The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform
Michael Sinapius - One of the best experts on this subject based on the ideXlab platform.
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Identification and quantitation of processing parameters controlling the surface quality of carbon fibre-reinforced composites
Journal of Reinforced Plastics and Composites, 2016Co-Authors: Johannes Kunze, Thorsten Mahrholz, Michael SinapiusAbstract:The paper investigates the effect of essential manufacturing parameters on the surface quality of uncoated carbon fibre-reinforced composites used as car body panels with visible surfaces (Class A properties). A series of carbon fibre-reinforced composites laminates were prepared by the Resin transfer moulding technique varying the fibre volume content (30 to 60 %), reinforcement material (woven fabrics vs. unidirectional fibre reinforcements), curing temperatures (40℃ to 120℃), additives (SiO2 nanoparticles as matrix fillers) and using a surface finish applied as an in-mould coating. Laminate surfaces were characterised by roughness analysis (white-light interferometry) and wave-scan measurement to quantify the influence of the different manufacturing parameters on the surface quality. Especially, the used Resins were intensively characterised concerning thermal properties and total Resin Shrinkage. These results correlate very well with the performed analysis of surface roughness. It is found that the f...
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Magnetostrictive properties of epoxy Resins modified with Terfenol-D particles for detection of internal stress in CFRP. Part 2: evaluation of stress detection
Journal of Materials Science, 2013Co-Authors: M. Kubicka, Alexandra Kühn, Thorsten Mahrholz, Peter Wierach, Michael SinapiusAbstract:The mechanical performance of carbon fibre reinforced polymers is predominantly limited by internal stress induced by Resin Shrinkage of the polymer matrix. Terfenol-D particles are investigated as internal sensors to detect the stress situation on a non-destructive way. Part 1 of the article describes the preparation and characterization of the samples used in the investigation of the sensory effect (Kubicka et al. J Mater Sci 47:5752–5759, 2012). Part 2 presents the results of the evaluation of the stress detection. A fundamental discussion is given how these magnetostrictive particles act as stress sensors in epoxy Resins using the Villari effect. Analysing this effect in terms of particle content, particle size and particle distribution the most promising parameters are identified. Obviously the higher the particle content (20 wt%) and the smaller the particle size (
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Fundamental Characterization of Epoxy-Silica Nanocomposites Used for the Manufacturing of Fiber Reinforced Composites
Adaptive tolerant and efficient composite structures, 2012Co-Authors: Thorsten Mahrholz, Michael SinapiusAbstract:Nanocomposites based on silica nanoparticles and high performance epoxy Resins are investigated for their suitability as a new type of matrix for fiber-reinforced polymers (FRP) using injection technologies (LCM). The key focus is on the determination of the processing parameters at varying silica nanoparticle content. The homogeneous distribution of the nanoscaled silica in the epoxy matrix is proven by photon cross correlation spectroscopy (PCCS) and scanning electron microscopy (SEM) analysis. Depending on the silica content of the composite, its stiffness, strength and toughness can be increased significantly compared with the neat Resin. The mechanical performance is discussed by failure mechanisms based on the analysis of the fracture surface morphology. Moreover, Resin Shrinkage and the thermal expansion are significantly reduced both important for lowering internal stress in FRP. The injectability of the nanocomposite for the purpose of lamination using the LCM technology is nearly unaffected. Epoxy-silica nanocomposites are now proven to be a new high performance polymer matrix for FRP structures manufactured by the low cost LCM techniques.
