bluuebunny/crossref_metadata_2025 huggingface dataset:
Ablation Behaviour and Microstructure of Carbon/Carbon and Hybrid Carbon/Carbon Composites Based on Plasma Torch Heating
Authors: Ma Li , He Lu Jv , Mo Cai Song , Zhang Li Bin , Pan Mao Sen , Huang Yang F feng
Published: January 2019

The ablation properties and morphologies of two kinds of fine Fine-woven pierced composites materials, carbon/carbon (C/C) and hybrid C/C with tungsten (W) filaments in z directional carbon fibre bundles, were investigated. A plasma torch was used to explore the ablative characteristics in terms of linear/bulk ablation rate and microscopic pattern of ablation. Surface and in-depth temperatures during ablation were measured by using optical pyrometers and thermocouples. The experimental results showed that the C/C composite presented the best ablation resistance performance, followed by the hybrid C/C composite, while that of graphite was the worst. It was found that the thermo-mechanical ablation resistance of carbon matrix is equal to that of carbon fibres. The existence of WC not only had a faster intrinsic ablation velocity, but also accelerated the ablation velocity of the carbon fibres and carbon matrix, and significantly improved the ablation velocity of the carbon fibres.
Preparation and Properties of Poly(AM-AA)/MMT Nanocomposites Hydrogel Particles Coated Alginate
Authors: Zhang Dingjun , Bai Xue , Qu Chaoyun , Li Xianwen , Wu Youzhi , Lu Wenjiang
Published: January 2019

The poly(AM-AA)/MMT composites hydrogel particles coated alginate were successfully prepared by the method of microcapsule technology. The obtained particles were spherical, smooth-surfaced, hollow-structural and non-aggregated with a diameter of 1.5∼2.0 mm. The diameters of particles can be controlled and depended on the size of initial drop on the concentration of Al(NO3)3, SA(Sodium alginate) and their time of solidification, as well as on the concentration and size of core materials. The water-absorbent rate of coated plugging agent was remarkable in different conditions and fell based on the sequence of fax (fa1: tap water at 25 °C; fa2: physiological saline solution at 25 °C; fa3: tap water at 45 °C; fa4: physiological saline solution at 45 °C). The particles are stable for 15 days in the medium of pH ranged from 3 to 6, while the particles are degraded in simulated fluid with pH of 1, 2, 11 or 12.
Effect of an Interleave Natural Viscoelastic Layer on the Dynamic Behaviour of a Bio-Based Composite
Authors: Daoud H. , Rebiere J.-L. , Mahi A. El , Taktak M. , Haddar M.
Published: January 2019

The purpose of the present letter is to analyse the damping properties of a bio-based composite with flax fibre. Damping parameters were investigated using beam test specimens and an impulse technique. Through a series of resonance vibration tests, the natural frequencies and modal damping were evaluated. The second part of the work was to investigate the effect of an interleave viscoelastic layer made of natural rubber on the dynamic behaviour of the composite. A comparison of the different results was performed; it shows that the viscoelastic layer had a significant influence on vibration behaviour, bending stiffness and damping factors.
Calculating the Effective Permittivity and Permeability of Composites Based on the Dilution Process Model
Authors: Yuan Liming , Wang Bin , Xu Yonggang , Wu Qilin
Published: January 2019

In order to solve the engineering problem of calculating the effective permittivity and permeability of composites, this paper introduced a dilution process model (DPM) which sets the composite of the highest particle volume fraction as the new matrix medium and the old matrix medium as the inclusion. With DPM, complex permittivity and permeability of composites could be calculated by the Maxwell Garnett (MG) formula, the Bruggeman (BG) formula and the generalized effective medium theory (GEMT) with a fitting parameter of V which is a second-degree polynomial of new particle volume fraction. With the proposed method, the effective complex permittivity and permeability of composites consisting of isotropic spherical carbonyl iron particles (SCIPs) or anisotropic flaky carbonyl iron particles (FCIPs) embedded in paraffin are calculated. Comparisons are performed among the calculated results by different formulae and the measured results. It indicates that the calculated results by the GEMT formula with DPM are in great agreement with the measured results. The achievement of this paper has am important theoretical significance and engineering application.
Experimental Studies on the Elastic Properties of Carbon Fiber Reinforced Polymer Composites Prefabricated of Unidirectional Carbon Fiber Fabrics and a Modified Rule of Mixtures in the Parallel Direction
Authors: Sun Wenbin , Luo Ying , Sun Huasheng
Published: January 2019

Carbon fiber (CF) fabrics can be installed manually onto the surfaces of existing structural members to establish a carbon fiber reinforced polymer (CFRP) reinforcemenet system, even in areas of limited access. Actual mechanical properties, such as the ultimate tensile strength (UTS), elastic modulus (EM), and ultimate rupture strain (URS), are essential for application in engineering practice and theoretical analysis of CFRP strengthening system. In this study, 16 CFRP strips were prefabricated of unidirectional CF sheet by a wet lay-up technique, and were tested to evaluate their elastic parameters. Test results indicated that experimental values of all specimens were much lower than that of CF fabrics, which were provided by manufacturer, and the stress-strain curves were observed to deviate slightly from a perfectly linear relationship at the later stage of loading. Comparing with the predictions of the rule of mixtures (ROM), the experimental data have large deviations and opposite laws. An orientated-design model was derived to modify the linear ROM by the regression analysis. A modified rule of mixtures (MROM) was suggested to describe the elastic properties of CFRP composite in the parallel direction.
A Study on the Failure Mechanisms of Composite Laminates Simultaneously Impacted by Two Projectiles
Authors: Xiao-Yu Sun , Jian-Xin Teng , Zheng He , Xuan Gu
Published: January 2019

