bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterisation of the Interfacial bond Strength between Glass Fibre and Epoxy Resin using the Pull-Out and Push-Out Techniques
Authors: Mδder E. , Zhou X.-F. , Pisanova E. , Zhandarov S. , Nutt S. R.
Published: January 2019

Interfacial bond strength between epoxy resin and glass fibre was studied using the pull-out and push-out techniques. For untreated fibres, these micromechanical tests gave similar values of the local interfacial shear strength and critical energy release rate. In the case of fibres treated by γ-APS, both tests showed considerable increase in the bond strength. However, for the modified fibres, the pull-out test gave greater values of both interfacial parameters than the push-out test, a result attributed to the different modes of interfacial loading. The different loading patterns also cause different failure mechanisms in these two tests.
Mechanisms of Mode I Interlaminar Fracture of Glass Woven Fabric Composites
Authors: Kotaki M. , Kuriyama T. , Hamada H. , Maekawa Z. , Narisawa I.
Published: January 2019

Mode I interlaminar fracture behaviours were investigated on the laminated composites reinforced with plain glass woven fabrics which were treated with different silane concentrations. The low silane concentration specimen indicated higher fracture toughness, compared to the high silane concentration specimen. This is due to the occurrence of the micro crack in the fibre strands. In the low silane concentration specimen, larger damage zone due to the micro crack was formed ahead of the crack tip.
Interphase with Lamellar Interlocking and Amorphous Adherent – a Model to Explain Effects of Transcrystallinity
Authors: Karger-Kocsis J.
Published: January 2019

An interphase model emphasising the lamellar architecture and the role of the amorphous phase is proposed to explain possible effects of the transcrystalline layer in composites consisting of semicrystalline polymer and fibres acting heterogeneous nucleants therein. Based on this model biased findings reported on the effects of transcrystallinity can be rationalised.
Quantitative Evaluation of Wear Grooves in a Fine Particulate Reinforced, Soft Polymer Coating System by Laser Profilometry and Computer Aided Scratch Analysis
Authors: Nιder Zoltαn , Vαradi Kαroly , Friedrich Klaus
Published: January 2019

After certain periods of practical application, particulate reinforced polymer coated surfaces frequently contain many grooves due to a scratching contact with any abrasive counterparts. To characterise these scratch patterns a software package (SCRATCH) has been developed using digitised surface roughness data from a laser profilometer. The SCRATCH system identifies individual scratches by representing their locations (using a slicing technique) and specifies scalar parameters (such as the specific scratch area or mid-tangent of the bearing area curve). In this way, the magnitude of the scratch damage can be identified following an approximate technique. This is demonstrated here for wear grooves in a polymer coating system subjected to a particular scratch test. But the method can also be applied to other engineering surfaces, e.g. for wear evaluation of composite bearings, seals and other sliding composite elements.
Studies on Mixed Mode Interlaminar Fracture Toughness of M55J/M18 Carbon/Epoxy Laminates
Authors: Jose S. , Kumar R. Ramesh , Rao G. Venkateswara , Sriram P.
Published: January 2019

Experimental studies are carried out to determine the interlaminar fracture toughness of unidirectional laminates made of M55J/M18 carbon/epoxy material under different mixed mode ratios ( G I/ G II). A mixed mode delamination fracture criterion using mixed mode bending specimens is developed. It is observed that when loading in mode I is predominant, G II has a considerable value but the opposite is not true when mode II is predominant.
Failure Behaviour of Cross-Ply Carbon Fibre/Epoxy Laminates Subjected to Transverse Impact and Static Perforation
Authors: Yuan Q. , Czigany T. , Ye L.
Published: January 2019

Cross-ply carbon fibre reinforced epoxy laminates (CF/EP) were toughened with interleaf consisting of random PET fibre mat embedded in a modified epoxy resin. The interleaved laminate had a smaller delamination area but higher energy absorption than the base laminate during transverse impact perforation. In static tests, the interleaved laminate had a higher maximum load and greater deformation at the perforation, compared to the base laminate. The damage development was monitored using acoustic emission technique. The interleaved laminate had less cumulative acoustic emission events than the base laminate. The distribution of the rise time was used to identify the major failure mechanisms.
Damping Characteristics of Vibrated Composite Plates
Authors: Kostopoulos V. , Korontzis D. Th.
Published: January 2019

The free vibration response of [±Θ] ns orthogonal, simply supported (all around) composite laminated plates was studied, assuming linear viscoelastic behaviour of the constitutive lamina material. The problem was solved numerically and the results were verified in the special case of [0]2 n laminate against the analytical solution, which is also provided. Stability and convergence problems were discussed analytically. Eigenfrequency values and modal damping characteristics were calculated for the first nine mode shapes. Furthermore, keeping constant the plate thickness, the effect of the lamina thickness on the vibration characteristics of the plate was examined.
Determination of Cure Shrinkage in Sl Layer Built Plates using Lamination Theory
Authors: Aggelopoulos A. , Karalekas D.
Published: January 2019

This paper reports on a combined analytical and experimental investigation undertaken for the determination of polymerisation shrinkage strains resulted in photopolymer resin plates during the laser solidification process. A resin layer is laser cured on an identical layer of the same material that already has been cured and post cured under ultraviolet (UV) exposure. The assembled laminate is then UV cured, and the resulting warpage is recorded by means of the shadow moirtι method. The resulting warpage, consisting of elliptical equal deflection contours, is related to the polymerisation effective chemical shrinkage strain using the elastic lamination theory.
Thermal Degradation of Green and Upgraded Flax Fibres
Authors: George J. , Klompen E.T.J. , Peijs T.
Published: January 2019

