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Fiber orientation structures and mechanical properties of injection molded short glass fiber reinforced ribbed plates

2004; Wiley; Volume: 25; Issue: 3 Linguagem: Inglês

10.1002/pc.20019

1548-0569

P.J. Hine, R. A. Duckett,

Injection Molding Process and Properties

Abstract In this paper we describe a study of the fiber orientation structures present within a model ribbed injection molded plate. The details of the fiber orientation at each chosen location on the injection molded parts were measured using an in‐house developed image analysis system, which enabled large areas to be scanned (up to 200 mm 2 ) up to a limit of 1 million fiber images. Two materials were used for these experiments, short glass fiber filled PBT and short glass fiber filled nylon 66. First, a comparison was made between the fiber orientation at an identical position, 28 mm from the injection gate on a transverse rib, on two plates made from glass fiber filled PBT. It was found that the fiber orientation in these two separately manufactured components was virtually identical when comparing the whole scanned area, but the differences became more significant when comparing areas on the length scale of an individual fiber (∼ 200 μm). Second, the fiber orientation at the same position was compared for two plates made using the glass/PBT and glass/nylon 66 materials. The differences for the complete scanned areas were small, confirming that mold geometry plays a crucial role in determining fiber orientation structures, and that matrix properties are secondary. Third, the fiber orientation structures at various positions across one of the glass/PBT plates were examined in greater detail, in particular across a number of the transverse ribs: the chosen ribs were of various widths and heights. Differences in structure were found depending on the local rib geometry. Finally, the effect of the measured fiber orientation structures in determining the mechanical properties of the ribbed plate was investigated using simple modeling schemes. While the stiffness of the rib/web assembly was found to depend on the average fiber orientation of the two parts, the different thermal expansions of the web and the rib, caused by the different fiber orientation in the two regions, led to significant warpage of the rib/web assembly. Polym. Compos. 25:237–254, 2004. © 2004 Society of Plastics Engineers.