Fiber Layout Research Articles

High-performance composite bridge deck with prestressed basalt fiber-reinforced polymer shell and concrete

In this study, a basalt fiber-reinforced polymer (BFRP) shell–concrete composite bridge deck with prestressed BFRP strips was investigated. The effectiveness of the prestressed shell was verified based on a preliminary study. Eight full-scale specimens were designed to examine the static and fatigue behaviors, including the failure modes, ultimate capacities, load–displacement curves of the bridge deck, and key areas of the BFRP shell and prestressed BFRP strips. The parameters of the bridge deck included the surface conditions, fiber layout of the shell, position of the reinforcement, and adoption of the prestressed BFRP strips. The theoretical formulas of the composite bridge deck were also derived. The results show that the composite decks exhibit excellent integrated behavior including high stiffness, high capacity, and reliable interfacial bonds. The specimen with adhered sand achieved an evidently higher stiffness and capacity than the control specimen. The corrugated teeth were beneficial for the stiffness but irrelevant for the ultimate capacity of the specimens. The layout of the fiber mat rather than that of the fiber filament in the BFRP shell could slightly enhance the ultimate capacity but not affect the stiffness. The arrangement of the longitudinal steel bars in the tension zone and stirrups in the deck could significantly enhance the stiffness and capacity of the deck, respectively. The fatigue test proved that this bridge deck could survive 10 million cycles under a load level of 0.439 and a load amplitude of 96.5 kN, for which the residual capacity and stiffness reduced by less than 8%. The finite element models could reflect the real failure process and yielded a reliable capacity value, whereas the theoretical formulas provided conservative results of the capacity and stiffness.

Snap-through and stiffness adaptation of a multi-stable Kirigami composite module

Multi-stable composite laminates have been used to create adaptive and shape-morphing structures for many applications. However, it remains challenging to use these composites to obtain complicated shape changes and mechanical property adaptations. This study proposes a “Kirigami composite” concept to help address this challenge. By strategically placing slit cuts into the composite laminate with carefully designed fiber layout, one can release the internal constraints and significantly enrich the achievable shapes and adaptive functions. This study focuses on the elementary Kirigami composite module consisting of a single slit cut and two bistable patches. Experiments and finite element simulations show that this Kirigami module exhibits four different stable equilibria and its snap-through instability originates from a rapid “run-away” growth of surface curvature inversions due to connecting tab. This study also investigates a stiffness adaptation function. These results can be used for creating more sophisticated Kirigami composite structures with multiple patches and cuts.

Additive Manufacturing of 3D Structures Composed of Wood Materials

Abstract3D objects composed of 100% wood components are 3D printed utilizing wood flour microparticles dispersed in a matrix composed of cellulose nanocrystals and xyloglucan. In the printed object, a wood waste product is “glued” with extracted wood products, to be a substitute for pristine wood. 3D printing is used to maximize conversion of low value materials into final products that exhibit visual, textural, and physical properties of natural timber. Several 3D printing technologies are applied to achieve a wide range of densities, mechanical properties, colors, and morphologies as well as high thermal insulation. Furthermore, the 3D printing process enables predesigning of fiber layout in the printed wood, which enables control of shrinkage orientation.

Preliminary test and analysis of an ultralight lenticular tube based on shape memory polymer composites

Shape memory polymer composites (SMPCs) demonstrate the advantages of light weight, high strain rate, high strength, high stiffness, self-locking and self-deployment. In this study, the mechanical properties and deformation performance of SMPC-based lenticular tube are studied. Dynamic mechanical analysis (DMA) tests and three-point bending tests were carried out to determine thermomechanical properties, and +45°/−45° fiber layout was chosen as the optimum layout. Tensile tests were conducted to investigate the mechanical properties of SMPC at different temperature. The strain distribution during recovery process was obtained by digital image correlation (DIC) experiment. Bending and recovery process were simulated by finite element analysis, the stress distribution of curved state of lenticular tube were obtained. Comparing with traditional lenticular tube, SMPC-based lenticular tube exhibits the advantages of controllability and stability in deploying process, and they still work well after folding 30 deformation cycles. Due to its above advantages, several potential applications are proposed for deployable space structures and will be validated in near future.

