corrugations

Corrugations are a regular series of parallel ridges and grooves on a surface, typically formed by bending, folding, embossing, or natural processes. They are used to increase stiffness, reduce weight, or provide drainage and cushioning. Corrugations can occur in a wide range of materials, including metals, plastics, paper, and geological surfaces, and they may be engineered or result from wear and weathering.

In manufacturing, corrugation is achieved by passing material between rollers (corrugating) or by embossing. The most common example is corrugated cardboard, where a fluted sheet is sandwiched between flat liners, creating a lightweight, impact-resistant core. Variants include single-wall, double-wall, and triple-wall constructions.

Corrugated metal sheets serve as roofing and siding due to increased stiffness and water shedding. Corrugated plastics and fiber-reinforced composites are used in architectural cladding and marine applications. Corrugated pipes are used for drainage and culverts because the ridged profile resists collapse while allowing flexibility.

In geology or geomorphology, corrugations describe natural ridges and troughs on surfaces produced by erosion, deposition, or tectonic processes, while in optics and electromagnetism, surfaces with periodic corrugations are used as diffraction gratings or to tailor electromagnetic wave propagation.

The term derives from corrugare, Latin for to wrinkle or to fold.