With most studies concentrated on the single point isolated impact events, this work mainly investigates the failure mechanisms of composite laminates simultaneously impacted by two projectiles over low energies. A 3D intralaminar damage model combining continuum damage mechanics to analyze the in-ply damage and cohesive interface elements to simulate the delamination are applied to model the damage evolution of E-glass/epoxy composites simultaneously impacted by two projectiles. The damage model is incorporated into the Abaqus/Explicit by the subroutine VUMAT. A comparison between the simulated predictions and the experimental observations of laminates impacted by one projectile is made to verify the reasonability of the damage model applied. The simulation results indicate that the delamination initiation is not largely affected by the impact energy and the number of the projectiles. As the combined effects of the two projectiles on the laminate, the intersection of matrix damage areas in plies and the connection of delamination regions at interfaces, largely decrease the overall stiffness of the laminate and result in more serious damage.
Hygro-Thermally Curvature-Stable Free-Layer Composite Laminates with Extension-Twist Coupling
Authors: Cui D , Li D K , Zhou S M
Published: January 2019

The tensile strength and compressive strength are indispensable indexes during the design process of composite laminates. For hygro-thermally curvature-stable extension-twist coupled laminates, the improved Differential Evolution Algorithm combined with penalty function is adopted to solve the nonlinear strong constraint of free-layer laminates. The synchronous optimization of multiple targets is achieved, which includes extension-twist coupled effect, tensile strength, compressive strength and buckling strength. Results are presented for free-layer graphite/epoxy composites laminates that consist of 1–18 plies. Finally the hygro-thermal effect, extension-twist coupled effect and buckling strength are simulated and verified.
Preparation, Microstructure and Compressive Properties of Silicone GEL/SiC Composites for Elastic Abrasive
Authors: Li Ning , Ding Jinfu , Hu Liguang , Wang Xiao , Lu Lirong , Huang Jianmeng
Published: January 2019

An elastic abrasive tool based on micropore silica gel was designed and reinforced with silicon carbide (SiC) particle. The abrasive internal structure presents porous chain network structure, and the enhanced particles uniformly distributed in the matrix. The compression performance of modified composites is nonlinear increasing. The experimental results show that the accumulating energy of the self microporous structure is easy to overcome the internal friction in a certain deformation quantity of the materials. When the deformation quantity is large enough, the microporous structure and the chain segment structure of the matrix silica gel affect weakened, so that the properties of the composite decreased. And there is a synergistic relationship between the particles size and the matrix silica gel. That is, when the particle size is near the silicon chain length, the effect of particle enhancement is obvious. When the particle size is small, the effect of particles was reduced because the particles are inlaid between the slots in the silicon chain. On the other hand, when the particle size is larger, the particles are not work in the composites.
Ultrasonic Analysis of Damage in CFRP Resulting from Static Indentation and Low Velocity Impact
Authors: Kaczmarek H.
Published: January 2019

In order to reduce hidden damage caused in CFRP by low velocity transverse impact, testing procedures must be established by understanding the impact phenomena and the roles of various parameters on damage initiation and growth. Hence, composite plates were stressed and an original method, “ultrasonic tomography,” was applied to detect delaminations on the interfaces. The results show the similarity of the damage growth resulting from static indentation and low velocity impact.
Compressive Behaviour of Unidirectional Carbon/Epoxy Composites
Authors: Effendi R-Riesdam
Published: January 2019

An experimental study of the fracture of unidirectional carbon fibre-organic matrix composites under compression show that fibre kinking is the principal compressive failure mode. All materials tested have a non linear elastic behaviour during loading. This behaviour can be attributed to the intrinsic non linear elastic behaviour of the fibres.
Extraction of void fraction in metal matrix composite using morphological image processing
Authors: He Lun X. , Hsu David K. , Basart John P.
Published: January 2019

In continuous fiber reinforced metal matrix composites, the volume fraction of voids in the matrix material is an important parameter for material property characterization. In analyzing a cross-sectional micrograph of such a composite, the presence of fiber images and voids occurring on the perimeter of fibers complicates the determination of void content. This paper describes image processing steps using mathematical morphology for the extraction of void fraction in a composite.
A Comparison between Interlaminar and In-plane Shear Strength of Unidirectional Glass Fibre-epoxy
Authors: Wisnom Michael R. , Jones M. I.
Published: January 2019

Short beam shear tests have been carried out on square cross-section specimens cut from a 32 ply plate. By rotating the beams through 90° both interlaminar and in-plane strength can be measured with identical specimens. The in-plane shear strength was found to be at least 10% higher than the interlaminar strength.
Low Cost Dynamic Optical Strain Measurements in Glass Reinforced Polymer
Authors: Reed G T , Hadjiprocopiou M , Möller A , Garden H , Thorne A , Hollaway L
Published: January 2019

