SwePub - sökning: L773:1359 835X OR L773:1878 58...

Numrering	Referens	Omslagsbild	Hitta
1.	Andersons, J., et al. (författare) Estimation of the tensile strength of an oriented flax fiber-reinforced polymer composite 2011 Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 42:9, s. 1229-1235 Tidskriftsartikel (refereegranskat)abstract Unidirectional orientation of natural fibers in a polymer composite ensures the highest efficiency of reinforcement. Flax fiber reinforcement is discontinuous due to limited fiber length and heterogeneous due to the presence of elementary fibers and their bundles. In order to assess the upper limit of tensile strength of such slightly misoriented, nominally UD natural fiber composite, a statistical strength model of continuous UD fiber reinforced composites is applied. It is found that the experimental strength of UD flax composites, produced from rovings or manually aligned fibers, approaches the theoretical limit only at relatively low fiber volume fraction ca. 0.2, being markedly below it at higher fiber content.
2.	Ansari, Farhan, et al. (författare) Cellulose nanofiber network for moisture stable, strong and ductile biocomposites and increased epoxy curing rate 2014 Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 63, s. 35-44 Tidskriftsartikel (refereegranskat)abstract Nanocomposites with high volume fractions (15-50 vol%) of nanofibrillated cellulose (NFC) were prepared by impregnation of a wet porous NFC network with acetone/epoxy/amine solution. Infrared spectroscopy studies revealed a significant increase in curing rate of epoxy (EP) in the presence of NFC. The NFC provided extremely efficient reinforcement (at 15 vol%: 3-fold increase in stiffness and strength to 5.9 GPa and 109 MPa, respectively), and ductility was preserved. Besides, the glass transition temperature increased with increasing NFC content (from 68 degrees C in neat epoxy to 86 degrees C in 50 vol% composite). Most interestingly, the moisture sorption values were low and even comparable to neat epoxy for the 15 vol% NFC/EP. This material did not change mechanical properties at increased relative humidity (90% RH). Thus, NFC/EP provides a unique combination of high strength, modulus, ductility, and moisture stability for a cellulose-based biocomposite. Effects from nanostructural and interfacial tailoring are discussed.
3.	Baghaei, Behnaz, et al. (författare) Manufacture and characterisation of thermoplastic composites made from PLA/hemp co-wrapped hybrid yarn prepregs 2013 Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier Ltd. - 1359-835X .- 1878-5840. ; 50, s. 93-101 Tidskriftsartikel (refereegranskat)abstract PLA/hemp co-wrapped hybrid yarns were produced by wrapping PLA filaments around a core composed of a 400 twists/m and 25 tex hemp yarn (Cannabis Sativa L) and 18 tex PLA filaments. The hemp content varied between 10 and 45 mass%, and the PLA wrapping density around the core was 150 and 250 turns/metre. Composites were fabricated by compression moulding of 0/90 bidirectional prepregs, and characterised regarding porosity, mechanical strength and thermal properties by dynamic mechanical thermal analysis (DMTA) and differential scanning calorimetry (DSC). Mechanical tests showed that the tensile and flexural strengths of the composites markedly increased with the fibre content, reaching 59.3 and 124.2 MPa when reinforced with 45 mass% fibre, which is approximately 2 and 3.3 times higher compared to neat PLA. Impact strength of the composites decreased initially up to 10 mass% fibre; while higher fibre loading (up to 45 mass%) caused an increase in impact strength up to 26.3 KJ/m2, an improvement of about 2 times higher compared to neat PLA. The composites made from the hybrid yarn with a wrapping density of 250 turns/metre showed improvements in mechanical properties, due to the lower porosity. The fractured surfaces were investigated by scanning electron microscopy to study the fibre/matrix interface.
4.	Baghaei, Behnaz, et al. (författare) Novel aligned hemp ﬁbre reinforcement for structural biocomposites : Porosity, water absorption, mechanical performances and viscoelastic behaviour 2014 Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier. - 1359-835X .- 1878-5840. ; 61, s. 1-12 Tidskriftsartikel (refereegranskat)abstract This paper examines the thermal and mechanical behaviour as well as moisture absorption of aligned hemp composites using hemp/PLA wrap spun yarns. Uniaxial composites were fabricated with 30 mass% hemp using compression moulding. The properties of composites in terms of hemp fibre orientation (aligned and random), off-axis angle and alkali treatment were investigated. It was found that the testing direction influenced the mechanical properties of the composites. Compared with all the fabricated composites, the aligned alkali hemp/PLA yarn composite possessed the best mechanical properties, including tensile, flexural and impact strengths, lower porosity and water absorption. The water absorption for all composites was higher than for neat PLA, both at room temperature and 80 C. The PLA in its treated composites had higher crystallinity, which was attributed to effective heterogeneous nucleation induced by hemp. Based on SEM observation and theoretical analysis of DMTA data, there was a favourable interfacial adhesion in all composites.
