A sandwich panel is any structure made of three layers: a low-density core (PIR, mineral wool, XPS), and a thin skin-layer bonded to each side. Sandwich panels are used in applications where a combination of high structural rigidity and low weight is required.
The structural functionality of a sandwich panel is similar to the classic I-beam, where two face sheets primarily resist the in-plane and lateral bending loads (similar to flanges of an I- beam), while the core material mainly resists the shear loads (similar to the web of an I-beam). The idea is to use a light/soft but thick layer for the core and strong but thin layers for face sheets. This results in increasing the overall thickness of the panel, which often improves the structural attributes, like bending stiffness, and maintain or even reduce the weight.
Sandwich panels are an example of a sandwich-structured composite: the strength and lightness of this technology makes it popular and widespread. Its versatility means that the panels have many applications and come in many forms: the core and skin materials can vary widely and the core may be a honeycomb or a solid filling. Enclosed panels are termed cassettes.
A cleanroom or clean room is an engineered space, which maintains a very low concentration of airborne particulates. It is well isolated, well-controlled from contamination, and actively cleansed. Such rooms are commonly needed for scientific research, and in industrial production for all nanoscale processes, such as semiconductor manufacturing. A cleanroom is designed to keep everything from dust, to airborne organisms, or vaporised particles, away from it, and so from whatever material is being handled inside it.
A cleanroom can also prevent the escape of materials. This is often the primary aim in hazardous biology and nuclear work, in pharmaceutics and in virology.
Cleanrooms typically come with a cleanliness level quantified by the number of particles per cubic meter at a predetermined molecule measure. The ambient outdoor air in a typical urban area contains 35,000,000 particles for each cubic meter in the size range 0.5 μm and bigger, equivalent to an ISO 9 certified cleanroom. By comparison an ISO 14644-1 level 1 certified cleanroom permits no particles in that size range, and just 12 particles for each cubic meter of 0.3 μm and smaller. Semiconductor facilities often get by with level 7 or 5, while level 1 facilities are exceedingly rare.