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A critical milestone to the adoption of 3D tow reinforced hybrid-molded structures is the development of design guidelines and analysis techniques for accurate performance modelling. The cross-sectional dimensions of the tow bundle leads to fiber length discrepancies between the inner fibers and the outer fibers which manifest as tow spreading and local fiber waviness. The effects of simulating the resulting fiber orientations and effective elastic properties is investigated by modelling a representative beam in tension and bending load cases and comparing to previous experimental results. Accounting for fiber waviness in tension demonstrated greatly improved part stiffness predictions. Spread tow bundles improved predicted strength and stiffness over simulations where tow was constrained to a uniform cross section. Increased tow reinforcement increased bending stiffness, but failure behavior was significantly influenced by the overmolding material. [ABSTRACT FROM AUTHOR]

The mechanical performance of three-dimensional woven composites is usually modeled by an ideal model with straight tow paths and constant cross-sectional areas. This ideal model predicts inaccurate properties due to oversimplification of tow shapes. In this paper, we present a more accurate method to predict properties of the 3D woven composite considering waviness and contraction of tows due to interference between them. The tow waviness is defined by elliptic and trigonometric functions. The shrinkage of the tow cross-sectional area is modeled using a cubic polynomial. The elastic moduli are predicted using the modeled tows and the weighted average model. The predicted properties are compared with test results to verify the accuracy. In addition, the usefulness of the present method is verified by comparing the calculated moduli using the ideal model. We conclude that the present method is useful for the design of structures to which 3D woven composites are applied. [ABSTRACT FROM AUTHOR]

SiC‐based fibers are subjected to slow crack growth, a crack growth mechanism activated by stresses and the chemical environment, as identified by static fatigue testing. Such tests can be performed on filaments or bundles. Although both types of specimens show a similar lifetime variation, testing of bundles is often preferred. This work compares the scatter of lifetimes predicted for filaments and for tows using a dedicated Monte Carlo simulation tool relying on the following hypotheses: The stress applied to a single filament can be defined, whereas the size of its most critical flaw cannot; on a bundle, neither the applied stress nor the strength of the critical filament (which triggers the cascade failure and the tow failure) can be defined. Depending on the parallelism of fibers inside the bundle and their strength dispersion, the lifetime scatter can be narrower for filaments compared to tows or vice versa. [ABSTRACT FROM AUTHOR]

This work investigates the scale effect observed on slow crack growth parameters for SiC-based fibers (Nicalon® and Tyranno® ZMI) and how it can be affected by the variability from a batch of tow to another one. A 10% difference on the stress exponents (n t) was numerically estimated using a dedicated Monte Carlo simulation. This effect is however marginal when compared to the lifetime scatter itself. This partly originates from the fiber slack in used tow specimen, assessed by tensile test completing the experimental work. The number of tensile tests to be performed is discussed. Specimen gauge length is an additional and significant source of discrepancies affecting the fiber alignment and subsequently the tow stress exponent. [Display omitted] Consequences of the fiber slack on static fatigue testing of Nicalon® tows: stress exponent which equals 10 on a single filament falls to 7.7 or 7.2 in tows. ς is the standard deviation of the filament load and γ the fraction of initially broken filaments. • Lifetime follows a power law, with a scale dependent stress exponent (n). • Difference of exponent from filament to tow linked to fiber misalignment. • n t found to evolve from batch to batch for a given testing method. • n t could this way vary by 10% which marginally affects the projection. • Sampling size related error for the tow structure assessment. [ABSTRACT FROM AUTHOR]

Copyright of Retos: Nuevas Perspectivas de Educación Física, Deporte y Recreación is the property of Federacion Espanola de Asociaciones de Docentes de Educacion Fisica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The present paper proposes a model of the specimen size effect on the critical flaw strength distribution in fiber tows for composite reinforcement. The model is based on the basic assumption of brittle fracture that the failure probability at a given strength increases with specimen size in the p-quantile vs. strength relation and on the normal distribution. Empirical results derived from force–strain curves determined on tows made of 1000 and 500 Nicalon SiC filaments and with various gauge lengths show some discrepancy with predictions using the model. The empirical p-quantile diagrams and cumulative distributions of critical flaw strengths exhibited excellent reproducibility at longer gauge lengths, which suggests the absence of a size effect above a critical tow size. The reproducibility of flaw strength distributions at gauge lengths above 60 mm and the higher strengths obtained at lower gauge lengths despite structural effects were related to the features of the critical flaw distribution in tows of parallel fibers. [ABSTRACT FROM AUTHOR]

