Micro perforated panels for acoustic damping

With the current worldwide attention for quieter aircraft, acoustic damping is applied inside the engines as well as around, i.e. in the nacelle. Micro perforated panels are applied in and around the engine to achieve desired noise reduction levels. These panels typically contain several millions of holes and are good example of a process where parallel hole drilling is essential to become commercially interesting.

The around 1 mm thick CFC panels contain millions of holes with diameters of several hundreds of micrometers. As the heat-affected zone is very limited or even absent, the material between the holes maintains its original strength.

Cooling holes in jet engine components

In modern jet engines a dense network of up to a million of holes is produced for air film cooling.

The UV laser drilling of metals and thermal barrier coatings can be integrated in one drilling process, resulting in high quality holes, with limited heat affected zone, absence of cracking and delamination, thin recast layers and no structural changes. The drilling angle can vary from perpendicular to a very shallow angle to the material.

Mounting holes

Because of its absorption characteristics the excimer laser is very suitable for drilling CFC’s. With UV no delamination or structural damage occurs.

This example shows a large mounting hole in approx. 5 mm thick CFC and also its remaining core. The quality of the edge of the core shown in the figure shows that the drilling process can be so well controlled that the structure of epoxy and fiber layers is still intact.

Hole drilling for drag reduction panels

Micro perforated panels mounted on aircraft wings can be used for boundary layer control to reduce drag and saving up to 10 % in fuel consumption. NCLR has demonstrated that the perforation of these panels can be accomplished at economically viable drilling rates.