bluuebunny/crossref_metadata_2025 huggingface dataset:
EPDM-based heat-shielding materials modified by hybrid elastomers of silicone or polyphosphazene
Authors: Wu Shaojun , Zhang Shuangkun , Akram Raheel , Yasir Abbas , Wang Bowen , Han Zhongqiang , Wu Zhanpeng , Wu Dezhen
Published: January 2019

The erosion resistances of ethylene propylene diene monomer (EPDM) insulations are often inadequate for advanced solid rocket motor (SRM) applications. EPDM modification by blending secondary matrixes is a feasible approach to improve the ablative properties of EPDM insulations. The addition of flexible inorganic hybrid rubbers as a secondary matrix, such as silicones and polyphosphazenes, may impart EPDM insulations with better ablative performance. The blends of EPDM/hybrid rubbers represent the state-of-the-art heat-shielding materials for SRM. In the present work, methyl-phenyl silicone/EPDM and poly(diaryloxyphosphazene)/EPDM insulation systems with various blending ratios of secondary matrixes have been prepared. The ablative properties of the insulations were examined by oxy-acetylene ablation tests, and the results showed that these properties could be enhanced accordingly by blending with hybrid rubbers under appropriate proportions. The unique charred layers resulting from the hybrid rubbers contributed to their excellent ablation properties. For example, the silicone/EPDM insulations exhibited a more significant improvement of ablation resistance properties. With a 1:1 blending ratio of silicone/EPDM, the linear ablation rate was 0.06 mm s−1 after 20 s of oxy-acetylene ablation. The enhancement in the ablative resistance was attributed to the charred layers with bunches of embedded compact microtubes with a length of 2–3 mm, which consisted of silicon carbide, silicon dioxide, and Si–O–C ceramics.
Robust control for railway transport networks based on stochastic P-timed Petri net models
Authors: Gaied Mouhaned , M’halla Anis , Lefebvre Dimitri , Ben Othmen Kamel
Published: January 2019

This article is devoted to the modeling, performance evaluation and robust control of the railway transport network in Sahel Tunisia. The regular increase in the number of passengers makes the management of transportation systems more and more complex. Railway transport requires specific needs. Indeed, many decision and optimization problems occur from the planning phase to the implementation phase. Railway transport networks can be considered as discrete event systems with time constraints. The time factor is a critical parameter, since it includes schedules to be respected in order to avoid overlaps, delays and collisions between trains. The uncertainties affect the service and the availability of transportation resources and, consequently, the transport scheduling plan. Petri nets have been recognized as powerful modeling and analysis tools for discrete event systems with time constraints. Consequently, they are suitable for railway transport systems. In this article, stochastic P-time Petri nets are used for the railway transport networks in Sahel Tunisia. A global model is first detailed. Then, this model is used to analyze the network traffic and evaluate the performance of the system. Robustness again disturbances is introduced and a control strategy is developed to reduce the consequences of the disturbances in order to maintain the expected schedule.
The Holocene history of the NE Black Sea and surrounding areas: An integrated record of marine and terrestrial palaeoenvironmental change
Authors: Marret Fabienne , Bradley Lee R , Tarasov Pavel E , Ivanova Elena V , Zenina Maria A , Murdmaa Ivar O
Published: January 2019

Here we present an almost complete and integrated Holocene record of marine and terrestrial palaeoenvironmental change from the NE shelf of the Black Sea. A dinoflagellate cyst record used to reconstruct Holocene sea-surface conditions highlights that the NE shelf was a brackish water environment, with a minimum salinity of 7 psu in the early-Holocene before changing at a gradual rate to a more saline environment with maximum salinities of ~18 psu being reached around 3 cal. ka. A warming phase was detected from 6 cal. ka BP, with warmest conditions between 3 and 2.5 cal. ka BP. A pollen record is used to examine the major climate and land-use changes in the eastern Black Sea region. Biome reconstructions show that the temperate deciduous forest dominates throughout the record, although with an overall decline. From early-Holocene to the first hiatus around ~9 cal. ka BP, Pinus pollen dominates, while taxa representing a mixed oak-hornbeam-beech forest are less abundant, indicating relatively cool and dry conditions. Between ~7.9 and ~6.1 cal. ka BP, a thermophilous deciduous forest established, suggesting an overall warming trend and humid conditions. From 4 cal. ka BP, Pinus dominates the pollen record, accompanied by an increase of herbs, implying an opening of the landscape, which would coincide with the beginning of the Meghalayan Age. The integrated record of the marine and terrestrial climate indicators supports the notion that this change in landscape may have been triggered by a combination of warmer and drier conditions and human activities in this region.
Damage Detection and Vibration Control of a Delaminated Smart Composite Plate
Authors: Chattopadhyay Aditi , Nam Changho , Kim Youdan
Published: January 2019

In this paper, the effects of delamination on the dynamic characteristics of a composite plate are investigated. The refined higher order theory is used to model the smart composite plate in the presence of delaminations. The theory accurately captures the transverse shear deformation through the thickness, which is important in anisotropic composites, particularly in the presence of discrete actuators and sensors and delaminations. Next, the detection of delamination is investigated using the Root Mean Square (RMS) values of the response of the composite plate subject to disturbances. An active control system is designed to minimise the effect of delamination. The pole placement technique is applied to design the closed loop system by utilising piezoelectric actuators. Numerical results show that the RMS information can be used to estimate the location of the delamination. The controller designed makes the delaminated plate behave like a healthy plate model. The controller also reduces the magnitudes of RMS responses due to disturbance.
Hygrothermal Deformation of Composite Sandwich Panels
Authors: Wolff Ernest G. , Chen Hong , Oakes Darrell W.
Published: January 2019

