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Modelling of Low Velocity Impact Damage in Laminated Composites
Jounghwan Lee,Changduk Kong,Costas Soutis 대한기계학회 2005 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.19 No.4
In this study a simple model is developed that predicts impact damage in a composite laminate avoiding the need of the time-consuming dynamic finite element method (FEM). The analytical model uses a non-linear approximation method (Rayleigh-Ritz.) and the large deflection plate theory to predict the number of failed plies and damage area in a quasi-isotropic composite circular plate (axisymmetric problem) due to a point impact load at its centre. It is assumed that the deformation due to a static transverse load is similar to that occurred in a low velocity impact. It is found that the model, despite its simplicity, is in good agreement with FEM predictions and experimental data for the deflection of the composite plate and gives a good estimate of the number of failed plies due to fibre breakage. The predicted damage zone could be used with a fracture mechanics model developed by the second investigator and co-workers to calculate the compression after impact strength of such laminates. This approach could save significant running time when compared to FEM solutions.
Modelling of Low Velocity Impact Damage In Laminated Composites
Lee Jounghwan,Kong Changduk,Soutis Costas The Korean Society of Mechanical Engineers 2005 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.19 No.4
In this study a simple model is developed that predicts impact damage in a composite laminate avoiding the need of the time-consuming dynamic finite element method (FEM). The analytical model uses a non-linear approximation method (Rayleigh-Ritz) and the large deflection plate theory to predict the number of failed plies and damage area in a quasi-isotropic composite circular plate (axisymmetric problem) due to a point impact load at its centre. It is assumed that the deformation due to a static transverse load is similar to that oc curred in a low velocity impact. It is found that the model, despite its simplicity, is in good agreement with FEM predictions and experimental data for the deflection of the composite plate and gives a good estimate of the number of failed plies due to fibre breakage. The predicted damage zone could be used with a fracture mechanics model developed by the second investigator and co-workers to calculate the compression after impact strength of such laminates. This approach could save significant running time when compared to FEM solutions.
두꺼운 일방향 탄소-에폭시 라미네이트의 정적 압축강도에 관한 연구
이정환,Costas Soutis,공창덕 朝鮮大學校 機械技術硏究所 2006 機械技術硏究 Vol.9 No.1
Existing test methods for thick-section specimens (4mm) have not provided precise compressive properties to date for the analysis and design of thick structure. A survey of the failure behavior of such thick specimens revealed that the failure initiated at the top corner of the specimen and propagated down and across the width of the specimen as premature failure, not typically reported for thin compression specimens. In the current study, the cause of the premature failure for thick specimens (T800/924C and IM7/8552) was identified experimentally and numerically. The premature failure was successfully avoided during compressive testing and the failure mode was quite similar regardless of increasing specimen thickness and specimen volume. Furthermore it was identified that the failure location within gauge section does not have an influence on the compressive strength from the experimental result performed with the unwaisted specimens (failure around junction of end tab and gauge section) and the waisted specimens (failure at the middle of gauge section). Finally, clear 1-D thickness and 3-D scaling effects on the compressive strength of unidirectional composite laminates existed. The main factors influencing the effects were due to manufacturing defects such as void content and fibre waviness.
