Modification of Porous Aluminum by Cold Rolling for Low-Noise Trailing Edge Applications

Noise reduction of aircrafts during take-off and landing has become an important part of research in aviation. The circulation of air around the airframe is a major source of noise during landing. This includes noise generated at the trailing edge. Open porous materials, such as porous aluminum, are investigated for the reduction of this noise. In this study, cold rolling is used to enhance the structure of porous aluminum in matters of aeroacoustics and mechanical properties. An important parameter characterizing the acoustic behavior is flow resistivity which is measured using the alternating airflow method. The flow resistivity is highly dependent upon the pore structure which is analyzed using three-dimensional computer tomography (CT). Additionally, CT combined with discontinuous tensile testing is used to study the influence of cold rolling on the damage behavior of porous aluminum. Besides the damage behavior, mechanical parameters have been determined to identify reasonable degrees of deformation. A cold rolling technique to produce material with a gradient in porosity is described and experimental porous trailing edges for measurements in an acoustic wind tunnel are shown. The findings of this study show that cold rolling is a promising way to customize porous aluminum for low-noise trailing edge applications.