Energy- and resource-saving lightweight-construction solutions are playing an increasingly important role across all sectors. Hybrid material composites thereby form a particular focus of attention. Through the combination of different materials, positive material properties can be specifically exploited. This results in high-performance, lightweight components. In the mobility sector, this enables large quantities of CO2 emissions to be saved, as less weight has to be moved during the journey. The utilization of renewable raw materials has an additional positive effect on the life-cycle assessment, because CO2 is bound in the material and smaller amounts of finite raw materials are consumed. Furthermore, renewable raw materials are often available regionally. This saves transport energy and could help to make Germany less dependent on imports.
In the automotive industry, the combination of metal and wood is of particular interest – not only due to the specific material advantages, but also with regard to the simplest possible, economically viable adaptation of established production processes. For the joining of wood and metal to form force-fit composites, adhesive bonding is a prime option. In the mobility sector, however, the application of adhesives to entire component surfaces has not yet been established. Consequently, vehicle parts are seldom made from molded laminated wood, despite the favorable material properties.
A switchable adhesive for large surfaces would enable the material production to be outsourced. Vehicle manufacturers could purchase plywood or wood-metal laminates as sheet material and form them into three-dimensional components by means of targeted heating. This facilitates the adaptation of process chains and production lines for the manufacture of components made from wood or with a high wood content. In addition, companies that only produce in moderate numbers of units, such as those in the rail sector, can produce more flexibly by utilizing semi-finished, storable products.
The switchability of the adhesive offers advantages not only for production, but also for the reparability and recycling of (hybrid) bonded laminates. The objective is to ensure that the individual material layers can be separated from one another as cleanly as possible through targeted heating.
The utilization of renewable raw materials for adhesive production makes manufacturers less dependent on petrochemical resources and additionally increases the sustainability of the components.
Fraunhofer Institute for Wood Research 
