Innovative Organosandwich semi-finished products

Innovative Organosandwich semi-finished products consisting of a thermoplastic honeycomb core and fiber-reinforced skin layers with thermoplastic matrix (organic sheets) can be produced in a continuous process and are therefore much less expensive than sandwich structures with conventional core materials (such as expanded honeycomb cores). By applying a top layer of fabric-reinforced organic sheets or thermoplastic laminates of UD single layers, application-optimized and load-adapted sandwich structures suitable for large-scale production can be produced. For use in complex components, these organosandwich semi-finished products must be reshaped and where applicable further functionalized. In the Organosandwich research project the feasibility of this has been demonstrated. This contribution gives a brief overview of the findings.

Sandwich structures have very high weight-specific stiffnesses and strengths. With top layers made of fiber-reinforced plastics and a lightweight plastic-based core (foam or a honeycomb core, for example) high-strength structures can be realized in, among other things, aircraft construction, shipbuilding or wind turbine rotor blades. For large-area structures mainly subject to bending loads, sandwich construction permits an enormous potential for saving weight. By using a lightweight core material that keeps two thin face layers apart, weight savings of more than 80% are possible compared with a monolithic construction. Here the thickness of the skin layers can be just a fraction of the thickness of a monolithic material. In this way, in addition to the weight savings, significant material cost savings are also possible. Common processing methods, such as the prepreg or vacuum infusion process in which the material components (skin layer and core) are introduced separately into a mold and then joined together are, however, very time-consuming and costly and therefore hardly suitable for mass production. For this reason, foam injection-molding methods have for some years been investigated with regard to the production of thermoplastic sandwich structures. The combination of thermoplastic foams and endless-fiber-reinforced face sheets makes heavyduty lightweight sandwich constructions possible. It is therefore predestined above all for use in structures where weight is an important consideration, such as in the construction of electric vehicles.