5.	Butylina, Svetlana, et al. (författare) Accelerated weathering of wood-polypropylene composites containing minerals 2012 Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier. - 1359-835X .- 1878-5840. ; 43:11, s. 2087-2094 Tidskriftsartikel (refereegranskat)abstract Accelerated weathering tests were carried out on wood-polypropylene composites containing minerals. Three different mineral fillers were studied: calcium carbonate, wollastonite and talc. Colour changes were evaluated after distinct periods; the total time of exposure of the composites to UV irradiation was 2000 h. The weathering resulted in significant colour fading of the composites. The composites containing mineral fillers had higher changes of colour (lightness) than the reference composite. Scanning electron microscopy analysis revealed deterioration of the polymer surface layer in all weathered composites. Exposure of the reference composite to UV irradiation resulted in the disappearance of the polypropylene surface layer and disclosure of wood fibres, which led to a higher drop in the lignin content of this composite compared to mineral-containing composites. A substitution of part of the wood with mineral fillers resulted in decreased water absorption and thickness swelling of mineral-containing composites, compared to the reference composite. Exposure to water immersion-freeze-thaw cyclic treatment and UV irradiation led to a decrease in the Charpy impact strength of the composites, except for the composite containing talc
6.	Craven, R., et al. (författare) Delamination buckling: A finite element study with realistic delamination shapes, multiple delaminations and fibre fracture cracks 2010 Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 41:5, s. 684-692 Tidskriftsartikel (refereegranskat)abstract This paper presents a finite element model of a carbon fibre composite laminate with multiple delaminations of realistic shape and including fibre fracture cracks loaded under compression. The modelling technique is initially applied on circular and elliptical delaminations of single ply sublaminates, which are compared with existing analytical solutions. The techniques are then applied to models with multiple delaminations of realistic shape and their behaviour in buckling and post-buckling is captured. An inverse method is used to determine the stiffness reduction caused by the damage, and shows significant stiffness reduction caused by peanut shaped delaminations. When fibre fracture cracks are added, their contribution to further stiffness reduction is minimal but they have some significant effects on the buckling shapes. © 2010 Elsevier Ltd. All rights reserved.
7.	Duanmu, Jie, et al. (författare) Studies on mechanical properties of wood fiber reinforced cross-linked starch composites made from enzymatically degraded allylglycidyl ether-modified starch 2010 Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 41:10, s. 1409-1418 Tidskriftsartikel (refereegranskat)abstract In a previous work we introduced a new family of thermoset composites of softwood fiber and allylglycidyl ether modified potato starch (AGE-starch with a degree of substitution of 1.3 and 2.3) prepared by hot pressing. To improve the processability of AGE-starch with a DS = 1.3 (LDS-3) and to increase hygromechanical properties, the LDS-3 matrix has now been partially degraded by a-amylase at 45 degrees C (pH 6) for 0.5, 6 and 18 h. The study shows that already a 30 min enzymatic hydrolysis has a marked effect on the modified starch molecular weight and its thermal properties. The new composites with enzyme hydrolyzed AGE-starch, generically named D-LDS-3, showed good fiber dispersion and excellent interface between the fiber and matrix as studied by SEM. Premixes of D-LDS-3 matrix and fiber showed improved processability. The water vapor absorption was evaluated at 43.2% and 82.2% RH and the stiffness and strength properties were measured. The water uptake was shown to be reduced. The strength of neat matrix D-LDS-3-6 at ambient 68% RH reached 63 MPa and Young's modulus 3200 MPa and with 40 wt.% wood fiber reinforcement impressive 128 MPa and 4500 MPa, respectively.