Coefficients of thermal and moisture expansion (CTE and CME) can be predicted for many composite laminates and sandwich panels. Core and adhesive properties, such as geometry and stiffness are important variables. Laminate theory is augmented with a modified model for anisotropic core properties to predict the CTE and CME of sandwich panels. Procedures to measure both CTE and CME are described. Since these are thermodynamic properties, methods to obtain equilibrium moisture strains are needed. Results are given for CFRP facesheets with Al and NOMEX honeycomb cores, and for woven Kevlar facesheets with Al cores. Agreement with predictions is good and depends highly on knowledge of properties of all constituents.
Analysis of Explanted Silicone/Silica Composite Breast Implants
Authors: Brandon Harold J. , Young V. L. , Jerina K.L. , Wolf C.J.
Published: January 2019

A study was conducted to examine the physical, mechanical and chemical properties of composite (silicone/silica) breast implants as a function of implantation time. In the study the properties of SILASTC®II gel-filled explants with in vivo duration times ranging from 4 months to 10 years were compared to lot-matched control (unimplanted) samples. Tensile strength properties were measured for both explant and control shells using identical testing protocols. The tensile strength properties of shells which were extracted with hexane to remove non-cross linked silicones were also measured. In addition, swelling measurements were used to determine the average molecular weight between cross-links (and/or entanglements). The tensile strength properties obtained from the present study were correlated with implantation time. The results of the study suggest that the silicone elastomer shells do not undergo appreciable degradation during in vivo aging.
Processing Map for Hot Working of Powder Metallurgy 2124 AL - 20 VOL% SiCP Metal Matrix Composite
Authors: Murty S.V.S. Narayana , Rao B. Nageswara , Kashyap B.P.
Published: January 2019

A simple instability condition based on the Ziegler's instability criterion is found to be more appropriate in delineating the regimes of flow instabilities in the processing maps of 2124 Al-20 Vol% SiCp metal matrix composite. Applicability of the criterion is demonstrated using the reported microstructural observations in open literature.
New Numerical Model of Composite Fabric Behaviour: Simulation of Manufacturing of thin Composite Part
Authors: Billoet J.L. , Cherouat A.
Published: January 2019

The present study concerns the modelling of the behaviour of pre-impregnated woven fabric during the forming process. The mechanical approach is based on a mesostructural model. It allows us to take into account the mechanical properties of fibres and resin and the various dominating mode of deformation of woven fabrics during the forming process. Shear and tensile tests of composite fabric specimens are proposed and compared with the experimental results in order to demonstrate the efficiency of our approach. Different numerical simulations and experiments of shaping process have been carried out in order to validate the proposed computational formulation. The various forming parameters examined have included the initial shape of fabric, fibre orientations and viscosity of resin.
The Fracture Properties of Fibre-Metal Laminates Based on Glass Fibre Reinforced Polyamide
Authors: Guillen F. , Cantwell W.J.
Published: January 2019

The aim of this paper is to investigate the interfacial fracture properties of a novel fibre-metal laminate based on a unidirectional glass fibre reinforced polyamide 6,6 composite. Interfacial fracture tests using a modified single cantilever beam geometry have shown that good adhesion between the aluminium and glass fibre polyamide plies can be achieved using a simple stamping operation. Further testing has shown that the basic fracture properties of this system do not depend on the cooling rate employed during consolidation of the laminates.
Geometrical Non-Linearity of Textile Composites in Large Deformation
Authors: Lim T. C. , Zako M. , Sakata S. , Ramakrishna S.
Published: January 2019

In considering small deformation of solids, it is common to assume linear elasticity. Where large deformation is concerned, material non-linearity – whether hyper elasticity, strain hardening, etc – must be considered. In large deformation of textile composites, overall material non-linearity consists of (a) constituent material non-linearity, and (b) geometrical non-linearity due to strain-deformation relation. This paper firstly proposes a finite element procedure for obtaining the stiffness matrix of a representative volume element. The procedure involved is simple due to an effective decoupling methodology. Secondly, co-ordinate updating of the FE mesh is performed to allow readjustment to the fibre bundle elements in the RVE. This enables the process of fabric realignment to be theoretically mimicked to consider the influence of fibre bundle reorganisation on the overall stiffness of the textile composite – hence geometrical non-linearity.
Effect of Insertion of Buffer-Strip on the Response of Carbon-Epoxy System in Short Beam Tests
Authors: Kishore  , Khan Bijoysri , Viswanath B.
Published: January 2019

The work looks at the response to three-point loading of carbon-epoxy (CF-EP) composites with inserted buffer strip (BS) material. Short beam Shear tests were performed to study the load-deflection response as well as fracture features through macroscopy on the CF-EP system containing the interleaved PTFE-coated fabric material. Significant differences were noticed in the response of the CF-EP system to the bending process consequent to the architectural modification. It was inferred that introduction of small amounts of less adherent layers of material at specific locations causes a decrement in the load carrying capability. Further the number and the ease with which interface separation occurs is found to depend on the extent to which the inserted layer is present in either single or multiple layer positions.
Modelling the Effects of Resin Shrinkage in Pultrusion of Composites Sections
Authors: Joshi Sunil C. , Lam Y.C.
Published: January 2019