Existing Through-Thickness Reinforcement (TTR) methods for laminated composites using semi or fully rigid reinforcing elements, like tufting, stitching, and z-pinning, present limitations on reinforcing element geometry, strength, and stiffness. Where these application envelopes are exceeded, TTR element insertion results in unacceptable levels of damage to both the composite and/or TTR elements. Here, we demonstrate that low-speed insertion of rigid reinforcements into heated prepreg preforms is a feasible and robust reinforcement process capable of providing accurate TTR element placement with minimal tow disturbance compared with existing methods for similar pin sizes. The insertion process is characterised with respect to insertion forces, and mesoscale laminate deformation/damage for carbon-benzoxazine prepreg preforms. The research investigates the influence of pin leading edge on insertion for a range of pin diameters (1.2, 1.5, and 2.0 mm) and preform consolidation states, describing low insertion forces and good quality laminate preforms. Insertion forces increase with pin diameter, typically resulting from increased pin-tow contact area and friction. Large diameter sizes and low insertion forces expand the range and forms of materials that can be inserted compared to existing TTR methods and show that this method can potentially be transferred to benefit work on composite hole creation, joining, and repair.

Friction between the tow and tool surface normally happens during the tow production, fabric weaving, and application process and has an important influence on the quality of the woven fabric. Based on this fact, this paper studied the influence of tension and relative velocity on the three kinds of untwisted-glass-fiber tow-on-roller friction with a Capstan-based test setup. Furthermore, an improved nonlinear friction model taking both tension and velocity into account was proposed. According to statistical test results, firstly, the friction coefficient was found to be positively correlated with tension and relative velocity. Secondly, tension and velocity were complementary on the tow-on-roller friction behavior, with neither being superior to the other. Thirdly, an improved model was found to present well the nonlinear characteristics between friction coefficient and tension and velocity, and predicational results of the model were found to agree well with the observations from Capstan tests. [ABSTRACT FROM AUTHOR]

Piezoinductance (the influence of stress/strain on the inductance) enables inductance-based structural self-sensing and inductance-based investigation of the microstructural effect of loading. The first report of piezoinductance in a carbon material is provided. The piezoinductance of a carbon fiber tow (12K) involves the inductance increasing upon tension. The stress is in the low range of the elastic regime (2.17–10.83 MPa). The piezoinductance is attributed to the tightening of the fiber-fiber contacts in the tow upon tension. The partial nature of the reversibility of the inductance increase means that the tightening is not completely reversible upon unloading. Twisting enhances the inductance (as previously reported by the present authors), because the number of fiber-fiber contact points increases. Twisting strengthens the piezoinductance, with the effect being due to the abovementioned tightening. An increase in either the frequency (1–5 kHz) or voltage (0.9–5.0 V) enhances the inductance, but weakens the piezoinductance. The latter is probably due to the effect of the abovementioned tightening on the inductance being diminished by an increase in the frequency or voltage. Tension reduces the number of fiber-fiber contact points and reduces the effect of twisting on the inductance. Upon combined tension and twisting, the inductance increases, such that the fractional increase in inductance is below that for twisting without tension, but above that for tension without twisting. [Display omitted] [ABSTRACT FROM AUTHOR]

The present paper proposes a model of the specimen size effect on the critical flaw strength distribution in fiber tows for composite reinforcement. The model is based on the basic assumption of brittle fracture that the failure probability at a given strength increases with specimen size in the p-quantile vs. strength relation and on the normal distribution. Empirical results derived from force–strain curves determined on tows made of 1000 and 500 Nicalon SiC filaments and with various gauge lengths show some discrepancy with predictions using the model. The empirical p-quantile diagrams and cumulative distributions of critical flaw strengths exhibited excellent reproducibility at longer gauge lengths, which suggests the absence of a size effect above a critical tow size. The reproducibility of flaw strength distributions at gauge lengths above 60 mm and the higher strengths obtained at lower gauge lengths despite structural effects were related to the features of the critical flaw distribution in tows of parallel fibers.

