Showing papers in "Plastics Rubber and Composites in 2011"
TL;DR: In this article, carbon black (CB) and carbon nanotubes (CNTs) filled natural rubber (NR) composites were prepared through an ultrasonic assisted latex mixing process.
Abstract: Carbon black (CB) and carbon nanotubes (CNTs) filled natural rubber (NR) composites were prepared through an ultrasonic assisted latex mixing process. Carbon nanotubes were dispersed into NR latex by ultrasonic irradiation and then the mixed latex were co‐coagulated to obtain the CNTs/NR masterbatch. The structure and properties of the composites were characterised. The results show that the ultrasonic assisted latex mixing process disperses CNTs more uniformly in the matrix than the conventional mixing methods. The well dispersed CNTs and CB exhibited a synergistic reinforcing effect. When the weight ratio of CB/CNTs was 20∶5 (parts per hundred of rubber), the mechanical properties reached the maximum. Dynamical mechanical analysis revealed that with increasing CNT contents, the elastic modulus of composites at room temperature increased, while the maximum loss tangent decreased. Dynamic rheological measurement showed the storage modulus and complex viscosity of rubber composites increased and th...
45 citations
TL;DR: A procedure for preparing polyamide-6 (PA-6) reinforced with cellulose nanofibres was described in this paper, where cellulose was obtained from flax and micro-crystalline cellulose (MCC) using combinations of acid hydrolysis, ball milling and ultrasound, then characterised by transmission electron microscopy (TEM) in order to determine their size and geometry.
Abstract: A procedure is described for preparing polyamide-6 (PA-6) reinforced with cellulose nanofibres. The cellulose nanofibres were obtained from flax and microcrystalline cellulose (MCC) using combinations of acid hydrolysis, ball milling and ultrasound, then characterised by transmission electron microscopy (TEM) in order to determine their size and geometry. The nanofibres produced from the different feedstock sources were of a similar order with lengths ranging from 21 to 300 nm and diameters between 2 and 22 nm. PA-6 nanocomposite films were subsequently prepared from these nanofibres using a solution casting technique. Their chemical and physical structure was analysed using Fourier transform infrared analysis (FTIR) and TEM. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were also applied to compare their thermal properties with unfilled polymer. Dynamic mechanical thermal analysis and tensile measurements demonstrated a significant enhancement in mechanical properti...
40 citations
TL;DR: In this article, two different grades of polyetheretherketone were used for in-house manufacturing of unidirectional carbon fiber reinforced thermoplastic composite tapes, which were then used for compression molding and tested.
Abstract: Processing of unidirectional (UD) carbon fibre reinforced thermoplastic composites using a laboratory scale modular composite line was investigated. Thin continuous tapes were manufactured from a 12k carbon fibre tow via wet impregnation impregnated using a slurry based polymer suspension. Hardware design as well as processing parameters influencing the tape quality and the fibre volume content of the resulting tapes, is discussed. Two different grades of polyetheretherketone were used for in‐house manufacturing of UD carbon fibre reinforced composite tapes. Laminates were prepared from the manufactured tapes via compression moulding and tested. Results from short beam strength, flexural and compression tests show that the properties of the manufactured composites match the properties of commercially available aromatic polymer composites (APC2). The flexibility of the process is demonstrated, showing that it is also possible to manufacture unidirectional carbon fibre reinforced polyvinylidene fluo...
36 citations
TL;DR: In this article, a mixture of acetic acid and acetone (1∶1) was used as an solvent to prepare random and aligned cellulose fibres by electrospinning.
Abstract: The goal of this work was to prepare random and aligned cellulose fibres by electrospinning. Cellulose acetate (CA) was used as a matrix and a mixture of acetic acid and acetone (1∶1) was used as an solvent. Cellulose nanowhiskers (CNWs) with different concentrations (0–5 wt‐%) were used as reinforcement. Microscopy studies showed fibres with smooth surfaces, different morphologies and diameters ranging between 200 and 3300 nm. It was found that the fibre diameters decreased with increased CNW contents. The microscopy studies also indicated well aligned fibres. Results from dynamic mechanical thermal analysis indicated improved mechanical properties with the addition of CNWs. The storage modulus of electrospun CA fibres increased from 81 to 825 MPa for fibres with 1 wt‐% CNW at room temperature. X‐ray analysis showed that the electrospun CA fibres had a crystalline nature and that there was no significant change in crystallinity with the addition of CNWs.
