| 1. |
- Tsampas, Spyros, et al.
(författare)
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The effect of high temperature on the mechanical performance of novel high Tg polyimide-based carbon fibre-reinforced laminates
- 2016
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Ingår i: ECCM 2016 - Proceeding of the 17th European Conference on Composite Materials. - : European Conference on Composite Materials, ECCM. - 9783000533877
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Konferensbidrag (refereegranskat)abstract
- In this study, the outcomes from the mechanical testing of the carbon fibre-reinforced polyimide composite system T650/NEXIMID® MHT-R at ambient and elevated temperatures are presented. These results are compared to assess the effect of mechanical loading at 320°C on the performance of the system in tension, compression and Short-Beam Shear. The experimental campaign indicated that the mechanical loading at 320°C had a trivial effect on the tensile properties (fibre-dominated) whilst a more pronounced effect was noted on the compression and Short-Beam Shear (matrix and fibre/matrix interface-dominated properties).
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| 2. |
- Aitomäki, Yvonne, et al.
(författare)
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Novel reactive bicomponent fibres : Material in composite manufacturing
- 2012
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Ingår i: Journal of Nanostructured Polymers and Nanocomposites. - 1790-4439. ; 8:1, s. 5-11
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Tidskriftsartikel (refereegranskat)abstract
- The hypotheses that reactive uncured, thermoset bicomponent fibres can be prepared and mixed with reinforcing fibres and ultimately used in preparation of a composite was tested and is described. It is thought that such fibres have the two potential advantages: (1) to enable manufacturing with particle doped resins e.g. nanocomposites which add functionality to composites and (2) increased efficiency of structural composite manufacturing by increasing the level of automation. The structure of the thermoset fibres comprises of a sheath of thermoplastic and a core of uncured thermoset resin. Once manufactured, the fibres were wound with a reinforced fibre onto a plate, consolidated and cured. The resulting composite was examined and compared to other composites made with the same manufacturing method from commercially available materials. The results show that a laminate can be produced using these reactive bicomponent fibres. The resin system successfully impregnates the reinforcing carbon fibres and that the thermoplastic separates from the epoxy resin system during consolidation. In comparison to reference material, the bicomponent laminate shows promising characteristics. However, the processes developed are currently on a lab-scale and considerable improvement of various bicomponent fibre properties, such as the strength, are required before the technology can be used on a larger scale.
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| 3. |
- Alnersson, Gustaf
(författare)
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Towards 3D modelling of Compression Moulding of SMC
- 2021
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The automotive industry is facing ever increasing demands for reduced emissions, and lightweight solutions are thusly required. One field that has significant potential in this regard is composite materials, which can offer a good combination of weight reduction and mechanical properties. However, the rapid development cycles in the automotive industry mean that tools for numerical modeling are necessary, both regarding manufacturing processes and prediction of mechanical properties. The material that has been of interest for this work is Sheet Moulding Compound (SMC). SMC consists of sheets of resin and chopped fibres. When used for manufacturing the sheets are cut into appropriate size and shape. The cut sheets are then placed in a pre-heated mould. When this mould is closed, the sheets melt and the fibre-filled resin flows out and fills the mould cavity; the resin then cures and solidifies. A significant advantage of SMC compared to other composite solutions is that the process has comparatively short cycle times, which is a necessity for automotive applications. However, it is a rather complicated process to model numerically for a number of reasons, including the complex rheological properties of the charge, the often rather significant temperature gradients throughout the thickness, often complicated three-dimensional effects in the flow, and the chopped fibres present in the charge. These fibres will move and change orientation as the charge is pressed, which is a significant challenge to model properly.The first part of this work is a review and discussion of the difficulties described above, and some solutions that have been suggested. The second part concerns a suggestion for a three-dimensional flow model for the compression moulding process, which takes into account factors that have been suggested to influence the flow behavior, such as temperature distribution and shear strain rate. Some simulation results are presented along with comparison to previous experimental results, and similar flow patterns are observed serving as a qualitative validation. The third part concerns the expansion of this model to include the effects of the flow on the fibre orientation.
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| 4. |
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| 5. |
- Carlson, Tony
(författare)
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Multi-functional composite materials : CFRP thin film capacitors
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The use of lightweight materials in structural applications is ever increasing. Today, lightweight engineering materials are needed to realise greener, safer and more competitive products. A route to achieve this could be to combine more than one primary function in a material or component to create multi-functionality, thus reducing the number of components and ultimately the overall weight. This thesis presents an approach towards realising novel multi-functional polymer composites. A series of structural capacitor materials made from carbon fibre reinforced polymers have been developed, manufactured and tested. In papers I and II, capacitors have been manufactured using different papers and polymer films as dielectric separator employing carbon fibre/epoxy pre-pregs as structural electrodes. Plasma treatment was used as a route for improved epoxy/polymer film adhesion. The manufactured materials were evaluated for mechanical performance by ILSS and tearing tests and electrical performance by measuring capacitance and dielectric breakdown voltage. In paper III the concept was extended in a parametric study using the most promising approach with a polymer film as dielectric separator. Three thicknesses of PET (50, 75 and 125 µm) were used as dielectric separator with carbon fibre/epoxy pre-pregs as structural electrodes. PET was chosen due to availability in different thicknesses as well as the frequent use in ordinary capacitors making it a suitable candidate. As in paper I and II, plasma treatment was used to improve the PET/epoxy adhesion. The capacitor materials were evaluated for mechanical performance by tensile tests and ILSS and for electrical performance by measuring capacitance and dielectric breakdown voltage. The multifunctional materials shows good potential for replacing steel and other materials with lower specific mechanical properties but cannot match the high specific mechanical performance of mono-functional materials. Both mechanical and electrical performance could have large benefits from developing new separator materials adapted for use in multifunctional applications and could be an interesting field for extended research.
