[Photo: Filament winding of a tapered pole]
Fibre glass manufacturer Silvercraft Products Ltd. recently approached the Department of Mechanical Engineering within the University's Faculty of Engineering to come up with an innovative solution for the manufacturing of composite poles using game-changing materials, and realise it.
The strong collaboration between local industry and University of Malta gave rise to the project “Advanced Revolutionary Manufacturing Solutions and Development of Novel GFRP Composite Poles (ARM-D-COP)” financed by the Malta Council for Science and Technology (MCST) through the FUSION; The R&I Technology Development Programme 2018.
The project, coordinated by Prof. Inġ. Duncan Camilleri, Head of the Department of Mechanical Engineering, saw the design synthesis for a revolutionary winding technique that addresses the shortcomings of the conventional filament winding technique. In a nutshell, the novel technique can produce filament wound tapered poles which can be over 22m long. A prototype machine was designed and constructed to show the novel technique in action.
A fully automated system was recently commissioned paving the way towards attracting future business and enhancing the GDP of Malta.
Fibre reinforced composite poles and masts are utilised in various sectors such as flag poles, sail masts, antenna masts, weather station masts, street lighting poles and utility poles.
These structures used to be manufactured in wood out of tree barks and later on, metallic alloys were the preferred choice to enhance strength, weight, supply and sustainably. Nowadays, these structures are also being produced from man-made composites like glass or carbon reinforced plastics.
These game-changing materials have several advantages over their metallic counterparts such as improved weight to strength ratio, enhanced corrosion resistance and they are intrinsically electrical insulators.
Tapered fibreglass poles are customary manufactured in a staggered manner using the filament winding technique established in the 1960s. In essence, the technique involves winding a resin impregnated fibre bundle around a horizontal mould called the mandrel. The mandrel is set to rotate about the horizontal axis while a carriage, holding the fibre impregnation mechanism, traverses along the length of the mandrel to lay the fibre bundle on the mandrel producing the final layup of the pole. With the relative movement of the carriage and the mandrel, the helical angle of the wound fibre bundle can be adjusted according to the structural needs of the product.
The filament winding technique gives the designer freedom to construct several different layups but in practice, the technique has its limitations when it comes to producing long tapered poles or masts. Namely, laying the fibres close to the axial direction of the mandrel is challenging due to fibre bundle slippage during the winding process.
Having fibres closely aligned with the axial direction is structurally essential for components subject to bending like utility poles, street lighting, flag poles, sail masts and antennas. Furthermore, the length of the final product is limited due to the fact that the mandrel is oriented horizontally hence mandrel sagging is expected leading to bent poles.