The present paper investigates the static fatigue behavior of Hi-Nicalon fiber-reinforced SiC–SiC minicomposites at high temperatures in the 900–1200 °C range, and under tensile stresses above the proportional limit. The stress–rupture time relation was analyzed with respect to subcritical crack growth in filaments and fiber tow fracture. Slow crack growth from flaws located at the surface of filaments is driven by the oxidation of free carbon at the grain boundaries. Lifetime of the reinforcing tows depends on the statistical distribution of filament strength and on structural factors, which are enhanced by temperature increase. The rupture time data were plotted in terms of initial stresses on reinforcing filaments. The effect of temperature and load on the stress–rupture time relation for minicomposites was investigated using results of fractography and predictions of minicomposite lifetime using a model of subcritical growth for critical filaments. The critical filament is the one whose failure by slow crack-growth triggers unstable fracture of the minicomposite. This is identified by the strength–probability relation provided by the cumulative distribution function for filament strength at room temperature. The results were compared to the fatigue behavior of dry tows. The influence of various factors related to oxidation, including multiple failures, load sharing, and variability, was analyzed. [ABSTRACT FROM AUTHOR]

Copyright of Tobacco Science & Technology is the property of Tobacco Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Application of automated fiber placement is limited by defects formed in the prepreg tows during the layup process. An extensive experimental study is performed to investigate the effect of compaction roller on the quality of the layup. Five different compaction rollers with different stiffness and architectures were manufactured and employed to dispense prepreg tows at various process conditions. Layup quality was examined and different defects including tow buckling and blister were identified. In addition to automated fiber placement trials, static testing and finite element simulations were performed to probe the pressure distribution and contact width of each roller. This data was used to support and understand the results of the automated fiber placement trials. Results indicate the solid elastomer rollers that are compliant enough to produce the same level of contact width under similar levels of compaction forces are superior to the perforated rollers in terms of achievable layup quality. [ABSTRACT FROM AUTHOR]

The aim of this paper is to present results of seakeeping experiments performed on a damaged ship hull and to compare them with numerical analysis results. The assumed damage opening in the ship hull, i.e. the damage extent, is determined based on probability distribution functions for damage size and location as specified by the Marine Environment Protection Committee. Two different sets of experiments are conducted in a large commercial towing tank. Firstly, rigid body motions of damaged and intact ship hulls in tow in head seas with small forward speed are measured for irregular waves. Secondly, ship motions and vertical wave bending moments are measured on the segmented model in regular waves. Experimental results are compared with the linear 3D Boundary Element Method using Hydrostar software. Satisfactory correlation of computations and experiments is achieved for ship in tow while discrepancies are found for the segmented model. An important finding of this experimental campaign is that measured vertical wave bending moments of the damaged ship considerably exceeds those of the intact ship. [ABSTRACT FROM AUTHOR]

The present paper investigates the static fatigue behavior of Hi-Nicalon fiber-reinforced SiC–SiC minicomposites at high temperatures in the 900–1200 °C range, and under tensile stresses above the proportional limit. The stress–rupture time relation was analyzed with respect to subcritical crack growth in filaments and fiber tow fracture. Slow crack growth from flaws located at the surface of filaments is driven by the oxidation of free carbon at the grain boundaries. Lifetime of the reinforcing tows depends on the statistical distribution of filament strength and on structural factors, which are enhanced by temperature increase. The rupture time data were plotted in terms of initial stresses on reinforcing filaments. The effect of temperature and load on the stress–rupture time relation for minicomposites was investigated using results of fractography and predictions of minicomposite lifetime using a model of subcritical growth for critical filaments. The critical filament is the one whose failure by slow crack-growth triggers unstable fracture of the minicomposite. This is identified by the strength–probability relation provided by the cumulative distribution function for filament strength at room temperature. The results were compared to the fatigue behavior of dry tows. The influence of various factors related to oxidation, including multiple failures, load sharing, and variability, was analyzed.

The thermal behavior of a thermal insulating wall made of tow and plaster is studied by analyzing the behavior of thermal impedance. The evolution in thermal impedance through the wall is shown by highlighting the behavior over time and the effect of the heat exchange coefficient on the front face. SDepending on the climatic stresses on the front face, the analysis shows that the wall stores and releases energy by capacitive effect or by inductive effect. The peaks of the impedance make it possible to evaluate the effective thermal insulation layer for the tow-plaster material according to the external climatic constraints. [ABSTRACT FROM AUTHOR]