8.	George, G., et al. (författare) Novel bio-commingled composites based on jute/polypylene yarns : Effect of chemical treatment on the mechanical properties 2012 Ingår i: Composites. Part A, Applied science and manufacturing. - : Pergamon. - 1359-835X .- 1878-5840. ; 43:1, s. 219-230 Tidskriftsartikel (refereegranskat)abstract This paper mainly investigates the fabrication process of jute yarn reinforced, bidirectional thermoplastic commingled composites (both untreated and treated). Commingling method was used to prepare the composites wherein the Polypropylene yarn (PP yarn) and jute yarn were wound together onto a metal plate in a particular configuration and then compression moulded. The mechanical properties of the composites prepared from chemically treated jute yarn were found to increase substantially compared to those of untreated ones. The surface morphologies of the fracture surfaces of the composites were recorded using scanning electron microscope (SEM). The SEM micrographs reveal that interfacial bonding between the treated jute yarn and the matrix has improved significantly by chemical treatments. The various chemical treatment mechanisms have been supported by FT-IR spectra. Theoretical modelling was used to predict the tensile properties and was found to be in accordance with the experimental results.
9.	George, Gejo, et al. (författare) Thermal, calorimetric and crystallisation behaviour of polypropylene/jute yarn bio-composites fabricated by commingling technique 2013 Ingår i: Composites. Part A, Applied science and manufacturing. - : Pergamon. - 1359-835X .- 1878-5840. ; 48, s. 110-120 Tidskriftsartikel (refereegranskat)abstract Commingled biocomposites based on polypropylene/jute yarns were prepared using commingling technique. The thermal and calorimetric behaviour of these commingled composites were studied with respect to fibre content and various chemical treatments. The thermal stability of the composites was found to be in between that of jute fibre and neat polypropylene (PP). Different chemical treatments increased the thermal stability of the composites due to increased interfacial adhesion between the matrix and reinforcement. Jute yarn acts as nucleating agents and favours the process of crystallisation thereby increasing the crystallisation temperature. Chemical treatments further increased the crystallisation temperature as a result of better interfacial adhesion between jute yarn and PP matrix. The close proximity of jute yarns weakens the mechanical bonds between PP molecules resulting in marginal lowering of melting temperatures. Polarized optical microscopic studies revealed the formation of transcrystalline layer around the jute fibre after 6 h.
10.	George, Gejo, et al. (författare) Viscoelastic behaviour of novel commingled biocomposites based on polypropylene/jute yarns 2012 Ingår i: Composites. Part A, Applied science and manufacturing. - : Science Direct. - 1359-835X .- 1878-5840. ; 43:6, s. 893-902 Tidskriftsartikel (refereegranskat)abstract Jute yarn reinforced polypropylene commingled composites were prepared by an environmentally benign technique called commingling method in which the matrix fibres and reinforcing fibres are intermingled together with good alignment. The dynamic mechanical properties or viscoelastic behaviour of these commingled composites were studied with reference to fibre content and various chemical treatments. The storage and loss modulus increased with fibre content where as tan δ decreased. KMnO4 and MAPP treated composites showed much higher storage and loss modulus values at all temperatures compared to untreated one. The glass transition temperature showed a marginal increasing tendency with fibre content and chemical treatments. The surface treatment mechanisms were supported by FT-IR spectra and the increase in interfacial adhesion after chemical treatments were supported by SEM images. Theoretical modelling was used to predict the values of storage modulus and tan δ and was found to be comparable with that of experimentally obtained results.
11.	Giannadakis, Konstantinos, et al. (författare) Analysis of non-linear shear stress-strain response of unidirectional GF/EP composite 2014 Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 62, s. 67-76 Tidskriftsartikel (refereegranskat)abstract Reasons for nonlinear stress-strain curves in shear of unidirectional glass fibre composite are analysed. Laminate with stacking sequence [45/-45]s is used in tensile quasi-static as well as in tensile creep and strain recovery tests to study the development of viscoelastic and viscoplastic shear strains in local coordinates of the ply. It is shown that Zapa’s integral representation of viscoplasticity is applicable for this material and methodology for parameter determination is given. Schapery’s nonlinear viscoelastic material model was used for shear response characterization and the nonlinearity parameters’ dependence on the shear stress was determined and described by fitting functions. Microdamage development is quantified by measuring axial modulus and Poisson’s ratio of the laminate. The obtained nonlinear viscoelastic, viscoplastic model with included effect of microdamage was successfully used to predict the nonlinear shear stress-strain curve in strain controlled tensile loading.