35 citations
TL;DR: The authors reviewed recent work on composite materials based on recycled thermoplastics and glass fibres (GFs) and found that GFs are one of the most cost-effective ways of reinforcing recycled polymers, as testified by several patents and commercial products which appeared in the last decade.
Abstract: The purpose of this paper is to review recent work on composite materials based on recycled thermoplastics and glass fibres (GFs) The high collection and separation cost of plastics waste, and the legislative push to increase recycling rates, require the inclusion of increasing proportions of low-quality plastic waste into recycled products A robust method for upgrading mixed plastics recyclates is the incorporation of fillers and reinforcements In particular, addition of chopped GF can lead to material systems with more favourable and consistent sets of mechanical properties Provided a good interfacial adhesion is achieved, the key structural properties of the composite (stiffness and strength) are mainly dictated by the reinforcement Therefore, a wide range of polymers, including blends, are accessible for recycling into semistructural products Glass fibres are one of the most cost-effective ways of reinforcing recycled polymers, as testified by several patents and commercial products which appeared in the last decade
34 citations
TL;DR: In this paper, the effect of refining and fractionation of wood fibres on fiber morphology and biocomposite properties was determined, and two different fibre fractions with distinct fibre properties were obtained by fractionation, and the use of a long fibre fraction provided improved mechanical properties for composites.
Abstract: In the study, the effect of refining and fractionation of wood fibres on fibre morphology and biocomposite properties was determined. Kraft pine pulp and thermomechanical pulp were selected for the fibre treatments. Effects of physical treatment on fibre morphology were analysed with a fibre analyser and microscopy techniques. For the composites, polylactic acid was used as a polymer matrix. Composites were produced by melt processing to a fibre content of 30 wt‐%, and the mechanical properties of the injection moulded biocomposites were investigated. In general, thermomechanical pulp fibres improved the mechanical properties of polylactic acid more than pine pulp fibres did. Two different fibre fractions with distinct fibre properties were obtained by fractionation, and the use of a long fibre fraction provided improved mechanical properties for composites. The refining of pine pulp led to clear fibrillation of the fibre surface, but it had a negative effect on the mechanical properties of biocomposites.
28 citations
TL;DR: In this article, the use of non-metallic materials in piping for the transport of oilfield fluids, onshore and offshore, is discussed, and uses of both thermoplastics and composites in several types of pipework are discussed.
Abstract: This paper relates to the expanding use of non-metallic materials in piping for the transport of oilfield fluids, onshore and offshore. Qualification processes for thermoplastic and composite pipework all involve long term stress rupture tests to establish a relationship between pressure and time to failure. These qualification tests are needed to account for particular long term failure process that occur in non-metallics, and are essential to the successful application of these materials. Uses of both thermoplastics and composites in several types of pipework are discussed. These include fibreglass pipe, spoolable thermosets, reinforced thermoplastic pipe, flexible risers, rigid risers and, finally, repair and rehabilitation.
27 citations
TL;DR: In this paper, a series of structural capacitor materials made from carbon fiber reinforced polymers have been developed, manufactured and tested, and the structural capacitor multifunctional performance was characterised measuring capacitance, dielectric strength and tearing force.
Abstract: In this paper, an approach towards realising novel multifunctional polymer composites is presented. A series of structural capacitor materials made from carbon fibre reinforced polymers have been developed, manufactured and tested. The structural capacitor materials were made from carbon fibre epoxy prepreg woven lamina separated by a polymer film dielectric separator. The structural capacitor multifunctional performance was characterised measuring capacitance, dielectric strength and tearing force. The developed structural carbon fibre reinforced polymer (CFRP) capacitor designs employing polymer film dielectrics (PA, PC and PET) offer remarkable multifunctional potential.
27 citations
TL;DR: In this paper, the mechanical and thermal properties of a proprietary blend of recycled polymers with a range of different fillers were investigated, and the effect varied with the aspect ratio of the filler and the mode of loading.