Twisting is commonly imposed on fiber tows to improve the processability, as needed for manufacturing composites and other products. Twist level (number of twists per unit length) determination commonly involves visual inspection. This work provides a method of sensing the twist level, as shown for carbon fiber tows up to 4 twists/inch. This method involves measuring the inductance (0.5–2.0 kHz), which increases monotonically with the twist level, due to Faraday's Law. The method is fast, low-cost, high-durability and large-format (scanning not needed). Uncoated and nickel-coated carbon fiber tows (PAN-based, 12K) give similar fractional increases in the inductance (≤46%) due to twisting. Magnetic character (as provided by nickel) is not required. A larger tow (24K) increases the inductance, but reduces the fractional increase due to twisting. Increasing the voltage enhances the inductance, but the fractional increase due to twisting is not affected. An increase in frequency also enhances the inductance, but the fractional change in inductance due to the twisting is diminished. The resistance decreases monotonically with the twist level (≤14% and ≤4% decrease for uncoated and nickel-coated carbon fibers, respectively), due to the increasing number of fiber-fiber contacts, which enable current detour when defects are encountered. Inductance-based sensing is superior in twist-level sensitivity to resistance-based sensing. Both sensitivities decrease monotonically with increasing twist level, with highest sensitivity below 1 twist/inch. The lowest twist level with demonstrated sensing is 0.1 twist/inch. This work also provides the first report of inductance-based structural self-sensing, which differs from the widely reported resistance-based structural self-sensing. [Display omitted] • Twisting has long been imposed on fiber tows or yarns to improve the handleability. • The sensing of the twist level in fiber tows is reported for the first time. • It is shown for carbon fiber by innovative inductance-based self-sensing. • Fast, low-cost and large-format sensing of the twist level is thus provided. • The inductance increases monotonically with the twist level, due to Faraday's Law. [ABSTRACT FROM AUTHOR]

Fibrous fabrics are used in a variety of applications, among them, for structural composites. Most fabrics are efficiently manufactured from tows or yarns. During textile manufacturing or during fiber reinforced composites manufacturing, the fabrics and tows undergo several movements and deformations. Although there have been several attempts by different authors to model micro structural mechanical behavior of fabrics, they often suffer from unknown geometric dimensions at various loads or unknown materials' mechanical parameters. This paper presents a method for measuring and comparing tows (or yarns) geometrical evolution during compaction perpendicular to the fibers. The tows are compacted and dimensions are continuously measured using confocal chromatograph. Fabrics and tows of the study are composed of glass or carbon fibers, in dry or lubricated states. Volume, compacity evolutions and Poisson's ratio are extracted for a wide range of compaction levels. Tables of material characteristics and experimental data are also provided for a further use or analysis. [ABSTRACT FROM AUTHOR]

As worldwide agricultural production rises, agro-industrial biomass becomes an abundant raw source for uses in energy and materials production. In Colombia fique plants ( Furcraea spp.) are traditionally used to extract hard cellulosic fibers using mechanical decortication. Juice, pulp and tow, the by-products of this process, represent almost 95% of the fique leaf weight and are produced in large quantities. Data on these materials is scarce and greatly needed to guide and fuel fique agro-industrial development in Colombia. In this contribution we study the physicochemical properties of fique fibers and by-products (tow and pulp), before and after alkaline hydrogen peroxide treatment (AHP), using spectroscopic and microscopic techniques. Raw/clean fique tow is similar in structure and composition to fique fibers with average cellulose, hemicellulose and lignin contents of 52.3, 23.8 and 23.9%; in this by-product cellulose exists as a highly ordered structure with crystallinity index of 57%. Raw/clean fique pulp, composed of cellulose filaments from secondary cell walls and leaf epidermis, has average cellulose, hemicellulose and lignin contents of 30.5, 29.7 and 9.6%, with cellulose exhibiting an amorphous structure with a crystallinity index of 35%. The AHP treatment of these by-products effectively removed non-cellulosic compounds such as hemicellulose and lignin. After AHP lignin content in fique tow decreases to 2.8% while cellulose crystallinity increases up to 73%, Likewise, fique pulp shows a reduction in lignin to 2.1% and an increase in cellulose crystallinity up to 47%. IR spectroscopic analysis, after AHP, show a decrease of signals attributed to hemicellulose and lignin and FESEM images show a disruption of the lamellar structure in the macro fiber by the removal of hemicellulose, lignin and ground tissue, leaving cellulose fibrils exposed. As the first in-depth report on fique by-products characterization, our results indicate that pulp and tow are interesting lignocellulosic materials due to their significant content of crystalline and amorphous cellulose. [ABSTRACT FROM AUTHOR]

