| 1. |
- Fernberg, Patrik, et al.
(författare)
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Development of novel high Tg polyimide-based composites. Part I : RTM processing properties
- 2018
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Ingår i: Journal of composite materials. - : SAGE Publications. - 0021-9983 .- 1530-793X. ; 52:2, s. 253-260
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Tidskriftsartikel (refereegranskat)abstract
- In this study, an assessment of the composite processing-related properties of a newly developed 6-FDA-based phenylethynyl-terminated polyimide (available under the tradename NEXIMID®MHT-R) is presented. Processing schemes, used for preparing high quality carbon fibre-reinforced composites by the use of conventional resin transfer moulding are developed and presented. The influences of manufacturing parameters on glass transition temperature of the composites are presented. The results confirm that composites with exceptionally high Tg, in the range between 350 and 460℃ can be achieved. A manufacturing scheme that yields in composites with Tg of 370℃ is presented and proposed as a good candidate to serve as baseline for further studies.
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| 2. |
- Fernberg, S. Patrik, et al.
(författare)
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Influence of post-cure on carbon fibre polyimide composites with glass transition temperatures above 400ºC
- 2015
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Ingår i: ICCM International Conferences on Composite Materials. - : International Committee on Composite Materials.
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Konferensbidrag (refereegranskat)abstract
- The current communication present results from work on polymeric composites with extreme temperature performance. We are studying carbon fibre composites based on a new phenyl ethynyl terminated polyimide formulation NEXIMID® MHT-R (Nexam Chemicals AB, Sweden) based on hexafluoroisopropylidene bisphthalic dianhydride (6-FDA), 4-(Phenylethynyl)Phthalic Anhydride (4-PEPA) and ethynyl bis-phthalic anhydride (EBPA). This study in particular investigates how post-cure conditions such as time, temperature and atmosphere influence Tg of the composites. In addition to this we also trace and analyse the consequences of post-cure on weight loss and occurrence of micro-cracks. We are considering three different post-curing temperatures: 400°C, 420°C and 440°C in the study. Two different atmospheres, air and inert by nitrogen, were also investigated. In summary the results reveal that remarkably high Tg, up to around 460°C, is achieved with only very limited weight loss. It was also observed that some, but limited amounts of, micro-cracks are developed within the laminates due to the inevitable high thermal stresses generated upon cooling from cure temperature.
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| 3. |
- Grammatikos, Sotirios, 1985, et al.
(författare)
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On the Mechanical Recycling of Decommisioned Insulation Polymer Composite Components
- 2020
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Ingår i: IOP Conference Series: Materials Science and Engineering. - : Institute of Physics Publishing. - 1757-8981 .- 1757-899X. ; 842:1
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Konferensbidrag (refereegranskat)abstract
- Fibre reinforced polymer composites (FRPs) are being increasingly used in aerospace and automotive applications due to their high specific mechanical properties. The construction industry has also started taking advantage of the potential of FRPs for both structural and non-structural purposes. The result of this remarkable absorption of FRPs within the worldwide production market, has led to an immense increase of decommissioned thermoset-matrix components. Nowadays, the majority of the decommissioned FRP components are recovered energy-wise through incineration or simply discarded in landfills around the globe. Within the framework of this paper, we present a solution for the extension of the service life of decommissioned FRP components. Decommissioned electrical insulation FRP pipes were granulated and incorporated as fillers within both cementitious and polymer matrix composites. The effect of FRP granulates on the mechanical performance of cementitious and polymer matrix composites is examined to determine the maximum granulate-filler fraction that can be recycled without compromising the mechanical performance and manufacturing process.
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| 4. |
- Grammatikos, Sotirios, 1985, et al.
(författare)
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Recycling and re-purposing decommisioned construction polymer composites for construction applications
- 2018
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Ingår i: ECCM 2018 - 18th European Conference on Composite Materials. - : Applied Mechanics Laboratory. - 9781510896932
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Konferensbidrag (refereegranskat)abstract
- Fibre reinforced polymer composites (FRPs) are being increasingly used in aerospace and automotive applications due to their high specific mechanical properties. The construction industry has also started taking advantage of the potential of FRPs for both structural and non-structural purposes. The result of this remarkable absorption of FRPs within the worldwide production market, has led to an immense increase of decommissioned thermoset-matrix components. Nowadays, the majority of the decommissioned FRP components are recovered energy-wise through incineration or simply discarded in landfills around the globe. Within the framework of this paper, we present a solution for the extension of the service life of decommissioned FRP components. Decommissioned electrical insulation FRP pipes were granulated and incorporated as fillers within both cementitious and polymer matrix composites. The effect of FRP granulates on the mechanical performance of cementitious and polymer matrix composites is examined to determine the maximum granulate-filler fraction that can be recycled without compromising the mechanical performance and manufacturing process.