Abstract: This paper is concerned with the formulation of composite materials for structural or semistructural applications using thermoplastic polymer waste. The mechanical and thermal properties of a proprietary blend of recycled polymers with a range of different fillers were investigated. The effect varied with the aspect ratio of the filler and the mode of loading. Spherical calcium carbonate gave a marginal improvement in modulus. Plate-like mica produced a significant increase in modulus without reduction in strength. Glass fibres caused a significant increase in modulus and strength while decreasing the linear coefficient of thermal expansion. Hybrid systems containing glass fibre and a lower aspect ratio filler were also investigated to obtain a material system which combines high properties and reasonably low cost. It was found that addition of small quantities of mica to glass fibre reinforced blends exhibited a significant synergy in tensile strength and modulus.
27 citations
TL;DR: In this paper, a comparison of existing aerospace and newly developed ATL prepreg tapes has revealed significant differences in tack response to temperature and feed rate, and it was found that tack and the two observed failure modes are somewhat dependent upon viscoelastic stiffness.
Abstract: The automated tape laying (ATL) process has been examined and found to be sensitive to tack and stiffness properties of the prepreg material being laid. A comparison of existing aerospace and newly developed ATL prepreg tapes has revealed significant differences in tack response to temperature and feedrate. Examination of constituent resin rheology has found that tack, and the two observed failure modes, are somewhat dependent upon viscoelastic stiffness. Observation of temperature and feedrate response revealed a time–temperature superposition relationship. The Williams–Landel–Ferry equation was utilised to make predictions of the temperature response based on the feedrate response. Tack levels were stabilised over the feedrate range by making temperature adjustments. Results from the peel test, where mould conditions at lay-up were recreated, were found transferable to the ATL, where a suitable lay-up feedrate under ambient conditions was predicted.
21 citations
TL;DR: In this article, a fracture mechanics approach was used to predict fatigue failure in rubber or elastomer components using a finite element analysis technique that calculates the strain energy release rate for cracks introduced into bonded rubber components.
Abstract: Earlier work has shown that a fracture mechanics approach can predict fatigue failure in rubber or elastomer components using a finite element analysis technique that calculates the strain energy release rate for cracks introduced into bonded rubber components. This paper extends this previous work to examine real fatigue measurements made at both room temperature and 70±1°C in both tension and shear using a cylindrical rubber to metal bonded component. This component generated fatigue failures not only in the bulk of the component but also at the rubber to metal bond interface. The fatigue crack growth characteristics were measured independently using a pure shear crack test piece. Using this independent crack growth data and an accurate estimate for the initial flaw size allowed the fatigue life to be calculated. This fracture mechanics approach predicted the crack growth rates well at both room temperature and 70±1°C.
TL;DR: In this article, the authors investigated the relationship between physical aging and embrittlement of polyvinyl chloride (uPVC) pipes using instrumented falling weight impact tests and found that a minor increase in transition temperature was observed for the water pipe grade with aging.
Abstract: Most failures of unplasticised poly(vinyl chloride) (uPVC) pipes used in the Dutch gas distribution network originate from third party damage. Brittle pipes should therefore be replaced to ensure safe operation of the network. In this study, the relation between physical aging and embrittlement of uPVC is investigated using instrumented falling weight impact tests. The ductile to brittle transition temperature was first measured for a water pipe grade uPVC at different stages of aging. As a hypothesis, a critical stress criterion is proposed above which failure is brittle. The evolution of the ductile to brittle transition temperature that followed from the use of this hypothesis and a model for the polymer yield stress agrees qualitatively with the experimental data. A minor increase in transition temperature was observed for the water pipe grade with aging. Applying the same hypothesis to a uPVC gas pipe grade shows a more pronounced influence of physical aging.
TL;DR: In this article, the effect of wood moisture content on the wood particle size and whether the drying process could be carried out in the same step was investigated using optical fiber analysis and microscopical methods were used to examine the microstructure of wood particles.
Abstract: Wood chips were used as raw material in extrusion of wood–plastic composites. Wood–plastic composites with ∼50 wt‐% wood content were manufactured by using two different compounding methods. Dried and undried wood chips were used to investigate the effect of wood moisture content on the wood particle size and whether the drying process could be carried out in the same step. Wood particle properties were measured using optical fibre analysis. Microscopical methods were used to examine the microstructure of wood particles. Furthermore, the prepared composites’ mechanical properties were studied. The particle size of wood chips was significantly reduced during extrusion in both processing methods. The undried wood chips had higher aspect ratios in comparison with the dried wood chips after extrusion. Despite the higher aspect ratio, the mechanical properties of composites manufactured with undried wood chips were not better than the properties of composites with dried wood chips.