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quantitation of the reinforcement effect of silica nanoparticles in epoxy Resins used in liquid composite moulding processes
Composites Part A-applied Science and Manufacturing, 2009Co-Authors: Thorsten Mahrholz, J Stangle, Michael SinapiusAbstract:Abstract Epoxy–silica nanocomposites are investigated for their suitability as a new type of matrix for fibre-reinforced polymers (FRP) using injection technology (LCM). The key focus is the determination of the processing characteristics of the nanocomposites. The silica nanoparticle content varies between 0 and 25 wt% for the high performance epoxy Resin. Photon Cross Correlation Spectroscopy (PCCS) and Scanning Electron Microscopy (SEM) analysis performed on the liquid and cured epoxy–silica nanocomposites indicate a nearly homogeneous distribution of the nanoscaled silica in the epoxy matrix, even at rather high weight percentages. Depending on the silica content of the composite, its stiffness, strength and toughness can be increased significantly compared with neat Resin. Moreover, Resin Shrinkage and the thermal expansion (CTE) can be significantly reduced and the thermal conductivity increased. Concomitant the glass transition temperature remains nearly constant. The initial viscosity of the Resin increases slightly depending on the nanoparticle content, while the gel-time slightly decreases. The injectability of the nanocomposite for the purpose of lamination using the LCM technology is nearly unaffected. The optimum filler content is at approx. 25 wt% silica. Epoxy–silica nanocomposites are now proven to be a new high performance polymer matrix for FRP structures manufactured by the low cost LCM techniques.
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Nanotechnology for novel High-performance Composites - Manufacturing, Characterization and Application
2006Co-Authors: Thorsten Mahrholz, Ulrich Riedel, Michael SinapiusAbstract:An innovative way to compensate the deficits of composites (FRP) produced by the well-established injection technique (LRI) compared to the prepreg technique was found at the DLR Institute for Composite Structures and Adaptive Systems. The improvement of the composite quality by using nanocomposites was tested with the Single Line Injection technique (SLI). A closer look was taken at an epoxy Resin filled with nanosized silicon dioxide (SiO2). With SiO2 the stiffness and strength could be improved significantly compared to the neat Resin. In addition, the Resin Shrinkage could be considerably reduced and thermal conductivity increased. The nanocomposites remained still injectable and the density of the nanocomposites was maintained at an almost constant level (lightweight aspect). The results could be transferred to fibre-reinforced composites made with the SLI technique. Particularly the significant increase of the Young’s modulus and its high linearity in the stress-strain diagram led to reduction of the inter-fibre fractures and improvement of the overall material performance in comparison to unfilled fibre composite and opens therefore new fields for aerospace applications.
Yong Wang - One of the best experts on this subject based on the ideXlab platform.
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Carbon Nanomaterials Based Smart Fabrics with Selectable Characteristics for In-Line Monitoring of High-Performance Composites
Materials, 2018Co-Authors: Guantao Wang, Yong WangAbstract:Carbon nanomaterials have gradually demonstrated their superiority for in-line process monitoring of high-performance composites. To explore the advantages of structures, properties, as well as sensing mechanisms, three types of carbon nanomaterials-based fiber sensors, namely, carbon nanotube-coated fibers, reduced graphene oxide-coated fibers, and carbon fibers, were produced and used as key sensing elements embedded in fabrics for monitoring the manufacturing process of fiber-reinforced polymeric composites. Detailed microstructural characterizations were performed through SEM and Raman analyses. The resistance change of the smart fabric was monitored in the real-time process of composite manufacturing. By systematically analyzing the piezoresistive performance, a three-stage sensing behavior has been achieved for registering Resin infiltration, gelation, cross-linking, and post-curing. In the first stage, the incorporation of Resin expands the packing structure of various sensing media and introduces different levels of increases in the resistance. In the second stage, the concomitant Resin Shrinkage dominates the resistance attenuation after reaching the maximum level. In the last stage, the diminished Shrinkage effect competes with the disruption of the conducting network, resulting in continuous rising or depressing of the resistance.
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Carbon Nanomaterials Based Smart Fabrics with Selectable Characteristics for In-Line Monitoring of High-Performance Composites
Materials, 2018Co-Authors: Guantao Wang, Yong WangAbstract:Carbon nanomaterials have gradually demonstrated their superiority for in-line process monitoring of high-performance composites. To explore the advantages of structures, properties, as well as sensing mechanisms, three types of carbon nanomaterials-based fiber sensors, namely, carbon nanotube-coated fibers, reduced graphene oxide-coated fibers, and carbon fibers, were produced and used as key sensing elements embedded in fabrics for monitoring the manufacturing process of fiber-reinforced polymeric composites. Detailed microstructural characterizations were performed through SEM and Raman analyses. The resistance change of the smart fabric was monitored in the real-time process of composite manufacturing. By systematically analyzing the piezoresistive performance, a three-stage sensing behavior has been achieved for registering Resin infiltration, gelation, cross-linking, and post-curing. In the first stage, the incorporation of Resin expands the packing structure of various sensing media and introduces different levels of increases in the resistance. In the second stage, the concomitant Resin Shrinkage dominates the resistance attenuation after reaching the maximum level. In the last stage, the diminished Shrinkage effect competes with the disruption of the conducting network, resulting in continuous rising or depressing of the resistance.
