Laser Welding of Fabric
Laser welding of fabric made from synthetic fibres results in flexible, high-strength bonds. For production of airbags, for instance, the technique achieves high processing speeds and lends itself to automation.
Airbags are installed in the seats and roofs of automobiles as supplemental restraint systems for increased occupant safety. They offer protection in the event of side-impact collisions or rollovers. However, in case of a rollover in particular, the airbags must remain inflated for ten seconds in order to provide meaningful protection. This can be assured only if the seams are airtight.
Usually, airbags are sewn or produced on special looms. There are, however, situations where a welded seam offers benefits. With most traditional welding processes for fabrics, the entire thickness of material is melted. As a consequence, the seams are stiff. In contrast, with laser transmission welding only the contact surfaces of the thermoplastic fabrics melt. The resultant weld seam is softer and more flexible, yet retains very high flexibility. The outer condition of the fabric also remains unchanged.
The laser welding process produces watertight and sealed seams in a single operation. This opens up new design possibilities, since seams with tight radii are now possible. In addition, laser welding of airbags can be more highly automated, resulting in increased productivity. The process also reduces noise levels and the risk of injury in the workplace.
Unfinished synthetic fibres transmit radiation in the near infrared (NIR) region of the spectrum. For this reason, an NIR absorber is incorporated to absorb the radiation. The infrared absorber is either placed between the materials or applied as a thin layer at the intended weld seam. The laser beam is guided along the seam. The beam is transmitted through the first layer of fabric and converted into heat in the absorber layer. The fabrics melt locally and then bond under pressure.
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