Over the last couple of years, an increasing amount of research has been dedicated to the use of flax fibres as an environmentally friendly alternative to glass fibres in engineering composites. Because of the relatively poor thermal stability of flax fibres compared to glass fibres, knowledge of the thermal degradation profile of these natural fibres is essential for the selection of potential matrix candidates and/or the development of feasible processing and recycling routes. Especially in combination with thermoplastic resins, composite (re)processing may have a detrimental effect on the mechanical properties of the natural fibres. This study reports on the effect of the exposure of two types of flax fibres, green flax and a new upgraded flax fibre called Duralin, to elevated temperatures using thermogravimetric analysis (TGA), residual strength measurements and environmental scanning electron microscopy (ESEM) studies.
A Study of the Mechanical and Permeability Properties of Nano- and Micron-Tio2 Filled Epoxy Composites
Authors: Ng C.B. , Ash B.J. , Schadler L.S. , Siegel R.W.
Published: January 2019

Polymer nanocomposites consisting of 32 nm diameter TiO2 nanoparticles and epoxy resin were ultrasonically processed and the mechanical and permeability properties of the resulting composites were compared to composites containing 0.24 μm TiO2 particles and to neat resin. It was found that the nanocomposites with well-dispersed nanoparticles at 10 wt% loading exhibited a unique combination of properties showing increases in both scratch resistance and modulus, as well as gains in strain-to-failure and swelling resistance, while maintaining toughness. The micron filled composites showed no increase in scratch resistance and a decrease in strain-to-failure relative to the neat resin.
Determination of Elastic Constants of Composites with a Circular Disk Specimen
Authors: Prabhakaran R. , Xu H.
Published: January 2019

The in-plane elastic constants of orthotropic composite materials need to be determined in order to perform stress analysis and design of composite structures. Several specimen configurations have been proposed and the majority suffer from one of two drawbacks: either multiple specimens are required or the experimental method involves a scientific rather than an engineering approach. In the present investigation a simple procedure involving a single calibration specimen is suggested. The method utilises a theoretical solution available in the literature for an orthotropic circular disk under diametral compression, measured strains at specific locations on a circular disk specimen, and a least squares procedure that gives average rather than localised elastic constants.
Preliminary Results on the Effect of Methanol-Based Fuels on the Tensile Properties of Frp Micro-Specimens
Authors: Goh A.Y.L. , Kariuki J. K. , Skelhorne A. W. , Bhattacharyya A. , McDermott M.T. , Forest T.W. , Steadman G.
Published: January 2019

This paper reports a simple experimental technique developed to measure strains in fibre-reinforced plastic (FRP) tensile micro-specimens (nominal thickness: 254 μm) before and after these were exposed to a 50–50 volumetric mixture of methanol and ASTM Fuel C. Micro-specimens were used to reduce the time required for the fuel mixture to diffuse into the FRP. The developed technique is then used to study the effect of the methanol-based fuel on the tensile properties of the micro-specimens. In particular, the stress of the specimens at a strain of 1.5% is seen to be significantly lower when the specimens are tested immediately after exposure to the fuel for 3 day and 7 day periods as compared to the stress for specimens not exposed to the fuel. The loss in stress is found to be significantly recoverable when the exposed specimens are tested after allowing them to dry for an equal length of time, i.e. 3 days and 7 days. These results point to two possibilities: 1. Design of FRP structures exposed to alcohol-based fuels, e.g. underground fuel storage tanks, may have to account for noticeable mechanical property changes of the FRP during the service period, 2. Any property changes may be partially reversed by allowing the structures to “dry” over an appropriate period of time.
Influence of Tool Status on Flexural Strength of Machined CFRP Components
Authors: Ramkumar J. , Krishnamurthy R. , Malhotra S.K.
Published: January 2019

Machining trials have been carried out on Carbon Fibre Reinforced Plastics (CFRP) High Speed Steel (HSS) traditional & modified point geometry and Tungsten Carbide (WC) tipped drills. Among the drills, modified point geometry out performed others by sustaining higher order life. This has been supported by monitoring thrust, torque and Acoustic Emission (AE) during drilling trials.
Composite Material Based Laminated Object Manufacturing (LOM) Process Simulation
Authors: Park Joohyuk , Kang Moon K. , Hahn H. Thomas
Published: January 2019

In laminated object manufacturing process (LOM) as a rapid manufacturing technique, the key process parameters for achieving a successful prototype are the roller temperature, the roller speed, the roller indentation and the laser cutting time. In addition to these basic process parameters, the material properties and the configuration of the parts affect the internal stresses, local deformations built during the process and the bonding quality. A finite element method was adopted to simulate the thermal aspects of the bonding process along with the structural deformation of the part. Thermal and stress analysis was carried out to calculate the interlaminar shear strength between layers. Experiments were conducted to verify the simulation result for the internal temperature profiles. The finished prototype was tested mechanically to measure interlaminar shear strength to estimate the bonding quality. The calculated bonding quality was compared with the bonding strength converted from the measured interlaminar shear strength, showing a good agreement between the two. In compliance with the increasing demand for high-strength working prototypes, the developed simulation code can simulate the incorporation of new material for the LOM process.
Strain Measurement in Tests on Fibre Fabric by Image Correlation Method
Authors: Launay Jean , Lahmar Fathia , Boisse Philippe , Vacher Pierre
Published: January 2019