TL;DR: In this paper, the reliability and effectiveness of innovative non-destructive techniques for damage characterisation and evaluation of aerospace materials and structures is investigated. Infrared thermography (IrT) was used with the aim of assessing the integrity of bonded repair on aluminium substrates.
Abstract: The present study is concerned with the reliability and effectiveness of innovative non-destructive techniques for damage characterisation and evaluation of aerospace materials and structures Infrared thermography (IrT) was used with the aim of assessing the integrity of bonded repair on aluminium substrates For this purpose, artificial damage of various dimensions was introduced in composite laminates These defects were successfully monitored with IrT using different imaging techniques IrT was also employed for the online monitoring of the loaded structure The real time evolution of progressive debonding owing to fatigue loading was monitored No external thermal stimulation was necessary as the cyclic loading provided thermal excitation on the system The experimental results provided evidence that the innovative technique was capable of qualitatively and quantitatively assessing the integrity of patched repairs In other words, this technique can be efficiently employed for damage identification and quantification
TL;DR: In this article, 30 mass-% basalt fiber and 0·5-2 mass-wall carbon nanotube reinforced polyamide 6 hybrid systems were prepared by extrusion and injection molding.
Abstract: In this study, 30 mass-% basalt fibre and 0·5–2 mass-% multiwall carbon nanotube (MWCNT) reinforced polyamide 6 hybrid systems were prepared by extrusion and injection moulding. The effect of nanotube content on the mechanical properties was investigated by tensile and flexural tests. The results showed that the combination of macroscopic and nanosized reinforcements improved the mechanical properties significantly, and synergetic effects can also be observed. Good dispersion of the MWCNT was proven by transmission and scanning electron microscopy.
TL;DR: In this article, the motion of particles through a system of permeable fiber bundles is considered and the system is discretised with Voronoi diagrams and the dissipation rate of energy is minimised with respect to the stream function in a system with periodic boundary conditions.
Abstract: The motion of particles through a system of permeable fibre bundles is considered. The system is discretisised with Voronoi diagrams and the dissipation rate of energy is minimised with respect to the stream function in a system with periodic boundary conditions. The flow of the particles is in the transversal direction to the fibre bundles and the particles are hindered to move out of the plane allowing for two‐dimensional calculations. The motion of particles is assumed to be slow with respect to the flowrate so that particles are driven by the Stokesian force for stationary particles. In this case, the flow distribution is essentially dependent on the particle configuration and strictly follows the motion of particles. When testing different sizes of the particles, it is shown that there is a qualitative agreement between model and experiments previously performed. In particular, stationary flow leads to particle depositions in front of the fibre bundles and small particles move into the fibre bundles ...
TL;DR: In this article, two different methods have been investigated for optimising the preparation of hydrogenated acrylonitrile butadiene rubber/clay nanocomposites, and the influence of organoclays on permeability has been studied.
Abstract: In this research, two different methods have been investigated for optimising the preparation of hydrogenated acrylonitrile butadiene rubber/clay nanocomposites. Commercially available organoclay (Cloisite 20A) has been considered for the preparation of rubber nanocomposites. A detailed analysis has been made to investigate the morphological structure and mechanical behaviour at room temperature and at elevated temperature. Also the influence of organoclays on permeability has been studied. Structural analysis indicates very good dispersion for a low loading of 5 parts per hundred (phr) amount of nanoclays. Significant improvements in mechanical properties have been observed with the addition of organoclays at both room and elevated temperatures. Even with the low level of addition of nanoclays, there was a remarkable reduction in permeability.
TL;DR: In this paper, thermoplastic vulcanisates (TPVs) based on ethylene vinyl acetate copolymer (EVA)/styrene butadiene rubber (SBR) blends were prepared by dynamic vulcanisation.
Abstract: In this study, thermoplastic vulcanisates (TPVs) based on ethylene vinyl acetate copolymer (EVA)/styrene butadiene rubber (SBR) blends were prepared by dynamic vulcanisation. The increase in EVA content in blends contributes to the increase in tearing strength and hardness properties, while tensile strength and elongation at break reach a maximum at 40 wt-% of EVA content. The stress–strain curves of EVA/SBR TPVs show obvious elastomer behaviour. The morphological study of the fracture surface of EVA/SBR TPVs reveals the quite smooth surface, which was caused by the strong recovery effect of vulcanised SBR. The phase structure shows that the SBR vulcanisate particles are dispersed finely in TPVs.