This paper discusses the development, implementation and application of numerical schemes for modelling the effects of temperature-dependent material properties including chemical shrinkage and thermal expansion of resin on the curing of thermosetting composites in pultrusion. The results of the three-dimensional simulation of heat and mass transfer in pultrusion of regular as well as irregular and hollow sections are presented.
Development of Braided Carbon/Peek Composite Bone Plates
Authors: Fujihara K. , Huang Zheng-Ming , Ramakrishna S. , Satkunanantham K. , Hamada H.
Published: January 2019

In this study, a novel fabrication method using braiding technique was applied to fabricate carbon/PEEK composite bone plates. Four-point bending tests of the composite plates were carried out to compare with the conventional stainless-steel bone plate. The braided composite bone plates with considered braiding angles displayed a maximum bending moment in the range of 38.2 ∼ 44.0 % and bending stiffness in the range of 26.6 ∼ 30.2 % of those of a stainless-steel plate. The bending properties of braided composite plates are comparable with those of the polymer composite bone plates reported in the literature. The potential of braided carbon/PEEK composite material for bone fracture fixation applications is indicated.
Impact Properties of Interleaved Carbon Fibre Reinforced Epoxy Composite Tubes
Authors: Yuan Q. , Karger-Kocsis J. , Ye L.
Published: January 2019

Composite tubes were manufactured using unidirectional carbon fibre (CF) reinforced epoxy (EP) prepreg with tough interleaf which consisted of random PET mat embedded in a modified epoxy resin. Impact tests were carried out in both the axial and transverse directions with different incident energy levels, and compression strength after impact of composite tubes was measured. The residual compressive strength of interleaved tubes was clearly higher than that of base tubes. Composite tubes subjected to multiple impacts in the transverse direction were evaluated. It was found that addition of interleaves could effectively reduce damage growth during repeated impact.
Mechanical Properties of an Igneous Aggregate-Modified Hydraulic Concrete
Authors: Alonso E. , Martvnez-Gomez L. , Martvnez W. , Villaseρor L. , Castapo V.M.
Published: January 2019

Portland cement concretes were prepared by adding different igneous materials from west central Mexico. The results of the mechanical testing of these materials show the feasibility of employing igneous minerals to produce concretes and mortars, provided a careful control of granulometry and the geochemistry involved is attained. The mechanical performance, as well as the workability of the slurries can be managed by the convenient use of commercial additives (i.e. water reducers and aging accelerators). These results open the attractive possibility of expanding the natural sources of concrete-forming elements.
All-Plant Fibre Composites: Self Reinforced Composites Based on Sisal
Authors: Lu Xun , Zhang Ming Qiu , Rong Min Zhi , Shi Guang , Yang Gui Cheng
Published: January 2019

In the present work slight benzylation of sisal fibre was carried out to prepare natural resource based self reinforced composites. By controlling the degree of benzylation, the outer layer of the ultimate cells was converted into thermoplastic and the inner part maintained the load bearing ability. When these modified fibres were moulded under certain temperature and pressure, the thermoplasticised portion flowed freely and served as matrix, while the unaffected parts in the core can still provide reinforcing effect. Such an all-plant fibre composite is characterised by self-reinforcement, easy processing and low cost.
Viscoelastic Behaviour of Polypropylene-Based Nanocomposites in the Melt State
Authors: Shumsky V.F. , Privalko E.G. , Karaman V.M. , Privalko V.P. , Walter R. , Friedrich K. , Zhang M. Q. , Rong M. Z.
Published: January 2019

Nanoparticles of the standard pyrogenic Aerosil 1380 (Degussa) pregrafted by γ-irradiation with styrene were melt-compounded with the general purpose isotactic polypropylene (PP) homopolymer by a single-screw extruder. Storage G’(ω) and loss G”(ω) shear moduli of the neat PP (PP-0) and of the nanocomposite with the filler volume content 4.68 % (PP-4.68) were treated to derive the relaxation times spectra h (τ) using the NLREG computer program based on Tikhonov's method of non-linear regularisation. Drastic changes in the pattern, and broadening of the h (τ) to longer relaxation times for the PP-4.68 were attributed to the onset of plastic yield of a spatial network of filler particles coated with polymer boundary layer, preceding the macroscopic melt flow.
Analysis of Weight Change in Fly Ash – Epoxy Particulate Composites Immersed under Hot Water
Authors: Kulkarni S.M. , Kishore
Published: January 2019

Weight changes in epoxy filled with low-cost abundantly available filler, fly ash subjected to immersion in water maintained at an elevated temperature are studied. The effect of volume fraction of the filler on the water absorption characteristics is analysed. The extent and possible modes of water transport in the matrix and in the filler or filler-matrix interface are inferred through the study of absorption data. An attempt to explain this movement through the percolation model is made and support for the inferences arrived at is sought from microscopic observation using Scanning Electron Microscope.
Determination of Interfacial Shear Strength and Critical Fibre Length in Injection Moulded Flax Fibre Reinforced Polypropylene
Authors: Aurich T. , Mennig G.
Published: January 2019

