Glass-reinforced polyester has a lower coefficient of thermal expansion than those of other plastics, but higher than those of steel, glass or concrete, and similar to that of aluminium and wood. The coefficient of expansion is linked to the amount of glass-fibre content in the laminate: the higher the glass-fibre content, the lower is the coefficient of expansion.The expansion rate for a chopped strand mat laminate is
higher than that of a combination of chopped strand mat and woven rovings.
In calculating thermal movements the designer needs to assume a realistic figure for the temperature gradient set up within the cross-section of the panel.
3.19 Plan of glazing mullion at Herman Miller factory
3.20 Neoprene jointing gaskets used at the Herman Miller factory Bath: (1)6 mm surface-modified solar control glass; (2) resilient packing strip; (3) continuous neoprene gasket fitted to U-shaped aluminium beading screwed back to carrier; (4) extruded aluminium carrier screwed back to steel hollow section; (5) GRP sandwich panel, overall thickness 75 mm, outer insulation 19 mm polyurethane foam, inner insulation 25 mm polyurethane foam; (6) 127 mm x 63.5 mm hollow section steel sub-frame mullion; (7) 6 mm mild steel assembly shoe bolted to concrete slab; (8) 127 mm x 63.5 mm hollow section steel horizontal rail; (9) pressed aluminium sill fixed back behind carrier
This will depend upon factors such as orientation, colour of cladding, any insulation that may be behind it (sandwich panel), and its fixing and jointing aspects.
It is important to take account of thermal expansion in the design of fixings at the interface of GRP panels and some other finish material or component within the structure.
Was this article helpful?