L. James Lee - One of the best experts on this subject based on the ideXlab platform.
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Control of Shrinkage and final conversion of vinyl ester Resins cured in low‐temperature molding processes
Journal of Applied Polymer Science, 2003Co-Authors: Xia Cao, L. James LeeAbstract:Vinyl ester Resin is a major thermoset polymer used in low-temperature composite manufacturing processes such as the Seemann composite Resin infusion-molding process (SCRIMP). Volume Shrinkage and residual styrene are important concerns for composites produced in such processes. A low-Shrinkage additive (LSA) is a typical agent added to control the volume Shrinkage of vinyl ester Resins during molding. In this study, the effects of LSA content and the temperature profile (the temperature gradient and peak temperature) on the volume Shrinkage control of a vinyl ester Resin were investigated. The reaction kinetics of the Resin system were also studied. We achieved good volume Shrinkage control if we raised the curing temperature slowly to allow sufficient time for phase separation and if the curing temperature reached a high value after phase separation to allow microvoid formation. On the basis of experimental results, we designed an improved SCRIMP to increase Resin conversion, reduce Resin Shrinkage, and produce composites with better properties. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1486–1496, 2003
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Control of Shrinkage and residual styrene of unsaturated polyester Resins cured at low temperatures: I. Effect of curing agents
Polymer, 2003Co-Authors: Xia Cao, L. James LeeAbstract:Abstract In low temperature molding processes, control of Resin Shrinkage and residual monomer is an important concern. The presence of low profile additives (LPAs) can reduce the Shrinkage of unsaturated polyester (UP)/styrene (St) Resins under proper processing conditions but may increase the residual styrene content. A systematic study was carried out to investigate the effect of the initiator system and reaction temperature on sample morphology, final Resin conversion, and Resin Shrinkage of UP Resins with LPA. It was found that the final conversion of the Resin system could be improved by using dual initiators. The effect is more obvious at low temperatures. Volume Shrinkage measurements of the Resin system initiated with dual initiators revealed that good LPA performance was achieved at low (e.g. 35 °C) and high (e.g. 100 °C) temperatures but not at intermediate ones. This can be explained by how temperature affects phase separation, reaction kinetics in the LPA-rich and UP-rich phases, micro-void formation, and thermal expansion.
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Effect of co‐promoter and secondary monomer on Shrinkage control of unsaturated polyester (UP)/styrene (St)/low‐profile additive (LPA) systems cured at low temperatures
Journal of Applied Polymer Science, 2001Co-Authors: Xia Cao, L. James LeeAbstract:The Shrinkage of unsaturated polyester (UP)/styrene (St) Resins cured at low temperatures can be reduced by the presence of low-profile additives (LPAs). It is believed that the reaction-induced phase separation and the polymerization Shrinkage in both the LPA-rich and UP-rich phases result in the formation of microvoids, which partially compensates the Resin Shrinkage. The relative reaction rate in the two phases plays an important role in Shrinkage control. In this study, secondary monomers [such as divinylbenzene (DVB) and trimethylopropane trimethacrylate (TMPTMA)] and a co-promoter, 2,4-pentandione (2,4-P), were added into the UP/St/LPA Resin systems to investigate their effect on the Shrinkage control of Resins cured at low temperatures. Dilatometery results showed that the addition of both TMPTMA and 2,4-P resulted in an earlier volume expansion during curing and better Shrinkage control. The phase separation, reaction kinetics, and viscosity changes in the LPA-rich and UP-rich phases during curing were also investigated. The results confirmed that the increased reaction rate in the LPA-rich phase led to an earlier formation of microvoids and, consequently, less volume Shrinkage of the cured Resin. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 738–749, 2001
Peter J Schubel - One of the best experts on this subject based on the ideXlab platform.