Natural fibres are becoming more and more important as reinforcement in polymer based materials. Knowledge of interfacial shear strength and critical fibre length is important for the assessment of the mechanical properties of the composite and the estimation of the resultant fibre length distribution. This is particularly true for injection moulded reinforced thermoplastic parts. Because of the problems with the preparation of micro-mechanical specimens from natural fibres and thermoplastics, in the presented paper the characteristic values are calculated from macroscopic composite strength data.
Preparation of High-Temperature Resistant Sic Fibre with Low Content of Oxygen and Free Carbon
Authors: Cao Feng , Li Xiaodong , Wang Wenyuan , Wang Jun , Song Yongcai , Kim Dong-pyo
Published: January 2019

High-temperature resistant and fine diameter SiC fibre was prepared by a series of combined curing and sintering processes at 1800°C of polyaluminocarbosilane fibre. Slight air curing avoids excessive oxygen incorporation, and subsequent thermal curing rendered the infusible green fibre for pyrolysis. It appears that Al content plays an important role when the fibre is fired at high temperature to remove oxygen and excess carbon.
An Experimental Study on the Thermoplastic Filament Winding Process using Commingled Yarns
Authors: Kim Sun Kyoung , Kim Gong Min , Kim Hee June , Lee Woo IL
Published: January 2019

A filament winding process of commingled yarn is investigated. This study aims to verify the feasibility of the proposed winding process experimentally. A laboratory scale winding system is built which can perform in situ consolidation using a hot nitrogen gas torch. The degree of impregnation is evaluated for different process parameters including the hot nitrogen gas temperature, the process speed and the compaction force to provide a process window.
Failure of Composite Sandwich Beams
Authors: Daniel I. M. , Gdoutos E. E. , Wang K.-A.
Published: January 2019

A thorough investigation of failure behaviour of composite sandwich beams under three- and four-point bending was undertaken. The beams were made of unidirectional carbon/epoxy facings and a PVC closed-cell foam core. The constituent materials were fully characterised and in the case of the foam core, failure envelopes were developed for general two-dimensional states of stress. Various failure modes including facing wrinkling, indentation failure and core failure were observed and compared with analytical predictions. The initiation, propagation and interaction of failure modes depend on the type of loading, constituent material properties and geometrical dimensions.
Morphological Study of Sisal Fibres
Authors: Bai S.-L. , Li R. K.Y. , Mai Y.-W. , Wu C.M.L.
Published: January 2019

A sisal fibre has microstructures very different from those of synthetic fibres. The special microstructures consist of parallel cells and a cuticle-interface in the form of a continuous network around each cell. The flexible interface and solid cells play an independent role to toughen and strengthen the sisal fibre, respectively. Upon loading, the cell can behave in a brittle or a ductile fashion. The main failure mechanisms of a sisal fibre are the pullout and uncoiling of cells and the debonding of a not very strong interface/cell interface. Therefore, debonding of this interface represents the first initial damage of a sisal fibre composite.
A New Design Methodology for High Temperature Structural Components Made of Continuous Fibre Ceramic Composites Exhibiting Thermally Induced Anisotropic Damage
Authors: Vlachos D.E. , Pappas Y.Z. , Innocenti Marco , Kostopoulos V.
Published: January 2019

Continuous Fibre Ceramic (Matrix) Composites (CFCCs) have found during the last decade numerous of industrial applications in a variety of technological areas, where structural components are subjected to high temperature combined with significant mechanical loading. The present work deals with the application of an innovative design methodology for the development of an industrial gas turbine combustor chamber made of oxide/oxide composite materials. Oxide/oxide composites offer high-temperature structural stability without the need of any kind of oxidation protection and thus permit the increase of working temperature of the gas turbine, increasing the efficiency of the system and decreasing NOx emissions. Since, oxide/oxide composites degrade their structural properties as a function of the operating temperature (for temperature higher than 1000°C) and the exposure time, an incremental approach has been introduced as a structural design methodology for the combustion chamber, where each increment represents a thermal exposure stage. The data set required for the application of the present design approach, was obtained through an extensive material characterization program based on the measurement of the anisotropic properties of oxide/oxide composites using ultrasonic techniques.
An Analytical Model to Predict Fracture of Off-Axis Unidirectional Composites
Authors: Petermann J. , Plumtree A. , Schulte K.
Published: January 2019

An analytical model based on isotropic homogeneous material behaviour is proposed to predict fracture in unidirectional composites under general loading. The model calculates the internal stress distribution corresponding to the applied load. In conjunction with the respective strength values, the model is capable of assessing the dominant stress component for failure initiation. For uniaxial tensile loading a comparison of calculated analytical stress distributions reasonably agrees with results from FE-analysis. A comparison of the analytical predictions with fractographic results for different off-axis angles provides good agreement.
In-Plane Testing of Damaged Masonry Wall Repaired with FRP
Authors: Fam Amir , Musiker Daniel , Kowalsky Mervyn , Rizkalla Sami
Published: January 2019