Strain measurements are investigated by an image correlation method, for tensile tests, in order to analyse the non-linearities due to crimp. The interest of the method is the possibility to study the phenomena at different scales and so to contribute to a better understanding of the yarn interactions and of their influence on the fabric mechanical behaviour
Continuous Monitoring of Resin Content in Prepreg Unidirectional Tapes by Beta-Ray Method
Authors: Huang Y.D. , Liu L. , Sun Y.F. , Qiu J.H. , Nakayama N. , Kumazawa T.
Published: January 2019

A beta-ray monitoring technique has been developed to measure the resin content during the manufacture of prepreg unidirectional tapes by solution impregnation process. A series of calibration relations have been obtained for aramid, carbon and glass fibres reinforced epoxy prepreg tapes, and good agreements with resin content have been shown by the beta-ray system and conventional solvent extraction method. Moreover, the effect of the variation of the fibre areal weight on measuring accuracy has been analysed.
Preparation and Characterisation of Ancient-Like Masonry Mortars
Authors: Alonso E. , Martinez-Gomez L. , Martinez W. , Castano V.M.
Published: January 2019

The characterisation of mortars prepared according to ancient methods from the colonial period in Mexico is reported. The materials were prepared by mixing limestone, sand, water and an additive (bovine blood, milk or cactus sap) and the compression strength, flexural strength and tensile strength were measured according to ASTM standards and at different aging stages. The technology developed allows, on the one hand, counting with a reliable methodology for restoring ancient buildings, similar to the originally employed, and, on the other to offer a low cost technique for construction by using agricultural by-products.
A Parametric Study of the Effect of Geometric Imperfections on the Buckling Behaviour of Composite Laminated Cylinders
Authors: Petreli A.S. , Tsouvalis N.G.
Published: January 2019

This paper presents the results of a parametric study about the type and magnitude of initial imperfections on the buckling behaviour of composite laminated cylinders under external hydrostatic load. Using the FE method, cylinders with two particular types of initial imperfections are non-linearly analysed. Results show that significant improvement of the cylinder buckling strength is observed when initial imperfections have a selected shape and magnitude, which induces a final cylinder deflected shape different from the modeshape of the geometrically perfect cylinder.
Development of Permeability Models for Saturated Fluid Flow across Arrays of Fibre Clusters
Authors: Gravel E.M. , Papathanasiou T.D.
Published: January 2019

Dual porosity fibrous media are important in a number of applications, ranging from bioreactor design and transport in living systems to composites manufacturing. In the present study we are concerned with the development of predictive models for the hydraulic permeability ( Kp) of various arrays of fibre bundles. For this we carry out extensive computations for viscous flow through arrays of fibre bundles using the Boundary Element Method (BEM) implemented on a multi-processor computer. Up to 350 individual filaments, arranged in square or hexagonal packing within bundles, which are also arranged in square of hexagonal packing, are included in each simulation. These are simple but not trivial models for fibrous preforms used in composites manufacturing – dual porosity systems characterised by different inter- and intra-tow porosities. The way these porosities affect the hydraulic permeability of such media is currently unknown and is elucidated through our simulations. Following numerical solution of the governing equations, ( Kp) is calculated from the computed flowrate through Darcy's law and is expressed as function of the inter- and intra-tow porosities (φ, φt) and of the filament radius ( Rf). Numerical results are also compared to analytical models. The latter form the starting point in the development of a dimensionless correlation for the permeability of such dual porosity media. It is found that the numerically computed permeabilities follow that correlation for a wide range of φ i, φt and Rf.
Quantifying the Plastic Anisotropy for Particulate Metal Matrix Composites
Authors: Kourkoulis S. K.
Published: January 2019

The failure of orthotropic materials, traditionally described by Hill's criterion, in terms of the anisotropy ratio r, i.e. the ratio of transverse to through thickness increments of logarithmic strain, is studied in the present work. In spite of the critical role of r for the description of the failure of such materials, its quantification is not yet standardized. Based on results obtained from long series of experiments r is here quantified, for the case of a modern particulate composite material, extensively used in aerospace applications. The variation of r versus the level of the plastic strain is determined and it is concluded that its values depend both on the orientation of the specimen and load with respect to the initial orthotropy axes as well as on the plastic strain induced in case the specimen and load are not oriented along one of the axes of orthotropy.
Numerical Analysis of the Mechanical Properties of Rice Husk-Polyester Composites
Authors: Salgado-Delgado R. , Vasquez S. , Garcia E. , Lopez-Castanares R. , Alvarez-Castillo A. , Martinez E. , Castano V.M.
Published: January 2019

The production of hot-pressed composite materials based on unsaturated polyester resin reinforced with rice husk is described. A correlation equation relating the tensile and compressive mechanical properties as a function of both rice husk concentration and the pressure applied to the mold was obtained.
Theoretical Aspects of a Tension Schedule Proposed for the Pyrolysis of Polycarbosilane Bundles
Authors: Chu Zeng-yong , Feng Chun-xiang , Song Yong-cai , Jiang Da-zhi , Wang Ying-de , Wang Jun
Published: January 2019