30kW 풍력터빈용 아마섬유 복합재 블레이드 제조를 위한 구조 시험 분석 연구
신혜진 ( Hye-jin Shin ),이지현 ( Ji-hyun Lee ),문성영 ( Sung-young Moon ),이정환 ( Jounghwan Lee ) 한국복합재료학회 2023 Composites research Vol.36 No.1
최근 탄소 중립 등 지속 가능한 발전을 위한 지구환경 문제가 대두되면서 기존 풍력터빈의 소재인 유리섬유 복합재의 폐기 시 처리 방안이 문제가 되고 있다. 이를 해결하기 위해 본 연구에서는 기존의 유리섬유 복합재를 대체할 수 있는 친환경 복합재인 아마섬유 기반 복합재를 활용하여 30kW 풍력터빈 블레이드를 제조하고 적합성을 평가하였다. 먼저 친환경 천연 아마섬유 복합재의 풍력터빈 블레이드 소재로 활용 가능성을 검증하기 위해 기계적 강도 시험을 수행하였으며, 그 결과 선행 아마섬유 복합재 물성 연구 대비 좀 더 우수한 강도가 측정된 것을 확인하였다. 또한 제작된 30kW 급 아마섬유 복합재 블레이드를 활용하여 아마섬유 복합재 블레이드의 정적 강도를 측정하는 정적강도 성능평가 시험을 통하여 적합성을 확인하였다. Recently, as global environmental issues for sustainable development, such as carbon neutrality, have emerged, disposal methods of glass fiber composites, a material of existing wind turbines, have become a problem. To solve this problem, in this study, 30kW wind turbine blades were manufactured using flax fiber-based composites, which are eco-friendly natural fiber composites that can replace existing glass fiber composites, and their suitability was evaluated. First, mechanical strength tests were conducted to verify the feasibility of using eco-friendly natural flax fiber composites as a wind turbine blade material, and as a result, better strength were confirmed compared to previous studies on the properties of flax fiber composites. In addition, the suitability was confirmed through a static strength performance evaluation test to measure the static strength of the flax fiber composite blade using the manufactured 30kW class flax fiber composite blade.
비환원적 이성주의로서 칸트의 비판철학 ― 칸트의 『교수취임논문』과 『순수이성비판』에서 드러나는 이성의 부정성 ―
이정환 ( Lee¸ Joung-hwan ) 한국헤겔학회 2020 헤겔연구 Vol.0 No.48
본 논문은 비환원적 이성주의의 주창자인 셸링에 앞서 이성 또는 지성의 부정성을 통찰해가는 칸트의 사유 여정을 면밀히 고찰해 보려는 시도이다. 이를 통해 장차 셸링에게서 만개하게 될 비환원적 이성주의의 원형으로서 칸트의 비판철학이 가지는 면모를 조명해 보고자 한다. 이와 관련하여 본 논문은 우선, 칸트가 지성의 부정성에 대한 통찰을 처음으로 명시적인 형태로 드러내는 『교수취임논문』을 고찰의 중심 대상으로 삼는다(II장). 이 고찰을 통해 본 논문은, 지성의 부정성에 대한 칸트의 통찰은 감성에 대한 새로운 이해로부터 시작된다는 점, 감성에 대한 칸트의 새로운 이해의 핵심은 감성을, 지성으로 결코 환원될 수 없는 타자로 간주한다는 점에 있음을 밝힌다. 이어지는 본문 III장에서는 감성에 대한 새로운 이해로부터 추동된 지성의 부정성에 대한 칸트의 통찰을 『순수이성비판』의 논의를 중심으로 짚어본다. 사물의 있음과의 직접적인 소통가능성이 부정되어 버린 지성이 사물의 있음과 관계하는 방식에 대한 칸트의 구체적인 해명을 통해 비환원적 이성주의가 그의 철학에서 어떻게 구체화되는지를 밝히고자 한다. 본문 IV장에서는 이상의 고찰을 통해 밝혀진 지성의 부정성에 대한 칸트의 통찰이 가지는 특징이자 한계를 간단히 짚어보고자 한다. 이를 통해 칸트 이후에 전개되는 이성의 부정성에 대한 셸링의 논의가 칸트의 그것과 비교하여 가지는 의미를 지적해 보고자 한다. The purpose of this paper is to closely examine Kant's insight into the negativity of intelligence in his Inaugural Dissertation of 1770 and Critique of Pure Reason. Through the examination, this study aims to clarify aspects of Kant's critical philosophy as a prototype of non-reductive rationalism that will be in full bloom in Schelling’s later philosophy. First, I will examine the discussion of Inaugural Dissertation of 1770, which provides important clues for insight into the negativity of reason. Second, I will clarify how Kant's insight into the negativity of intellect is elucidated concretely in Critique of Pure Reason. Based on these considerations, I will finally point out the limitations of Kant's insight into the negativity of intelligence and the characteristics of Schelling's insight into the negativity of reason compared to that of Kant.