12.	Gong, Guan, et al. (författare) Tensile behavior, morphology and viscoelastic analysis of cellulose nanofiber-reinforced (CNF) polyvinyl acetate (PVAc) 2011 Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 42:9, s. 1275-1282 Tidskriftsartikel (refereegranskat)abstract Cellulose nanofiber-reinforced (CNF) polyvinyl acetate (PVAc) composites were prepared using the twin-screw extrusion technique. The influence of CNF content on nanocomposites morphology, tensile, and viscoelastic properties was studied. The tensile modulus and strength increased with increasing CNF content, being 59% and 21% higher in 10 wt% CNF composite compared to neat PVAc. The activation volume at yielding of PVAc was decreased by CNFs, indicating restricted chain mobility. The fracture surfaces of nanocomposites showed bridging of CNFs inside the micro-cracks. The storage modulus increased for all nanocomposites compared to the matrix, being more significant in the rubbery state. Also, the activation energy for the transition increased with increased CNF content. A slight shift and broadening was observed in the tan delta peak for 10 wt% CNFs composite. The creep strain of PVAc was reduced, whereas the creep elasticity and viscosity calculated from Burger’s model were increased by the addition of CNFs.
13.	Grubbström, Göran, et al. (författare) Silane-crosslinking of recycled low-density polyethylene/wood composites 2010 Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 41:5, s. 678-683 Tidskriftsartikel (refereegranskat)abstract The aim of this work was to study silane-crosslinking of recycled low-density polyethylene wood composites and its effect on composites properties. The composites were produced in a one-step twin-screw extrusion process and the silane-peroxide solution was pumped into the extruder. Degree of crosslinking, mechanical properties, short-term creep, fractured surfaces and nature of crosslinking were studied to understand the relationship between composite structure and properties. The results showed that crosslinked composite strength, toughness and creep resistance were improved compared to uncrosslinked composites. The flexural strength was doubled compared to uncrosslinked samples and the creep strain was reduced. The crosslinked composites stored under room conditions showed the highest strength, whereas storage in a sauna resulted in a higher degree of crosslinking. The Fourier transform infrared spectroscopy indicated formation of silane-bridges between wood and polyethylene, accordingly improving the interfacial adhesion between the wood and LDPE. The low concentration of peroxide in the silane-solution was shown to be a preferred composition to limit unintentional crosslinking during the process.
14.	Hallander, Per, et al. (författare) An experimental study of mechanisms behind wrinkle development during forming of composite laminates 2013 Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier. - 1359-835X .- 1878-5840. ; 50, s. 54-64 Tidskriftsartikel (refereegranskat)abstract A general problem when forming quasi-isotropic, multilayer unidirectional (UD) prepreg over a double curved geometry is out-of-plane wrinkling. The presented study aims to show the existence of compression in the laminate in a recess area that is globally under tension during forming. Further it aims to investigate the influence of compression on the out-of-plane wrinkle development.An experimental study is performed with pre-stacked UD prepreg on a forming tool with varying cross section. Investigated parameters include lay-up sequence, prepreg ply thickness, inter-ply friction and prepreg ply impregnation. Experimental evaluation is performed on the out-of-plane defect height, type, location and number. Further, measurements are performed on the outer-ply deformation in the z-direction and inside the formed component using Micro CT. The study show that compression is to some degree always developed during forming of a recess area but that the lay-up sequence has a dominant effect on the wrinkling development.
15.	Hietala, Maiju, et al. (författare) The effect of pre-softened wood chips on wood fibre aspect ratio and mechanical properties of wood-polymer composites 2011 Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 42:12, s. 2110-2116 Tidskriftsartikel (refereegranskat)abstract The objective of this work was to study the effect of chemical pre-treatment and moisture content of wood chips on the wood particle aspect ratio after compounding in a twin-screw extruder and on the mechanical properties of wood-polymer composites (WPC). Composites with 50 wt% wood content were manufactured using pre-treated and untreated wood chips. The effect of wood moisture content on composite properties was studied by using dried and undried wood chips. The mechanical properties and fracture surfaces of the composites as well as the microstructure and aspect ratio of wood particles after compounding were studied. The highest wood particle aspect ratio after extrusion was achieved by using pre-treated, undried wood chips as raw material. The chemical pre-treatment was found to enhance the defibration of wood chips as well as the mechanical properties of the composites.
