Wyniki wyszukiwania - Biblioteka Nauki

1

Selection of the heat transfer coefficient using swarming algorithms

100%

Gawrońska E. , Dyja R. , Zych M. , Domek G.

Acta Mechanica et Automatica

|

2022

|

tom Vol. 16, no. 4

325--339

EN

The article presents the use of swarming algorithms in selecting the heat transfer coefficient, taking into account the boundary condition of the IV types. Numerical calculations were made using the proprietary TalyFEM program and classic form of swarming algorithms. A function was also used for the calculations, which, during the calculation, determined the error of the approximate solution and was minimalised using a pair of individually employed algorithms, namely artificial bee colony (ABC) and ant colony optimisation (ACO). The tests were carried out to select the heat transfer coefficient from one range. Describing the geometry for a mesh of 408 fine elements with 214 nodes, the research carried out presents two squares (one on top of the other) separated by a heat transfer layer with a κ coefficient. A type III boundary condition was established on the right and left of both edges. The upper and lower edges were isolated, and a type IV boundary condition with imperfect contact was established between the squares. Calculations were made for ABC and ACO, respectively, for populations equal to 20, 40 and 60 individuals and 2, 6 and 12 iterations. In addition, in each case, 0%, 1%, 2% and 5% noise of the reference values were also considered. The obtained results are satisfactory and very close to the reference values of the κ parameter. The obtained results demonstrate the possibility of using artificial intelligence (AI) algorithms to reconstruct the IV type boundary condition value during heat conduction modelling.

2

Screw Extrusion as a Scalable Technology for Manufacturing Carbon Nanotube-Filled Polylactide Composites

88%

Kaczor D. , Bajer K. , Raszkowska-Kaczor A. , Domek G. , Schroeder P.

Advances in Science and Technology. Research Journal

|

2024

|

tom Vol. 18, no 3

99--110

EN

The bottleneck in the widespread use of carbon multiwall nanotube polymer composites is the lack of manufacturing technology that can be used on an industrial scale. In this article, we describe a two-step composite manufacturing technology based on screw extrusion that produces composites characterizing with good dispersion of carbon nanotube filler in polylactide matrix. The first stage involved the fabrication of highly filled masterbatches of 25 wt% of carbon nanotubes. In the second stage, by screw extrusion of the masterbatch mixture with neat polymer, we obtained homogeneous composites with the target filler concentration. The resulting composites with nanotube content ranging from 0.1 to 2 wt%. Mechanical tests including static tension, tensile strength, tensile modulus, three-point bending and impact strength has shown that optimal concentration of the carbon nanotube filler is ranged between 0.5 and 1 wt%. Samples were examined also by SEM, FTIR-ATR, DSC and MFR methods.

3

Screw Extrusion as a Scalable Technology for Manufacturing Polylactide Composite with Graphene Filler

75%

Kaczor D. , Bajer K. , Raszkowska-Kaczor A. , Krasinska O. , Domek G. , Szroeder P.

Advances in Science and Technology. Research Journal

|

2024

|

tom Vol. 18, no 2

226--237

EN

The use of carbon nanomaterials as fillers in the process of obtaining polymer composites by extrusion poses many problems. The high agglomeration ability and low bulk density of carbon nanomaterials do not allow to easy production of composites characterized by very good dispersion of the filler in the polymer matrix, which is required to obtain a high-quality product. The advantage of this type of fillers is that the improvement of the composite properties can be achieved even at a low degree of filling. In this article, we describe a method for obtaining polylactide composites with a nanofiller in the form of graphene nanoplatelets. To overcome the difficulties associated with the use of graphene, we divided the process of obtaining composites into two stages. In the first stage, we made a masterbatch containing 25 wt.% graphene, from which, in the second stage, we obtained target composites containing from 0.1 to 2 wt.% graphene. A twin-screw extruder was used in both stages. The tested filling levels had no significant impact on the recorded processing parameters. The composites obtained by the described method are characterized by good dispersion of graphene. However the graphene agglomerates can be observed in the polymer matrix. Composites were tested by SEM, FTIR, DSC and MFR methods. Mechanical tests such as static tension, three-point bending, impact strength showed that the addition of 0.5 wt% of graphene improves tensile strength by 10 %, Young's modulus by 19 % and both flexural strength and flexural modulus by 15 %. The carbon filler has an impact on crystallization process of the polymer matrix by acting as a nucleating agent.

4

Influence of extruder plasticizing systems on the selected properties of pla/graphite composite

75%

Kaczor D. , Bajer K. , Domek G. , Madajski P. , Raszkowska-Kaczor A. , Szroeder P.

Acta Mechanica et Automatica

|

2022

|

tom Vol. 16, no. 4

316--324

EN

Twin-screw extrusion is a crucial method for the direct inserting of carbon micro- and nanomaterials into a polymer matrix using a dry procedure. The study aimed to determine the influence of the parameters of the twin-screw extruder plasticizing system on the dispersion homogeneity and distribution of graphite filler in the polylactide polymer matrix and overall quality of the composite. As a filler, a graphite micropowder with a 5 μm lateral size of platelets was used at concentration of 1 wt.%. Three configurations of screws with different mixing intensity and various types segments were considered in the extrusion experiments. Morphology and chemical structure of the obtained composites were examined using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy – attenuated total reflectance (FTIR-ATR) and Raman spectroscopy. Differential scanning calorimetry (DSC) and melting flow rate measurements (MFR) were used to asses thermal and rheological properties of the composites. Samples of the polylactide/graphite composites were also subjected to mechanical tests. The results show that the selection of the mechanical parameters of twin-screw extruder plasticizing system plays a key role in the preparation of the homogeneous PLA/graphite composites. Incorrect selection of the screw geometry results in poor mixing quality and a significant deterioration of the mechanical and thermal properties of the composites. Optimised mixing and extrusion parameters can be the starting point for the design of efficient twin-screw extruder plasticizing system for fabrication of PLA composites with carbon nanotube and graphene fillers.