Fibre length and loading impact on the properties of glass fibre reinforced polypropylene random composites

In injection moulding, long glass fibre reinforced thermoplastics (LGFT) are an attractive way to produce large parts at low cost. The strength of the part depends chiefly on the average fibre length, fibres which are subjected to considerable attrition during processing in conventional three stage screws. First of all, in this study we have coupled a melting analysis in a conventional screw to a model of fibre breakage whereby a fibre anchored at one end in the solid bed is submitted, at its other end, to the intense shear stress of the molten polymer flowing in the film close to the barrel. As the melting of the solid bed progresses, more fibres are unlayered and submitted to bending which intensity is depending on both the fibre length and orientation. When the bending is too high, the fibre breaks. Bimodal fibre length distribution are obtained and compared to existing data. The sensibility of the model to main processing parameters such as screw rotation, initial fibre length, viscosity, barrel temperature and screw geometry are also investigated. Next, we present a new analytical solution for flow of a viscous fluid in a single screw channel that takes into account the torsion and curvature of the channel. Contrary to common knowledge in polymer processing based on the Parallel Plate Model, we found that, in the case of cross-sections with large aspect ratio, torsion effects can be significant. The implication of the model on velocity field, residence time and mixing efficiency is investigated and compared to the predictions of the classical Parallel Plate Model, to finite elements calculations, and to 3D experimental measurements. Indeed, an innovating device has been developed in our laboratory to visualize the flow of a viscous fluid in the channel of a screw. It consists of a transparent barrel and of a rotating screw, pumping a transparent viscous fluid at room temperature. A particle plunged in the flow is constantly monitored by four video-cameras placed around the barrel and recording its position in a frame. The 3D path lines are then computed.

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Influence of Fibre Length on Properties of Glass-Fibre Reinforced Bark Particleboards

Drvna industrija ◽

10.5552/drvind.2020.1948 ◽

2020 ◽

Vol 71 (4) ◽

pp. 411-415

Author(s):

Zoltan Pásztory ◽

Zoltan Börcsök ◽

Dimitrios Tsalagkas

Keyword(s):

Thermal Insulation ◽

Glass Fibre ◽

Mechanical Performance ◽

Fibre Length ◽

Physical And Mechanical Properties ◽

Modulus Of Rupture ◽

Conductivity Measurements ◽

Bending Properties ◽

Glass Fibres ◽

Glass Fibre Reinforced

This study was carried out to assess the feasibility of glass fibres of various lengths (12 mm, 18 mm, 24 mm and 30 mm) as reinforcement on the mechanical performance of bark particleboards intended for thermal insulation. To evaluate their efficiency, the results of fibre reinforced particleboards at mass of 3wt% concentration were compared with plain bark based boards. Thermal, physical and mechanical properties (modulus of rupture, modulus of elasticity and internal bond) were determined on unreinforced and reinforced specimens. In general, the results of the thermal conductivity measurements indicated that the bark panels could potentially be used as feedstock for thermal insulation panels. However, the glass fibres lengths had a direct adverse effect on the mechanical behaviour of the bark particleboard, instead of providing synergistic reinforcement. Furthermore, the static bending properties, mainly the modulus of rupture, gradually decreased with increasing lengths of glass fibre.

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