufacturing parameters, experimentally verified and validated with X-ray µCT. Also, it can compute 2D ODFs of various types of RFNs to evaluate 2D behaviour of fibrous structures. The obtained results are useful for applications in many fields including finite element analysis, computational fluid dynamics, additive manufacturing, etc.

Polarimetric techniques for the structural studies and diagnosis of brain

Abstract The polarimetric techniques are used in various biomedical applications for a non-contact and fast diagnosis of tissue that is known as optical biopsy approach. These optical modalities provide relevant information on micro-architecture of biological tissue and its alterations induced by different diseases, thus, helping in staging and precise delineation of the pathology zones. In this review, we summarize the work of different research groups on using polarized light for brain tissue studies. This includes the investigations of polarimetric properties of brain tissue (both scattering and optical anisotropy) for brain connectome reconstruction, the visualization of in-plane brain fiber tracts for brain tumor contrast enhancement during neurosurgery, and the histopathology analysis for disease staging in Alzheimer’s subjects. We discuss also further perspectives for the pre-clinical studies of brain with polarized light.

Automated computation of nerve fibre inclinations from 3D polarised light imaging measurements of brain tissue

The method 3D polarised light imaging (3D-PLI) measures the birefringence of histological brain sections to determine the spatial course of nerve fibres (myelinated axons). While the in-plane fibre directions can be determined with high accuracy, the computation of the out-of-plane fibre inclinations is more challenging because they are derived from the amplitude of the birefringence signals, which depends e.g. on the amount of nerve fibres. One possibility to improve the accuracy is to consider the average transmitted light intensity (transmittance weighting). The current procedure requires effortful manual adjustment of parameters and anatomical knowledge. Here, we introduce an automated, optimised computation of the fibre inclinations, allowing for a much faster, reproducible determination of fibre orientations in 3D-PLI. Depending on the degree of myelination, the algorithm uses different models (transmittance-weighted, unweighted, or a linear combination), allowing to account for regionally specific behaviour. As the algorithm is parallelised and GPU optimised, it can be applied to large data sets. Moreover, it only uses images from standard 3D-PLI measurements without tilting, and can therefore be applied to existing data sets from previous measurements. The functionality is demonstrated on unstained coronal and sagittal histological sections of vervet monkey and rat brains.

The relation between in-plane fiber waviness severity and first ply failure in thermoplastic composite laminates

The influence of in-plane fiber waviness on the first ply failure of quasi-isotropic thermoplastic composite laminates was investigated. The failure mode and stress at first failure were studied by using a four-point bending test and an end-loaded bending (ELB) test. The experimental results confirm that no undesirable stress concentration due to load introduction occurred in the ELB test, thereby supporting the use of this test as an alternative method to measure stress at failure. The experiments demonstrated that waviness severity affects stress at first failure and compressive damage development. The stress at first failure initially decreases with increasing maximum waviness angle and levels off as the angle starts exceeding 20°. These results reinforce the hypothesis from previous research which suggests that wavy ply compressive strength is less sensitive to changes in severity at larger angles. Furthermore, it was found that kinking failure was the dominant failure mode for maximum waviness angle up to about 45°. No kink band was observed in wavy regions with maximum angles above 45° when there was another wavy region with a lower maximum angle in the same specimen. This means that failure is not necessarily initiated at the location where waviness is most severe.

Acoustic and thermal performance of polypropylene nonwoven fabrics for insulation in buildings

Thermal insulation and acoustic absorption materials play a significant role in the characteristics of energy-saving and comfortable modern buildings. However, these two types of materials are generally developed independently. This study highlights the potential of lightweight polypropylene nonwoven fabrics for building applications and investigates how fabric structure affects thermal and acoustical properties. An industrial-scale melt spinning machine was used to produce polypropylene fibers at linear densities of 1.4 and 1.8 dtex. A semi-industrial needle punching line was used to fabricate nonwoven samples with three thicknesses (2, 3, and 4 cm), four porosities (0.83, 0.88, 0.93, and 0.96), and different in- and through-plane fiber orientation distributions. Totally, 31 samples were produced and their sound absorption and thermal insulation performance were assessed using impedance tube and guarded hot plate techniques. Accordingly, the thermal conductivity (Keff) and sound absorption average (SAA) of the samples could be engineered in the range of 0.0270–0.0404 W m-1K-1 and 0.270–0.675, respectively. It was found that fabrics made of finer fibers provide superior acoustic absorption and thermal insulation performance. An increase in through-plane fiber orientation adversely affected the thermal insulation properties, while its effect on acoustic properties depends on the porosity of samples and the sound frequency. The results of statistical analysis showed that in-plane fiber orientation does not have a significant effect on sound absorption behavior, except at frequencies between 4000 and 6300 Hz. It was also found that in-plane fiber orientation does not significantly affect the thermal insulation properties. The best acoustic and thermal performance were achieved by fibrous samples of layered structure made of 1.4 dtex fibers with a thickness of 3 cm (Keff =0.0278 W m-1K-1, SAA = 0.552) and 4 cm (Keff =0.0277 W m-1K-1, SAA = 0.675). The performance of these samples was compared with some commercial products and literature data. The results pointed to the superior acoustic and thermal properties of the designed samples.

