Sandwich Structures
Sandwich components are structural light-weight design elements. Usually, sandwich components consist of thin, however rigid cover layers and a layer of light core material of major thickness.Cover layers of fibre-reinforced plastics possess good properties as to tensile and compressive strength. The foam core material primarily serves as spacer and is used to transmit the emerging shear forces.
Sandwich structures are well-suited for carrying distributed loads while showing very good flexural and twisting resistances. As fin printouts do not occur sandwich moulds are more form-stable which results in higher quality surface finishes. Further advantages to be mentioned are their low specific weight, high stability, rich noise and heat insulation properties, as well as their high vibration stability:
These advantages become effective with composite parts and panels, because they allow to cover large spans between the supporting points. Furthermore, even and smooth surfaces on both sides of the mould make up a further aesthetic advantage of sandwich structures.
Hahlbrock has been using a vacuum method to produce sandwich panels for many decades – for ship superstructures, radomes and antenna housings plus other high-quality presentation surfaces, e.g. the Landscape for the BMW Group.
In the field of radomes and antenna housings in particular, Hahlbrock has considerable experience in applying GRP and aramid facings with a constant, minimal thickness to flat or curved core materials. CNC-assisted formatting of the panels guarantees highly accurate butt joints even without metal components. The core materials – homogeneous foam boards of different densities based on PUR and PVC – are chosen according to structural, dynamic or thermal requirements. We also use the higher-quality PMI foam for radomes (e.g. Nippon radome) and special applications. Furthermore, boards of different densities and thicknesses can be combined to form the core materials to comply with special radar technology specifications.
Hahlbrock is also experienced in the use of honeycomb materials made from sheet aluminium or plastic films. One type of special sandwich material is 3D glass-fibre fabric; the spacer fibres remain upright due to the impregnation with resin and separate the two layers of fabric. This twin-wall, gastight GRP material is also known as a spacer fabric and can be used to form a leakage warning cavity in a tank lining material, for instance. Hahlbrock has used this corrosion-resistant GRP material on various waste-water tanks.