To meet the increasing demand for lightweight materials with multifunctional capabilities, a new high-rate manufacturing method and material system, referred to as M-TOW® (multifunctional-tow) is introduced. Overbraiding is used to incorporate highly conductive wire onto the continuous fiber reinforced tow (M-TOW®), offering a solution for integrating thermal and electrical conductivity into hybrid-molded composite structures. The conductivity performance of different wire configurations are compared before and after forming the M-TOW®, measuring electrical conductivities up to 5.5 x 10 5 S / c m and thermal conductivities up to 21 W / m K. Results conclude that the integration of conductive wires into thermoplastic preforms is a viable means of expanding the functionality of lightweight, high strength composite structures. [ABSTRACT FROM AUTHOR]

In this paper, the authors study periodic vibrations of variable stiffness composite laminates excited by a harmonic force. The plates have geometrical imperfection in the form of various sinusoidal out-of-plane initial deflections associated with zero stress. The angle of the curvilinear fibre path is introduced as a function of the horizontal Cartesian coordinate. The theory used to extract equations of motion for VSCLs is a third order shear deformation theory that retains rotary inertia. The relations of von Kármán for elastic large deflection are used. A p -version finite element is employed and, to find the solution of the equations of motion, the shooting method is applied; frequency response curves are obtained. Static condensation and a modal summation method are applied to reduce the number of degrees of freedom. A damage analysis based on Tsai-Wu criterion is carried out during the studies on vibration. The effects of curvilinear fibres and the influence of modal interactions on the vibration of imperfect VSCLs are investigated. The stability of the periodic solutions is determined by applying Floquet's theory. The effect of geometric imperfections on the vibrational behaviour is studied. [ABSTRACT FROM AUTHOR]

The aim of the present work is to study the hydrodynamics of sphericalcapbubble, rise bubble velocity, shape of bubble, and drag coefficient. Theexperimental work of two-phase ,air-water system was carried out using a Perspexcolumn of 14.5 cm diameter and 180 cm height. A known volume of air wassupplied to the cup from a syringe. The single gas bubble rose through theentrance region by turning the cup instantaneously. The rise bubble velocity wasmeasured by visual observation. In order to measure the terminal velocity anelectronic timer (Stop-Watch) was used. The drag coefficient of air spherica–l capbubble rising in water was measured and found to be a value between (2.8-3.8) forall Reynolds number. The experimental results are compared with the theoreticalresults of some investigators.

Automated fibre placement was used to optimise the tow steering of carbon fibre reinforced plastic/polymer whereby the minimum defect-free steering radius (Rmin) achievable. The results revealed that in the case of the woven ply surface with unheated tool the Rmin, using 1/4 inch tows, is found to be 1350 mm. For the bare tool surface, the tool temperature had to be raised to 30℃ in order to achieve the same Rmin of 1350 mm. To attain a seamless transition from part design to manufacture using CAD, automated fibre placement was equipped with software tools (TruPLAN and TruFIBER). From the results of software validation and steering trials on a variable radius tool having a pre-laid UD ply, it is found that the ability to steer around a tighter radius was a vast asset of the 1/8 inch tow over the 1/4 inch one, which makes it the preferred choice for the more geometrically complex parts. [ABSTRACT FROM AUTHOR]

For historic buildings, where an alteration of the exterior façade is not wanted, interior insulation can be the solution to improve the indoor climate and reduce heat loss, but might also introduce moisture problems like condensation in the wall. Capillary active/hydrophilic insulation materials have been introduced to cope with the moisture problem. An extensive amount of calculations indicating where the challenges lie in the complex work with interior insulation in cool temperate climate has been carried out. In areas with high precipitation like Denmark, capillary active insulation may not be feasible without additional driving rain protecting of the façade. [ABSTRACT FROM AUTHOR]

Composite-forming processes involve mechanical interactions at the ply, tow, and filament level. The deformations that occur during forming processes are governed by friction between the contacting tows on the mesoscopic level and consequently between filaments on the microscopic level. A thorough understanding of the frictional properties at the level of individual filaments is essential to understand and to predict the macroscopic deformations of a textile reinforcement during forming. This work presents a contact mechanics modeling approach to provide a theoretical background of the frictional behavior of dry fibrous tows in contact with each other. The predicted frictional behavior is in qualitative and quantitative agreement with experimentally observed frictional forces of carbon fiber tows in sliding contact. The relative orientation of the contacting tows is of great importance for the developed frictional forces in the contact. [ABSTRACT FROM PUBLISHER]

