| 1. |
- Allen, D.H., et al.
(författare)
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Modeling the viscoelastic response of GMT structural components
- 2001
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Ingår i: Composites Science And Technology. - 0266-3538 .- 1879-1050. ; 61:4, s. 503-515
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Tidskriftsartikel (refereegranskat)abstract
- A glass-mat-reinforced thermoplastic (GMT) composite material has been fabricated from randomly oriented continuous glass fibers embedded in a polypropylene matrix. The mechanical constitution of this composite has been characterized by using a linear viscoelastic micromechanically based material model. This material model has subsequently been implemented to several finite-element computer codes for analysis of structural components fabricated from polypropylene GMT. In this paper several example problems have been studied in order to determine the applicability of this modeling approach to predicting time-dependent deformations due to creep in GMT components. These example problems have been solved by utilizing two commercially available codes: ABAQUS, and ANSYS. Furthermore, results obtained with the codes have been compared to both analytic and experimental results, with varying degrees of success. The paper details these results for each of the example problems considered herein. © 2001 Elsevier Science Ltd. All rights reserved.
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| 2. |
- Suárez, A., et al.
(författare)
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Surface integrity and fatigue of non-conventional machined Alloy 718
- 2019
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Ingår i: Journal of Manufacturing Processes. - : Elsevier Ltd. - 1526-6125 .- 2212-4616. ; 48, s. 44-50
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Tidskriftsartikel (refereegranskat)abstract
- Alloy 718 is a high-strength, corrosion-resistant nickel chromium-based superalloy frequently used for applications, such as aerospace, marine, nuclear reactor and chemical industries, due to its outstanding inherent properties such as high strength and corrosion resistance at high temperatures together with good creep behaviour. Although, the use of conventional manufacturing processes is prevalent for their use on Alloy 718, alternative manufacturing technologies are gaining importance. This work compares the effects of alternative manufacturing processes, such as Abrasive water jet (AWJ), Wire Electrical Discharge Machining (WEDM) and ultrasound vibration assisted milling (UVAM) with conventional milling during the manufacture of Alloy 718 parts. Surface integrity, hardness, residual stress and fatigue strength obtained from these machining processes have been examined for cutting alloy 718. Results show that both residual stresses and surface roughness are correlated with fatigue strength. UVAM results shown an improvement on the surface integrity of the final workpiece. AWJ and WEDM show poorer results, further work on post-process technologies or process condition selection must be carry out to establish them as an alternative in Alloy 718 cutting operations.
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| 3. |
- Bridarolli, Alexandra, et al.
(författare)
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Evaluation of the Adhesion and Performance of Natural Consolidants for Cotton Canvas Conservation
- 2018
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society. - 1944-8244 .- 1944-8252. ; 10:39, s. 33652-33661
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Tidskriftsartikel (refereegranskat)abstract
- Recent developments in paper and canvas conservation have seen the introduction of nanocellulose (NC) as a compatible treatment for the consolidation of historical cellulosic artifacts and manuscripts. However, as part of the assessment of these new materials for canvas consolidation, the adhesion of the consolidation treatment (which takes place between the applied material and the substrate) has not yet been evaluated, and as a result, it is poorly understood by both the scientific and conservation communities. After evaluating the potential of NC treatments for the consolidation of cotton painting canvas, we investigate a route to promote the interaction between the existing canvas and the nanocellulose treatment, which is in our case made of cellulose nanofibrils (CNF). This was carried out by introducing a cationic polymer, polyamidoamine-epichlorohydrin (PAAE), as an intermediate layer between the canvas and the CNF. The morphological, chemical, and mechanical evaluation of the canvas samples at different relative humidity (RH) levels demonstrated how the adhesion of the added PAAE layer is a dominant factor in the consolidation process. Improvement in the coating of canvas single fibers by the CNF, higher adhesion energy between the canvas fibers and the CNF treatment, and finally overall stronger canvas reinforcement were observed following the introduction of PAAE. However, an increase in mechanical response to moisture sorption and desorption was also observed for the PAAE-treated canvases. Overall, this study shows the complexity of such systems and, as such, the relevance of using a multiscale approach for their assessment.
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| 4. |
- Holmberg, M, et al.