The combination of sensors and structural components to create “Smart Structures” or “Smart Skins” represents a new, fast developing branch of engineering. The monitoring of such systems will require accurate and fast strain measurements. Optical sensing techniques are receiving considerable attention for monitoring of such systems. In this work an optical fibre sensor has been embedded with the protective coating on, in glass reinforced polymer (GRP) coupons, to perform strain measurements. We show that the system can be used for measurements up to 2000με. The sensor was made using only commercially available, low cost components. The optical measurements show good agreement with conventional strain gauge measurements.
Curing Kinetics Analysis of Dgeba-Mda System
Authors: Carotenuto G. , Nicolais L.
Published: January 2019

Thermoset polymers and thermoset based composites are normally polymerized and performed in a step process. This work studies the kinetics behavior of a commercial epoxy system used as matrices of medium and high performance composite materials. The characterization study was performed by differential scanning calorimetry (DSC) and spectroscopic analysis.
Optimisation of Coating Properties for Fibre Optic Smart Structures using Finite Element Analysis
Authors: Hadjiprocopiou M. , Reed G.T. , Hollaway L. , Thorne A.M.
Published: January 2019

Finite Element analysis is used to determine and to minimise the stress concentrations which arise in a “Smart” material system due to the embedded optical fibre sensors. The FE results show that with careful selection of the coating stiffness and thickness the stress concentrations caused by the fibre inclusion in the host material can be reduced.
Viscoelastic Effects on Interfacial Shear Strength in Composite Materials
Authors: Rouse D. B. , Slivka M. , Schwartz P.
Published: January 2019

Microbond techniques at varying extension rates are used to evaluate the effects of viscoelasticity on the interfacial shear strength (IFSS) of Kevlar®/Epoxy microcomposites. An increase in IFSS is shown to occur with an increase in the testing rate following a semi-logarithmic relationship.
A Study on an Application of Corrosion Behavior to Glass Fiber Composite Disposal and Recycling
Authors: Kubouchi Masatoshi , Tsuda Ken , Nishiyama Toshiaki , Hojo Hidemitsu
Published: January 2019

An immersion test was made with an amine cured epoxy resin under nitric acid solution. Amine cured epoxy showed very poor resistance in nitric acid solution. An application of this behavior to glass fiber composite disposal or recycling was tried and discussed its possibility.
The Influence of Loading Rate on the Interlaminar Fracture Properties of a Toughened Carbon Fibre Reinforced Plastic
Authors: Cantwell W.J.
Published: January 2019

The response of high performance composite materials to localised impact loading has been a source of considerable concern for many years. Low energy impacts, although sometimes difficult to detect often result in the formation of numerous planes of delamination extending well away from the point of contact. The presence of such regions of interlaminar fracture can subsequently result in a dramatic reduction in load-bearing capacity of the composite structure.
Localised Stress Measurements in Composite Laminates Using a Raman Stress Sensor
Authors: Arjyal Bish , Galiotis Costas
Published: January 2019

A new remote laser Raman stress/ strain sensor for localised measurements in polymer based composites, has been developed and tested. Measurements can be conducted in reinforcing fibres near the surface of laminates. For measurements in the bulk of composites, the exciting laser light has to be transported to the reinforcing fibres via an embedded fibre optic cable. The backscattered light is transmitted through the same fibre optic and is sent to the Raman spectrometer for analysis. The effect of the direction of the fibre optic cable with respect to the axis of the reinforcing fibres is examined. Finally, the relationships between the local fibre stress or strain obtained from the Raman sensor and the far field stress or strain measured conventionally, are established.
Mechanical Characterisation of Polybutadiene-Cellulose Diacetate Composites
Authors: Hernández G. , Rodríguez R. , Maciel A. , García-Garduño M.V. , Castaño V.M.
Published: January 2019

Mechanical testing the behaviour of polybutadiene-cellulose diacetate (functionallized) was performed. The cellulose diacetate was chemically modified to improve the interfacial bonding between the components. The results indicate that the Young's modulus is increased substantially as the content of the functionallized component is increased. Finally, a comparison to theoretical mechanical models is shown.
Net-Shape Preform Manufacture using Automated Fibre Placement
Authors: Turner M R , Rudd C D , Long A C , Middleton V , McGeehin P
Published: January 2019

Liquid composite moulding processes such as resin transfer moulding (RTM) are becoming increasingly popular for a range of commercial applications. The major barrier to their more widespread use is the lack of an efficient method for the manufacture of reinforcement preforms. To address this problem, an automated fibre placement facility is under development, capable of laying either random or aligned fibres to produce net-shape preforms. This has been applied to a number of components including a load bearing flange used in marine applications and an aviation propeller blade.
Permittivity and Loss of Composites of Epoxy Resin and Kevlar Fibres
Authors: Tsangaris G.M. , Psarras G.C.
Published: January 2019

The dielectric behaviour of composites with epoxy resin and kevlar fibres is investigated in a wide range of frequency and temperature. Dielectric permittivity is increasing with filler content and temperature, being always higher in the low frequency range. Dielectric permittivity and loss of the composites is mostly affected by interfacial polarization arising from inhomogeneities at interfaces introduced by the filler.
A New Equation for the Determination of the Thermal Expansion Coefficient of Particulate Composites
Authors: Boccaccini A. R.
Published: January 2019