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evaluation of cure Shrinkage measurement techniques for thermosetting Resins
Polymer Testing, 2010Co-Authors: Darshil U Shah, Peter J SchubelAbstract:Resin chemical Shrinkage dictates the surface integrity and the roughness of a composite structure. Thus, to minimize surface failures and to produce a good surface quality it is a requisite to be able to measure and track Resin Shrinkage during the cure process. This manuscript investigates and evaluates the measuring and monitoring of real-time Resin Shrinkage using a rheometer, a helium-based pycnometer and a thermo-mechanical analyzer (TMA) for ambient curing UP and epoxy Resins. Shrinkage readings obtained from the newly developed robust technique with the rheometer concur well with readings from the traditional pycnometric method. They also coincide within the accepted literature values of 7–10% and 3.5–4.5% for the UP and epoxy systems, respectively. Shrinkage measurements during post-cure were effectively carried out at an elevated temperature, suggesting that the methodology provided can be applied to non-ambient curing systems. The TMA was found to be unsuccessful in measuring Shrinkage reliably.
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Characterisation of thermoset laminates for cosmetic automotive applications: Part III - Shrinkage control via nanoscale reinforcement
Composites Part A: Applied Science and Manufacturing, 2006Co-Authors: Peter J Schubel, M. Johnson, Nicholas A. Warrior, Chris D. RuddAbstract:Exfoliated clays were examined as a means to control Resin Shrinkage within styrene based unsaturated polyester Resins via a so-called nanocomposite. Two clays (Cloisite® 10A and Garamite® 1958) were investigated and compared to a conventional low profile additive (polyvinyl acetate) with calcium carbonate filler at various loadings. A suitable exfoliation process was established using in-situ, intercalative polymerisation followed by measurement of volumetric Shrinkage and glass transition temperature. A series of hybrid matrices consisting of clay and PVAc were used to impregnate random E-glass preforms via RTM. The laminates were monitored for changes in volumetric Shrinkage and subsequent changes in surface quality of pre- and post-painted surfaces. Residual volatile organic compounds (VOCs) were monitored for each system. Tensile, flexural and impact properties were compared to the base Resin and a conventional low profile matrix. The results suggest that the exfoliated clay systems work synergistically with conventional additives to reduce Shrinkage and residual VOCs whilst in many cases improving properties above the level of the base Resin.
Thorsten Mahrholz - One of the best experts on this subject based on the ideXlab platform.
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Identification and quantitation of processing parameters controlling the surface quality of carbon fibre-reinforced composites
Journal of Reinforced Plastics and Composites, 2016Co-Authors: Johannes Kunze, Thorsten Mahrholz, Michael SinapiusAbstract:The paper investigates the effect of essential manufacturing parameters on the surface quality of uncoated carbon fibre-reinforced composites used as car body panels with visible surfaces (Class A properties). A series of carbon fibre-reinforced composites laminates were prepared by the Resin transfer moulding technique varying the fibre volume content (30 to 60 %), reinforcement material (woven fabrics vs. unidirectional fibre reinforcements), curing temperatures (40℃ to 120℃), additives (SiO2 nanoparticles as matrix fillers) and using a surface finish applied as an in-mould coating. Laminate surfaces were characterised by roughness analysis (white-light interferometry) and wave-scan measurement to quantify the influence of the different manufacturing parameters on the surface quality. Especially, the used Resins were intensively characterised concerning thermal properties and total Resin Shrinkage. These results correlate very well with the performed analysis of surface roughness. It is found that the f...