TL;DR: In this article, a new fully biobased thermoset composite with aligned flax fibre textiles was developed using a bioderived matrix resin, which showed good mechanical performance and excellent fire resistance.
Abstract: The development of aligned natural fibre reinforced composites utilising biobased thermosets is an essential step towards the manufacture of ecofriendly composite systems. In many cases, the matrix system, which is usually oil based in nature, is disregarded. Therefore, a new fully biobased thermoset composite with aligned flax fibre textiles was developed using a bioderived matrix resin. The thermoset furan resin has recently received interest due to its good environmental profile containing no petrochemicals, using water as solvent and biomass as raw material. The new resin also shows good mechanical performance and excellent fire resistance. In the present study, aligned natural fibre textiles, randomly oriented natural fibre textiles and glass fibre textiles have been hand laid up and impregnated with the furan resin to form prepregs. After precuring, the prepregs were consolidated into composites using an industrial scale compression moulding machine, and their material properties were analys...
TL;DR: The offset sandwich mount design is often considered for application on rail vehicles as discussed by the authors, and a design concept, balancing the internal moments in different layers of the component, is proposed for this type of the product.
Abstract: The offset sandwich mount design is often considered for application on rail vehicles. This paper reviews several different aspects of the product. These include the more commonly evaluated benefits of higher order material properties, the product design and its associated geometry optimisation. It is shown that a large error occurs when calculating the rubber shrinkage using a constant coefficient in the moulding process. Hence a postulation is made to link the compressibility with temperature change, which leads to the accuracy increased by fivefold against the measurement. A design concept, balancing the internal moments in different layers of the component, is proposed for this type of the product. Finally the paper suggests an effective stress criterion which takes into account all stress components when considering the complications associated with multiaxial loadings. The objective is to identify which can be considered the best approach for crack initiation evaluation.
TL;DR: In this paper, a new process for the production of carbon black master batches with enhanced mechanical properties has been developed, and the competence of the new technique was established by comparing the characteristics of the carbon black incorporated natural rubber (NR) by mill mixing process (control).
Abstract: A new process for the production of carbon black master batches with enhanced mechanical properties has been developed. The unit operations in the process are the preparation of carbon black slurry in the presence of a suitable surfactant, addition of the slurry to the fresh natural rubber (NR) latex under stirring, coagulation of the mixture by the addition of acid, dewatering of the coagulum and drying to obtain carbon black incorporated NR. The competence of the new technique was established by comparing the characteristics of the carbon black incorporated NR by mill mixing process (control). The mechanical properties of the vulcanisates obtained from the latex stage and the dry rubber incorporated mixes were evaluated. The effect of aging on the mechanical properties was also discussed. The carbon black filled mixes prepared by the new process showed better cure characteristics as compared to the dry rubber incorporated mix. The mechanical properties, like tensile strength, modulus, tear strength and ...
TL;DR: In this article, a highly integrated redesign of a generic wingbox section was made and a low cost, room temperature, open mould (non-autoclave) resin infusion production process was developed using a collaborative research project aimed at achieving significant cost reductions in the manufacturing of advanced composites for aerospace applications.
Abstract: Advanced fibre reinforced composites are already extensively used in modern aircraft, due to advantages offered for weight reduction, durability, mechanical performance, etc. However, composite structures in aerospace are usually not associated with low costs. Traditional design methods are very time consuming, materials and production processes very expensive as well as labour intensive. To make full use of the potential of composites, a complete redesign of aircraft structures is necessary. Owing to qualification and certification procedures the introduction of low cost materials or low cost production processes is hindered. The current paper describes the results of a collaborative research project aimed at achieving significant cost reductions in the manufacturing of advanced composites for aerospace applications. A highly integrated redesign of a generic wingbox section was made and a low cost, room temperature, open mould (non‐autoclave) resin infusion production process was developed using ...
TL;DR: A series of waterborne polyurethane/inorganic (WPU/TiO2) hybrid composites were synthesized by a sol-gel process on the basis of isophorone diisocyanate, polyether polyol (GE-210), dimethylolpropionic acid, tetrabutyl titanate (TBT), and 3-glycidyloxypropyl trimethoxysilane as a coupling agent as discussed by the authors.