16.	Jonoobi, Mehdi, et al. (författare) Thermoplastic polymer impregnation of cellulose nanofibre networks : Morphology, mechanical and optical properties 2014 Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 58, s. 30-35 Tidskriftsartikel (refereegranskat)abstract Biobased nanocomposite sheets of cellulose nanofibres (CNF) and cellulose acetate butyrate (CAB) were prepared using a resin impregnation technique. Porous nanofibre networks together with a low viscosity thermoplastic resin were the key elements in the processing. SEM images of the network before the impregnation showed high porosity and after the impregnation indicated impregnated fibre network. A significant improvement in the visible light transmittance was observed for the nanocomposite compared to the nanofibre network, which is explained on the filling of the pores with a transparent matrix. The tensile tests showed an increase of 364% and 145% for stiffness and strength respectively for nanocomposites with 60 wt.% CNF when compared to CAB. Dynamic mechanical properties showed a good interaction between the CAB and cellulose nanofibres. These results show that CAB impregnated cellulose nanofibre networks are promising biocomposite that could be used in applications where transparency and good mechanical properties are of interest.
17.	Jäger, Andreas, et al. (författare) The relation between indentation modulus, microfibril angle, and elastic properties of wood cell walls 2011 Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 42:6, s. 677-685 Tidskriftsartikel (refereegranskat)abstract Nanoindentation is a well known tool for identification of mechanical properties at the micrometer scale of materials. When applied to study wood cell walls the commonly used isotropic indentation theory is not applicable. In this study, anisotropic nanoindentation theory was employed for analyzing nanoindentation test results on wood cell walls. The influence of elastic stiffness components, microfibril angle, and cell wall composition on the indentation modulus was studied. The indentation modulus was found to depend on longitudinal, transverse, and shear modulus to a similar extent. A significant influence of the microfibril angle on the indentation modulus was observed and discussed with respect to experimental scatter and sample preparation. It is concluded, that application of anisotropic nanoindentation theory provides a tool for quantitative instead of qualitative investigation of wood cell walls, with the goal of identifying all elastic properties of the transversely isotropic cell wall from nanoindentation tests.
18.	Kaufmann, Markus, 1980-, et al. (författare) Cost/weight optimization of composite prepreg structures for best draping strategy 2010 Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier. - 1359-835X .- 1878-5840. ; 41:4, s. 464-472 Tidskriftsartikel (refereegranskat)abstract The application of hand-laid carbon fiber prepreg is very expensive from a labor perspective. Therefore the manufacturing cost should be included in the design process. In this work, we propose a novel optimization framework which contains a draping simulation in combination with a detailed cost estimation package and the calculation of the structural performance based on FE. We suggest applying the methodology in two steps. First, a draping knowledge database is generated in which combinations of seed points and reference angles are evaluated in terms of fiber angle deviation, scrap, ultrasonic cuts and material shear. Second, a cost/weight optimization framework picks the best sets of plies during the subsequent optimization. The methodology is tested by means of a curved C-spar which is designed using plain weave and unidirectional prepreg. Different objectives in the generation of the draping database lead to different design solutions.
19.	Kazemahvazi, Sohrab, et al. (författare) Residual strength of GRP laminates with multiple randomly distributed fragment impacts 2014 Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier. - 1359-835X .- 1878-5840. ; 60, s. 66-74 Tidskriftsartikel (refereegranskat)abstract The residual tensile strength of glass fibre reinforced composites with randomly distributed holes and fragment impact damages have been investigated. Experiments have been performed on large scale panels and small scale specimens. A finite element model has been developed to predict the strength of multi-axial panels with randomly distributed holes. Further, an effective analytical model has been developed using percolation theory. The model gives an estimation of the residual strength as function of removed surface area caused by the holes. It is found that if 8% of the area is removed, the residual strength is approximately 50% of the un-damaged strength.
20.	Larberg, Ylva, et al. (författare) In-plane deformation of multi-layered unidirectional thermoset prepreg - Modelling and experimental verification 2014 Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier. - 1359-835X .- 1878-5840. ; 56, s. 203-212 Tidskriftsartikel (refereegranskat)abstract Sheet forming of unidirectional prepregs is gaining increased interest as a cost efficient alternative manufacturing method. Its potential lies within the use of automatically and efficiently stacked flat prepregs, which in a second step can be formed. A successful forming requires understanding of the properties of the uncured material. Here, the in-plane deformation behaviour of two different unidirectional thermoset prepregs is investigated. Experimental measurements are performed, showing the importance of stacking sequence and its effect on the forming behaviour of stacked prepreg. Finite element models are developed, using material models calibrated from bias extension tests and interlaminar friction tests. The method developed can be used to predict the reaction force and fibre reorientation during in-plane forming of thermoset prepreg, for one of the considered material systems. Further, it enables prediction of the effect of stacking sequence, which is promising for future full-scale forming simulations.