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| 5. |
- Khosroshahi, S. F., et al.
(författare)
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Feasibility study on the use of a hierarchical lattice architecture for helmet liners
- 2018
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Ingår i: Materials Today Communications. - : Elsevier BV. - 2352-4928. ; 14, s. 312-323
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Tidskriftsartikel (refereegranskat)abstract
- Helmets are the most important piece of protective equipment for motorcyclists. The liner of the helmet is the main part of the helmet which dissipates the impact energy and mitigates the load transmitted to the head. Therefore, optimizing the material that absorbs most of the impact energy would improve the helmet's protection capacity. It is known that the energy absorption of the helmet liner can be optimized by means of using liners with varying properties through the thickness, however currently the majority of used liners exhibit constant properties through the thickness. Advances in the field of topology optimization and additive manufacturing provide the ability of building complex geometries and tailoring mechanical properties. Along those lines, in the present work the feasibility of using a hierarchical lattice liner for helmets was studied. Finite element method was employed to study whether a hierarchical lattice liner could reduce the risk of head injuries in comparison to currently used liner materials. The results show that using a hierarchical lattice liner has the potential of significantly reducing the risk of head injury compared to a helmet with traditional EPS liner and could potentially be considered as the new generation of energy absorbing liners for helmets.
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| 6. |
- McElroy, Mark, et al.
(författare)
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Interaction of delaminations and matrix cracks in a CFRP plate, Part I : A test method for model validation
- 2017
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Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 103, s. 314-326
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Tidskriftsartikel (refereegranskat)abstract
- Isolating and observing the damage mechanisms associated with low-velocity impact in composites using traditional experiments can be challenging, due to damage process complexity and high strain rates. In this work, a new test method is presented that provides a means to study, in detail, the interaction of common impact damage mechanisms, namely delamination, matrix cracking, and delamination-migration, in a context less challenging than a real impact event. Carbon fiber reinforced polymer specimens containing a thin insert in one region were loaded in a biaxial-bending state of deformation. As a result, three-dimensional damage processes, involving delaminations at no more than three different interfaces that interact with one another via transverse matrix cracks, were observed and documented using ultrasonic testing and X-ray computed tomography. The data generated by the test is intended for use in numerical model validation. Simulations of this test are included in Part II of this paper.
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| 7. |
- Monti, Marco, et al.
(författare)
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Fire reaction of nanoclay-doped PA6 composites reinforced with continuous glass fibers and produced by commingling technique
- 2015
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Ingår i: Polymer degradation and stability. - : Elsevier Ltd. - 0141-3910 .- 1873-2321. ; 121, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we report the development of a glass fiber commingled composite (GFCC) based on a nanoclay-doped polyamide 6 (PA6) and the evaluation of its fire reaction. The preparation of the composite comprised several steps. Firstly, the nanoclay was dispersed in the PA6 matrix. Then, the produced compound was spun in filaments and commingled with continuous glass fibers. Finally, the laminate preform was consolidated. Reference samples based on the neat PA6 were produced as well. As a results, although it is well known that, in the presence of a relevant amount of continuous fibers, the behavior of the material is mainly driven by the fibers themselves (e.g. mechanical, thermal, conductive, and so on), the effect of the clay was interesting, especially in flammability test (UL94 vertical burning test), where the total burning time passes from 227 s to 146 s.
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| 8. |
- Monti, Marco, et al.
(författare)
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Montmorillonite-doped commingled composites for improved fire performance
- 2014
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Konferensbidrag (refereegranskat)abstract
- In this paper, we report the development of a glass fiber commingled composite (GFCC) based on a nanoclay-doped polyamide 6 (PA6) and the evaluation of its combustion behavior. The preparation of the composite has involved several steps. Firstly the nanoclay was dispersed in the PA6 matrix. Then, the produced compound was spun in filaments and commingled with glass fibers. Finally, the laminate preform was consolidated. In order to evaluate the effect of the nanoclay on the combustion behavior of the GFCC, samples based on the neat PA6 were produced as well. The results show that the effect of the nanocomposite matrix was a significant improvement regarding heat release when a continuous external heat flux is applied (cone calorimeter), whereas in the presence of the glass fibers the positive effect is more pronounced in tests where a small flame is induced to ignite the vertically oriented sample (UL94 vertical burning test). This is connected to the different mechanisms by which the nanoclay affects the combustion behavior, whether in the presence of glass fibers or not.
