• Title, Summary, Keyword: Layup sequences

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Natural Frequency and Mode Characteristics of Composite Pole Structures for Different Layup Sequences (복합소재 기둥 구조의 적층배열 변화에 따른 고유진동 및 모드 특성)

  • Kim, Gyu-Dong;Rus, Guillermo;Lee, Sang-Youl
    • Journal of the Korean Society for Advanced Composite Structures
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    • v.4 no.1
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    • pp.9-14
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    • 2013
  • The dynamic analysis of poles made of advanced composite materials is carried out for different length-thickness ratios and layup sequences. The numerical results using ABAQUS obtained for plates and shells are in good agreement with those reported by other investigators. The new results for laminated composite pole structures in this study mainly show the effect of the interactions between the radius-length ratio and other various parameters. The effect of fiber angles of long composite poles also investigated. Key observation points are discussed and a brief design guideline is given.

Ultrasonic Characterization on Sequences of CFRP Composites Based on Modeling and Motorized System

  • Im, Kwang-Hee;David K. Hsu;Song, Sung-Jin;Park, Je-Woung;Sim, Jae-Ki;Yang, In-Young
    • Journal of Mechanical Science and Technology
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    • v.18 no.1
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    • pp.65-73
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    • 2004
  • Composites are a material class for which nondestructive material property characterization is as important as flaw detection. Laminates of fiber reinforced composites often possess strong in-plane elastic anisotropy attributable to the specific fiber orientation and layup sequence when waves are propagating in the thickness direction of composite laminates. So the layup orientation greatly influences its properties in a composite laminate. It could result in the part being .ejected and discarded if the layup orientation of a ply is misaligned. A nondestructive technique would be very beneficial, which could be used to test the part after curing and requires less time than the optical test. Therefore a ply-by-ply vector decomposition model has been developed, simplified, and implemented for composite laminates fabricated from unidirectional plies. This model decomposes the transmission of a linearly polarized ultrasound wave into orthogonal components through each ply of a laminate. Also in order to develop these methods into practical inspection tools, motorized system have been developed for different measurement modalities for acquiring ultrasonic signals as a function of in-plane angle. It is found that high probability shows between the model and tests developed in characterizing cured layups of the laminates.

Determination of Degraded Properties of Vibrating Laminated Composite Plates for Different Layup Sequences (적층배열 변화에 따른 진동하는 복합재료 적층 구조의 미시역학적 물성변화 추정)

  • Kim, Gyu-Dong;Lee, Sang-Youl
    • Composites Research
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    • v.28 no.5
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    • pp.277-284
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    • 2015
  • This paper presents a method to detect the fiber property variation of laminated GFRP plates from natural frequency response data. The combined finite element analysis using ABAQUS and the inverse algorithm described in this paper may allow us not only to detect the deteriorated elements from the mirco-mechanical point of view but also to find their numbers, locations, and the extent of damage. To solve the inverse problem using the combined method, this study uses several natural frequencies instead of mode shapes in a structure as the measured data. Several numerical results show that the proposed system is computationally efficient in identifying fiber stiffness degradation for complex structures such as composites with various layup sequences.

Geometrical nonlinear dynamic analysis of laminated skew plates made of advanced composite materials (적층된 ACM 경사판의 기하학적 비선형 동적 해석)

  • Lee, Sang-Youl;Chang, Suk-Yoon
    • Journal of the Korean Society for Advanced Composite Structures
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    • v.1 no.4
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    • pp.28-34
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    • 2010
  • W e performed a geometrical nonlinear dynamic analysis of laminated skew plates made of advanced composite materials (ACM ) based on the first-order shear deformation plate theory (FSDT). The Newmark method and Newton-Raphson iteration are used for the nonlinear dynamic solution. The effects of skew angles and layup sequences on the nonlinear dynamic response for various parameters are studied using a nonlinear dynamic finite element program developed for this study. The several numerical results were in good agreement with those reported by other investigators for square composite and skew plates, and the new results reported in this paper show the significant interactions between the skew angle and layup sequence in the skew laminate. Key observation points are discussed and a brief design guideline is given.

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Characterization of CFRP Laminates′Layups Using Through-Transmitting Ultrasound Waves

  • Im, Kwang-Hee;David K. Hsu;Cho, Young-Tae;Park, Jae-Woung;Sim, Jae-Ki;Yang, In-Young
    • Journal of Mechanical Science and Technology
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    • v.16 no.3
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    • pp.292-301
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    • 2002
  • Ultrasound waves interact strongly with the orientation and sequence of the plies in a layup when propagating in the thickness direction of composite laminates. Also the layup orientation greatly influences its properties in a composite laminate. If the layup orientation of a ply is misaligned, it could result in the part being rejected and discarded. Now, most researchers cut a small coupon from the waste edge and use a microscope to optically verify the ply sequences on important parts. This may add a substantial cost to the production since the test is both labor intensive and performed after the part is cured. A nondestructive technique would be very beneficial, which could be used to test the part after curing and requires less time than the optical test. Therefore we have developed, reduced, and implemented a novel ply-by-ply vector decomposition model for composite laminates fabricated from unidirectional plies. This model decomposes the transmission of a linearly polarized ultrasound wave into orthogonal components through each ply of a laminate. High probability is found, by comparisons between the model and tests, in characterizing cured layups of the laminates by using the proposed method.

