Dissemination of IT for the Promotion of Materials Science (DoITPoMS)

DoITPoMS Teaching & Learning Packages Thermal Expansion and the Bi-material Strip Results: Measuring the thermal expansivity of polycarbonate

# Results: Measuring the thermal expansivity of polycarbonate

For the aluminium-polycarbonate bi-material strip the following measurements were made

 δ = 0.04 m x = 0.189 m

From equation (3) the curvature

$\kappa = \frac{{2 \times \sin \left[ {{{\tan }^{ - 1}}\left( {0.04/0.189} \right)} \right]}}{{\sqrt {{{0.04}^2} + {{0.189}^2}} }} = 2.1$

From equation (6), the misfit strain

$\Delta \varepsilon = \frac{1}{{12}}\kappa h\left( {{E_*} + 14 + \frac{1}{{{E_*}}}} \right) = \frac{1}{{12}} \times 1.2 \times 0.001 \times \left( {\frac{{70}}{{5.5}} + 14 + \frac{{5.5}}{{70}}} \right) = 4.7 \times {10^{ - 3}}$

And so, from equation (5)

${\alpha _{\rm{B}}} = {\alpha _{\rm{A}}} - \frac{{\Delta \varepsilon }}{{\Delta T}} = 2.3 \times {10^{ - 5}} - \frac{{4.7 \times {{10}^{ - 3}}}}{{ - 213}}4.5 \times {10^{ - 5}}{{\rm{K}}^{ - 1}}$

So the thermal expansivity of the polycarbonate material is 4.5 x 10-5 K-1.