Dow Automotive Systems has extended its technology for carbon fibre bonding solutions and added an innovative injection bonding technique for BETAFORCE composite bonding adhesives.
Dow explains that injection bonding is a further example for the customising capabilities of BETAFORCE to address specific customer requirements for production, such as open times and cycle times, without affecting mechanical properties. By adjusting these parameters individually, it helps customers improve their assembly process efficiencies. Further, this enables the wider application of carbon fibre parts in mix material assembly and thus supports manufacturers’ lightweight strategies, such as those at BMW Group and its recent BMW 7er series.
According to Dow, one special process to bond carbon fibre parts to metal in side frame applications along the roof is injection bonding. Here the carbon fibre part is used as inlay in a metal housing running along the A-pillar into the roof and down the D-pillar to ensure stability of the occupant cell engaged in side-pole impact and rollover as well as increase vehicle torsional stiffness with subsequent improved ride-handling and NVH at the lowest mass. The challenge integrating such long carbon fibre composite parts is the management of the differential Coefficient of Linear Thermal Expansion (CLTE) along the assembly as well as during the operative life of the vehicle.
Dow adds that based on a two-component polyurethane structural adhesive technology, BETAFORCE is characterised by a high elongation factor and outstanding modulus. While the high modulus provides the needed stiffness, the elongation factor enables a high level of energy absorption and flexibility to manage differential CLTE. To achieve the joining of both materials, the adhesive is injected by a robot and surrounds the carbon fibre for a durable bonding of differential substrate components. Further, BETAFORCE provides a superb adhesion to multi-material substrates, such as carbon fibre or coated metal, enabling advanced lightweight solutions for automotive manufacturers such as BMW Group.