CNG Rack LightweightingwithComposites

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Armstrong, Robin
Nirza, Mel
Smagh, Harmanpreet
Zhang, Tianyi
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This report outlines the design changes of a structural steel rack that holds tanks containing compressed natural gas (CNG), for the purpose of weight reduction and ease of assembly. The CNG rack is mounted on the roof of New Flyer’s transit buses, therefore weight reduction was requested by the client, namely New Flyer Industries(NFI). The team, Bus Riders Consulting, was successful in achieving the needs of the client having gone through analysis of the rack and making required design changes. To achieve weight reduction, the team intends to replace the main structural steel beams of the rack frame with glass fibre reinforced polymer (GFRP) 2x2 inch square tubes with a ¼” wall thickness. An aluminium sheet panel that spans along the rack will be replaced with a sandwich structure panel comprised of GFRP skin and Balsa core. To achieve an easier assembly of the frame, the team intends to change four joints (corner nodes) that connect the perimeter beams with a die-cast Aluminum6061-T6corner node, in which the beams can be slotted into, bolted, and bonded with ease. The new single piece corner node alleviates the need of welding together multiple steel pieces to join beams. The existing total weight of the parts in scope amounted to 223.3 lbs. The total weight of the new parts totals to 124.6lbs.With the changes implemented, a 44% weight reduction of the overall rack will be achieved.