Program for the thickness of composite surface layer counting
Elżbieta Bociąga, Paweł Palutkiewicz Politechnika Częstochowska, Wydział Inżynierii Mechanicznej i Informatyki, Instytut Przetwórstwa Polimerów i Zarządzania Produkcją al. Armii Krajowej 19c, 42-200 Częstochowa, Poland
Quarterly No. 3, 2008 pages 225-231
DOI:
keywords: the polyethylene, composite materials, carbon fibres
abstract The investigation of the influence of wall thickness of injection moulded parts on their structure and properties was the aim of this work. The results of investigation of structure and mechanical proprieties of moulded parts from HDPE and composite material (HDPE with 30% carbon fibre) have been presented. Stair-shape moulded parts with the different thickness, 1, 2, 3 and 4 mm moulded in an insert of two-cavity injection mould were used in experiments. Examinations allowed to determine the influence of carbon fibre addition in polyethylene on structure and selected mechanical proporties of moulded parts, like: tension strength, impact resistance, hardness, and shrinkage. In the section of moulded part of 1 mm thickness the highest degree of carbon fibres orientation appears all-over the cross-section of the moulded part, instead in section of the greatest thickness 4 mm carbon fibres are oriented only in the boundary layer of the part. The degree of the orientation is dependent on the thickness of the moulded part. In thick wall of a HDPE moulded part section, an orientation of the fibers is lower than in thin-wall parts. Fibers are oriented in the material flow direction. Orientation in the traverse direction is much lower due to high shear forces at the mould wall. In the case of filled polymers conditions of their flow in mould channels influence significantly orientation of filler particles, especially in fibres form, affecting consequently mechanical proprieties of moulded parts. Described phenomena occurring during the flow of material in the injection mould depend on shape and cross-section of mould channels. The size of cross-section of channels, and especially the cavity, influences conditions of polymer shearing what in turn affects the formation of the determined structure and proporties of moulded parts. Parts from HDPE filled with carbon fibre has better mechanical proporties and lower shrinkage than parts from unfilled HDPE. Because of the variable depth of injection mould the flow and shearing conditions of polymer in each sections of injection mould are different. In section of the large thickness (4 mm) material flows with the lower speed than in section of the smallest thickness (1 mm). The value of shrinkage depend on thicknesses of the injection moulded part. When the thickness of the HDPE part section increases the value of the transverse shrinkage increases as well, instead for HDPE filled with carbon fibres the influence of the thickness of moulded part on the value of the shrinkage is low. The carbon fibre in moulded parts permits to limit the shrinkage of parts significantly.