Injection molding of punctiform load-introduction elements

The relatively low strength of FRP sandwich structures in the thickness direction requires special adaptations in the joint area for punctiform load transfer, for example, by means of screws. Different connecting concepts may be found in the literature, which are applied depending on the load and application case. For medium and high loads the core structure must be reinforced locally, which can be done, for example, by filling the core with a curable resin-catalyst compound, known as potting. Depending on the load case, additional metallic inserts are embedded in the potting material.

During the processing of organosandwich semi-finished products in the hybrid injectionmolding process, it is possible to use injection molding and thermoplastic for the potting fillings. It has already been demonstrated in experimental studies that a reproducible filling of a previously prepared core area by means of an adapted injection-molding cycle is possible within a few seconds. As an injection-molding material for the plastic potting, polypropylene with an MFI of 23g/10min, appropriate for the matrix material of the organosandwich semifinished products, was processed in the experiments. Not only could pure potting fillings be produced by injection molding but metallic inserts could also be embedded in the sandwich.