Improved IP Sunload Performance Through Structural Design

As automobile designs become more aerodynamic, the windscreens become larger and flatter, magnifying the intensity of solar radiation at the instrument panel surface. Temperatures of over 110°C (230°F) are not uncommon for IP surfaces in desert testing, with substrate temperatures approaching 94°C (200°F). Designers must anticipate the effects of such harsh service environments and seek ways to accommodate and control the thermal expansion of thermoplastic IP substrates and minimize the distortion that can result.

Adding to the problem of greater solar effects from flatter windscreens are recent design trends toward more sweeping, cockpit-like automotive interiors. These configurations place additional structural demands on the large injection molded IP substrates that support many components. Passenger-side airbags too, have added to the size and strength requirements of these thermoplastic structures. The resulting weight increase is sometimes offset by reducing the wall thickness of the entire part by as much as 1 mm (0.04 in.).

The principal intents of this discussion are to improve the understanding of distortion effects on instrument panels caused by sunloads and to present several new design methods for reducing sunload distortion.