Linear thermal expansion of polycarbonate

When the air temperature changes, polycarbonate sheets are subject to dimensional changes. These changes are so small that they are not visible to the naked eye. Calculating the degree of change in the linear dimensions of the sheets is not difficult when designing and assembling the structure, and it is absolutely necessary so that the sheets can compress and stretch to the required size without damaging the design and their condition.

Neglecting the factor of changing the linear dimensions of the sheet with changes in ambient temperature in practice means that during installation, gaps are not left between the plastic sheets and the metal structure, gaps in the connection nodes, as well as in the places of fastening with screws.

When the temperature increases (in summer), the size of the sheet increases, it "bumps" into the structure and, as a consequence, internal stress, warping occurs, the sheet deforms and cracks, covering with waves.

And the opposite mistake, when insufficient allowance is made in the structure — with a decrease in temperature, the size of the sheet decreases, and it slips out of the fastening elements.
Polycarbonate has a coefficient of thermal expansion equal to 0.065 mm/m°C (for colorless and white panels)
For the correct calculation of the mounting structure, it is necessary to consider the following formula:
∆L = L * ∆T * K, where

L - length (width) of the sheet (m),
∆T - temperature change (°C),
K = 0.065 mm/m°C - coefficient of linear thermal expansion for multiwall polycarbonate.
For example, if the temperature in summer is +40°C and in winter -20°C (a difference ∆T = 60 degrees), then each meter of the sheet will "move" by 3.9 mm (∆L = 1×60×0.065).

At the same time, it should be noted that colored sheets heat up 15-20 °C more than transparent and white ones. ∆L for colored panels can reach 5-6 mm for every meter of their length and width.
Regarding mechanical fastening, the diameter of the drilling holes in the sheets should provide sufficient space for natural expansion/contraction. Based on experience, it should be 2-3 mm larger than the diameter of the fastening element (screw, bolt, etc.).
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