Buckling optimization of composite cylinders for axial compression: A design methodology considering a variable-axial fiber layout

Fiber steering is an outstanding capability for producing composite structures with spatially tailored properties. The ability of tailoring the reinforcement arbitrarily in the space generates laminate with variable-stiffness, possessing substantial scope for outperforming traditional constant-stiffness laminates. This investigation presents a methodology to optimize composite cylinders with a variable-axial (also known as variable angle-tow and variable-stiffness) layout under axial compression for the adopted design space, loads and boundary conditions, using a novel optimization concept based on the manufacturing characteristics of the Tailored Fiber Placement (TFP) process. Next, a post-buckling analysis is carried out in order to make a first assessment of the imperfection sensitivity of the cylinders. The current approach locally optimizes both thickness and fiber angle of each finite element (FE), where thickness accumulation is reached through a smooth overlapping of rovings, a typical characteristic of TFP process. The optimized cylinders have significantly higher linear buckling loads than the corresponding initial layouts and are less sensitive to affine initial geometrical imperfections. The current work on optimization of the linear buckling behavior of variable-axial (VA) shells shows both the potential of using VA-configurations to exploit their tailoring ability and the capabilities of the current optimization framework to improve and optimize the behavior of VA structures.

Interlaminar damage detection through the understanding of direct current spreading in continuous fiber reinforced composites

In this article, we present the results from a study of flow of DC current in ceramic matrix and polymer matrix composite materials with different fiber layouts. We provide insight into the spread of DC current in a direction transverse to the primary direction of flow. A ladder network of resistors based model is proposed to understand the overall electrical behavior. A DC electrical simulation of the proposed model agrees well with the experimental data and can be used to estimate the out-of-plane resistivity of composite from the known value of in-plane resistivity. The nature of current spreading is proposed to be used in identifying the interlaminar or other sizable cracks existing in the bulk of the continuous fiber composite materials. The results presented can potentially contribute towards developing the method of direct current potential drop (DCPD) as a reliable technique for inspection in manufacturing of composite panels.

Temperature Field Reconstruction of Concrete Dams based on Distributed Optical Fiber Monitoring Data

Mastering the real temperature distribution of the concrete dam is the basis for solving the problem of temperature control and crack prevention. In this paper, Distributed Temperature Sensing (DTS) technology was applied to temperature monitoring of a high-arch dam under construction in southwest China. In order to obtain a more comprehensive temperature distribution of the dam, optical fiber layout principles for arch dams were studied, and horizontal and vertical optical fiber layout schemes were first proposed according to these principles. The real temperature variation processes of the dam were obtained in real time with a line temperature measurement pattern instead of a point temperature measurement pattern. Additionally, a framework of distributed optical fiber data acquisition and remote transmission was proposed. Interconnection of multiple DTS hosts and remote transmission of temperature data were realized. Then, two-dimensional temperature fields of a typical dam block in different ages and longitudinal profiles of dam blocks with embedded fibers were reconstructed based on large amounts of temperature monitoring data and the Kriging difference algorithm. Temperature field reconstruction results showed that the temperature distribution law of the concrete arch dam was in accordance with the actual situation.

Effect of fiber layout on signal analyzing of carbon/glass/epoxy hybrid composite laminates flexural loading using acoustic emission

In this study, Glass, Carbon and Epoxy Hybrid Composite laminates were loaded under flexural loading and monitored by an acoustical sensor and therefore, the effect of fiber layout in hybrid composite laminates on acoustical signal processing was studied. In fact, in order to diagnosis full frequency areas of the emitted signals and determining fracture mechanisms, also to obtain maximum load frequency and time; signal processing is necessary. Wavelet and Choi–Williams transforms, two analytical methods, were used to investigate the acoustic signal. Based on the results, Choi–Williams Analysis maximum frequencies have 0, 5%, −5% and −4% variation in compare with Wavelet Analysis maximum frequencies in Specimens A, B, C, and D respectively.Adding Nanoparticles to the polymer matrix composites increases inter-laminar adherence, and the possibility of delamination occurrence decreases considerably. Also, Wavelet coefficients are 4.5, 33.3, 6.3 and 18.75 times less than Choi–Williams coefficients in Specimens A, B, C, and D respectively. For more detailed studies, SEM images have been prepared.