Abstract: Flexible textile composites like woven Kevlar fabrics are widely used in high velocity impact (HVI) applications. Upon HVI they are subjected to both longitudinal tensile and transverse compressive loads. To understand the role of transverse properties, the single fiber and tow transverse compression response (SFTCR and TTCR) of Kevlar KM2 fibers are numerically analyzed using plane strain finite element (FE) models. A finite strain formulation with a minimum number of 84 finite elements is determined to be required for the fiber cross section to capture the finite strain SFTCR through a mesh convergence study. Comparison of converged numerical solution to the experimental results indicates the dominant role of geometric stiffening at finite strains due to growth in contact width. The TTCR is studied using a fiber length scale FE model of a single tow comprised of 400 fibers transversely loaded between rigid platens. This study along with micrographs of yarn after mechanical compaction illustrates fiber spreading and fiber–fiber contact friction interactions are important deformation mechanisms at finite strains. The TTCR is also studied using homogenized yarn level models with properties from the literature. Comparison of TTCR between fiber length scale and homogenized yarn length scale models indicate the need for a nonlinear material model for homogenized approaches to accurately predict the transverse compression response of the fabrics. [Copyright &y& Elsevier]

Various operations in petroleum processing, textile technology, printing and composite processing involve wetting and spreading phenomena of liquids in porous media. These phenomena are being investigated using various tools, prominent among them being the spreading of a liquid drop on a porous medium. The spreading is governed by the inertial, gravitational, viscous and capillary forces and their relative importance have been studied to understand the underlying phenomena. In this work, drop spreading on heterogeneous porous media, such as composite reinforcing fabrics, has been investigated. The liquid drop spreading has been modelled in two stages: the flow of liquid on the surface of fabric and the imbibition of the liquid into the fabric due to inter-tow and intra-tow flow of the fluid. The model equations are formulated by making a hypothetical equivalent model of the fabric. The resulting equations are solved numerically. The model is used to simulate the spreading of liquid drops on glass fabrics. The drop spreading is characterized by height, contact radius and contact angle. The front of the liquid within the porous media can also be monitored through the model. Initially, a parametric study on the effect of fabric and tow porosities, the tow radius and the droplet volume on the imbibition time is presented. Finally, the model results are compared with the experimental results from literature. It is shown that the model can capture the essential features and provide insight into drop spreading on heterogeneous porous media. [ABSTRACT FROM AUTHOR]

[Display omitted] • New method for insertion of large diameter pins in prepreg composite laminates. • Conical leading-edge pins exhibit low insertion force with better insertion quality. • Insertion forces increase exponentially with pin diameter. • Prepreg stack consolidation improves insertion quality by reducing tow distortions. Existing Through-Thickness Reinforcement (TTR) methods for laminated composites using semi or fully rigid reinforcing elements, like tufting, stitching, and z-pinning, present limitations on reinforcing element geometry, strength, and stiffness. Where these application envelopes are exceeded, TTR element insertion results in unacceptable levels of damage to both the composite and/or TTR elements. Here, we demonstrate that low-speed insertion of rigid reinforcements into heated prepreg preforms is a feasible and robust reinforcement process capable of providing accurate TTR element placement with minimal tow disturbance compared with existing methods for similar pin sizes. The insertion process is characterised with respect to insertion forces, and mesoscale laminate deformation/damage for carbon-benzoxazine prepreg preforms. The research investigates the influence of pin leading edge on insertion for a range of pin diameters (1.2, 1.5, and 2.0 mm) and preform consolidation states, describing low insertion forces and good quality laminate preforms. Insertion forces increase with pin diameter, typically resulting from increased pin-tow contact area and friction. Large diameter sizes and low insertion forces expand the range and forms of materials that can be inserted compared to existing TTR methods and show that this method can potentially be transferred to benefit work on composite hole creation, joining, and repair. [ABSTRACT FROM AUTHOR]