A new equation has been derived for the determination of the thermal expansion coefficient of isotropic particulate composites. An original analysis by Tummala and Friedberg was modified by incorporating the dependence of the internal thermal stress on the inclusion volume fraction, as known from the literature. For low volume fractions of inclusions the new equation gives similar values to the original Tummala and Friedberg equation. For intermediate volume fractions, however (≈0.3 ≤ f ≤ ≈0.7), the present equation is shown to be in better agreement with experimental values for different composite systems investigated.
Effective Elastic Properties of 3D Carbon-Carbon Composites at High Temperature
Authors: He X.D. , Han J.C. , Du S.Y.
Published: January 2019

This paper describes a mini-finite element model for evaluation of high temperature elastic modulus of 3D C/C composite and the variation of tensile properties with substrate parameters such as xy-woven layers, fiber boundles and fiber spacing was analyzed. The results predicted suit the experimental data well.
Correlation between Flexural and Tensile Fatigue Response of Short Glass Fibre Reinforced Plastics
Authors: D'Amore A. , Caprino G. , Facciolo F.
Published: January 2019

Preliminary tests were performed on short glass fibre reinforced polypropylene in four-point bending and in pure tension, adopting a stress ratio R=0.5 and R=0.1, respectively. The flexural fatigue data were used to calculate the constants appearing in a previous model, aiming to predict the classical S-N curve. Then, theory was utilised to predict the tension fatigue response of the material. A quite good correlation was found between theoretical estimates and experimental results.
Fabrication and Mechanical Properties of Multi-Reciprocal Braided Composite Tube
Authors: Nakai A. , Masui M. , Hamada H.
Published: January 2019

In this study, braided composite tube with through-the-thickness fibers was fabricated by new braiding process and its lateral compressive properties were measured. The propagation of interlaminar delamination was impeded and the lateral compressive properties were enhanced by fiber bundles which are oriented in the interlamina.
Approximate Biaxial Stress Solution for Orthotropic Open-Hole Composite Laminates
Authors: Filiou C. , Soutis C.
Published: January 2019

A simple approximate solution has been derived for the stress distribution near a circular hole applicable to any orthotropic composite laminate subjected to biaxial loading. The degree of accuracy of this solution was found to be overall acceptable, but strongly dependent upon the laminate lay-up and biaxiality ratio.
Investigation of Interlaminar Defects and their Influence on Interlaminar Strength
Authors: Ziao J , Tao J
Published: January 2019

In this paper, we directed our attention to the interlaminar defects and their influence on the interlaminar strengths. With the aid of a S-570 scanning electron microscope, the morphology and distribution of interlaminar defects were inspected and documented. According to their shape, size and cause of formation, the defects were classified into five types: flakiness void, irregular shaped debond, local imperfectly cured resin, debond in two multi-directional plies, and inhomogeneous fibers and the large scale debond by these fibers. The cause of defects formation was discussed by analyzing the manufacturing process of composites. The influence of defects on the interlaminar strength and its mechanism was analyzed experimentally and theoretically. The results indicate that these defects, with different effects, decrease the interlaminar strength because they form interlaminar cracks, and the interlaminar shear strength is less affected than interlaminar tensile strength, which is measured according to GB4944 test method. To comprehend defects distribution effect, a four-point-bending test method was introduced to measure the interlaminar peel strength, and a discussion was made on the correlation between the interlaminar tensile strength, interlaminar peel strength and in-plane transverse tensile strength. Finally the concept of interlaminar defect coefficient, which can be used to characterize the defects, was set up and the formula to calculate it was proposed.
Evaluation of the Ko-Len Model for Enterlaminar Stresses in Composite Laminates with an Open Hole
Authors: Hu F. Z. , Soutis C.
Published: January 2019

The purpose of this paper is to evaluate a recently developed analytical model [1] which determines the interlaminar stress distributions around a circular hole in symmetric composite laminates under in-plane tensile loading. For this purpose, a three-dimensional finite element analysis is performed and the stress distributions for symmetric cross-ply laminates are presented This work is relevant to the prediction of delamination onset load and location around the discontinuity.
A Micromechanical Model for Mechanical Properties of Two Constituent Composite Materials
Authors: Ramakrishna S. , Huang Z. M.
Published: January 2019

This letter reports a new and general micromechanical model for estimating the mechanical properties of composites made of two component materials, i.e. fibers and bodys. The backbone of the model is a bridging matrix of coefficients connecting the macro-stresses of a body with those of a fiber in a representative volume. A semi-empirical approach has been proposed to identify the matrix with which all the mechanical properties of the composite can be easily obtained.
Mode I Interlaminar Fracture Toughness of Organic Fiber Reinforced Plastics
Authors: Sembokuya Hideki , Hojo Masaki , Kemmochi Kiyoshi
Published: January 2019