RETRACTED: Experimental investigation of parameters affected on behavior of composite tubes under quasi static and dynamic axial loading

Abstract Composite tubes mayhap subjected to impact loads during placement or operation. By determining the impact properties of composite tubes and using them in the design process, the accuracy of the behavior of these structures is guaranteed under dynamic and quasi-static loading conditions. In the present study, the effect of changing parameters such as tube diameter, fiber density and fiber layout on the behavior of glass/epoxy composite tubes under dynamic and quasi-static axial loading is investigated. The Force-displacement diagrams were extracted for all experiments and compared with other experiments. Also, the rate of specific energy absorption of each test was calculated for all samples. The results of this study showed the change of parameters mentioned is effective on the energy absorption of composite tubes. In both groups of dynamic and quasi-static axial tests, variations of fiber density and samples diameter caused to change the specific absorbed energy. But the change in fiber layout from [0.90] to [± 45] reduced the specific absorbed energy. In the following, the results of dynamic and quasi-static tests were compared. Comparison of the results showed that for predicting of the average crushing force of the dynamic test for 10-layer samples with a height of 100 mm and [0.90] fiber layout, the average force of the quasi-static test can be used with coefficients of 1.1–1.3. Also, a model was proposed for predicting the average crushing force, maximum force and sample destruction in the dynamic test according to the quasi-static test results. Also, according to the results, in the dynamic and quasi-static impact tests, increasing the fiber density and internal diameter of the samples, increases the amount of specific energy absorption. In the case of changing the fiber orientation for samples made with 200 gr/m2 and 400 gr/m2 fibers in the dynamic impact tests, compared to quasi-static tests, have a different effect on the amount of specific energy absorption.

Influence of layer thickness variations on the structural behaviour of optimised fibre reinforced plastic parts

Fibre reinforced plastics (FRP) are considered as a modern high-tech material. The enormous lightweight potential, especially of carbon fibre reinforced plastics, accelerates its spreading in many industrial applications. However, as good as the lightweight potential of FRP is, as difficult is the optimal use in products because of its anisotropic material properties. Recently, methods considering the anisotropic material behavior during the product development process have been developed. These result in optimized nominal laminate layouts with defined laminate parameters like fibre orientation, ply thickness and ply stack-up order. Yet, during the manufacturing process, variations of these parameters, compared to the nominal design, occur. The variations result in asymmetric laminates, which causes couplings in the stiffness matrix and consequently undesired deformations. The effects of varying laminate design parameters have so far mainly been investigated with focus on manufacturing activities. However, to support the design engineer in considering the influence of varying laminate parameters on product behavior, this paper studies the effects on the structural behavior of optimized FRP-parts. The main novelty and contribution of the paper can be found in providing a new approach for the consideration of uncertainties in the ply thickness on FRP parts with optimized fibre layout. For this purpose, sensitivity analyses are performed with the aim of investigating the importance of the parameters on the structural behavior. With this knowledge, the product developer is able to distinguish between critical and non-critical laminate parameters and consider their variations in the product development process as early as possible.

Experiment and Numerical Study on Deformation Measurement of Cast-in-Place Concrete Large-Diameter Pipe Pile Using Optical Frequency Domain Reflectometer Technology

The Cast-in-place concrete large-diameter pipe (PCC) pile has been used as the foundation reinforcement and embankment in China due to its low cost and high bearing capacity. The deformation of PCC pile under different vertical loads is very important for the application of engineering. In order to study the deformation characteristics of PCC pile, a small-scale model test was carried out. The new distributed measuring technology, named Optical Frequency Domain Reflectometer (OFDR), was applied to measure the strain on the PCC pile. A single mode fiber (SMF) was used, and the methods of layout, packaging and protection of optical fiber are introduced in detail. The obtained data was dealt with by wavelet transform, and the strain curves were analyzed based on the experiments. The finite element (FE) analysis model was established by COMSOL Multiphysics, and the numerical results compared with the experiment results. It showed that the optical fiber sensor can measure the strain of PCC pile, and that the deformation of PCC pile can be successfully obtained by OFDR technology. The strain of the pile decreases with depth and increases with loading. The measured result agrees well with numerical simulation result. The potential application of OFDR technology to PCC pile in situ and PCC energy pile is discussed.

Research on the layout of optical fibers applied for determining the integrity of cast-in-situ piles

Abstract Distributed optical fiber temperature sensing technology has the potential to be used to determine the cast-in-situ pile integrity. This study proposed an arrangement of optical fibers for obtaining the pile integrity in situ, and it provided a calculation model for the temperature distribution. A model pile was constructed with the dimensions of 1.5 m × 0.5 m × 0.5 m. The fibers were implanted parallel to the center axis of the pile with a spacing of 0.04 m. The heat conduction area generated because of the heating of the fiber in the center of the pile was tested. The test results indicated that the heating conduction area was limited for certain heating powers. Furthermore, for the heating conduction area and heating power, care must be taken while arranging the optical fibers in the piles to determine the integrity.