21.	Larberg, Ylva, 1980-, et al. (författare) On the interply friction of different generations of carbon/epoxy prepreg systems 2011 Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier. - 1359-835X .- 1878-5840. ; 42:9, s. 1067-1074 Tidskriftsartikel (refereegranskat)abstract Using pre-stacked material that is formed as a first step in the manufacturing process offers reduced process cycle time for production of complex structural components. The forming is achieved by forcing layers to deform by e.g. intraply deformation and interply slippage, where the latter is the scope of this study. The prepreg-prepreg friction is experimentally determined for four unidirectional carbon/epoxy prepreg systems. The materials differ considering volume fraction of fibres, fibre stiffness and phase of thermoplastic toughener (solved or particles). The study shows large individual differences between the tested materials, where the material systems with particle tougheners seem to obey a boundary lubrication friction, while the other materials show hydrodynamically dominated friction. A large difference between the high and low friction materials, almost a factor of 10, correlates to trends seen in the herein performed surface roughness measurements. Vacuum as well as autoclave consolidated materials are tested.
22.	Loukil, Mohamed Sahbi, et al. (författare) Engineering expressions for thermo-elastic constants of laminates with high density of transverse cracks 2013 Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 48:1, s. 37-46 Tidskriftsartikel (refereegranskat)abstract Thermo-elastic constants of symmetric and balanced laminates with intralaminar cracks in 90-layers depend on the opening displacement (COD) of the crack. The COD dependence on the interaction between cracks in the same layer is studied using FEM. The COD dependence on crack density is described by interaction function in form of tanh(). This interaction function multiplied with COD of non-interactive crack is the input parameter in analytical model for thermo-elastic properties of damaged symmetric and balanced laminates. Predictions performed for cross-ply laminates with cracks in inside and in surface layers and for quasi-isotropic laminates with different position of the 90-layer are in a very good agreement with direct FEM calculations.
23.	Lundström, Staffan, et al. (författare) Bubble formation and motion in non-crimp fabrics with perturbed bundle geometry 2010 Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 41:1, s. 83-92 Tidskriftsartikel (refereegranskat)abstract The motion of the liquid front during impregnation of non-crimp fabrics has been considered by using Sethian's level set method. Particular attention is put on the creation of bubbles at the liquid front and a virtual 3D model mimicking biaxial fabrics has been built for this purpose. The saturated fluid flow is governed by the Navier-Stokes Equations and Darcy law, while capillary pressure has been accounted for at the liquid flow front and continuity maintained. The influence of perturbation in the bundle geometry has been investigated. Local correlations of the dimensions of neighbouring gaps formed between the bundles are of paramount importance. Focus is on inter-bundle bubbles. An existing model for bubble dynamics is used based on a probabilistic approach for bubbles moving, splitting, merging, and dissolving. The same approach was used for intra-bundle bubbles, the difference being that their motion appears to be much slower. The obtained void fractions of inter-bundle bubbles at different vacuum levels applied at the liquid flow front are compared to those from real mouldings with a high degree of conformity.
24.	Moriana, Rosana, et al. (författare) Improved thermo-mechanical properties by the addition of natural fibres in starch-based sustainable biocomposites 2011 Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 42:1, s. 30-40 Tidskriftsartikel (refereegranskat)abstract Sustainable biocomposites based on thermoplastic starch copolymers (Mater-Bi KE03B1) and biofibres (cotton, hemp and kenaf) were prepared and characterised in terms of their thermo-mechanical and morphological properties. Biocomposites exhibit improved thermal stability and mechanical properties in comparison with the Mater-Bi KE. Biofibres act as suitable thermal stabilizers for the Mater-Bi KE, by increasing the maximum decomposition temperature and the Ea associated to the thermal decomposition process. Biofibre addition into the Mater-Bi KE results in higher storage modulus and in a reduction of the free-volume-parameter associated to the Mater-Bi KE glass transition. The influence of different biofibres on the thermo-mechanical properties of the biocomposites has been discussed. Hemp and kenaf enhance the thermal stability and reduce the free volume-parameter of Mater-Bi KE more significantly than cotton fibres, although the latter exhibits the highest mechanical performance. These differences may be explained by the improved interaction of lignocellulosic fibres with the Mater-Bi KE, due to the presence of hemicellulose and lignin in their formulation. © 2010 Elsevier Ltd. All rights reserved.
