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Sandwich Structural Design

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Sandwich composites are becoming increasingly popular in structural design, mainly for their ability to substantially decrease weight while maintaining mechanical performance. This weight reduction results in a number of benefits including increased range, higher payloads, decreased fuel consumption and a positive impact on cost as well as the environment.

High shear strength

Typical sandwich composite: The skins are thin, strong and stiff and the core is light and structurally strong enough to keep the skins in their relative positions under loading.

Also, a long known fact is that separating two materials with a lightweight material in between increases the structure’s stiffness and strength. This difference along with many other material characteristics available through strategic choice of core material such as, thermal insulation, low water absorption, sound and dielectric properties, among others can help benefit a wide range of industries and applications.

Case Studies

Malmo Station Entrances, Sweden

At the Malmo (Sweden) City tunnel infra-structure project, the architects by combining sandwich composites with glass and steel created two self-supporting entrances that maximize natural light and create a feeling of spaciousness. The flowing form of the entrances resembles futuristic spaceship and enables natural light to even filters down to the platforms, 25 meters below street level.

The station entrances were produced by Gothenburg-based Skandinaviska Glassystem AB (SG), specialists in the design and fabrication of façades and cladding systems (www.skandglas.com) in close association with DIAB (www.diabgroup.com). The key requirement of the sandwich composites for this project was lightweight, high strength performance. Thus, the sandwich components in addition to being capable of supporting the weight of any maintenance crews and equipment also feature hidden run-off channels for rainwater.

The sandwich composite elements were based on Divinycell P, DIAB’s recyclable, thermoplastic foam which offers excellent FST (fire, smoke & toxicity) properties, a wide processing envelope and very good fatigue properties. To achieve the complex geometry and the +/- 0.5mm tolerances that were required, the core was accurately machined to shape using a three axis CNC milling machine. Reinforcements were then applied directly to the core thereby eliminating the need for molds.

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