Improving spatial and spectral resolution of TCV Thomson scattering

The recently completed MST2 upgrade to the Thomson scattering (TS) system on TCV (Tokamak à Configuration Variable) at the Swiss Plasma Center aims to provide an enhanced spatial and spectral resolution while maintaining the high level of diagnostic flexibility for the study of TCV plasmas. The MST2 (Medium Sized Tokamak) is a work program within the Eurofusion ITER physics department, aimed at exploiting Europe's medium sized tokamak programs for a better understanding of ITER physics. This upgrade to the TCV Thomson scattering system involved the installation of 40 new compact 5-channel spectrometers and modifications to the diagnostics fiber optic design. The complete redesign of the fiber optic backplane incorporates fewer larger diameter fibers, allowing for a higher resolution in both the core and edge of TCV plasmas along the laser line, with a slight decrease in the signal to noise ratio of Thomson measurements. The 40 new spectrometers added to the system are designed to cover the full range of temperatures expected in TCV, able to measure electron temperatures (Te) with high precision between (6 eV and 20 keV) . The design of these compact spectrometers stems originally from the design utilized in the MAST (Mega Amp Spherical Tokamak) TS system located in Oxfordshire, United Kingdom. This design was implemented on TCV with an overall layout of optical fibers and spectrometers to achieve an overall increase in the spatial resolution, specifically a resolution of approximately 1% of the minor radius within the plasma pedestal region. These spectrometers also enhance the diagnostic spectral resolution, especially within the plasma edge, due to the low Te measurement capabilities. These additional spectrometers allow for a much greater diagnostic flexibility, allowing for quality full Thomson profiles in 75% of TCV plasma configurations.

Introduction.

The pulvinar can be subdivided into well-delimitated regions based on chemoarchitectural, cytoarchitectural, myeloarchitectural, connectivity, and electrophysiological criteria. Subdivisions of the pulvinar based on its chemoarchitectural features are the most consistently preserved across species of New and Old World monkeys. It is reasonable to speculate that the occurrence and distribution of calcium-binding proteins in the pulvinar, such as calbindin and parvalbumin, have been preserved along evolution. Therefore, they have proven to be valuable tools capable of probing the basic pulvinar scaffold across primate species. Along this review, we will provide an overview of the available data regarding the various subdivisions of the pulvinar that have been proposed based on architectural criteria such as the distribution of molecular markers, neuronal morphology, and fiber layout.

Experimental method to determine anisotropic permeability of hollow fiber membrane bundles

The hydrodynamic flow resistance at low Reynolds numbers through hollow fiber membrane bundles is modeled, e.g. for computational fluid dynamics (CFD), as Darcy permeability K following the porous media approach. Experimental determination of the permeability of a particular hollow fiber bundle arrangement (fiber angle, diameter, and distance) is limited to one-directional flow measurements due to problems preparing representative elementary volume (REV) and following permeability is usually assumed to be isotropic. This ignores the fact that hollow fibers are usually arranged in an organized manner, or fiber bundle, and that resistance to flow is assumedly anisotropic. In this study, we developed a method of creating scaled-up REVs of almost any kind of geometry (by rapid prototyping) that can be measured in multi-dimensional directions within a permeameter. By means of a dimensional analysis the measured anisotropic flow resistances can be expressed in dimensionless friction factors, which can then be transformed into directional permeabilities on an arbitrary scale. The method was developed on two different fiber angle configurations (24° and 90°) in staggered and in-line fiber arrangements that are usually applied as blood oxygenator fibers. As a result, maximum anisotropy of the permeabilities were proven for flow along the fibers compared to cross-flow to the fibers with Kmax/Kmin = 4.77 for the 24° fiber layout. A comparison between the implementation of anisotropic vs. the commonly assumed isotropic permeabilities promises an improvement, especially in a more accurate estimation of stagnation zones in such modules.