Mode I Interlaminar fracture behaviors of organic (aramid and polyarylate) fiber reinforced plastics were investigated. The values of interlaminar fracture toughness increased with the increase of crack length. The increase of intrelaminar fracture toughness was due to the fiber bridging between crack surfaces.
Fem Analysis and Comparison of Single Fiber Pull-Out Tests
Authors: Feih S. , Schwartz P.
Published: January 2019

This work analyses the stress distributions during the pull-out test and the microbond test by FEA. Both tests are found to lead to the same results. The simulation result predicts the in praxis calculated IFSS value. Fiber coating leads to a more uniform shear stress distribution.
Tensile behaviour of Bolted Joints in Low Temperature Cure CFRP Woven Laminates
Authors: Andréasson N. , Mackinlay C. P. , Soutis C.
Published: January 2019

In this work, the stress results of a two-dimensional finite element (FE) analysis are used to understand failure modes of a bolted joint in low temperature cure CFRP woven laminates loaded in tension and predict the bearing strength. Good agreement with experimentally observed damage modes and strengths is achieved; in some cases the difference is less than 10%.
Evaluation of Crush Energy Absorption of Woven CFRP Laminates
Authors: Soutis C. , Poubady V. Ramany Bala
Published: January 2019

Axial compressive tests have been performed on several low temperature cure woven carbon fibre-epoxy laminates. A 45° chamfer was machined at one end of the plate to trigger progressive crushing. The force-deflection characteristics were almost ‘ideal elastic-plastic’ and the specific energy values ranged between 60-80 kJ/kg, which are comparable to values reported for carbon-epoxy and carbon - Kevlar epoxy hybrid composite plates from previously published data. Simple analytical expressions were derived for the specific sustained crushing stress in terms of plate geometry and energy dissipated in terms of tearing and delamination.
Interlaminar Shear Strength of Carbon Fibre Reinforced Epoxy Composite under the Influence of Environments
Authors: Zhang M. , Mason S.E.
Published: January 2019

The influences of contamination, using a range of contaminants introduced under postcure and pre-cure curing conditions, on the interlaminar shear strength (ILSS) of a cured structural carbon fibre reinforced epoxy composite have been investigated. A careful comparison between the post-cure and pre-cure conditions subjected to the different type of contaminants (water, seawater, acid, alkali and organic) confirmed a definite reduction in the ILSS properties. The results demonstrate that the control of environmental factors such as water, acids, alkalis, salts and organic solvents can have significant effects on the mechanical performance of laminate composite components during the manufacturing process and usage.
Interfacial Fracture in Fibre-Metal Laminates Based on Glass Fibre Reinforced Polypropylene
Authors: Reyes G. , Cantwell W.J.
Published: January 2019

This papers examines the interfacial fracture properties of a new fibre-metal laminate based on glass fibre reinforced polypropylene (GFPP). Tests have shown that excellent adhesion between aluminium and GFPP can be achieved by incorporating a maleic-anhydride modified polypropylene interlayer between the composite and aluminium layers. Single cantilever beam tests have shown that the fracture energy of these systems initially increases with loading rate and then decreasing. In spite of this, the fracture energy is extremely high at all rates.
A Ligature Model for Fiber Reinforced Porous Composites
Authors: Huang Xinyu , Reifsnider Ken L.
Published: January 2019

The authors have developed a modeling approach that has the ability to analyze porous fiber reinforced composite materials. The meso-level geometry is modeled by ligatures and effective media. Ligatures represent fiber tows, the major load-carrying components in the material. Effective media represent the porous matrix. The properties of the ligatures and effective media come from micro-mechanical models. Global stiffness can be successfully predicted. Residual strength and life prediction could also be made from this representation. The approach is validated by an example calculation for a filament wound tubular structure with porosity of the order of 60 percent.
Effect of the Addition of Cellulose on the Mechanical Performance of Fibre-Reinforced Mortars
Authors: Hernández-Zaragoza J.B. , Márquez-Avila L. A. , Horta J. , Olivares M. , Alarcón-Chaires P. , Castaño V.M.
Published: January 2019

The effect of adding cellulose, a rheological modifier, to a fibre-reinforced mortar was studied. The results show that the proper combination of the components of the composites can lead to good workability and compressive strength, whereas the arbitrary use of cellulose, as recommended by some authors, may lead to a poor mechanical performance.
Tensile Fracture of Graphite / Epoxy Laminates Contaning Central Holes and Cracks
Authors: Potti P.K. Govindan , Rao B. Nageswara , Srivastava V.K.
Published: January 2019

A simple relation is proposed for the characteristic length to improve the accuracy while evaluating the tensile fracture strength of graphite/ epoxy AS4/3502 off-axis symmetric laminates, [± θ2]s, containing central holes and cracks, through Whitney- Nuismer fracture models.
A Simple Non-Linear Global-Local Finite Element Methodology for Composite Structures
Authors: Falzon B. G. , Hitchings D. , Davies G. A. O.
Published: January 2019

A simple non-linear global-local finite element methodology is presented. A global coarse model, using 2-D shell elements, is solved non-linearly and the displacements and rotations around a region of interest are applied, as displacement boundary conditions, to a refined local 3-D model using Kirchhoff plate assumptions. The global elements’ shape functions are used to interpolate between nodes. The local model is then solved non-linearly with an incremental scheme independent of that used for the global model.
On Consolidation of Powder Impregnated / Sheath Surrounded Thermoplastic Composite Bundles
Authors: Haupert F. , Krebs J. , Friedrich K.
Published: January 2019

