• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.930-932
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• 2017

본 논문은 모드 I 하중하에서 곡률이 있는 복합재 적층판의 점진적 층간파손 예측에 대해 서술하였다. 곡률을 갖는 복합재 적층판의 층간파손 예측은 ABAQUS V6.13의 응집영역모델을 사용하여 수행하였다. 응집영역모델의 입력값인 층간파괴인성치는 모드 I, 모드 II, 그리고 혼합모드에 대한 층간파괴인성 시험을 통해 도출하였다. 곡률을 갖는 복합재 적층판의 점진적 층간파손 거동은, 시험과 수치해석결과가 잘 일치하는 것을 확인하였다.

• Advances in materials Research
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• 제7권2호
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• pp.119-136
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• 2018

In this paper, static and vibration analysis for anti-symmetric cross-ply and angle- ply carbon/glass hybrid laminates rectangular composite plate are presented. In this analysis, the equations of motion for simply supported thick laminated hybrid rectangular plates are derived and obtained through the use of Hamilton's principle. The closed-form solutions of anti-symmetric cross-ply and angle- ply laminates are obtained using Navier solution. The effects of side-to-thickness ratio, aspect ratio, and lamination schemes on the fundamental frequencies loads are investigated. The study concludes that shear deformation laminate theories accurately predict the behavior of composite laminates, whereas the classical laminate theory over predicts natural frequencies. The excellent accuracy of the present analytical solution is confirmed by making some comparisons of the present results with those available in the literature. It can be concluded that the proposed theory is accurate and simple in solving the free vibration behaviors of anti-symmetric cross-ply and angle- ply hybrid laminated composite plates.

• 한국안전학회지
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• 제12권2호
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• pp.27-36
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• 1997

This paper evaluates the static and fatigue bending strengths of CFRP (carbon fiber reinforced plastic) laminates subjected to hygrothermals. The specimens which had different stacking composition, orthotropic and quasi-isotropic laminated plates, were prepared for this experiment. A steel ball launched by the air gun collides against CFRP laminates to generate impact damages, and the 3-point fatigue bending test is carried out by using the impacted laminates to investigate the influence of hygrothermals on the effect on the residual bending fatigue strength of CFRP laminates.

• Composites Research
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• 제14권3호
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• pp.1-9
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• 2001

피로 손상을 입은 복합재료 적층보의 모재 균열로 인한 유효 휨 강성 저하 모델를 제시하고 이 모형에 대한 고유 진동수 변화를 예측하는 새로운 비파괴 예측 모델을 개발하였다. 인장 하중하에서 피로 손상을 입은 직교 복합재료 적층보의 고유진동수는 유효 휨 강성 저하를 $0^{\circ}$층과 $90^{\circ}$층의 탄성 계수와 함수 관계로 둠으로서 복합재료 적층보의 피로수명을 예측하였다. 피로 하중하에서 복합재료 적층보의 $90^{\circ}$층 탄성 계수 저하와 다른 층($0^{\circ}$층)에 본래 갖고 있는 탄성 계수를 적층판 이론에 적용하여 유효 휨 강성을 유도하였다. 직교 복합재료 적층보에 대해 피로 실험시 초기의 파단 양상은 대개 $90^{\circ}$층에서의 모재 균열이 지배적으로 나타나는데, 이를 이용하여 고유진동수 감소 모델은 직교 복합재료 적층보에서의 고유진동수 대 피로 사이클 곡선을 나타낼 수 있었다. 이와 같은 고유진동수 감소 모델의 타당성을 입증하기 위하여 $[{90}_2/0_2]_s$ 탄소섬유/에폭시 복합재료 적층보에 대한 진동 실험을 수행하였다. 본 모델의 예측 결과와 실험 결과가 잘 일치하는 바 본 논문에서 제시한 강성 저하 모델의 타당성을 입증하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.734-739
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• 2001

In this paper, an algorithm for stacking sequence optimization which deals with discrete ply angles is used for optimization of composite laminated plates. To handle discrete ply angles, the branch and bound method is modified. Numerical results show that the optimal stacking sequence is found with fewer evaluations of objective function than expected with the size of feasible region, which shows the algorithm can be effectively used for layup optimization of composite laminates..

