Modification of the fiber/matrix bonding by a plasma treatment to reduce the structure-borne sound transmission

In order to improve the sound emission in a structure that is made out of fiber reinforced plastics, the structure-borne sound propagation is selectively manipulated by a local or global modification of the fiber-matrix bonding. This manipulation is induced by a reduction of the fiber-matrix bonding by using a hydrophobic and therefore non-polar surface treatment of the dry fiber. The content of this paper is to present the preliminary investigations regarding the effectiveness of test specimens with two different hydrophobic plasma treatments compared to a reference without any modification. To this end, several tests were performed in order to prove the effectiveness of the respective modification to the fiber-matrix bonding. The specimens are composite laminated plates with a uni-directional lay-up. The materials which is used for the composite laminate is carbon fiber in combination with an epoxy matrix. Positive results are demonstrated regarding the feasibility to apply a hydrophobic plasma coating on a dry NCF (non-crimp-fabric) with sharp and defined edges. Since the determination of the loss factor and storage modulus according to the standard DIN EN ISO 6721-3 (Procedure B) did not show any relevant changes in comparison to the reference, a simplified test according to the standard DIN EN ISO 6721-3 (Procedure A) was performed in order to check if a suitable test environment was chosen. The results showed a measurable growth of the loss factor up to 71% in comparison to the reference.