Abstract: Due to market and regulatory factors, Rajidae skates are routinely discarded by commercial otter trawlers in the western North Atlantic. Accounting for post-release mortality is therefore essential to total fishing mortality estimates, stock status and management of this group of fishes. However, despite a presumed species-specific range in tolerance, few studies have investigated the short-term post-release mortality among skates indigenous to the western North Atlantic following capture by mobile fishing gears, and never in the Gulf of Maine. This study addresses this shortfall for the prohibited thorny skate, Amblyraja radiate and smooth skate, Malacoraja senta, and the targeted winter skate, Leucoraja ocellata, and little skate, Leucoraja erinacea. Of 1288 skates evaluated, negligible immediate mortality was observed at the time of capture, even in relation to the largest catches and/or most prolonged tows. However, injury frequency was moderate, with highest levels in the smooth (60%) and thorny (52%) skates. Aside from the smooth skate (59%), 72h mortality rates were low overall (19% across all species when accounting tow durations indicative of the fishery), with the winter skate (8%) exhibiting the lowest levels. Logistic regression modeling revealed tow duration as the most universal predictor of condition and 72h mortality, while catch biomass, sex, temperature changes, and animal size also held influence in certain species. Although in general the studied species appear more resilient to trawl capture and handling than previously estimated, interspecific differences must be accounted for when managing this group. [Copyright &y& Elsevier]

Abstract: Braiding is a manufacturing process for making tubular braided products like braided ropes, sutures and braided composite tubes. A yarn or tow tensioning system is required that consists of pulleys, two springs and a ratchet with the ratchet gear on the spool. The tension is nearly constant, varying within an acceptable range during braid formation and releasing a discrete amount of material from a spool when an upper limit on the tension is reached. A mathematical model of tension versus yarn displacement of a standard package tensioning system is presented. The response before ratchet release is a series of piecewise linear kinematic regions that include two separate spring preload regions, a single spring tensioning region, and a two spring tensioning region. During ratchet release the system is first modeled as kinematic, and later, more accurately as a single degree-of-freedom dynamic model. Ratchet reengagement that incorporated impact with an elastic yarn was required to improve model accuracy of response. Correlated experiment and simulation response validate the mathematical model, for use as a designer''s tool. [Copyright &y& Elsevier]

Because hemp is a short-day plant, postponing the sowing date might be a suitable strategy to obtain shorter and smaller plants around flowering, when primary fibres are ‘ripe’ enough to be harvested. Smaller plants can be processed on existing flax scutching and hackling lines and might have fibre characteristics that are desirable for producing high-quality ‘long fibres’ for yarn spinning. It was investigated whether sowing beyond the normal sowing period in the Netherlands affects the ratio in which fibres and wood are produced, and what proportion of these fibres are long fibres, suitable for long fibre spinning. About 400 stem samples were fractioned into retting losses, wood, tow, and long fibre, and the ratios between fractions were analysed using multiple linear regression analyses. A normal sowing date at the end of April was compared with a postponed sowing date at the end of May. The total fibre/wood ratio was not affected. More than 95% of the variance in total fibre was accounted for by the wood weight per stem (55.5%), the variety (+33.3%) and the stem part (+6.5%). The amount of long fibre per stem mainly depended on the amount of the total fibre per stem (95.4% variance was accounted for) and the stem part (+2.0%). For economic reasons, it could be interesting to grow two successive high-quality hemp crops in one growing season. Therefore, in an additional experiment with one variety, the effect of sowing fibre hemp up to 12 weeks later than normal on the quantity and quality of the fibres was studied. Postponing the sowing date up to 12 weeks had no important effects on retting losses, the total fibre/wood ratio, and the long fibre/total fibre ratio. It is therefore technically possible to grow two successive hemp crops. Whether this fits well in farming systems and a hemp production chain remains to be studied. [ABSTRACT FROM AUTHOR]

Sowing density and harvest time are considered important crop management factors influencing fibre quantity and quality in hemp ( Cannabis sativa). We investigated whether the effects of these factors are essentially different or that both factors affect stem weight and thereby total and long-fibre content. The effects of all combinations of three sowing densities and three harvest times were studied for six different stem parts. Almost 500 samples consisting of stem parts from 50 plants and with a length of 50 cm were tested. Fibres were extracted by a controlled warm-water retting procedure, followed by breaking and scutching. The initial sample weight was fractionated into retting losses, wood, tow and long fibre. In both Italy and the Netherlands, crops were successfully established with different stem densities (99–283 m−2), plant heights (146–211 cm) and stem diameters (4.5–8.4 mm) at harvest. Stem dry matter yields (6.8–11.7 Mg ha−1) increased with a delay in harvest time but were not affected by sowing density. Retting loss percentages were lower in lower stem parts and decreased with later harvest because maturation was associated with increasing amounts of fibre and wood. Within a certain stem part, however, the absolute retting losses were constant with harvest time. Multiple linear regression analyses showed that the amount of fibre in a hemp stem is almost completely determined by the weight and the position of that stem part. When the plant grows, the increase in dry matter is split up into fibres and wood in a fixed way. This total fibre/wood ratio was highest in the middle part of the stem and lower towards both bottom and top. Sowing density and harvest time effects were indirect through stem weight. The long-fibre weight per stem increased with the total fibre weight and hence with stem weight. Stem weight increased with harvest time; as harvest time did not affect plant density, the highest long-fibre yields were obtained at the last harvest time. The long fibre/total fibre ratio was lowest in the bottom 5 cm of the stems but similar for all other parts. Sowing density and harvest time effects again were indirect. Fibre percentages in retted hemp decreased with increasing stem weights towards a level that is presumably a variety characteristic. The dry matter increase between harvests, however, is much more important with respect to total and long-fibre yield. [ABSTRACT FROM AUTHOR]