Processing of composite materials with thermoplastic matrices is very complicated due to the high viscosity of the matrix material. Therefore, the impregnation parameters have to be investigated in order to achieve both a good impregnation of the fibres and a high consolidation quality of the different layers. The aim of the present study was to consolidate tows consisting of polymer powder between glass fibre bundles with a surrounding polymer sheath. Since impregnation was meant to occur under nearly the same conditions as in continuous processes, such as, thermoplastic filament winding or pultrusion, only one or two tows were impregnated during the experiments under defined processing parameters, such as, impregnation temperature, pressure, and time.
The Effect of Water Absorption on Mode I Intterlaminar Fracture Toughness of Aramid Fibre Reinforced Plastics
Authors: Sembokuya Hideki , Hojo Masaki , Kemmochi Kiyoshi
Published: January 2019

Mode I interlaminar fracture toughness tests were carried out for aramid fibre reinforced epoxy laminates. Specimens immersed in water were also tested for comparison. The effect of water absorption on interlaminar fracture toughness was small for the aramid/epoxy laminates used in this study.
A New Approach in Utilising Inherent Flaw Model for Tensile Fracture of Composite Laminates with a Circular Hole
Authors: Potti P.K. Govindan , Rao B.Nageswara , Srivastava V.K.
Published: January 2019

This paper improves the inherent flaw model proposed by Waddoups, Eisenman and Kaminski (known as the WEK model) to predict the strength of composite laminates with a circular hole. A simple relation is used for the inherent flaw length to improve the accuracy while evaluating the notched strength of laminates. A cubic equation is developed for the fracture strength of an infinite width plate having a circular hole. This model is applied to a host of experimental data from the open literature. Most of the experimental results are found to be in very good agreement with the analytically produced ones. The proposed model which is more simple could be more applicable for fracture strength evaluation of notched composite laminates.
A Study of Matrix Crack Tip Delaminations and their Influence on Composite Laminate Stiffness
Authors: Kashtalyan Maria , Soutis Costas
Published: January 2019

Reduction of the stiffness properties of cross-ply [0m/90n]s laminates due to delaminations, growing at the 0/90 interface from the tips of transverse cracks in the 90° plies and splits in the 0° plies, is analysed by means of a theoretical approach based on the Equivalent Constraint Model (ECM). Reduced stiffness properties of the damaged lamina are derived as explicit functions of the crack density and relative delamination area associated with that lamina and implicit functions of the two damage parameters associated with the neighbouring laminae. Transverse crack tip delaminations are found to cause significant reduction in the laminate shear modulus and Poisson's ratio. Contribution of each damage mode (transverse cracking, transverse crack tip delaminations, splitting and split tip delaminations) into stiffness loss is established.
The Structural Behaviour of Monocoque Fibre Composite Truss Joints
Authors: Humphreys Matthew F. , Van Erp Gerard , Tranberg Charles H.
Published: January 2019

This paper presents early experimental results of an ongoing research project into the structural behaviour of monocoque fibre composite truss joints. The testing of three different types of joints will be discussed. Descriptions of the test procedures are presented as well as design and analysis of each jointing method.
Optimisation of Hollow Glass Fibres and their Composites
Authors: Hucker Martyn , Bond Ian , Foreman Andrew , Hudd Jennifer
Published: January 2019

Hollow glass fibre reinforced plastics have a structural performance niche in a class of their own. They offer increased flexural rigidity compared to solid glass fibre reinforced plastics, they offset the need for thin sandwich construction which is both difficult and expensive, and they provide an opportunity to develop laminates with improved or tailored characteristics. An experimental hollow glass fibre manufacturing facility is in operation at the University of Bristol. The facility is capable of drawing precision hollow glass fibres of various diameters with varying degrees of hollowness under precise parameter control. Hollow borosilicate glass fibres have been manufactured from tubular preforms with a variety of internal and external diameters, which correspond to a range of hollowness values. In all cases, the resulting hollowness was reduced from that present in the preform state, regardless of drawing rate or furnace temperature. In fact, temperature has been demonstrated to be of paramount importance in controlling fibre hollowness due to the interaction between glass viscosity and surface tension effects. These results suggest that for a given temperature and draw rate there is a single condition where fibre hollowness is maximised and external diameter minimised.
Post-Impact Behaviour of Polymeric Composites and the Effects of Salt Water Aging on Tensile Properties
Authors: Veazie D.R. , Park S.W. , Zhou Min
Published: January 2019

The study described in this report uses the split Hopkinson pressure bar (SHPB) apparatus to induce damage in a polymer matrix composite by low-velocity, transverse impact. The configuration used a three-point bend fixture in the SHPB for controlled loading and real-time diagnosis. The material analysed was a glass-fibre reinforced bismaleimide matrix composite designated S2 glass/5250-4. Experiments were conducted to characterise the response of the composite by relating a range of impact energies to the post-impact tensile strength following salt-water aging. Results showed that following salt-water aging, a monotonic relation exists between the amount of impact energy absorbed by the specimens and both the post-impact tensile strength and the moisture absorbed by the specimens. In the S2 glass/5250-4 system examined, the effects of exposure to 5000 hours of saltwater following impact were minor, illustrating the insignificance of this type of environmental effect on the post-impact tensile strength.
Interfacial Effects on the Mechanical Properties of Glass/Phenolic Composites
Authors: Morii Tohru , Ivens Jan , Verpoest Ignaas
Published: January 2019

