Korean Journal of Materials Research (한국재료학회지)

Materials Research Society of Korea (한국재료학회)
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Experimental Determination of Complex Moduli and Internal Damping of Laminated Composites

적층 복합재료의 내부감쇠와 복소탄성계수 측정에 관한 연구

  • Lee, Jae-Hyeok (Dept.of Mechanical Engineering, Myongji University) ;
  • Park, Se-Man (Dept.of Mechanical Engineering, Myongji University) ;
  • Kim, Hyeong-Sam (Dept.of Mechanical Engineering, Myongji University)
  • 이재혁 (명지대학교 기계공학과) ;
  • 박세만 (명지대학교 기계공학과) ;
  • 김형삼 (명지대학교 기계공학과)
  • Published : 1998.10.01
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Abstract

Damping is a property for materials and systems to dissipate energy during periodic deformations. Generally, damping causes stiff decrease in amplitudes and shifts in phases. Also, even at resonance, amplitudes are substantially attenuated. This phenomenon of damping helps in reducing stresses developed during vibrations and consequently improves fatigue lives of materials. In this work internal damping and complex moduli are experimentally determined. An impulse technique is utilized in experiments and cantilever beams are selected as test subjects for the measurements of flextural vibrations since the beams lend themselves easily as simplistic ideal models. A resonance method is employed to determine resonance frequencies which are utilized to compute storage moduli. Also, loss moduli are evaluated from damping capacities and storage moduli. The storage and loss moduli combined yield complex moduli. Finally internal damping is evaluated from bandwidth technique, the real component of the transfer function.

감쇠란 주기적인 변형하에 에너지를 소산시킬 수 있는 시스템이나 재료의성질을 말하며, 이로서 공진에서 진폭을 감소시키며 아울러 전달하는 파의 빠른 감소를 유발한다. 이것은 진동을 일으키는 응력을 감소시키게 되는데 결국은 피고 수명을 연장시키는 결과를 가져오게 된다. 본 연구에서는 적층된 복합재료의 내부감쇠와 복소탄성 계수를 실험적으로 측정하였다. 실험은 충격 기법을 사용하였으며 비교적 간단한 모델러서 외팔보의 휨진동을 측정하였다. 복소 탄성계수는 공진법을 이용하여 공진주파수를 측정 storage modulus를 계산하고 이를 통해 loss modulus를 구한 다음 계산하였고, 내부감쇠는 bandwidth technique과 전달함수의 실부부분 이용방법에 의해 각각 구하였다.

Keywords

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