This paper describes the performance of a masonry wall repaired with glass fibre reinforced polymer, GFRP sheets. The original reinforced clay brick masonry wall was tested under in-plane lateral cyclic loading. Failure occurred due to yielding of the steel reinforcement and crushing of the bricks. After epoxy injection of the cracks and patching of the missing portions, the wall was repaired using GFRP sheets, applied in the horizontal and vertical directions, on one face of the wall, including the joint between the wall and concrete footing. The repaired wall was tested to failure in the same manner of the original wall. The results show that the strength and displacement capacities of the wall were completely restored and even exceeded the original capacities.
Validation of a Parametric Constant-Life Model for Fatigue-Life Prediction for Carbon-Fibre Laminates
Authors: Harris B , Carroll HE , Davies AJ
Published: January 2019

This letter describes an experimental validation of a parametric model for the prediction of the fatigue lives of carbon-fibre composites. The constant-life model, which has been developed at Bath over a number of years, offers the possibility of predicting life for any CFRP laminate on the basis of a very limited amount of new data. It has now been tested against fatigue data from an independent laboratory for a laminate material and lay-up different from those on which the model was based. The level of accuracy of the predicted lives is high.
Monitoring of Filler Distribution in Resin with an Electromagnetic Wave Transmission Line
Authors: Okabe Tomonaga , Urabe Kei
Published: January 2019

The authors previously presented a new method for monitoring resin flow and curing with a high-frequency electromagnetic wave transmission line constructed inside a structure. This method can provide information on discontinuities or distributions by using frequency characteristics or the time-domain response. In this paper, we applied our method for monitoring the defects in resin, such as uneven distribution of reinforcement or filler, voids or contamination, in the manufacturing process. The experimental results demonstrated the possibility of a transmission line as a monitoring tool and showed that the area with defects can be characterized by comparing with results of theoretical calculations.
Bending Failure Characterisation of Laminated Beams with Braided Fabric Reinforcement
Authors: Huang Zheng-Ming , Fujihara K. , Ramakrishna S.
Published: January 2019

An experimental procedure has been performed in this work to characterise failure behaviour of braided fabric reinforced composite laminates subjected to flexural load. The material system used was carbon/epoxy. The laminated beams were made using eight layers of diamond braid reinforcement. Two braiding angles, i.e., 5° and 15°, were applied. Six beams with laminate arrangements of [5/5/5/5/5/5/5/5], [15/15/15/15/15/15/15/15], [5/5/15/15/15/15/5/5], [15/15/5/5/5/5/15/15], [5/5/15/15/5/5/15/15], and [15/15/5/5/15/15/5/5] were loaded under 4-point bending to their ultimate failure, where the braiding angle is measured with respect to the beam axis. Bending stiffnesses, ultimate bending strengths, and load-deflection curves of the tested beams were reported. It was found that all the bending failures of the laminated beams were initiated from their top surface inwards, as a consequence of an excessive compressive stress in the beam cross-section. Further evidence in failure mechanism was recognised through a matrix combustion and fabric peeling out technique. It was shown that after the bending test the only un-failed lamina in some of the laminates was its bottom surface ply. The evidence clearly indicates that the neutral plane in a laminated beam keeps shifting once a lamina in the laminate has failed. The failed lamina in the laminate can hardly sustain any additional load. Thus the present experiment confirms that a total stiffness discount should be adopted in the layer-by-layer progressive failure analysis of a laminated composite. Using this discount procedure, a simulation method is highlighted in the paper. The predicted load-deflection curves up to the third-ply failure agreed reasonably with the measured ones.
Acoustic Emission Applied to Failure Analysis of Commingled Yarn GF/PP Composites in Transverse Tension and Mode I Delamination
Authors: Lariviere D. , Krawczak P. , Tiberi C. , Lucas P.
Published: January 2019

This work aims to analyse the influence of the fibre/matrix interface on the acoustic response of commingled yarn thermoplastic composites submitted to transverse tension and mode I fracture mechanics loading. For this purpose, different interfacial qualities were obtained by modification of the fibre reinforcement sizing and the matrix coupling. The acoustic emission rate (number of acoustic events emitted per time unit) has appeared suitable to quantify the damage involved by the mechanical loading according to the interfacial quality. The comparison of the acoustic emission obtained for the two loading modes has shown that, although the amplitude range [59-66dB] is characteristic of interfacial debondings in transverse tension, it is no more the case for a mode I delamination test for these commingled GF/PP composites.
Influence of the Damage Sequence in the Mechanical Strength of a Composite Material of Pei Reinforced with Woven Carbon-Fabric. A Statistical Analysis
Authors: Garcia M.A. , Arguelles A. , Castrillo M.A. , Fernandez-Canteli A. , Vina J.
Published: January 2019

The aim of the present study is to characterise statistically the degradation produced in the tensile breaking strength of a material composed of a PEI thermoplastic matrix reinforced with woven carbon fibre under a sequential permutation of damage. To do so, the statistical theory of extreme values was applied to the experimental results, which enabled us to calculate the probability of failure of the material. The simulated damage corresponding to said series was the following: fatigue up to one million cycles at a maximum stress of 20% of the tensile strength, impact damage with an energy of 2.7 J, accelerated ageing under conditions of 95% relative humidity, a temperature of 70'IC for a period of 96 hours and finally, thermal ageing at 150'IC for 360 hours. The experimental results obtained show increments of 5% to losses of 22% in residual strength of that presented by the material in its original state.
The Optimisation of Flax Fibre Yarns for the Development of High-Performance Natural Fibre Composites
Authors: Goutianos S. , Peijs T.
Published: January 2019