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| 9. |
- Pakkam Gabriel, Vivek Richards
(författare)
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Analysis of transverse cracking in cross-ply laminates: Weibull distribution based approach
- 2022
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Fiber reinforced polymer composite laminates make up more than 50% of modern aircrafts. Such composite laminates are exposed to various environmental and in-service thermo-mechanical load conditions. Transverse/intralaminar cracking is usually the first form of damage appears in a composite laminate and they tend to increase in number during the service life. The growth in number of these cracks significantly degrades the thermo-elastic properties of the composite laminate and eventually leads to final failure. Thus, it is important to predict the crack density (number of cracks per unit length) growth in both non-interactive crack density region and interactive crack density region and its effect in thermo-elastic properties degradation. Non-interactive crack density region is the region where the cracks are far apart and stress perturbation between cracks do not overlap. Interactive crack density region is where the cracks are close to each other and stress perturbation between cracks overlaps and affects the formation of new cracks. In this study, transverse cracks in thick Glass Fiber Epoxy (GF/EP) cross-ply composite laminates under quasi-static tensile loading and tension-tension fatigue loading have been analyzed and predicted.In the first paper attached here, increase in number of transverse cracks in GF/EP cross-ply laminates under quasi-static tensile loading at room temperature (RT) are analyzed using 2 material systems. The failure stress distribution in 90° plies of the laminates is defined by Weibull distribution and the Weibull parameters are determined from crack density versus applied thermo-mechanical transverse stress in 90° layer (σTCLT) data points within the non-interactive crack density region. The crack density growth is then predicted versus the σTCLT and applied mechanical strain in the laminate from the determined Weibull parameters using Monte Carlo method and the stress distribution models between adjacent cracks. The predicted results using the novel stress distribution model introduced here were in good agreement with the non-interactive and interactive crack density regions of test results. The importance of using the Monte Carlo method and novel stress distribution model to predict the whole crack density region have been emphasized in the article, in addition to that it also redefined the interval of non-interactive crack density region. The second paper expands the concept from the first paper, to address the tension-tension fatigue loading at RT. It deals with the crack density analysis and prediction in [0/90]s GF/EP laminate under fatigue loading at RT. The fatigue tests were performed at 3 maximum stress levels. Here the Weibull parameters were determined from the data points within the non-interactive crack density region in quasi-static and fatigue loading. From the determined Weibull parameters of each stress level and using Monte Carlo method and the novel stress distribution model, the crack density versus the number of fatigue cycles were predicted and in good agreement with the fatigue test results at the respective stress level. The intention here was to use Weibull parameters of one stress level to predict crack density at arbitrary stress levels. Based on it, the predicted results were not sufficiently good and suggested to revisit the Weibull parameter determination by performing fatigue tests at two stress levels. In the attached paper 3, new methodology on crack density growth simulation and Weibull parameter determination in tension-tension fatigue loading has been developed. In the newly developed methodology, in detailed fatigue tests are performed at one maximum stress level to obtain all data points and at higher stress level to obtain one data point that is a crack density data point at certain number of cycles to determine Weibull parameters. Using the determined Weibull parameters from non-interactive crack density region, the whole crack density region was successfully predicted for other stress levels.
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| 10. |
- Pakkam Gabriel, Vivek Richards, et al.
(författare)
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Transverse Cracking Characterization and Prediction in Heat Treated Polymer Composites under Quasi-Static Tensile Loading at Elevated Temperature
- 2022
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Ingår i: ECCM 2022 - Proceedings of the 20th European Conference on Composite Materials. - : EPFL Lausanne, Composite Construction Laboratory. ; , s. 23-30
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Transverse cracking in high temperature polymer cross-ply composite laminate was experimentally studied. In the tests, pristine as well as heat treated cross-ply laminate specimens were subjected to quasi-static tensile loading at room temperature and 150°C. Microscopy studies revealed that manufacturing induced transverse cracks were present in 90° layer of pristine cross-ply laminates. An increase in number of transverse cracks were observed after the heat treatment. Transverse crack density (number of cracks/unit length) growth upon applied thermo-mechanical transverse stress in 90° layer was analyzed using 3-parameter Weibull failure stress distribution. The Weibull location parameter, in efforts to address the influence of temperature and heat treatment of crack density growth, is modified based on empirical data. The predicted results were in good agreement with the test results.
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