Preliminary investigation of fabrication composite structures by using shape memory alloys

The paper shows method of smart forming composite structures and fundamentals of propose fabrication technology. The presented method is based on innovative 3D printing technics with SMA (Shape Memory Alloy) fibres application. The SMA fibres layout cause an eccentric axial load after thermal activation. The result of this process is composite structures deflection in a predictable direction. The technology demonstrator sample was fabricated as well as numerical simulations were performed in aim of proof of concept. The identification process was developed to determine the layout of SMA fibres. The simulations were performed in MATLAB and ANSYS environment, where the genetic algorithm was used to identify geometrical parameters. The MAC (Modal Assurance Criterion) criterion was used to compare nodal solution with the predefined shape pattern. The simulation results shows possibilities of forming composite structures on the example of deflected beam.

A study for optical fiber multi-direction strain monitoring technology

Distributed measurement is truly achieved by Pulse-Pre Pump Brillouin Optical Time Domain Analysis (PPP-BOTDA) technique with its high spatial resolution and strain precision. A systematic distributed fiber-optic multi-direction strain monitoring (FOMDSM) technology is proposed according to the basic monitoring principle, testing parameters and layout scheme based on PPP-BOTDA. The reasonable layout scheme, temperature compensation formula, etc are also given. This article also determines the more reasonable specimen size, the position of optical fiber layout and the basic layout range. The article is an experimental feasibility inquiry into spatial multi-direction stain simultaneous monitoring, which is an urgent problem to be solved. The structure is not merely under drawing force in a practical project, and therefore this article also explores the studies common combination of bending and drawing in engineering, besides the tensile test. The technique utilizes the highest spatial resolution for the research field. From the monitoring efficacy, the high precision and good practical application have emerged. The article’s final purpose is to be proved reasonable and applicable in putting forward the spatial multi-direction stress and strain monitoring idea by the common 0°/45°/90° strain monitoring based on PPP-BOTDA technology. It illustrates important guiding significance for forming actually spatial FOMDSM ability.

Shear strength of reinforced concrete beams strengthened in shear using externally-bonded FRP composites

A shear strength estimation model for reinforced concrete (RC) beams, the so-called dual potential capacity model (DPCM), has previously been proposed by the authors. In this study, the DPCM is extended to estimate the shear strength of RC beams strengthened in shear by using externally-bonded fiber-reinforced polymer (FRP) composites. The proposed model has been derived so as to take into account the effects of the type of FRP composite, fiber-bonding configuration, and fiber layout, and it can also determine the critical shear failure modes of RC beams strengthened by externally-bonded FRP composites. To verify the accuracy of the proposed model, shear test results of 227 RC beams strengthened by externally-bonded FRP composites were collected from previous studies, and it is shown that the analysis results estimated by the DPCM agree well with those test results.

Electromagnetic configurable architectures for assessment of Carbon Fiber Reinforced Plastics

Carbon Fiber Reinforced Plastics are used in most wide domains due their low density, lack of mechanical fatigue phenomena and high strength–to weight ratio. From electromagnetic point of view, Carbon Fiber Reinforced Plastics structure represents an inhomogeneous structure of electric conductive fibers embedded into a dielectric material, thus an electromagnetic configurable architecture can be used to evaluate above mentioned defects. The paper proposes a special sensor, send receiver type and the obtaining of electromagnetic image by post-processing each coil signals in each point of scanning, using a sub-encoding image reconstruction algorithm and super-resolution procedures. The layout of fibers can be detected interrogating only diagonal reception coils.

Experimental and Analytical Evaluation of Confined Masonry Walls Retrofitted with CFRP Strips and Mesh-Reinforced PF Shotcrete

AbstractThis study evaluates the performance of retrofitted confined unreinforced masonry walls using carbon fiber–reinforced polymer (CFRP) strips and mesh-reinforced shotcrete. Polypropylene-fiber (PF) concrete was applied in the shotcrete retrofitting. Four full-scale confined unreinforced masonry walls were experimentally tested under in-plane lateral cyclic loading. The first nonretrofitted wall was built as a reference model. The second and third walls were retrofitted with carbon fiber–reinforced polymer strips in grid and diagonal layout, respectively. The fourth wall was retrofitted with mesh-reinforced PF shotcrete. The stiffness, strength, ductility, and modes of failure of the nonretrofitted confined masonry wall and the retrofitted confined masonry walls were determined and compared. The strength of the retrofitted walls with the grid and diagonal layout of carbon fiber–reinforced polymer increased up to 35 and 15%, respectively. However, the strength of the mesh-reinforced shotcrete retrofit...