To prepare high strength SiC fibres that cannot be broken with a shear force because of the absence of bend portions, a firing tension is necessary in the pyrolysis of polycarbosilane bundles. However, up to now, no theoretical discussions were released on the tension schedule. Some theoretical aspects, therefore, such as constitutive model, Weibull parameters, peak load/stress, survival probability and upper limit tension were discussed and a theoretical tension schedule was proposed in the paper.
A Method to Measure the Interfacial Shear Stress for Optical Fibres Embedded in Fibre Reinforced Composites
Authors: Etches J A , Fernando G F
Published: January 2019

This paper reports on the development of a prepreg-based fabrication technique to manufacture single fibre pull-out test specimens for conducting interfacial bond strength studies. Optical fibres were embedded in 2 and 16-ply unidirectional glass fibre prepreg and processed in an autoclave using conventional procedures. Fibre pull-out tests were conducted on these specimens and the data obtained are comparable to those reported in the literature.
In-Situ MMC Production through VXBY Intermetallics Formation in an Al Matrix
Authors: Polyzos C. , Skolianos S. , Lefakis H. , Tsipas D.N.
Published: January 2019

The production of in-situ MMC's (Metal Matrix Composite) of an aluminum matrix with VxBy intermetallic compounds as the reinforcing phase has been investigated. The approach is modelled after that of Al-Ti-B alloys and salts added to an Al matrix to produce in-situ grain-refining TiB2. In the present work, V was used instead of Ti in an effort to investigate the possibility of an in-situ synthesis of a new, alternative, B-V reinforcing compound. Al, Al-V4.5wt% and Al-B5.5wt% alloys and a B-salt (KBF4) were used as starting materials. The synthesis temperature, the stirring time and the reaction holding time (RHT) were 1000°C, 5 min and 5 or 10 min respectively. The microstructure of the resulted MMC's consisted of second-phase particles, ranging in size between 1 and 10 μm, dispersed within an Al matrix. The second phase particles were identified by X-ray diffraction (XRD) analysis as VB2 and VB.
Fatigue Behaviour of Unidirectional Single-Walled Carbon Nanotube Reinforced Epoxy Composite under Tensile Load
Authors: Ren Y. , Li F. , Cheng H. M. , Liao K.
Published: January 2019

Tension-tension fatigue behaviour of unidirectional, aligned single-walled carbon nanotube (SWNT) rope reinforced epoxy composites were studied. While the slope of the stress-life (S-N) curve of the SWNTs in SWNT/epoxy composites obtained is flat, similar to those of carbon fibre reinforced epoxy composites, the fatigue strength of the former is at least twice that of the latter. Morphology of the fatigue fracture surface of SWNT reinforced epoxy involves matrix plastic deformation and SWNT-bridged matrix cracks. Evidence of good adhesion between SWNTs and epoxy was seen, and pullout length of SWNTs from the matrix is about 30 μm. Results suggest that carbon nanotubes can be used for fatigue resistant, high fracture toughness composites.
Study on Humidity Aging Property of Adhesive/Carbon-Carbon Composites Joints
Authors: Wang C. , Huang Y. D. , Zhang G.Y.
Published: January 2019

This paper studied the property of adhesive/C-C composites joints in humidity aging with infrared spectrum (IR) energy dispersive X-ray spectroscopy (EDX) scanning electron microscopy (SEM) and shear strength. The decline ratio of shear strength of adhesive/C-C composites joints treated by silane coupling agent were lowest than that treated by sand paper burnish or by chemical oxidation in humidity aging. And shear strength tests also proved time-temperature equivalence between temperature and humidity aging time. SEM of adhesive/C-C composites joints showed that there were no marked changes of the interface and surface of adhesive/C-C composites joints in humidity aging. The changes of IR of the adhesive and EDX of adhesive/C-C composites joints indicated that water penetrative speed on the surface of C-C composites was faster than that on the surface of the adhesive, and water penetrative speed on the surface of the adhesive and C-C composites during humidity aging depended on temperature and humidity aging time
Detection of Local Preform Defects by Gas Flow Method and Statistical Analysis
Authors: Kim Sun K. , Opperer Jeremy G. , Daniel Isaac M.
Published: January 2019

A method for testing the quality of fibrous preforms using gas flow is proposed. The method detects defects caused while placing the fibre preform in the mould by checking the deviations of measured pressures from the reference expected value at various locations in the mould during steady state gas flow through the enclosed preform. A statistical method is employed to classify the test preform into a normal group or any one of several groups associated with specific types of defects.

To implement this method experimentally, a specially designed mould with multiple ports for gas injection and pressure measurement was used. Results obtained for various cases with and without preform defects were compared and analysed.
Mechanical and Erosion Behaviour of Ti47Al-3W/TI2ALC Composites by Reactive Arc-Melting
Authors: Ramkumar Janakarajan , Kakitsuji Atsushi , Malhotra S.K. , Krishnamurthy R. , Mabuchi H. , Tsuda H. , Matsui T. , Morii Kenji
Published: January 2019