• 한국항공우주학회지
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• 제30권2호
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• pp.59-66
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• 2002

광섬유 브래그 격자/외부 패브리-페로 간섭 (FBG/EFPI) 복합 센서를 이용하여 여러 가지 복합재료 적층판의 성형과정 동안 발생하는 변형률과 온도를 동시에 모니터링하였다. 일방향 적층판, 대칭 직교 적층판, 그리고 평직 적층판에 대하여 각각 두개씩의 FBG/EFPI 센서를 방향과 위치를 달리하여 삽입하고 오토클레이브 내에서의 성형 동안 복합재료 적층판 내부의 두 지점에서의 성형변형률과 온도를 실시간으로 측정하였다. 이러한 실험들을 통해 FBG/EFPI 센서는 보합재료 구조물 성형시의 스마트 모니터링에 효율적임을 알 수 있었다.

• 한국전산구조공학회논문집
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• 제28권5호
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• pp.497-502
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• 2015

본 논문에서는 굽힘하중이 가해지는 스마트 복합재 적층판의 자유단에서 발생하는 박리응력을 압전 작동기를 이용해서 감소시키는 방법을 응력함수를 이용해 해석하는 방법을 제안하였다. 전기-기계 연성에 의해 나타나는 지배방정식은 최소 보족일의 원리를 이용해 구하였다. 응력상태는 일반적인 고유치 해석과정을 통해 구하였다. 스마트 복합재 적층판의 자유단 박리응력은 압전 작동기를 이용해 감소시킬 수 있었다. cross-ply 복합재 적층판의 박리응력 감소가 angle-ply 복합재 적층판 보다 크게 나타났다.

• Structural Engineering and Mechanics
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• 제67권2호
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• pp.165-173
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• 2018

A simple predicted model using a modified Shear-lag method was used to represent the moisture absorption effect on the stiffness degradation for $[0/90]_{2s}$ composite laminates with transverse cracks and under flexural loading. Good agreement is obtained by comparing the prediction model and experimental data published by Smith and Ogin (2000). The material properties of the composite are affected by the variation of temperature and moisture absorption. The transient and non-uniform moisture concentration distribution give rise to the transient elastic moduli of cracked composite laminates. The hygrothermal effect is taken into account to assess the changes in the normalised axial and flexural modulus due to transverse crack. The obtained results represent well the dependence of the stiffness properties degradation on the cracks density, moisture absorption and operational temperature. The composite laminate with transverse crack loaded in axial tension is more affected by the hygrothermal condition than the one under flexural loading. Through this theoretical study, we hope to contribute to the understanding of the moisture absorption on the composite materials with matrix cracking.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 춘계학술발표대회 논문집
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• pp.67-70
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• 2005

The carbon fiber reinforced/epoxy laminated composites were fabricated with initial fiber failures within the unidirectional fiber pre-pregnated ply. The fiber failures were made intentionally either parallel to and/or perpendicular to the unidirectional fibers within the ply. The pre-made clear-cut cracks were found to be healed partially after laminating process. The laminates were impacted with or without initial fiber failures within the laminates. The force versus deflection curves were compared. The partially healed laminates showed the reduced laminate stiffness as compared to those without any intentional fiber failures. The impact curves were compared with size and the location of the initial failures varied.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2007년도 제28회 춘계학술대회논문집
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• pp.212-216
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• 2007

Predicting microcracking properties of the composite laminates in nonuniform stress conditions was the subject in this paper. The uniform stress field meant the stresses were independent of the width direction. The material was the 954-2A/IM7 laminates containing a central hole. Microcracks initiated at the edge of the hole and propagated into the laminate. Because the tensile stress concentration decreased with distance, the microcracks were arrested before the edge of the laminate. Because carbon fiber composites were opaque, a x-ray method was used to detect the length of the propagating microcracks. The microcracking at the near edge of the hole could be reasonably predicted by considering the local laminate stresses and the microcracking toughness measured in unnotched laminates. However, the date away from the hole did not agree with the predictions. The local microcrack density was always much higher than that predicted by the local laminate stress.