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Automotive Series: Surface Preparation of Composite Surfaces

Building a More Fuel-Efficient Automobile

The pursuit of producing a more fuel-efficient automobile does not rely solely on the efficiency of the engine. A great amount of fuel efficiency gains are possible not because of improvements to engine design but because of improvements in materials. Automotive manufacturers have looked to the aerospace industry for inspiration and, much like modern fighter jets, have settled on the use of composite materials in car frames and interiors to reduce weight. 

As the use of composite materials continues to grow– and even become integrated into more critical parts such as automobile frames--the issue of safety becomes more important. Due to the structure of composite materials, mechanical fasteners sacrifice compatibility. The strength of composite materials dwindles when fibers break due to holes used for fasteners. Rather than using mechanical fasteners, adhesives replace fasteners to bond these composite materials to the frame. These bonds are strong enough to withstand the stresses of a wreck. This allows composite material utilization on critical components of the car frame. That is, of course, assuming the strength of the bond remains consistent – and that is where matters become complicated.

Ensuring a Reliable Bond

When using adhesives, the material surface requires a specific level of cleanliness in order to hold strong, reliable bonds. Ensuring surface condition and consistency is a vital component for guaranteeing success in sealing, coating, bonding, painting, printing, or cleaning.

All surfaces contaminate upon exposure, and the presence of contaminants is inevitable. But, by using data to understand the state of a material surface, manufacturers can gain confidence that their bonds will reliably hold every time. 

Experimentation is needed to determine the best method of preparing a surface in a way that maximizes the available surface energy. Once an ideal method for preparation has been determined, manufacturers can use the Surface Analyst to monitor surface quality on the factory floor. 

Rethink your adhesion manufacturing processes with Surface Intelligence.

Measuring Surface Cleanliness Levels with the Surface Analyst

The Surface Analyst deposits a highly purified drop of water on any surface and determines the contact angle. This contact angle reveals the surface cleanliness level of a substrate. When a surface is clean, it emits high energy; water, as a high-energy molecule, spreads out on the surface in attraction to other high-energy molecules. This produces a low contact angle. A contaminated surface emits low energy and will cause water to bead up in attraction to itself rather than the low-energy surface molecules, producing a high contact angle. By knowing the volume and area of a drop of water, the contact angle of the water against a given surface can be determined. The more contaminated the surface, the higher the contact angle. The lower the contact angle, the cleaner the surface.

Using the Surface Analyst in the laboratory allows manufacturers to develop an effective surface preparation method. Its portability allows for surface testing on the manufacturing floor and ensures proper surface preparation. Even better, the Surface Analyst™ performs its calculation of average contact angle in a few seconds, reducing delays in the manufacturing process.

With the Surface Analyst™, automotive manufacturers can ensure consistent bond strength between a composite surface and the car frame, allowing them to accurately predict and model how the material will react in a high-stress situation. In turn, this means manufacturers can be more confident in experimenting with composite materials as a way of further reducing the weight of a car, thus increasing its fuel efficiency.

To learn more about developing an effective and fulsome root cause analysis plan, download the Checklist: Adhesion Failure Root-Cause Analysis for Manufacturers eBook. 

The Future of Manufacturing: A Guide to Intelligent Adhesive Bonding Technologies & Methodologies

Image above: BMW i8 with a body constructed with carbon fiber composite, aluminum, and plastic.