Abstract: Hedgehog (Hh) signalling plays a crucial role in the development and patterning of many tissues in both vertebrates and invertebrates. Aberrations in this pathway lead to severe developmental defects and cancer. Hh signal transduction in receiving cells is a well studied phenomenon; however questions still remain concerning the mechanism of repression of the pathway activator Smoothened (Smo) in the absence of Hh. Here we describe a novel repressor of the Hh pathway, Target of Wingless (Tow). Tow represents the Drosophila homolog of a conserved uncharacterised protein family. We show that Tow acts in Hh receiving cells, where its overexpression represses all levels of Hh signalling, and that this repression occurs upstream or at the level of Smo and downstream of the Hh receptor Patched (Ptc). In addition, we find that like Ptc, overexpression of Tow causes an accumulation of lipophorin in the wing disc. We demonstrate that loss of tow enhances different ptc alleles in a similar manner to another pathway repressor, Suppressor of Fused (SuFu), possibly through mediating Ptc dependant lipophorin internalisation. Combined, these results demonstrate that Tow is an important novel regulator of the Hh pathway in the wing imaginal disc, and may shed light on the mechanism of Ptc repression of Smo. [Copyright &y& Elsevier]

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A simple analytical model has been developed for the impregnation of fiber bundles where the macroscopic flow is parallel to the fiber axis. Based on the study of the contribution of the axial and transverse flow mechanisms inside tows, this model shows that the main tow impregnation process is transverse to the fiber axis. A criterion has been established to indicate when the axial flow can be neglected to simplify the tow impregnation model. This case represents the majority of situations in the RTM of woven fabrics and the model predicts that the flow front in tows has a pointed meniscus shape whose length depends on the effective permeability of the large pores formed between the tows, transverse permeability of tows and thickness. A new boundary condition at the unsaturated tow surface is proposed. It conveys the interactions between the flows occurring inside and outside axial tows during a constant pressure driven impregnation. Two air entrapment mechanisms have been observed. Although the source of these void formation processes is the local difference in fiber arrangement, the dependence of the amount of formed bubbles on the impregnation front length has been clearly identified. In addition, a few means for voids mobilization or bubbles dividing have been investigated. [ABSTRACT FROM PUBLISHER]

Resin Transfer Molding (RTM) can be described as a two step process: fiber preforming followed by resin infusion and cure. In the first stage, the fabric form making up the preform element is placed in the tool and is compacted due to the pressure from tool closure. During this process, the microstructure, and the resultant properties, change considerably since compaction flattents the weft yarn bundles from the initial configuration into flat ellipsoids of higher aspect ratio, while simultaneously reorienting and flattening the bundles in the warp direction. The movement also results in nesting and inter-layer packing yielding a higher localized fiber volume fraction.An aspect unique to RTM and other allied resin infusion processes is the compaction of fibers in the dry (unlubricated) form. This gives rise to rather unique behavior at the fiber tow level, which in turn affects the compaction of the fabric form itself. It is thus essential that any model constructed for the specific purpose of investigating the compaction stage in RTM (or allied processes that involve the compaction of a dry preform) be able to reflect that the tow is dry, usually untwisted and when compressed in bulk it has frictional resistance to the shear mode of deformation. In this paper we focus on the possible tow behavior, rather than the behavior of the fabric structure, with the motivation being that of developing a simple, yet comprehensive model at that level which can then be intregrated into a fabric level model at a later stage. [ABSTRACT FROM PUBLISHER]