Abstract: A series of waterborne polyurethane/inorganic (WPU/TiO2) hybrid composites were synthesised by a sol–gel process on the basis of isophorone diisocyanate, polyether polyol (GE-210), dimethylolpropionic acid, tetrabutyl titanate (TBT) and 3-glycidyloxypropyl trimethoxysilane as a coupling agent. The physical properties of the WPU and WPU/TiO2 dispersions and hybrids were measured. Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, atomic force microscopy and X-ray diffraction were used to assess the fracture surface morphology and the dispersions of the WPU/TiO2 hybrids. The scanning electron microscopy, transmission electron microscopy and atomic force microscopy results showed that the TiO2 particles were dispersed homogeneously in the WPU matrix in nanoscale. The prepared hybrids showed good thermal stability and mechanical properties in comparison with pure WPU and showed tunable transparence with the TBT fraction in the film. Through suitable adjust...
TL;DR: In this article, an experimental and theoretical investigation on the effects of carbon nanotube (CNT) integration within neat epoxy resin (nanocomposites) and a carbon fabric-epoxy composite (multiscale composites).
Abstract: This research presents an experimental and theoretical investigation on the effects of carbon nanotube (CNT) integration within neat epoxy resin (nanocomposites) and a carbon fabric–epoxy composite (multiscale composites). An approach is presented for the prediction of mechanical properties of multiscale composites. This approach combines woven fibre micromechanics (MESOTEX) with the Mori-Tanaka model which was used for the prediction of mechanical properties of nanocomposites in this research. Nanocomposite and multiscale composite samples were manufactured using cast moulding, resin infusion, and hand lay-up process. The CNT concentrations in the composite samples were from 0 to 5 wt-%. The samples were characterised using tensile, shear and flexural tests. The discrepancy between the theoretical predictions and the experimental observations was hypothesised to be due to dispersion and bonding issues and SEM images are presented in support of the hypothesis.
TL;DR: In this paper, the authors studied the flow behavior of a polymer melt in the conveying region of an intermeshing corotating twin screw extruder using the combination of mixed finite element and fictitious domain method.
Abstract: The flow behaviour of a polymer melt in the conveying region of an intermeshing corotating twin screw extruder was studied using the combination of mixed finite element and fictitious domain method. The model was a combination of the governing equations of continuity and momentum with Carreau rheological model in a three-dimensional Cartesian coordinate system. The equations were solved by the use of a mixed Galerkin finite element technique. The Picard’s iterative procedure was used to handle the non-linear nature of the derived equations. The particle tracking technique was used to obtain residence time distribution and analyse distributive mixing in conveying region. The shear rate distribution was investigated as a criterion for dispersive mixing. The applicability of this model was verified by the comparison of experimentally measured pressure and simulation results for high density polyethylene melt. This comparison shows that there is a good adequacy between experimental data and model pred...
TL;DR: In this article, the motion of dispersed carbon nanotubes during impregnation of dual scale fabrics in composites manufacturing is modeled using numerical simulations and analysis and numerical simulations are used to show that the distribution and orientation of carbon fiber is mainly deterministic on mesoscale, while typically random on microscale.
Abstract: Interest is growing in the development of hierarchical composites, in which nanoscale particles are used alongside the traditional microscale reinforcing fibres. To produce high quality multiscale materials, knowledge of mechanisms governing nanofibre distribution and orientation is crucial. In this work, analysis and numerical simulations are used to model the motion of dispersed carbon nanotubes during impregnation of dual scale fabrics in composites manufacturing. Results suggest that nanofibre displacement and orientation is mainly deterministic on mesoscale, while typically random on microscale. The randomising Brownian torque may still influence the motion and trigger the fibre to make 180° rotations in the former, however, when acting together with the fluid shear. Fibre deposition may lead to a total blockage of the flow within the microchannels, whereas only minor deposition is expected in the mesochannels.
TL;DR: The effects of incorporating different coupling agents on the physical properties and morphology of the composites were studied in this paper, where extrusion technology and injection molding techniques were used to prepare standard tensile and impact test pieces.