Ti-50Al alloy and Ti-47Al-3W alloy and its composites have been prepared by reactive arc melting technique using elemental powders. Composites have been reinforced using 3.5, 10 and 18 vol% of Ti2AlC in the matrix of TiAl with and without addition of W and C. By the addition of tungsten and carbon to TiAl alloy, we have produced composites that are reinforced randomly by reacted rod like Ti2AlC particles with fine precipitate of Ti2AlC particles and B2 particles. Compared to Ti-50Al alloys, the Ti-47Al-3W alloy and its composites have superior mechanical properties like bending strength, hardness, fracture toughness and erosion. Ti-47Al-3W/3.5 vol% Ti2AlC has excellent erosion resistance because of the dispersion of fine Ti2AlC and B2 particles in the matrix.
On the Low Velocity Impact Response of Laminated Composite Plates using the P-Version Ritz Method
Authors: Markopoulos Y.P. , Kostopoulos V.
Published: January 2019

Low energy impact in composite laminates is often a crucial and destructive loading condition since it leads to significant internal damage, undetectable by visual inspection. Low velocity impact upon a laminated plate imposes a complex stress state mainly due to the structural heterogeneity resulting by the ply orientation of the constituent laminae and the contact boundary conditions, which lead to a loading path that varies with the impact energy and the properties of the impactor-impacted plate system. The present work deals with the development of a numerical scheme for the calculation of the dynamic response of any type of laminated composite plates under low-velocity impact. The governing non-linear, second order differential equations are derived using p-Ritz admissible polynomial functions and the elastoplastic version of the Hertzian contact law. The dynamic response of fully clamped, cross ply and angle ply composite plates are investigated.
Neat Uhmwpe Filament Wound Composites by Crosslinking Compaction
Authors: Ratner Stanislav , Weinberg Amotz , Marom Gad
Published: January 2019

A novel hot compacted crosslinked filament wound structure was prepared form Ultra High Molecular Weight Polyethylene fibres, characterized and shown to possess improved properties. Three different compaction temperatures (140°C, 145°C and 150°C) were tested for both crosslinked and non-crosslinked control systems. The optimal temperature for the hot compaction process was selected on the basis of maximum fibre skin melting for better fibre-fibre fusion and tensile strength, combined with minimum core melting for higher Young's modulus. The crosslinked compacts exhibited better mechanical properties than the non-crosslinked ones; for example, for compacts prepared at 145°C the tensile strength was higher by about 55% and the Young's modulus by about 36%, respectively. The improvement was attributed to stronger fibre-fibre bonding via the crosslinked network formed at their skins. From the chemical surface analysis it could be concluded that some 43%) of the C-H groups at the fibre surface turned into C-C bonds as a result of the crosslinking compaction process.
Strength of Sandwich Panel ‘Cut and Fold’ Joints
Authors: Joulia N. , Grove S.M.
Published: January 2019

Right-angle ‘cut and fold’ joints in aluminium-honeycomb sandwich panels have been tested for strength and stiffness. The results indicate that joint strength increases with adhesive content, and that simple modifications to the way in which the core is cut can result in significantly higher strengths
Mechanical and Tribological Properties of Ti3Al Reinforced Aluminium Matrix Composites
Authors: Busquets-Mataix D. , Martvnez N. , Salvador M.D. , Amigσ V.
Published: January 2019

Mechanical properties and tribological behaviour of AA6061 and AA7015 aluminium matrix composites reinforced with Ti3Al intermetallics have been studied. Processing of the composites consisted of a combination of powder metallurgy and extrusion techniques. High tensile strength was attained on both alloys, although composites did not improve these properties. Also ductility was impaired on composites, but values above 10% were obtained in every case. Regarding friction coefficient, all composites showed a lower value with respect to base alloys, being lower as the amount of reinforcement increased. Wear behaviour of composites was improved.
Thermal and Rheological Characterisation of a Thermoset Matrix for Filament Winding Modelling
Authors: Calabrese L. , Celona A. , Valenza A.
Published: January 2019

Rheo-kinetic behaviour of an epoxy resin, coupled with an aliphatic polyamines hardener, used in fibre reinforced plastics, was analysed comparing experimental data to theoretical models. Then the modelling of technological filament winding process for thermoset matrix composites, developed through a numerical code realized with MATLAB, is reported. The model includes winding and curing phase decoupling the manufacturing process into sub-models. Four sub-models are used: fibre motion, thermal, kinetic and rheological model. Considerable differences are obtained in process condition, using several thermal treatments. The numerical modelling helps to detect the process conditions to optimise the filament winding process.
Internal Stresses and Warpage of Thin Composite Parts Manufactured by RTM
Authors: Ruiz Edu , Trochu Francois , Gauvin Raymond
Published: January 2019

Resin transfer moulding (RTM) is a widely used manufacturing technique of composite parts. A proper selection of process parameters is the key to yield successful moulding results and obtain a good part. Among other things, when thermoset resins are processed, the shrinkage that occurs due to the polymerisation reaction further complicates the situation. In this paper, a finite difference analysis is proposed to simulate the effect of thermal and rheological changes during thin plates cooling after processing. Classical Laminate Theory is here implemented to compute composite internal stresses resulting from these thermo-rheological conditions. Laminate stresses are then computed and warpage obtained with the proposed numerical algorithm. Samples of thin plates were moulded combining two glass reinforcement materials. During cooling, after processing plates warpage was recorded and results compared to model predictions. This analysis presents the basis of a further numerical optimisation for thick composite parts.
Selection of Sewing Threads for Preform Manufacturing
Authors: Ogale A. , Weimer C. , Mitschang P.
Published: January 2019