The effect of interface on the mechanical properties of glass fibre/phenolic composites is discussed in this paper. Standard and silane modified resins are used as matrix, and a yarn and two kinds of rovings with different sizing are used as reinforcement. The effect of fibre on wetting is evaluated, and it is shown that sizing specially developed for phenolic resin is quite effective to improve resin impregnation into the fibre bundle. The mechanical properties are evaluated by using the resin impregnated unidirectional fibre bundle composite specimens. The effects of resin and fibre on strength and crack propagation are evaluated by the lateral compression test. The type of the fibre affected the dispersion of fibres in the matrix resin, and the roving developed for phenolic resin gave the best dispersion of the fibre. This led the high mechanical properties and high resistance to the crack initiation.
Effects of Fibre Architecture on Deformation during Preform Manufacture
Authors: Long A.C. , Souter B.J. , Robitaille F. , Rudd C.D.
Published: January 2019

Simulations of fabric deformation during preform manufacture are usually based on a kinematic mapping of the fibres onto the component. Whilst this approach can anticipate excessive deformation, it takes no account of the effect of fabric construction on subsequent forming characteristics. The aim of this study is to establish a relationship between fibre architecture and formability, and to incorporate this within an enhanced draping simulation. The approach utilises a geometric model for woven or warp-knitted fabrics, which forms the basis of a mechanical model for fabric deformation. The model is then used to determine the shear strain energy required to produce a particular draped fibre pattern. This is implemented within an iterative procedure to determine the draped pattern resulting in minimum strain energy. The results compare favourably with experiments for hemispherical preforms, where initial fabric construction is shown to have a significant effect on the resulting fibre orientations.
Prevalence of Hypertension in Vietnam: A Systematic Review and Meta-Analysis
Authors: Meiqari Lana , Essink Dirk , Wright Pamela , Scheele Fedde
Published: January 2019

Studies on the prevalence of hypertension in Vietnam have reported various estimates. There is no up-to-date assessment of the evidence on the magnitude of hypertension in Vietnam. Search engines for scientific and gray literature were used to identify relevant records for eligibility screening and quality assessment. Data from selected articles were extracted using standardized spreadsheets. Statistical analysis included estimating pooled prevalence and odds ratio, heterogeneity evaluation, meta-regression, and subgroup analysis, in addition to sensitivity analysis and publication bias evaluation. The pooled prevalence of measured hypertension in Vietnam was 21.1% (95% confidence interval = 18.5-23.7) based on 10 studies, and 18.4% (95% confidence interval = 15.2-21.8) based on 3 national surveys. Lower pooled prevalence was estimated for hypertension awareness (9.3%) and hypertension treatment (4.7%). The pooled prevalence of measured hypertension is significantly higher among men. The pooled prevalence of measured hypertension and hypertension awareness and treatment were significantly lower in rural settings. There is a need to strengthen efforts for primary and secondary prevention and disease management to reduce morbidity and mortality, especially in rural residence settings.
The Determinants of and Barriers to Awareness and Treatment of Hypertension in the Korean Population
Authors: Park Jong Eun , Park Jong-Hyock , Chang Sun Ju , Lee Ju Hee , Kim So Young
Published: January 2019

This study investigated whether sociodemographic, health behavioral, biomedical, and health status factors are associated with the awareness and treatment status of hypertension. Data were analyzed from 13 180 adults with hypertension in a nationally representative sample collected from 2007 to 2015 through the Korean National Health and Nutrition Examination Survey. Among hypertensive Korean adults, only 65.2% were aware of their condition and being treated with antihypertensive medications. Younger age was identified as an important barrier to diagnosis and treatment of hypertension. Although there were slight differences between participants aged <65 and ≥65 years, higher risks of being untreated or being unaware of having hypertension were also associated with male gender, lower education levels, unhealthy behaviors, and a better health conditions. We suggest that aggressive interventions to improve the awareness, treatment, and/or control of hypertension should be applied to young and middle-aged people who are vulnerable to hypertension management.
Sensemaking as ‘Self’-defence: Investigating spaces of resistance in precarious work
Authors: Manolchev Constantine
Published: January 2019