25.	Pupurs, Andrejs, et al. (författare) Interface debond crack growth in tension-tension cyclic loading of single fiber polymer composites 2013 Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 44:1, s. 86-94 Tidskriftsartikel (refereegranskat)abstract Fiber/matrix interface debond crack growth from a fiber break is defined as one of the key mechanisms of fatigue damage in unidirectional composites. Considering debond as an interface crack its growth in cyclic loading is analyzed utilizing a power law, where the debond growth rate is a power function of the change of the strain energy release rate in the cycle. To obtain values of two parameters in the power law cyclic loading of fragmented single fiber specimen is suggested. Measurements of the debond length increase with the number of load cycles in tension-tension fatigue are performed for glass fiber/epoxy single fiber composites. Analytical method in the steady-state growth region and FEM for short debonds are combined for calculating the strain energy release rate of the growing debond crack. Interface failure parameters in fatigue are determined by fitting the modeling and experimental results. The determined parameters for interface fatigue are validated at different stress levels.
26.	Rouhi, Mohammad Sadegh, 1983, et al. (författare) Modeling of coupled dual-scale flow–deformation processes in composites manufacturing 2013 Ingår i: Composites Part A: Applied Science and Manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 46:1, s. 108-116 Tidskriftsartikel (refereegranskat)abstract The present contribution is a part of the work towards a framework for holistic modeling of compositesmanufacturing. Here we focus our attention onto the particular problem of coupled dual-scale deformation–flow process such as the one arising in RTM, Vacuum Assisted Resin Infusion (VARI) and VacuumBag Only (VBO) prepregs. The formulation considers coupling effects between macro-scale preform processesand meso-scale ply processes as well as coupling effects between the solid and fluid phases. Theframework comprises a nonlinear compressible fiber network saturated with incompressible fluid phase.Internal variables are introduced in terms of solid compressibility to describe the irreversible mesoscopicinfiltration and reversible preform compaction processes. As a main result a coupled displacement–pressure, geometrically nonlinear, finite element simulation tool is developed. The paper is concludedwith a numerical example, where a relaxation–compression test of a planar fluid filled VBO preform atglobally un-drained and partly drained conditions is considered.
27.	Tanpichai, Supachok, et al. (författare) Stress-transfer in microfibrillated cellulose reinforced poly(lactic acid) composites using Raman spectroscopy 2012 Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier. - 1359-835X .- 1878-5840. ; 43:7, s. 1145-1152 Tidskriftsartikel (refereegranskat)abstract Lyocell fibres were used to make microfibrillated cellulose (MFC) by combined homogenisation and sonication. A web-like structure was obtained with fibril diameters in the range of several micrometers to less than 80 nm. Composite samples with PLA resin reinforced with MFC networks were prepared using compression moulding. Young's modulus and tensile strength of these composites increased by ∼60% and 14% respectively, compared to the pure resin material. Raman spectroscopy was used to monitor the molecular deformation of networks and composite materials. A Raman band initially located at ∼1095 cm -1 was observed to shift towards a lower wavenumber position upon tensile deformation. The rate of Raman band shift with respect to strain for the composites was higher than for the pure MFC networks, indicating that the observed improvement in mechanical properties results from stress transfer from the PLA resin to the MFC fibrils.