Applying sewing technologies for manufacturing preforms, which later used for Liquid Composite Moulding processes (LCM), requires an adoption of different sewing resources. As the number of applications of stitched preforms are growing [ 1 , 2 ], the issue of improving thread quality and its compatibility with the Fibre Reinforced Plastic (FRP) is getting into the interest of both industry and science. Within this study the relationship between the thread design and the FRP quality with respect to the LCM technique was evaluated.
Modelling of the Initial Failure of Cfrp Structures by Partial Discretisation: Amicro / Macro-Mechanical Approach of First Ply Failure
Authors: Fiedler Bodo , Holst Stefan , Hobbiebrunken Thomas , Hojo Masaki , Schulte Karl
Published: January 2019

The formation of transverse matrix cracks is the early failure in carbon fibre reinforced composites (CFRP). Unidirectional laminates with 90° fibre orientation were tested by transverse tensile tests and in situ under 3 point bending load in the scanning electron microscope (SEM). Finite element analysis were carried on the microscopic level hexagonal unit cell of fibre and matrix, as on the macroscopic level based on homogenized fibre and matrix properties as well. To link the micromechanical approach with the homogenized description of composite structures was done by transferring boundary conditions from one model to the other. The influence of the temperature on the Young's modulus, the non-linear stress-strain behaviour and the strength of the matrix on the micro residual stresses and matrix failure was taken into account has been investigated in detail. Process induced thermal residual stresses and matrix failure of unidirectional carbon fibre reinforced composites (CFRP).
Preparation of a Novel Epoxy/SiO2 Hybrid Coating
Authors: Zhang C. H. , Bai Y. P. , Liu L. X. , Zhang Z. Q. , Li Q. Y.
Published: January 2019

In this paper, epoxy/SiO2 hybrid coating was successfully prepared through sol-gel technique, the structure and thermal properties of epoxy/SiO2hybrid coating were investigated. First, γ-isocyanatopropyltriethoxysilane “(KBE-9007)” was used to modify the epoxy resin so that the ethoxysilane could be grafted on the epoxy resin. Nano-SiO2 precursor was synthesized by tetraethoxysilane(TEOS) through sol-gel technique. Then the modified epoxy resin and the nano-SiO2 precursor were mixed for 4 hours to let the macromolecules of epoxy resin graft on the surface of nano-SiO2, and modified nano-SiO2 precursor was obtained. At last, epoxy/SiO2 hybrid coating was produced by using the modified nano-SiO2 precursor. The graft reaction was confirmed by the analyses of FT-IR. The analyses of XPS indicated that there are lots of SiO2 particles and Si-C covalent bonds on the surface of epoxy/SiO2 hybrid coating, they also suggested that most TEOS had changed into SiO2 particles and Si-C covalent bond had been formed between epoxy resin and SiO2. The analyses of SEM fracture surface image of epoxy/SiO2 hybrid coating showed that SiO2 particles dispersed in epoxy matrix homogeneously and the size of the particles was between 50nm and 100 nm. Thermoanalysis Instrument was employed to detect the thermal properties of epoxy coating and epoxy/SiO2 hybrid coating, the results indicated that the thermal decomposition temperature of epoxy/SiO2 hybrid coating is 21.7 °C higher than that of epoxy coating, the thermal properties of the epoxy/SiO2 hybrid coating were improved because of the introduction of nano-SiO2.
Applicability Range of the One-Parameter Ply Plasticity Model for Prediction of the Nonlinear Response of Laminates
Authors: Spβrnins E. , Andersons J. , Varna J.
Published: January 2019

A one-parameter lamina plasticity model is applied to predict the nonlinear deformation of an E-glass / epoxy cross-ply composite laminate under quasi-static uniaxial tensile loading at different angles to the material orthotropy axes. It is shown that the laminate theory yields accurate results within the plastic strain range covered in unidirectional continuous-fibre reinforced composite tests that are used to determine the plasticity model parameters.
A Study of the Effect of Acetylation and Propionylation on the Interface of Natural Fibre Biodegradable Composites
Authors: Tserki V. , Panayiotou C. , Zafeiropoulos N. E.
Published: January 2019

Composite materials are a class of materials used in many diverse applications. Very recently the attention has shifted to the development of green composites that are easily recycleable and in this case the use of biodegradable matrices and fibres appear to be highly attractive. In the present study a class of biodegradable polyesters are used as matrices to produce fully biodegradable composites, reinforced with lignocellulosic natural fibres. This new class of composites is fully biodegradable, but the key aspect that governs the behaviour of the composites remains the interface. Surface treatments, although having a negative impact on economics, may improve the compatibility and strengthen the interface in natural fibre composite materials. In the present study the effect of two surface treatments, namely acetylation and propionylation, upon the interface of natural fibre composites is assessed by means of fragmentation tests. It has been found that both treatments led to an improvement of the stress transfer efficiency at the interface, and both applied treatments were optimised, accordingly.
PIP Preparation of Silica Fibre Fabric Reinforced Silicon Nitride-Based Composites using Polyhydridomethylsilazane
Authors: Qi Gong-jin , Zhang Chang-rui , Hu Hai-feng , Zhou Chang-cheng
Published: January 2019