Currently most developments in the area of natural fibre reinforced composites have focused on random discontinuous fibre composite systems. The development of continuous fibre reinforced composites is, however, essential for manufacturing materials, which can be used in load-bearing/structural applications. The main problem in this case is the optimisation of the yarn to be used to manufacture the textile reinforcement. Low twisted yarns display a very low strength when tested dry in air and therefore they can not be used in processes such as pultrusion or textile manufacturing routes. On the other hand, by increasing the level of twist, a degradation of the mechanical properties is observed in impregnated yarns (e.g. unidirectional composites) similar to off-axis composites. Additionally, a high level of twist decreases the permeability of the yarns. This problem is addressed in the current work using yarns based on both long and short flax fibres.
Finite Element Modelling of Frequency-Dependent Dynamic Behaviour of Viscoelastic Composite Structures
Authors: Barkanov Evgeny , Chate Andris
Published: January 2019

Finite element analysis of sandwich and laminated composite structures with viscoelastic layers is performed. The present implementation gives the possibility to preserve the frequency dependence for the storage and loss moduli of viscoelastic materials exactly. Moreover, the storage and loss moduli in this case are defined directly in the frequency domain by an experimental technique for each material and can be used after curve fitting procedure in the numerical analysis. Damping characteristics of viscoelastic composite structures are evaluated by the energy method, the method of complex eigenvalues, from the resonant peaks of the frequency response function and using the steady state vibrations. Numerical examples are given to demonstrate the validity and application of the approaches developed for the free vibration, frequency and transient response analyses.
Behaviour of Hybrid Titanium Composite Laminate (HTCL) under In-Plane Loading
Authors: Allegri G. , Corradi S. , Marchetti M. , Suanno L.
Published: January 2019

The Hybrid Titanium Composite Laminate (HTCL) incorporates the mechanical advantages of existing hybrid composite laminates such as ARALL and GLARE while extending their applications to harsh environments. Hybrid composite laminates, consisting of layers of Titanium Grade 2 foils bonded together with fibre-reinforced prepreg plies, have been tested under fatigue loading. HTCL has proven to possess exceptional strength and fatigue resistance. Degraded stiffness and ultimate resistances are provided through experimental stress-strain response of HTCL laminates, which are compared with predicted results by a laminate analysis code. The roles of mechanical degradation, the static and dynamic behaviour and fatigue properties of HTCL are addressed. The development of damage in HTCL specimens during fatigue is shown including titanium ply cracking, interfacial debonding, and layer failure. These tests provided several parameters in order to calibrate a numerical Lamaitre's Continuous Damage Mechanics (CDM) fatigue model, which resulted in good agreement with experimental data. The influence of the fatigue properties of titanium layers on the fatigue of HTCL is discussed. The performance of HTCL laminates in fatigue is shown superior to that of the monolithic titanium alloy for room-temperature conditions.
Joining Techniques for Fibre Ceramic Structures
Authors: Kochendorfer R. , Lutzenburger N. , Weihs H.
Published: January 2019

This paper shows three different joining methods for fibre ceramic materials. The so called in-situ joining method is an integral part of the manufacturing process for CMC structures via the liquid silicon infiltration (LSI) process. Stiffening elements, local patches within attachment areas, inserts etc. are permanently joined to shell structures, thus enabling highly integrated components to be realised with low manufacturing costs. Mechanical joining methods are required for the attachment of CMC thermal protection systems and the assembly of large structures which can not be manufactured as one part due to the limited size of manufacturing devices (e.g. autoclave, furnaces). For these cases, two different principles are available. The first method takes advantage of interlocking effects of hardened castable ceramics for permanent joints and the so called ceramic rivet, which has similar properties to metallic rivets, however using only elastic and frictional properties of the CMC basic material. The last joining method presented within this paper deals with the attachment of hot structures to a cold substructure. To solve the problems associated with thermal mismatch, elastic or kinematic attachment systems, well adapted to the thermal expansion behaviour are suitable candidates.
Spectral Response and Effective Viscoelastic Properties of Mwnt-Reinforced Polycarbonate
Authors: Fisher F. T. , Eitan A. , Andrews R. , Schadler L. S. , Brinson L. C.
Published: January 2019

The impact of embedded carbon nanotubes on the effective viscoelastic response of a nanotube-reinforced polycarbonate system is characterized by studying the temperature- and frequency-dependent behaviour of the material. Macroscale experimental results demonstrate that the effective relaxation spectra of the samples is consistent with non-bulk polymer regions of restricted molecular mobility. Such low mobility regions are attributed to localized nanoscale interactions between the nanotubes and individual polymer chains.
The Fractal Dimension of X-Ray Tomographic Sections of a Woven Composite
Authors: Summerscales John , Russell Paul M , Lomov Stepan , Verpoest Ignaas , Parnas Richard S
Published: January 2019