Tuning interlaminar fracture toughness of fine z-pin reinforced polymer composite

This paper aims to improve the interlaminar fracture toughness of carbon fiber reinforced polymer (CFRP) composites by implanting fine z-pins with the minimum damage on in-plane fibers. Z-pins with diameters as small as 0.1 mm and 0.2 mm were prepared by using carbon fiber tows with different mechanical properties. The effect of the mechanical property of carbon fiber pin on the interlaminar fracture toughness of composite laminate was investigated to reveal the enhancement mechanism. The results show that fine z-pins significantly improve the interlaminar fracture toughness and simultaneously are favorable for maintaining high retentions of in-plane mechanical properties of composite laminate. Compared with control sample, the propagation GIC values of CFRPs implanted with 0.2 mm and 0.1 mm CCF800 z-pins increase by 276 % and 541 % respectively at a low pin volume fraction of 0.16 vol%. Both z-pin pull-out and z-pin fracture failure behaviors can be observed for these fine z-pin reinforced composites. The higher tensile properties of z-pins and better transverse shear resistance tend to result in the failure of z-pin pull-out. With the decrease of z-pin diameter, the probability of z-pin fracture failure becomes greater, and correspondingly stronger pinning effect and larger failure load are achieved.

Full-Range Optical Imaging of Planar Collagen Fiber Orientation Using Polarized Light Microscopy.

A novel method for semiautomated assessment of directions of collagen fibers in soft tissues using histological image analysis is presented. It is based on multiple rotated images obtained via polarized light microscopy without any additional components, i.e., with just two polarizers being either perpendicular or nonperpendicular (rotated). This arrangement breaks the limitation of 90° periodicity of polarized light intensity and evaluates the in-plane fiber orientation over the whole 180° range accurately and quickly. After having verified the method, we used histological specimens of porcine Achilles tendon and aorta to validate the proposed algorithm and to lower the number of rotated images needed for evaluation. Our algorithm is capable to analyze 5·105 pixels in one micrograph in a few seconds and is thus a powerful and cheap tool promising a broad application in detection of collagen fiber distribution in soft tissues.

Assessment of the 3D ply-by-ply fiber structure in impacted CFRP by means of planar Ultrasound Computed Tomography (pU-CT)

The manufacturing process of fiber reinforced polymer laminates could induce local distortions from the nominal fiber architecture. Further, low-velocity impact events may induce additional changes in the fiber architecture, due to local plasticity and delamination formation. These deviations could have a significant effect on the structural performance of composites. This study presents a planar ultrasound computed tomography (pU-CT) technique to reconstruct the local fiber architecture of impacted CFRP laminates. The proposed pU-CT technique employs a pulse-echo scanning modality, and the 3D reconstruction process consists of three subsequent analysis steps: Step 1: Extraction of front- and rear surfaces, delamination interfaces, and interply interfaces. Step 2: Estimation of the out-of-plane ply orientation. Step 3: Extraction of the in-plane fiber direction. The developed pU-CT technique is experimentally demonstrated on an impacted 24-layer CFRP laminate with a stacking sequence [45/0/−45/90]3S. The obtained 3D reconstruction result reveals that the impact event introduced a complex delamination cluster, as well as local plasticity resulting in distorted out-of-plane ply orientation. The in-plane fiber angles remain unaffected and closely match the nominal quasi-isotropic stacking sequence. It is anticipated that the pU-CT method could complement X-ray computed tomography measurements for the inspection of (damaged) CFRP laminates with sizeable dimensions.

Ultrasonic tomographic reconstruction of local fiber orientation in multi-layer composites using Gabor filter-based information diagram method

Fiber waviness and ply stacking errors compromise the mechanical performance of multi-layer composites. Measuring the local in-plane fiber orientation layer-by-layer is therefore important to assure the structural integrity of a composite. The Radon transform and the Gabor filter methods have been reported to be appropriate for extracting the fiber orientation from an ultrasonic dataset, where the Radon transform method was found to be more accurate and stable. This paper proposes a tomographic reconstruction method on the basis of classical ultrasound pulse-echo testing, in view of reconstructing the local in-plane fiber orientation in multi-layer composites. A 3D ultrasonic dataset is first sliced successively through depth, and each 2D slice is locally analyzed by a Gabor filter method coupled to the concept of an Information Diagram (GF-ID). The GF-ID improves the Gabor filter method by constructing local Gabor filters with optimal orientation and wavelength from which the local in-plane fiber orientations can be obtained in an automated way. The performance of the developed GF-ID method is investigated on both synthetic texture images and an experimental ultrasonic dataset obtained from a 24-layer [45/0/-45/90]3S carbon fiber reinforced composite. It is found that the GF-ID method yields a high-quality tomographic reconstruction of the local orientations at different scales, and shows high noise resistance. Comparison with the classical Radon transform approach reveals the higher performance of the GF-ID method for ultrasonic reconstruction of the local in-plane fiber orientation in multi-layer composites.

Investigation into the effects of inter-ply sliding during double diaphragm forming for multi-layered biaxial non-crimp fabrics

The effect of inter-ply sliding was investigated for multi-ply Non-Crimp Fabric (NCF) preforms during the Double Diaphragm Forming (DDF) process. A Finite Element (FE) model was employed to investigate the influence of the ply layup sequence and the coefficient of friction between fabric-fabric and fabric-diaphragm interfaces. Simulation results indicate that in-plane fibre compression, caused by dissimilar shear deformation between adjacent plies, can lead to out-of-plane wrinkles, where the wrinkle length is a function of the relative fibre angle at the ply-ply contact interface. The most severe wrinkles occurred when the inter-ply angle was 45° for a multi-ply biaxial NCF preform with a pillar stitch at 45° to the primary yarns. A second parametric study was conducted by incrementally reducing the coefficient of friction at the ply-ply interface. Experiments confirmed that out-of-plane wrinkles are sensitive to the friction resistance between NCF plies and therefore lubricating the fibres can minimise wrinkling defects caused by dissimilar inter-ply deformation.