A new type of composites, three-dimensional silica fibre fabric reinforced silicon nitride-based composites, were prepared by PIP method through repeated infiltration of polyhydridomethylsilazane and pyrolysis at 773-873K in ammonia atmosphere. The density of the composites reached 1.66g/cm3 after four PIP cycles, and the flexural strength was 56.3 MPa. The composites showed a near-brittle fracture mode without long fibre pull-out in the fracture surface. It was the relatively strong fibre/matrix interface bonding that led to the moderate mechanical property.
Studies on Turning of Carbon/Phenolic Ablative Composite Using PCBN Tools
Authors: Sreejith P. S. , Krishnamurthy R.
Published: January 2019

Carbon/phenolic composites are used in high performance applications because of their high temperature resistant properties. Studies on the machining aspects of these composites are very few. This paper presents an investigation on machining of this composite material using PCBN tools. The studies on specific cutting pressure revealed a critical speed of machining at which the specific cutting pressure is minimum. A critical range of temperature has been identified at which the specific cutting pressure is almost steady. Range of effective hardness for the tool has been identified for machining.
Embrittlement Behaviour and Mechanism of Silica Fibres with Polymer-Derived Silicon Nitride Coatings
Authors: Qi Gong-jin , Zhang Chang-rui , Hu Hai-feng
Published: January 2019

Silicon nitride coatings were prepared on silica fibres using two polysilazanes, respectively, by dip coating with subsequent pyrolysis at 873 K in ammonia atmosphere. The silica fibres with polyhydridomethylsilazane derived coatings exhibited a residual tensile breaking force about 3.87% of the original fibres, while the fibres with perhydropolysilazane derived coatings showed a lower strength with the tensile breaking force approaching null. Besides the intrinsic degradation of silica fibres, the chemical reactions between the hydroxyl groups on silica fibres and the active radicals in polysilazanes probably played an important role in the embrittlement of silicon nitride-coated fibres.
Transmission Light Microscopy of Carbon Nanotubes-Epoxy Nanocomposites Involving Different Dispersion Methods
Authors: Inam Fawad , Peijs Ton
Published: January 2019

Before employing carbon nanotubes (CNTs) in a polymer matrix as potential reinforcement elements, major obstacles, like inhomogeneous distribution and formation of agglomerates, need to be removed. Transmission Light Microscopy is a very quick, cheap and useful tool for roughly quantifying such problems. In this paper, various dispersion methods like simple hand mixing, low power ultrasonic bath, high power bath ultrasonication, tip ultrasonication, high speed mechanical mixing twin screw mini-extrusion and dual asymmetric mixing are used for dispersing amino-modified double walled nanotubes (DWNT-NH2) in epoxy matrix. From relative visual examination, high power bath ultrasonication proved to be the best, whereas, low power bath ultrasonication resulted in the maximum inhomogeneous distribution of nanotubes in epoxy.
A New Software Framework for Fatigue Life Prediction of Composite Materials under Irregular Loading
Authors: Vassilopoulos Anastasios P.
Published: January 2019

A new software framework for fatigue life prediction of composite materials under irregular loading is presented herein. The entire work is based on a well established methodology for the life prediction of GRP laminates under variable amplitude complex stress states. The process consists of the sequential execution of four main tasks, each one of which copes with a single subproblem in a straight forward manner. The aim of this on-going work is to create a generic software framework that will enable rapid prototyping of various life prediction schemes. Based on the software design, a software library is under development. In the current paper, the software framework is analytically presented. Two different modules are prepared for the first task of the entire methodology. Cycle counting of two different variable amplitude spectra is performed by rainflow counting technique and by simple range-mean technique. Results of both analyses are then processed by routines that solve subsequent steps of the entire methodology in order to predict time up to failure of the material system under consideration, a [0/(±45)2/0]T multidirectional laminate. Theoretical predictions are plotted against experimental data for comparison, and pros and cons of each one of the cycle counting algorithms are discussed.
Characterization of Mold Filling in Vacuum Infusion Process
Authors: Song Young Seok
Published: January 2019

A study on mold filling in vacuum infusion process was carried out analytically. Three different compaction models were used to describe compaction behaviour of preforms. New analytic solutions were proposed for fibre volume fraction and pressure distributions, and an effective permeability was defined based on the solutions. In this study, the closed form equations introduced by Lopatnikov et al. [1] were modified to consider the preform compaction behaviour more exactly and the results of the modified equations were employed in an effort to verify the proposed analytic model. It was found that the very different pressure and fibre volume fraction profiles were developed during the resin infusion depending on the compaction behaviour of the preforms.
Novel Semicrystalline Thermoplastic R-Bapb Type Polyimide Matrix Reinforced by Graphite Nanoplatelets and Carbon Nanoparticles
Authors: Vladimir Yudin E. , Joshua Otaigbe U. , Lawrence Drzal T. , Valentin Svetlichnyi M.
Published: January 2019