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| 6. |
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| 7. |
- Engström, Jonas, et al.
(författare)
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Characterization of carbon nanotube doped carbon fiber prepreg laminate
- 2012
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Ingår i: Proceedings of the 15th European Conference on Composite Materials. - Venice : European Conference on Composite Materials, ECCM. - 9788888785332
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Konferensbidrag (refereegranskat)abstract
- The current paper reports results from a preliminary study on PREGCYL™ NC R2HM-01 which is a carbon nanotube doped prepreg produced by Nanocyl. The work consisted of sample manufacturing in autoclave, microcopy analysis with XHR-SEM and mechanical testing. The mechanical testing consisted of tensile tests of unidirectional (in longitudinal direction) and cross-ply laminates. Test of unidirectional laminates showed that stiffness of the PREGCYL material is slightly higher than that of MTM55 composites (111GPa vs 102GPa). The results from tests of cross-ply laminates indicated that damage (transverse cracks) initiation is delayed in PREGCYL composites compare to the MTM55 material. Damage accumulation also seems to be slower in nano-doped composites.
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| 8. |
- Fernberg, Patrik, et al.
(författare)
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Carbon nanotube treated carbon fibre preforms for improved properties of aeronautical grade composites
- 2012
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Ingår i: ECCM 2012 - Composites at Venice, Proceedings of the 15th European Conference on Composite Materials. - Padova : European Conference on Composite Materials, ECCM. - 9788888785332
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Konferensbidrag (refereegranskat)abstract
- The current paper reports work on development of enhanced carbon fibre composites manufactured by resin transfer moulding (RTM). In particular, the possibility to obtain a toughened composite through deposition of carbon nanotubes (CNT) on the fibres is investigated. The hypothesis is that deposition of CNT on the fibre surface has two major advantages: a) filtering problems during manufacturing are eliminated and b) CNT can contribute to a local toughening in the vicinity of fibres, where stress concentrations often are high. Unidirectional and multi-axial composites, with and without CNT-modification, were manufactured using conventional RTM-technique and HexFlow®RTM6 epoxy resin. The composites were characterized by means of mechanical testing (interlaminar shear strength, ILSS) and microscopy. Significant improvements by 13 to37 % in ILSS values were achieved with the addition of CNT. Stiffness degradation tests were also performed. The results from these tests were not completely conclusive. Some treatments promoted stiffness degradation whereas others had no apparent effect.
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| 9. |
- Fernberg, Patrik, et al.
(författare)
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Damage detection in carbon fibre cross-ply laminates by aid of carbon nanotube doped resin
- 2008
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Ingår i: 13th European Conference on Composite Materials.
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Konferensbidrag (refereegranskat)abstract
- The possibility to use resistance variations of carbon nanotube (CNT) doped carbon fibre reinforced plastics (CFRP) to characterise the level of microstructural damage in the form of transverse cracking is experimentally investigated in the current work. The resistance of CNT-doped and unmodified CFRP was measured after they had been subjected to stepwise increased tensile loading. Both increase and decrease resistance was observed which made it difficult to make any firm statement that the changes we observed were due to damage. The conductivity along carbon fibres is dominating electrical conductivity of the studied cross-ply laminate. Any disturbance of conductive CNT based nanocomposite matrix by transverse cracks in 90-layer therefore caused too small changes of resistance to be measured with current experimental setup.
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| 10. |
- Fernberg, Patrik, et al.
(författare)
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"Detect" - a new defect detection method and its use on sheet moulding compound (SMC) substrates
- 2008
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Ingår i: Composites for sustainable progress. - Stockholm.
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Konferensbidrag (refereegranskat)abstract
- A novel optical method for detection of surface porosities on SMC substrates is presented. Detection is facilitated by observation of how a liquid film on the surface evaporates. The method utilizes the fact that complete evaporation takes longer time in the pores than elsewhere. The rate of change of a laser speckle pattern gives a measure of the changes at the surface and indicates where pores causes prolonged evaporation. A pilot measurement unit was built that shows that the principle ideas of the system work. Attempts were made to develop the pilot unit so that it could provide quantitative numbers of actual defects on an SMC substrate. The results are encouraging in the sense that the unit can automatically identify areas with higher number of defects.
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