The plight of workers inhabiting the lowest strata of the occupational hierarchy, their scope for progressive resistance and collectivization is a topic of lasting significance, addressed in a number of seminal studies. Since the advent of neoliberalism and rise of precarious, that is, insecure, atypical, zero-hour, short-term and temporary employment, the matter has, once again captured public attention and led to debates between labour market theorists and policy makers. Researchers have, so far, considered the complex neoliberal causes behind the phenomenon of precarious work and mapped in detail the antagonistic relationship between labour and capital in a variety of organizational contexts. However, there is an ongoing need to study worker resistance at the micro and symbolic levels, exhibited not only through mundane, covert and everyday behaviours but through identity work in defending against subjugation of a worker’s ‘Self’. Applying Weick’s framework in 71 in-depth interviews with workers in low-pay and low-skill industries such as hospitality and care, I identify three types of narratives, retrospective, collective and appreciative, through which participants practice sensemaking as ‘Self’-defence. In doing so, I propose that sensemaking narratives enable participants to orient and interpret the atomized terrain of postmodern work, finding both enjoyment and fulfilment. Through this argument, I contribute to the subjectivity debate by showing that ‘soft’ forms of resistance should not be dismissed as harmless substitutes of the real deal but underscore precarious workers’ lasting ability to construct meaningful ‘Selves’ within postmodern working contexts.
Optimization of the production of double-shell microparticles containing fish oil
Authors: Fadini Ana Lúcia , Dutra Alvim Izabela , Paganotti Katyri Bezerra de Freitas , Bataglia da Silva Lidiane , Bonifácio Queiroz Marise , Miguel Ana Maria Rauen de Oliveira , Rodrigues Rodney Alexandre Ferreira
Published: January 2019

Fish oil incorporation into food products is a challenge because long-chain fatty acids are susceptible to oxidation. Microencapsulation is an alternative for protecting and delivering fish oil besides masking undesirable flavours. This work aimed to produce spray-chilled microparticles using spray-dried microparticles loaded with fish oil as the core material and evaluate the effects of core concentration and lipid wall material composition on the apparent viscosity of the feeding material (suspension), microparticle mean diameter (D50), moisture content and eicosapentaenoic acid and docosahexaenoic acid losses. Double-shell microparticles containing fish oil were successfully obtained. Higher core concentrations resulted in higher feeding material viscosities and microparticles with higher D50 values and higher moisture content, but suitable for food applications. Less eicosapentaenoic acid and docosahexaenoic acid loss was achieved with lipid matrixes containing palm fat/vegetable fat ratios of up to 40/60 or a ratio of 50/50 when associated with a low concentration of core material. The remaining eicosapentaenoic acid and docosahexaenoic acid content observed in the final double-shell microparticles and its good oxidative stability can be considered sufficient for the successful application of these microparticles in foods. These findings may contribute to expanding the use of microencapsulated fish oil.
Glycemic Control in Children and Youth With Type 1 Diabetes Mellitus in Saudi Arabia
Authors: Al Zahrani Abdullah M , Al Shaikh Adnan
Published: January 2019

Objective:

To determine the glycemic control and cardio-metabolic complications of children and adolescents with type 1 diabetes mellitus (T1DM) attending a tertiary care diabetes clinic in Saudi Arabia.

Methods:

We conducted a retrospective cross-sectional study of children and adolescents with T1DM attending King Abdulaziz Medical City-Jeddah from 2010 to 2013. We assessed their glycemic control and diabetes management. Vitamin D status was compared with glycemic control and gender differences.

Results:

We identified 301 subjects (53.5% females); mean age was 13.9 ± 3.8 years. The mean duration of diabetes was 7.7 ± 3.7 years, body mass index (BMI) was 21.1 ± 4.5 kg/m2, and hemoglobin A1c (HbA1c) was 9.6% ± 1.9% in both genders. There were modest gender-specific differences in Saudi patients with T1DM, with males having more symptoms than females. Mean age at diagnosis of T1DM was slightly younger in males (6.01 ± 3.65 years) than in females (6.33 ± 3.45 years). Education was the most common reason for admission in males (32.9%), whereas diabetic ketoacidosis (DKA) was the most common reason in females (38.8%). Frequency of symptomatic hypoglycemic attacks was relatively higher in males (47.1%) than in females (42.9%). The majority of our patients (83%) were on intensive insulin regimen, having 4 injections or more per day. The remaining (17%) were on conventional insulin therapy. Only 26.2% had satisfactory HbA1c (⩽8%). The mean level of 25-hydroxyvitamin D was 35.15 ± 15.9 nmol/L and cholesterol was 4.75 ± 1.1 nmol/L. Vitamin D deficiency (25-hydroxyvitamin D ⩽ 37.5 nmol/L) was detected in 63.6% males and 67.7% females. No significant correlation between HbA1c and vitamin D deficiency was observed.

Conclusions:

Metabolic control among Saudi children with T1DM is less satisfactory compared with other countries. The high prevalence of vitamin D deficiency in this population supports the recommendation of vitamin D supplementation in T1DM subjects. Further studies in a larger cohort are needed to confirm our findings.
Real-time changes in emotion regulation and loss of control eating
Authors: Stevenson Brittany L , Wilborn Dexter , Kramer Matthew P , Dvorak Robert D
Published: January 2019

Difficulties in emotion regulation are an important theoretical construct implicated in the maintenance of loss of control eating. In this study, 45 community and college participants who reported loss of control eating at least once per week carried tablets for 2 weeks, responding to random assessments throughout each day. We compared trajectories of emotion regulation abilities before and after loss of control eating episodes (using average loss of control eating episode time to divide non-loss-of-control eating days). Emotion regulation abilities remained stable on non-loss-of-control eating days, but there was a significant increase in emotion regulation difficulties after loss of control eating episodes. These results suggest that increases in emotion regulation difficulties are not responsible for initiation of loss of control eating.