1st June 2017 by Richard Yen
For today’s look back at last year’s Altair Enlighten Award, we’re going to review Sika’s entry which concerned adhesives and mixed materials, a topic that is becoming hugely significant in the automotive world thanks to the weight saving potential of the approach.
Although mixed materials car bodies have been more common in the racing world or the luxury vehicle market, there’s been many high profile examples in recent years where the approach has been deployed on higher volume vehicles, including the Honda Acura, Audi A8 and Cadiallac CT6 to name just a few.
Mixed materials provides some huge weight saving potential for manufacturers but brings with it some challenges, chiefly, how to join different materials together in an efficient and reliable manner. Sika’s 2016 nomination centered on its SikaPower adhesive technology which was developed to address this challenge.
For the new BMW 7 Series, innovative adhesive technology was needed to strategically bond the CFRP to steel and to bond aluminum to steel. The adhesive solution must address the issue of different coefficients of thermal expansion (CTE) or Delta/Alpha of the different material substrates. SikaPower is a one-component, crash resistance adhesive designed to have the optimal balance of modulus, elongation and strength to give the adhesion performance necessary while preventing any failure from residual tension during the entire vehicle service life. The adhesive technology is a key enabler to making the use of mixed material including lightweight materials, such as CFRP and aluminum, possible in the BMW 7 Series.
SikaPower was used in applications including the B- and C-pillars, roof bows, along the center tunnel, on package tray, in sills and on the roofline from base of A-pillar to rear of the car, making a total of 15 CFRP parts bonded using the crash resistance adhesive.
Adhesive technologies are becoming hugely significant as the move to mixed materials in high volume vehicles continues and it’s easy to see why it’s an attractive prospect when considering that this SikaPower application enabled the use of mixed material resulting in 50 kg weight saving in the Body-In-White from previous 7 Series model. Since we introduced an ‘Enabling Technology’ award category this year, I expect we will see many more entries concerning adhesive applications and mixed material car bodies.