(författare)
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Surface force studies of Langmuir-Blodgett cellulose films
- 1997
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Ingår i: Journal of Colloid and Interface Science. - 0021-9797 .- 1095-7103. ; 186, s. 369-381
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Tidskriftsartikel (refereegranskat)abstract
- The interactions between cellulose surfaces, between chitosan coated surfaces and between one cellulose surface and one chitosan coated surface have been studied using the interferometric surface forces apparatus (SFA). The cellulose surfaces were prepared by depositing trimethylsilyl cellulose on hydrophobized mica using the Langmuir-Blodgett technique. The surfaces were desilylated in humid HCl atmosphere to obtain regenerated cellulose. ESCA measurements and wetting studies demonstrated that the desilylation process was effective. AFM studies showed the cellulose surfaces to be smooth with a root mean square roughness of 0.16 nm. Surface force and ellipsometry measurements illustrate that the cellulose film swells considerably in humid air and in water, suggesting that it is mostly amorphous. The interaction between two cellulose surfaces is dominated by a steric repulsion caused by a few dangling tails. On separation an attractive force was present both between two cellulose surfaces and between one cellulose surface and one chitosan surface. The long-range interaction between cellulose and chitosan was shown to be attractive.
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| 5. |
- Lee, L-T, et al.
(författare)
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Lipase-surfactant interactions studied by neutron reflectivity and ellipsometry
- 1999
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Ingår i: Journal of Physical Chemistry B. - 1520-6106 .- 1520-5207. ; 103, s. 7489-7494
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Tidskriftsartikel (refereegranskat)abstract
- The interaction between a microbial lipase and an anionic and a cationic surfactant at the air-water interface has been studied by neutron reflectivity. Sodium dodecyl sulfate (SDS) and tetradecyltrimethylammonium bromide (TTAB) were used as anionic and cationic surfactant, respectively. The same enzyme-surfactant systems were also studied at the interface between a hydrophobic solid surface and water by ellipsometry, and the results from the two techniques were compared. Surface tension measurements were also performed in order to monitor complex formation in bulk. The data obtained from neutron reflectivity and from ellipsometry were in very good agreement with each other. Both techniques show that lipase adsorbs readily at the interfaces and that SDS at low concentration does not interact strongly with this protein layer. At higher SDS concentration, the protein is displaced from the surface. On the other hand, when TTAB is added at low concentration, a thick lipase-surfactant layer is formed at the surfaces. This compact layer is solubilized by further addition of the cationic surfactant.
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| 6. |
- Nechyporchuk, Oleksandr, et al.
(författare)
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On the potential of using nanocellulose for consolidation of painting canvases
- 2018
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Ingår i: Carbohydrate Polymers. - : Elsevier Ltd. - 0144-8617 .- 1879-1344. ; 194, s. 161-169
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Tidskriftsartikel (refereegranskat)abstract
- Nanocellulose has been recently proposed as a novel consolidant for historical papers. Its use for painting canvas consolidation, however, remains unexplored. Here, we show for the first time how different nanocelluloses, namely mechanically isolated cellulose nanofibrils (CNF), carboxymethylated cellulose nanofibrils (CCNF) and cellulose nanocrystals (CNC), act as a bio-based alternative to synthetic resins and other conventional canvas consolidants. Importantly, we demonstrate that compared to some traditional consolidants, all tested nanocelluloses provided reinforcement in the adequate elongation regime. CCNF showed the best consolidation per added weight; however, it had to be handled at very low solids content compared to other nanocelluloses, exposing canvases to larger water volumes. CNC reinforced the least per added weight but could be used in more concentrated suspensions, giving the strongest consolidation after an equivalent number of coatings. CNF performed between CNC and CCNF. All nanocelluloses showed better consolidation than lining with synthetic adhesive (Beva 371) and linen canvas in the elongation region of interest.
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| 7. |
- Zangani, D., et al.
(författare)
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Numerical simulation of bending and failure behaviour of z-core sandwich panels
- 2007
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Ingår i: Plastics, rubber and composites. - 1465-8011 .- 1743-2898. ; 36:9, s. 389-395
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Tidskriftsartikel (refereegranskat)abstract
- The failure behaviour of fibreglass sandwich panels with structured internal cores (z-cored panels) was studied in bending. A finite element model was developed for the simulation of three point bending tests and this has been validated against experimental results. The model was able to predict both the elastic response and, more importantly, the failure behaviour of the structure. It is therefore suitable for use in the optimising the design of z-core sandwich panels for transport applications. The same modelling approach was also applied to the structural behaviour of a larger sandwich panel with a metallic insert which was employed in the design of a semitrailer as part of a demonstration of the viability of the technology. © 2007 Institute of Materials, Minerals and Mining.
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