Abstract: Composites of poly (lactic acid) (PLA)/wheat starch and PLA/wheat starch/methyldiphenyldiisocyanate, were prepared and characterised in this study. The effects of incorporating different coupling agents on the physical properties and morphology of the composites were studied. Extrusion technology and injection moulding techniques were used to prepare standard tensile and impact test pieces. Tensometry was used to investigate the tensile properties of the composites and impact testing using falling weight technique was used to investigate impact strength. To investigate the thermal behaviour of the composites, differential scanning calorimetry was employed. Water absorption properties of the composites were also investigated. Scanning electron microscopy was used to investigate the morphology of the composites. Starch can be incorporated in a PLA matrix at 10% level without difficulty in processing by extrusion followed by injection moulding to make shaped mouldings in the presence of MDI. With 10% wheat starch and 2% MDI, blends of wheat starch/PLA can reach the tensile strength, elongation, impact strength properties of raw PLA. In the presence of 2% MDI and 10% glycerol, blends of PLA and starch make an entirely flexible material.
TL;DR: The ultimate elastic wall stress (UEWS) test as discussed by the authors is used to identify, from the pressure-strain response, a pressure level below which damage growth is either negligible or at least sufficiently low to avoid failure within the design life.
Abstract: Procedures for qualifying fibreglass pipes are discussed here in relation to industry needs. The ultimate elastic wall stress (UEWS) test appears to provide an efficient means of rating pressure pipe, and indeed vessels, for the case where weepage failure occurs resulting from the accumulation of matrix cracks. The principle behind the UEWS test is to identify, from the pressure–strain response, a pressure level below which damage growth is either negligible or at least sufficiently low to avoid failure within the design life. The version of the UEWS test most often used involves the application of groups of 10 one-minute pressure cycles at increasing pressure values, recording the hoop or axial strain. The onset of non-linearity in the pressure–strain relationship can be accurately determined and enables a safe long term pressure level to be identified. The UEWS test appears to provide a desirable alternative to the currently used procedure laid down in ISO 14692, which involves an expensive series of long term constant pressure tests, as described in ASTM 2992, running for a period in excess of 10 000 h. It is shown here that the UEWS test reflects the cyclic fatigue behaviour of fibreglass pipe, but further work on the relationship between cyclic and static behaviour would be desirable. It has been shown that a Miner’s law approach is effective in modelling damage due to combined static and cyclic effects, and that damage can be directly related to matrix crack growth. This approach could form the basis of a future procedure for describing lifetime behaviour of glass reinforced epoxy pipes under any required combination of static, fatigue, hydrostatic and non-hydrostatic (multiaxial) loading.
TL;DR: In this paper, statistical methodology analysis of variance (ANOVA) and linear regression were applied to predict the mechanical performance of the styrene-butadiene rubber (SBR) containing a residue of the elastomer originated from shoe sole cuttings.
Abstract: Statistical methodology analysis of variance (ANOVA) and linear regression were applied to predict the mechanical performance of the styrene-butadiene rubber (SBR) containing a residue of the elastomer originated from shoe sole cuttings. A basic formulation was developed to which three different contents of SBR residue were added. Compositions were also prepared with three different concentrations of silica to compare the performance of the filler, as well as to verify the existence of any interaction between the components. Using of ANOVA have permitted the validation of the results of the mechanical properties stress rupture, elongation and tearing resistance. Linear regression analysis demonstrated that silica and SBR residue concentrations have an effect on the mechanical properties and this relationship can be expressed through behaviour models, which can be represented graphically. It was possible to predict a mechanical behaviour model including intermediate concentrations not experimentally measured within the observed limits of the sample.
TL;DR: In this article, the fracture behavior of composite matrixes was evaluated in terms of indentation cracks using both optical and scanning electron microscopies in microstructural observations and fracture mechanism qualification.
Abstract: The main goal of the work was to prepare a cost effective and simple to preform high temperature matrix for composite materials. To fulfil expectations, it was necessary to optimise the design of the composite to have an optimal fibre–matrix interaction. A number of modified polysiloxane resins were studied in various steps of heat treatment. This contribution deals with changes in the behaviour of the matrix as a stay alone material. This knowledge enables the optimisation of composite properties. A fully instrumented indentation technique for the determination of reliable parameters characterising the microstructural changes was used. The fracture behaviour of the prepared composite matrixes was evaluated in terms of indentation cracks. Both optical and scanning electron microscopies were employed in microstructural observations and fracture mechanism qualification.