Plain woven E-glass fibre-reinforced epoxy resin composites have been imaged using X-ray computed tomography. A data-set of 150 cross-sectional slices have been quantified using fractal dimensions. For this data set, the fractal dimension analysis returns a consistent numerical value for each of the slices in the two similar orthogonal planes.
Self-Sensing Fibre Reinforced Composites
Authors: Fernando Gerard F , Degamber Balkarransingh , Wang Liwei , Doyle Crispin , Kister Guillaume , Ralph Brian
Published: January 2019

This paper reports for the first time a demonstration of chemical process monitoring of conventional glass fibre reinforced composites where the reinforcing fibres themselves act as the optical fibre sensors. These fibres were used to study in real-time, the rate of chemical reaction between an epoxy resin and an amine hardener. These reinforcing fibre light guides were also subsequently used to study, in situ, the fracture sequence of the reinforcing fibres. This was achieved by imaging one end of the fibre bundle whilst illuminating the opposite end.
Observations on the Fibre Distribution and Fibre Strain in a Woven Fabric Reinforcement
Authors: Summerscales John , Russell Paul M
Published: January 2019

The distribution of the fibres within a tow of a plain weave fabric composite appears to be non-uniform with a systematic variation. In a different composite system, the strain along a fibre in a similar fabric has been shown to vary along each individual filament in an ordered manner. It is proposed that the highest fibre strains occur at the centre of the tow crossing points. An optical micrograph of matrix cracking in the transverse tows adjacent to the proposed highest strain point would appear to confirm this hypothesis. This analysis is based on limited evidence, but is presented to permit other researchers to confirm or refute the proposition.
Pei/Ptfe Nanocomposites as a Matrix for Glass Fibre-Reinforced Composites
Authors: Grozdanov Anita , Errico Maria Emanuela , Avella Maurizio , Bogoeva-Gaceva Gordana
Published: January 2019

Nanocomposite based on PEI and PTFE-nanoparticles was obtained by solution blending method, using dichloromethane as a solvent. PEI-PTFE nanocomposite was used as a matrix for glass fibre reinforced composite. The obtained composites were characterized by DSC, TGA, flexural test and DMTA. Using SEM analysis, the homogeneity of distribution of nanoparticles was analysed. The main improvement for fibre reinforced nanocomposite matrix was recorded in their thermal stability and thermal resistance.
Effect of Reinforcements on Mechanical and Thermal Properties of SiC Short-Fibre-Reinforced SiC Composites
Authors: Lee Jae-Seol , Yano Toyohiko
Published: January 2019

Tyranno SA fibre was higher strength at high temperatures and higher thermal conductivity than that of Hi-Nicalon fibre. Therefore, the aim of this study was to investigate the effect of reinforcements on the mechanical and thermal properties of SiC/SiC composites containing non-coated Tyranno SA short fibres. SiC/SiC composites containing 30 vol.% short fibres were fabricated by tape-casting and hot-pressing at 1650°C–1750°C under a pressure of 40 MPa using an Al2O3-Y2O3-CaO mixture as sintering additives independent of fibre type.
A Near-Stoichiometric Sic-Based Fibre Obtained from a Polyaluminocarbosilane Precursor
Authors: Yu Yuxi , Li Xiaodong , Cao Feng
Published: January 2019

A near-stoichiometric SiC-based fibre containing ∼2 wt% aluminum, called SiC(Al) fibre, has been developed. SiC(Al) fibre can be obtained from an organometallic polymer precursor polyaluminocarbosilane by melt-spinning, oxidation curing, sintering at 1800°C in argon. SiC(Al) fibre was characterised by elemental chemical analysis, tensile test, Scanning electron microscopy, X-ray diffraction and Auger electron spectroscopy. Physical and mechanical properties of SiC(Al) fibre under thermal exposure, oxidation resistance and creep properties at elevated temperature were examined. The SiC(Al) fibre has more excellent oxidation resistance than Nicalon, Hi-Nicalon fibre and better creep resistance than the Tyranno SA fibre.
Tensile Properties of Natural Fibre Reinforced Thermoset Composites
Authors: Yamamoto T. , Medina L. , Schledjewski R.
Published: January 2019

The processing and mechanical properties of natural fibre composites were investigated. Three kinds of kenafhemp-non-woven materials impregnated with an acrylic matrix were used. The natural fibre composites were press moulded and showed good mechanical properties. It was clarified on the basis of the microscopic observation of the fracture surfaces that the adhesion of natural fibres and matrix was important in order to obtain good mechanical properties.
Damage Evaluation of GLARE®4B under Interlaminar Shear Loading at Different Temperature Conditions
Authors: Hinz Stephan , Heidemann Jens , Schulte Karl
Published: January 2019

The fibre reinforced metal laminate GLARE®4B was investigated under interlaminar shear loading conditions at temperatures between −50°C and 110°C. Short beam shear (ILSS) and double notched shear (DNS) tests were performed. The interlaminar shear strength decreases strongly with increasing temperature. The DNS test shows that the shear strain increases and the interlaminar shear stiffness decreases with increasing temperature. The observed damage occurs mainly in the 90°-fibre layer. For low temperatures delamination between the fibre-layers is the dominant failure mode. The higher the temperature, the more cracks develop in the 90°-layers. These multiple cracks coalesce with increasing shear load and form the final fracture surface. Light and scanning electron microscopy showed that the cracks are mainly based on fibre-matrix interface failure.
Structural Health Monitoring of Bonded Composite Joints Using Embedded Chirped Fibre Bragg Gratings
Authors: Palaniappan J , Wang H , Ogin S L , Thorne A , Reed G T , Crocombe A D , Tjin S C
Published: January 2019