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Magnetostrictive properties of epoxy Resins modified with Terfenol-D particles for detection of internal stress in CFRP. Part 2: evaluation of stress detection
Journal of Materials Science, 2013Co-Authors: M. Kubicka, Alexandra Kühn, Thorsten Mahrholz, Peter Wierach, Michael SinapiusAbstract:The mechanical performance of carbon fibre reinforced polymers is predominantly limited by internal stress induced by Resin Shrinkage of the polymer matrix. Terfenol-D particles are investigated as internal sensors to detect the stress situation on a non-destructive way. Part 1 of the article describes the preparation and characterization of the samples used in the investigation of the sensory effect (Kubicka et al. J Mater Sci 47:5752–5759, 2012). Part 2 presents the results of the evaluation of the stress detection. A fundamental discussion is given how these magnetostrictive particles act as stress sensors in epoxy Resins using the Villari effect. Analysing this effect in terms of particle content, particle size and particle distribution the most promising parameters are identified. Obviously the higher the particle content (20 wt%) and the smaller the particle size (
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Fundamental Characterization of Epoxy-Silica Nanocomposites Used for the Manufacturing of Fiber Reinforced Composites
Adaptive tolerant and efficient composite structures, 2012Co-Authors: Thorsten Mahrholz, Michael SinapiusAbstract:Nanocomposites based on silica nanoparticles and high performance epoxy Resins are investigated for their suitability as a new type of matrix for fiber-reinforced polymers (FRP) using injection technologies (LCM). The key focus is on the determination of the processing parameters at varying silica nanoparticle content. The homogeneous distribution of the nanoscaled silica in the epoxy matrix is proven by photon cross correlation spectroscopy (PCCS) and scanning electron microscopy (SEM) analysis. Depending on the silica content of the composite, its stiffness, strength and toughness can be increased significantly compared with the neat Resin. The mechanical performance is discussed by failure mechanisms based on the analysis of the fracture surface morphology. Moreover, Resin Shrinkage and the thermal expansion are significantly reduced both important for lowering internal stress in FRP. The injectability of the nanocomposite for the purpose of lamination using the LCM technology is nearly unaffected. Epoxy-silica nanocomposites are now proven to be a new high performance polymer matrix for FRP structures manufactured by the low cost LCM techniques.
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quantitation of the reinforcement effect of silica nanoparticles in epoxy Resins used in liquid composite moulding processes
Composites Part A-applied Science and Manufacturing, 2009Co-Authors: Thorsten Mahrholz, J Stangle, Michael SinapiusAbstract:Abstract Epoxy–silica nanocomposites are investigated for their suitability as a new type of matrix for fibre-reinforced polymers (FRP) using injection technology (LCM). The key focus is the determination of the processing characteristics of the nanocomposites. The silica nanoparticle content varies between 0 and 25 wt% for the high performance epoxy Resin. Photon Cross Correlation Spectroscopy (PCCS) and Scanning Electron Microscopy (SEM) analysis performed on the liquid and cured epoxy–silica nanocomposites indicate a nearly homogeneous distribution of the nanoscaled silica in the epoxy matrix, even at rather high weight percentages. Depending on the silica content of the composite, its stiffness, strength and toughness can be increased significantly compared with neat Resin. Moreover, Resin Shrinkage and the thermal expansion (CTE) can be significantly reduced and the thermal conductivity increased. Concomitant the glass transition temperature remains nearly constant. The initial viscosity of the Resin increases slightly depending on the nanoparticle content, while the gel-time slightly decreases. The injectability of the nanocomposite for the purpose of lamination using the LCM technology is nearly unaffected. The optimum filler content is at approx. 25 wt% silica. Epoxy–silica nanocomposites are now proven to be a new high performance polymer matrix for FRP structures manufactured by the low cost LCM techniques.
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Nanotechnology for novel High-performance Composites - Manufacturing, Characterization and Application
2006Co-Authors: Thorsten Mahrholz, Ulrich Riedel, Michael SinapiusAbstract:An innovative way to compensate the deficits of composites (FRP) produced by the well-established injection technique (LRI) compared to the prepreg technique was found at the DLR Institute for Composite Structures and Adaptive Systems. The improvement of the composite quality by using nanocomposites was tested with the Single Line Injection technique (SLI). A closer look was taken at an epoxy Resin filled with nanosized silicon dioxide (SiO2). With SiO2 the stiffness and strength could be improved significantly compared to the neat Resin. In addition, the Resin Shrinkage could be considerably reduced and thermal conductivity increased. The nanocomposites remained still injectable and the density of the nanocomposites was maintained at an almost constant level (lightweight aspect). The results could be transferred to fibre-reinforced composites made with the SLI technique. Particularly the significant increase of the Young’s modulus and its high linearity in the stress-strain diagram led to reduction of the inter-fibre fractures and improvement of the overall material performance in comparison to unfilled fibre composite and opens therefore new fields for aerospace applications.