복합재 패치로 보수된 노치형 알루미늄 합금 평판의 음향방출 특성

Abstract

최근 항공기 표피에 결함이나 손상이 발생하였을 때 복합재 패치로 보수하는 방법이 각광을 받고 있다. 본 연구에서는 편측 노치가 존재하는 알루미늄 합금 평판에 대해 복합재 패치의 적층수를 변수로 하여 보수하고, 인장하중에 따른 시편의 손상 과정에 대해 음향방출법(Acoustic Emission, AE)으로 실시간 분석하였다. AE energy rate, Hit rate, AE amplitude, AE 파형 그리고 1st peak frequency의 주파수 대역을 분석하여, 시편 파괴시 알루미늄 크랙(Al cracking), 섬유파단(Fiber breakage), 모재균열(Matrix cracking), 층간분리(Delamination)를 분류하였다. 그리고 시편의 변위를 음향방출 특성에 따라 Region Ⅰ, Region Ⅱ, Region Ⅲ 구간으로 나눌 수 있었으며, 패치가 실제 파괴되는 구간인 Region Ⅱ를 세부적으로 분석하여 패치의 적층수에 따른 AE 특성의 차이를 정리할 수 있었다. 또한 GFRP와 CFRP 복합재 패치 종류에 따라 음향방출 거동이 상당히 달랐으며, 알루미늄 시편의 표면처리에 따라 패치와의 접착력이 우수해져 인장강도가 증가하고 음향방출 거동도 달라졌다. |Edge notched Al6061-T6 aluminum was repaired with a GFRP composite patch as a function of the number of stacking. Damage progress of specimen for tension load has been monitored by acoustic emission(AE). AE energy, hit rate, AE amplitude behavior, waveform, and distribution of 1st peak frequency were researched and fracture specimen were classified into Al cracking, Fiber breakage, Resin cracking, and Delamination. Displacement of specimen can be divided into Region Ⅰ, Ⅱ, Ⅲ according to acoustic emission characteristics. Region Ⅱ where the patch itself was actually fractured was focused on to clarify analyzed and the AE characteristics difference for the number of stacking. Also, the acoustic emission behavior was considerably different as the GFRP and CFRP composite patch kind. In addition, according to the surface treatment of the aluminum specimen, the adhesive strength with the patch was excellent and the tensile strength increased. The result, acoustic emission behavior was changed.; Edge notched Al6061-T6 aluminum was repaired with a GFRP composite patch as a function of the number of stacking. Damage progress of specimen for tension load has been monitored by acoustic emission(AE). AE energy, hit rate, AE amplitude behavior, waveform, and distribution of 1st peak frequency were researched and fracture specimen were classified into Al cracking, Fiber breakage, Resin cracking, and Delamination. Displacement of specimen can be divided into Region Ⅰ, Ⅱ, Ⅲ according to acoustic emission characteristics. Region Ⅱ where the patch itself was actually fractured was focused on to clarify analyzed and the AE characteristics difference for the number of stacking. Also, the acoustic emission behavior was considerably different as the GFRP and CFRP composite patch kind. In addition, according to the surface treatment of the aluminum specimen, the adhesive strength with the patch was excellent and the tensile strength increased. The result, acoustic emission behavior was changed.