Chirped fibre Bragg gratings (CFBGs) have been used to monitor disbond initiation and disbond growth in composite bonded joints. The CFBGs have been embedded within, but near the surface of, a transparent GFRP composite adherend that has been bonded to a second transparent adherend. The low wavelength end of the CFBGs has been arranged to be adjacent to the end of the first adherend. Disbond initiation is readily detected as a modification to the reflected spectrum of the CFBG, consisting of the low wavelength part of the reflected spectrum being shifted to lower wavelengths; this is due to the unloading of the adherend resulting from the disbond. Disbond growth is detected by the movement of a dip in the reflected spectrum of the CFBG (as a consequence of the load redistribution at the disbond front); this dip moves to higher wavelengths as the disbond propagates. The relationship between the shift of the dip in the reflected spectrum with the position of the disbond front has been determined directly through the use of transparent GFRP joints.
Influence of Acid Treatment on Dispersion of Carbon Nanotubes in PBO Matrix
Authors: Li X. , Huang Y.D.
Published: January 2019

Dispersion of carbon nanotubes (CNTs) in polymeric matrix has been a key factor on forming CNTs/polymer composites. In this paper, the O-MWNTs were first derived from raw multi-walled carbon nanotubes (MWNTs) which were purified with a mixed solution of concentrated H2SO4 and concentrated HNO3, then the O-MWNTs were dispersed with sonication in H3PO4 and the resultants were denoted as U-MWNTs. After processed with poly (p-phenylene–2, 6–benzoxazole)(PBO) by in-situ polymerisation successfully, the O-MWNTs and the U-MWNTs were finally formed into O-MWNTs/PBO composites and U-MWNTs/PBO composites, respectively. The SEM and AFM morphological analysis showed that a perfect dispersion of U-MWNTs in U-MWNTs/PBO composites was obtained. These composites can be widely used in photoelectric devices and engineering applications, etc.
Investigation of the Free Edge Interlaminar Stresses Dependence on the PLY Thickness and Orientation
Authors: Katerelos Dionisios T. G.
Published: January 2019

Among the principal damage modes in composite laminates, is delamination. Design details, such as free, straight or curved, edges, induce large local out-of-plane loads, generating interlaminar stresses. In the present work, the effect of ply thickness and the angle between two adjacent layers on the interlaminar stresses developed at the vicinity of straight and curved free edges in composite laminates under thermomechanical loading is examined. The results are obtained by the application of a 3-dimensional Finite Element Analysis.
Stereolithography Specimen to Calibrate Permeability Measurements for RTM Flow Simulations
Authors: Morren Gerd , Gu Jun , Sol Hugo , Verleye Bart , Lomov Stepan
Published: January 2019

The simulation of a resin flow through a porous medium by FE-models has become a very important aspect for the design of a high-performance RTM produced composite part. The key parameter to perform RTM flow simulations is the fibre reinforcement permeability. Unfortunately, permeability measurements are not yet fully standardized and thus many different set-ups have been proposed. A major problem in comparing different set-ups has always been the fact that there exists no reliable reference material on which a comparative permeability measurement can be performed. This paper presents a solid test specimen, produced with a stereolithography technique, which can be used as a reference sample for calibration of test rigs and for comparison of results from different test rigs. Since the permeability properties of the specimen do not vary from test to test, an excellent repeatability of the experiments is obtained and any measured difference must be attributed to the set-up.
The Effects of Seawater Environment, Material Direction and Thickness on the Fatigue Performance of Adhesively Bonded and Bolted Joints of Non-Crimp GRP Structures
Authors: Er Gϕkdeniz Ne , Altunsaray Erkin
Published: January 2019

In this experimental study, which was undertaken to evaluate the combined effects of material direction, thickness and seawater environment on the fatigue behaviour of adhesively bonded and bolted joints widely used in GRP boat building, the specimens, which were produced by composite system, which its matrix material was multi-purpose polyester (Dewester 196 from the Dewilux Inc.) and its reinforcing material was non-crimp, E-glass fibres, has been used. Unjoined control specimens taken from two different panels (thickness of 5 mm and 11 mm) with the direction of 0′I, were subjected to the tests carried out under both atmospheric and marine conditions, together with unjoined with the directions of 45′I and 90′I, bonded and bolted specimens taken from the same panels. The study was started with static tensile tests of unjoined and jointed specimens, which have two different thickness, 5 mm and 11 mm and have been aged in 3.5% of NaCl solution, which represents seawater environment, and the results obtained give suggestions on tensile values, which would be used in tension-tension fatigue tests. The cycling in tension-tension fatigue tests was between tensile maximum and zero stress value and the frequency value applied was 7.5 Hz. The specimens, which were subjected to tests in synthetic seawater environment, had been aged previously. The results occurred depending on the material direction, the thickness and the joining type of the material are given in conclusion by comparison. It was seen that the results obtained by testing the material in synthetic seawater is much lower than the results of obtained from testing similar specimens under atmospheric conditions. However, the cyclic stress curves indicate the same slope, suggesting that the fatigue failure mechanism of both testing conditions is the same and the fibre-related factors dominate.