A Study on Characterization for Stacking Fault Evaluation of CFRP Composite Laminates Using an EMAT Ultrasonics (전자기 초음파를 이용한 CFRP 복합적층판의 적층배향 특성평가에 관한 연구)

  • Im, Kwang-Hee;Na, Seung-Woo;Kim, Ji-Hoon;Lee, Chang-Ro;Hsu, David K.;Yang, In-Young
    • Transactions of the Korean Society of Automotive Engineers
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    • v.13 no.2
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    • pp.83-92
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    • 2005
  • An electromagnetic acoustic transducer (EMAT) is a unique probe that does not require a couplant or gel and also can usually generate or detect an ultrasonic wave into specimens across a small gap. It, therefore can be applied in a noncontact mode with a high degree of reproducibility. Especially stiffness of composites depends on layup sequence of CFRP(carbon fiber reinforced plastics) laminates. It is very important to evaluate the layup errors in prepreg laminates. A nondestructive technique can therefore serve as a useful measurement for detecting layup errors. This shear wave for detecting the presence of the errors is very sensitive. A decomposition model has been used in the interpretation and prediction of test results. Test results have been com pared with model data. It is found that the high probability shows between tests and the model utilized in characterizing cured layups of the laminates. Also a C-scan method was used for detecting layup of the laminates because of extracting fiber orientation information from the ultrasonic reflection caused by structural imperfections in the laminates. Therefore, it was found that interface C-scan images show the fiber orientation information by using two-dimensional fast Fourier transform (2-D FFT).

Characteristics Evaluation of CFRP Composite Laminates Using a Through-Transmission Method of Ultrasonic Transducers (초음파 트랜스듀셔 투과법을 이용한 CFRP 복합적층판의 특성평가)

  • Im, Kwang-Hee;Na, Sung-Woo;Kang, Tae-Sick;Kim, Sun-Kyun;Kim, Ji-Hyun;Lee, Hyun;Park, Jae-Woung;Sim, Jae-Ki;Yang, In-Young;Hsu, David K.
    • Proceedings of the KSME Conference
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    • pp.401-406
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    • 2001
  • When propagating the thickness direction of composite laminates ultrasound waves interacts strongly with the orientation and sequence of the plies in a layup. Also the layup orientation greatly influences its properties in a composite laminate. If one ply of the layup orientation is misaligned, it could result in the part being rejected and discarded. Now, most researchers cut a small coupon from the waste edge and use a microscope to optically verify the ply sequences on important parts. Those may add a substantial cost to the product since the test is both labor hard and performed after the part is cured. A nondestructive technique would be very beneficial, which could be used to test the part after curing and require less time than the optical test. Therefore we have developed, reduced, and implemented a novel ply-by-ply vector decomposition model for composite lam mates fabricated from unidirectional plies. This model decomposes the transmission of a linearly polarized ultrasound wave into orthogonal components through each ply of a laminate. It is found that a high probability shows between the model and tests developed in characterizing cured layups of the laminates.

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Finite element dynamic analysis of laminated composite shell structures considering geometric nonlinear effects (기하학적 비선형 효과를 고려한 복합재료 적층 쉘 구조의 유한요소 동적 해석)

  • Lee, Sang-Youl
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.14 no.11
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    • pp.5979-5986
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    • 2013
  • This study carried out a geometrical nonlinear dynamic analysis of laminated composite shell structures. Based on the first-order shear deformation shell theory and nonlinear formulation of Sanders, the Newmark method and Newton-Raphson iteration are used for dynamic solution considering nonlinear effects. The effects of radius, fiber angles, and layup sequences on the nonlinear dynamic response for various parameters are studied using a nonlinear dynamic finite element program developed for this study. The several numerical results were in good agreement with those reported by other investigators for square composite plates, and the new results reported in this paper show the significant interactions between the radius, fiber angles and layup sequence in the laminate. Key observation points are discussed and a brief design guideline of laminated composite shells is given.

Parametric effects on geometrical nonlinear dynamic behaviors of laminated composite skew plates (적층된 복합소재 경사판의 기하학적 비선형 동적 거동에 미치는 매개변수 영향)

  • Lee, Sang-Youl
    • Composites Research
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    • v.25 no.6
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    • pp.217-223
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    • 2012
  • This study investigates a geometrical nonlinear dynamic behaviors of laminated skew plates made of advanced composite materials (ACM). Based on the first-order shear deformation plate theory (FSDT), the Newmark method and Newton-Raphson iteration are used for the nonlinear dynamic solution. The effects of cutout sizes, skew angles and lay up sequences on the nonlinear dynamic response for various parameters are studied using a nonlinear dynamic finite element program developed for this study. The several numerical results were in good agreement with those reported by other investigators for square composite plates with or without central cutouts, and the new results reported in this paper show the significant interactions between the cutout, skew angles and layup sequence in the laminate. Key observation points are discussed and a brief design guideline of skew laminates is given.

Determination of Degraded Fiber Properties of Laminated CFRP Flat Plates Using the Bivariate Gaussian Distribution Function (이변량 Gaussian 분포함수를 적용한 CFRP 적층 평판의 보강섬유 물성저하 규명)

  • Kim, Gyu-Dong;Lee, Sang-Youl
    • Composites Research
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    • v.29 no.5
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    • pp.299-305
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    • 2016
  • This paper presents a method to detect the fiber property variation of laminated CFRP plates using the bivariate Gaussian distribution function. Five unknown parameters are considered to determine the fiber damage distribution, which is a modified form of the bivariate Gaussian distribution function. To solve the inverse problem using the combined computational method, this study uses several natural frequencies and mode shapes in a structure as the measured data. The numerical examples show that the proposed technique is a feasible and practical method which can prove the location of a damaged region as well as inspect the distribution of deteriorated stiffness of CFRP plates for different fiber angles and layup sequences.