Impact strength of adhesive bonding of CFRP parts made by hand lamination method

The continuous development of aircraft structures requires meeting increasingly stringent demands. They are expected to be robust, weatherproof but, above all, as light as possible while retaining the required strength parameters - all this to reduce the weight of the aircraft as much as possible. The answer to these requirements is composites, which are gaining increasing importance in modern aerospace equipment and seem to dominate the materials used so far. However, the use of composites introduces problems that did not occur with the use of metals. Conventional methods of joining components had to be supplemented with other types of joints, among which adhesive joining has gained the greatest importance. The static properties of adhesive joints in composite components have been the subject of extensive research described in the available literature. Thus, they are well understood. In contrast, the dynamic properties of such joints are rarely studied; therefore, the authors of this paper undertook research on impact resistance of adhesive joints in composite components made of CFRP. Due to their high popularity, the authors used lap joints in the research. Various structural adhesives differing in composition were used to create the joints. The obtained results made it possible to determine the adhesive joining properties of the components joined with various adhesives and to see the correlation between surface preparation methods and the nature of the breakages. As with metal bonding, adhesive joints made with an epoxy adhesive with a higher Young's modulus value show lower impact strength rather than joints made with an adhesive with a lower Young's modulus value. In the case of hybrid and polyurethane adhesives, there is no such relationship.