Automatically Connected Composite Parts Can Be Bonded More Economically

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The Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM was honored with the JEC Composites Innovation Award in the Aerospace—Processes category with this innovation ...

According to the IFAM researchers, adhesive bonding is the predestined joining method for the relatively productive manufacture of components made from fiber-reinforced plastics. This is the only way to economically meet the current and future industrial demand for targeted lightweight construction. Consistent and adaptive automation of these bonding processes is also becoming increasingly important in view of the growing shortage of skilled workers. At the same time, the special training of skilled workers with regard to both the bonding process and fiber composite technology is indispensable. Composite materials, also known as composites, place high demands on the bonding processes. The bonding situation and the right choice between pasty adhesives and adhesive films must be taken into account in order to be successful. R&D approaches developed by IFAM specifically for this purpose are called digital gap measurement, adaptive gap filling and automated application processes for pasty adhesives and adhesive films. Together, these make it possible to create high-precision, resilient and cost-effective bonding processes for the most demanding composite structures, even when mixed with metals—and with sufficient productivity.

Clean Abrasive Surface Pre-Treatment

Vacuum suction blasting is an automated and clean process used by IFAM for the surface pre-treatment of the components to be bonded. These are roughened in this way to create more adhesion surface for the adhesive. Because the abrasive particles are extracted directly, the surface is also cleaned, i.e. residue-free. The process also enables both the pre-treatment and activation of surfaces. It can also be used as a material removal method for individual composite layers in order to prepare the shafts for repairs, as the researchers from Stade point out.

If You Know the Gap, You Can Bond With Low Tension

Composite structures are also often characterized by considerable shape and position tolerances, the report continues. Standardized, mostly manual, compensation methods would not be of much use given the requirements. However, a 3D surface measurement of the components generates point clouds from which the local joining gap geometry can be determined by means of coordinate transformation and virtual joining. The resulting gap map then serves as the basis for planning specific filling strategies, minimizing stresses and optimizing the amount of material, which is also suitable for very large and complex assemblies, according to the IFAM. Pasty 1- and 2-component adhesives are then recommended for individual gap compensation. Specially developed, robot-assisted dispensing systems ensure precise application in terms of volume, even along complex component geometries. Depending on viscosity, ambient conditions and component geometry, agile applications of the adhesives would then also be feasible. In combination with gap measurement, the adhesive beads can be varied locally in order to achieve defined layer thicknesses and low-stress joining.