28.	Tanpichai, Supachok, et al. (författare) Stress transfer in microfibrillated cellulose reinforced poly(vinyl alcohol) composites 2014 Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier. - 1359-835X .- 1878-5840. ; 65, s. 186-191 Tidskriftsartikel (refereegranskat)abstract Combined homogenisation and sonication treatments of micron-sized lyocell fibres were used to generate microfibrillated cellulose (MFC) with fibril diameters of ∼350 nm. No further reduction in fibril diameter was observed after 30 min treatment. Poly(vinyl alcohol) (PVA) composites reinforced with these fibrils were fabricated using solvent casting and physical and mechanical properties were investigated. The presence of MFC in PVA increased the thermal degradation of the polymer. An increase in both the tensile strength and modulus of the composites was observed for up to 3 wt.% of fibrils; beyond this point no significant increases were observed. An estimate of ∼39 GPa is made for the fibril modulus based on this increase. Stress-transfer between the polymer resin and the fibrils was investigated using Raman spectroscopy. Stress transfer in the composite is shown to be greater than that of a pure network of fibres, indicating a good fibre-matrix bond
29.	Trey, Stacy, et al. (författare) Glass fiber reinforced high glass transition temperature thiol–ene networks 2011 Ingår i: Composites. Part A, Applied science and manufacturing. - 1359-835X .- 1878-5840. ; 42:11, s. 1800-1808 Tidskriftsartikel (refereegranskat)
30.	Trey, Stacy M., et al. (författare) Glass fiber reinforced high glass transition temperature thiol-ene networks 2011 Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 42:11, s. 1800-1808 Tidskriftsartikel (refereegranskat)abstract Although thiol-ene polymers have highly desirable processing properties the networks usually are limited to having characteristically low glass transition temperatures with low strength. This study is one of the first studies to examine a thiol-ene polymer thermoset matrix, having many industrial advantages compared to conventional polymer matrices, reinforced with continuous E-glass fibers. In order to control the interphase, a mercapto functional sizing of 1 wt% is applied to the glass fibers. The resulting composites of 12 vol% fibers are comparable to glass fiber reinforced polyesters in terms of strength with Young's modulus. This work contributes to the furthering of thiol-ene ultra-violet cure systems, with their range of advantageous properties, for use in a broader scope of applications by way of creating a stronger material based on a novel class of thermoset matrix.
31.	Vernet, Nicolas, et al. (författare) Experimental determination of the permeability of engineering textiles : Benchmark II 2014 Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier Ltd. - 1359-835X .- 1878-5840. ; 61, s. 172-184 Tidskriftsartikel (refereegranskat)abstract In this second international permeability benchmark, the in-plane permeability values of a carbon fabric were studied by twelve research groups worldwide. One participant also investigated the deformation of the tested carbon fabric. The aim of this work was to obtain comparable results in order to make a step toward standardization of permeability measurements. Unidirectional injections were thus conducted to determine the unsaturated in-plane permeability tensor of the fabric. Procedures used by participants were specified in the guidelines defined for this benchmark. Participants were asked to use the same values for parameters such as fiber volume fraction, injection pressure and fluid viscosity to minimize sources of scatter. The comparison of the results from each participant was encouraging. The scatter between data obtained while respecting the guidelines was below 25%. However, a higher dispersion was observed when some parameters differed from the recommendations of this exercise.
32.	Visakh, P. M., et al. (författare) Crosslinked natural rubber nanocomposites reinforced with cellulose whiskers isolated from bamboo waste: Processing and mechanical/thermal properties 2012 Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 43:4, s. 735-741 Tidskriftsartikel (refereegranskat)abstract Crosslinked natural rubber (NR) nanocomposites were prepared using cellulose nanowhiskers (CNWs) that were extracted from bamboo pulp residue of newspaper production, as the reinforcing phase. The coagulated NR latex containing bamboo nanowhiskers (master batch) was compounded with solid NR and vulcanizing agents using a two-roll mill and subsequently cured to introduce crosslinks in the NR phase. No evidence of micro-scaled aggregates of cellulose nanowhiskers in NR matrix was observed in scanning electron microscopy (SEM) images. The addition of CNWs had a positive impact on the tensile strength, E-modulus, storage modulus, tan delta peak position and thermal stability of the crosslinked NR. Theoretical modeling of the mechanical properties showed a lower performance than predicated and therefore further process optimization and/or compatibilization are required to reach the maximum potential of these nanocomposites.
33.	Wysocki, Maciej, 1969, et al. (författare) Anisotropic and tension-compression asymmetric model for composites consolidation 2010 Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 41:2, s. 284-294 Tidskriftsartikel (refereegranskat)abstract A constitutive model for anisotropic and tension-compression asymmetric response of a fibrous preform is developed and solved using a FE software. Applicability of the method to complex geometries is demonstrated by analysis the consolidation of an axisymmetric filament wound pressure vessel made from commingled yarns. Three different winding patterns are considered. In conclusions, the consolidation of the whole vessel, except at the opening, is prevented by the loading mode, where the pressure is applied on the interior. To succeed in manufacturing of this type of pressure vessel, use of an oversized preform that allows extension in the fibre direction is suggested.

Skapa referenser, mejla, bekava och länka

Länka till träfflistan

Träfflista för sökning "L773:1359 835X OR L773:1878 5840 srt2:(2010-2014)"

Avgränsa träffmängd

År