A new semicrystalline polyimide, based on 1.3-bis-(3,3′,4,4′-dicarboxyphenoxy)benzene (R) and 4,4′-bis-(4-aminophenoxy)biphenyl (BAPB), was modified by exfoliated graphite nanoplatelets of different shape, sizes and structure. This R-BAPB type polyimide, with a molecular weight Mw = 30000 g/mol has a low melting temperature of 320°C and a melt zero shear viscosity of about 1000 Pa s at 340°C, making it possible to mix it with particulates using classical melt-blending technology. By using calorimetric and rheological measurements, this study reports a dramatic crystal nucleating effect of the polyimide caused by the special nanographite platelets. In addition, the study shows that classical melt blending of R-BAPB type PI with exfoliated graphite nanoplatelets can be used to prepare useful polyimide nanocomposites with the added benefit of possibly accelerating the crystallization process of the polyimide matrix. Further, it was observed that the time of crystallization at 300°C for the nanocomposites filled with 5 wt% nanographite platelets was about 10 ± 5 minutes, a value corresponding to one-half that of the unfilled R-BAPB type PI matrix.
Experimental and Numerical Investigation on Optimization of Clamped Composite Columns: By the Example of Cedar and Oak
Authors: Pekbey Yeliz , Ozdamar Aydogan , Sayman Onur
Published: January 2019

In this study, the problem of finding the shape of the strongest column which has the largest fundamental buckling load with equal length and volume for the clamped–clamped ends was purposed. It was also proved that the solutions of Tadjbakhsk & Keller (1962) and Olhoff & Rasmussen (1977)-Masur (1984) were not optimum for columns with clamped ends. Then, true solution was obtained from Masur's analytical bimodal solution for clamped-clamped case by considering the crushing criteria. To test the accuracy of new optimized columns with clamped ends, both experimental and numerical studies were carried out. In this study, natural composite materials such as cedar and oak with variable circular cross-sections were used. Results of the optimum model proposed in this study were in agreement with results obtained by experimental data and numerical results.
Fabrication and Properties of Aluminum-Containing Silicon Carbide Fibres
Authors: Yu Yuxi
Published: January 2019

By introducing hetero-element aluminum into ceramic precursor and then sintering, polycrystalline, stoichiometric SiC fibres can be prepared. Two types of aluminum-containing SiC fibres were fabricated by the use of aluminum-containing polycarbosilane (Al-PCS). The air-cured Al-PCS fibres were pyrolyzed in inert gas up to 13 50 °C to obtain SiC(OAl) fibres, which were converted into SiC(Al) fibres by heating in argon up to 1800 °C. The properties and performances of SiC(OAl) and SiC(Al) fibres were studied by chemical element analysis, scanning electron microscopy (SEM), X-ray diffraction (XRD), tensile strength test, heat resistance and creep resistance. These results show SiC(Al) are polycrystalline SiC fibres, have a near stoichiometric composition. The tensile strength, Young's modulus and diameter of the SiC(OAl) fibres are 2.6 GPa, 210 GPa, 12 μm, respectively. The tensile strength, Young's modulus and diameter of the SiC(Al) fibres are 2.1 GPa, 405 GPa, 10 μm, respectively. The SiC(Al) fibres have higher thermal stability, and better creep resistance than the SiC(OAl), the Nicalon and the Hi-Nicalon fibres.
New Polymeric Additives for Allowing Photoelectric Sensing of Plastics during Manufacturing
Authors: Carotenuto G. , Nadal M.L. , Repetto P. , Perlo P. , Ambrosio L. , Nicolais L.
Published: January 2019

Metallic mercaptides are inert organic compounds (i.e., Mex( SR) y) that can be used to make thermoplastic polymers high luminescent to UV-light. Luminescence is strictly required in polymer manufacturing since this characteristic allows detection of polymer pieces by photoelectric sensors. Luminescent Au, CdS, and ZnS nanoparticles can be generated into thermoplastics like: polystyrene, polycarbonate, poly(vinyl acetate), etc. by thermolysis of the corresponding mercaptides. PL spectra of polymeric films embedding these nanoparticles show intensive visible light emission in different spectral regions. The formation of nanoparticles was probably related to the viscous nature of reaction medium which significantly limit the growth stage.
Butt Joining of Similar & Dissimilar Pipe Material by Cold Joining Process
Authors: Ramkumar J. , Singhal A.K. , Singh Ritesh Kumar , Kumar Prashant
Published: January 2019

In this work, cold butt FRP joints were developed between two similar & dissimilar pipe materials by winding up balanced glass fabric mats in varying orientation. The glass fabric mats were wetted with controlled quantity of resin and wound circumferentially at the place of joining. The strength of the cold butt joints was determined by flexural bend test, fatigue test and internal pressure leak test. It is clear from the experiments that the FRP joint strength is almost as good as the strength of the pipe material. The mechanisms of failure are also discussed.
An Experimental Investigation on Damage Loads of Butterfly Joints in Composite Structures
Authors: Topçu Muzaffer , Altan Gürkan , Ergun Emin
Published: January 2019

This study is performed experimentally to investigate damage forces formed on glass-fibre laminated composite plates that are jointed with a component in the shape of butterfly. Pressing it into the mould in a hot press machine produced a glass fibre-epoxy composite plate. Specimens and locking parts in the shape of butterfly were cut using water jet. Experiments were performed in different values of the ratio of the end width of butterfly to the width of the specimen ( w/ b), the ratio of the middle width of butterfly to the end width of butterfly ( x/ w) and the ratio of the half-length of butterfly to the width of the specimen ( y/ b). Using these values, the effects of joint geometry parameters were evaluated. To be able to see the effect of material variations as well, the joint lock in the shape of butterfly was made up of both metal and composite materials. Although the loading capacity of the composite butterfly is lower than that of the metal butterfly, it carries loads for much longer times. Before a composite structure develops damage, damage occurred in the composite butterfly can be seen and, with the repair of the butterfly lock, the life of the composite structure can be extended.