• Title, Summary, Keyword: Composite laminates

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Drop-weight impact damage evaluation for carbon fiber/epoxy composite laminates (탄소 섬유강화 복합재료의 중력 낙하 충격으로 인한 손상 평가)

  • Sohn, Min-Seok;Hu, Xiao-Xhi;Ki, Jang-Kyo;Hong, Soon-Hyung
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.89-92
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    • 2001
  • Drop weight impact tests were performed to investigate the impact behavior of carbon fiber/epoxy composite laminates reinforced by short fibers and other interleaving materials. Characterization techniques, such as cross-sectional fractography and scanning acoustic microscopy, were employed quantitatively to assess the internal damage of some composite laminates. Scanning electron microscopy was used to observe impact damage and fracture modes on specimen fracture surfaces. The results show that composite laminates experience various types of fracture; delamination, intra-ply cracking, matrix cracking and fiber breakage depending on the interlayer materials. Among the composite laminates tested in this study, the composites reinforced by Zylon fibers showed very good impact damage resistance with medium level of damage, while the composites interleaved by poly(ethylene-co-acrylic acid) (PEEA) film is expected to deteriorate the bulk strength due to the reduction of fiber volume fraction, even though the damaged area is significantly reduced.

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A Study on Low Velocity Impact and Residual Compressive Strength for Carbon/Epoxy Composite Laminate (탄소섬유/에폭시 복합적층판의 저속 충격 및 잔류 압축강도에 관한 연구)

  • Lee, S.Y.;Park, B.J.;Kim, J.H.;Lee, Y.S.;Jeon, J.C.
    • Proceedings of the KSME Conference
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    • pp.250-255
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    • 2000
  • Damage induced by low velocity impact loading in aircraft composite laminates is the form of failure which is occurred frequently in aircraft. Low velocity impact can be caused either by maintenance accidents with tool drops or by in-flight impacts with debris. As the consequences of impact loading in composite laminates, matrix cracking, delamination and eventually fiber breakage for higher impact energies can be occurred. Even when no visible impact damage is observed, damage can exist inside of composite laminates and the carrying load of the composite laminates is considerably reduced. The reduction of strength and stiffness by impact loading occurs in compressive loading due to laminate buckling in the delaminated areas. The objective of this study is to determine inside damage of composite laminates by impact loading and to determine residual compressive strength and the damage growth mechanisms of impacted composite laminates. For this purpose a series of impact and compression after impact tests are carried out on composite laminates made of carbon fiber reinforced epoxy resin matrix with lay up pattern of $[({\pm}45)(0/90)_2]s$ and $[({\pm}45)(0)_3(90)(0)_3({\pm}45)]$. UT-C scan is used to determine impact damage characteristics and CAI(Compression After Impact) tests are carried out to evaluate quantitatively reduction of compressive strength by impact loading.

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Application of silk composite to decorative laminate

  • Kimura, Teruo;Aoki, Shinpei
    • Advanced Composite Materials
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    • v.16 no.4
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    • pp.349-360
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    • 2007
  • Recently, natural fiber reinforced composite is attracting attention and considered as an environmentally friendly material. Usually cellulosic fibers are used to reinforce the composites, but some protein fibers such as silk and wool serve the same purpose. In this paper, we proposed a method of producing artistic composite from artistic fabric by using silk fiber reinforced biodegradable plastic, which is designated as 'silk composite', for reinforcement. In order to expand applications of the silk composite, we performed the compression molding of decorative laminates with woody material, which was selected as a core material, and examined the properties of molded decorative laminates with various content of the silk composite. Since plywood and medium-density fiberboard (MDF) are widely used for decorative laminates, we selected them as core materials. As a result, flexible decorative laminates with high flexural strength were obtained by compounding the silk composite with wood materials.

Damage Assessment of Curved Composite Laminate Structures Subjected to Low-Velocity Impact (곡률을 가진 적층복합재 구조에서의 저속충격손상 평가)

  • 전정규;권오양
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.69-73
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    • 2001
  • Damage induced by low-velocity impact on the curved composite laminates was experimentally evaluated for CFRP cylindrical shells with the radius of curvatures of 50, 150, 300, and 500 mm. The result was then compared with that of flat laminates. The radius of curvatures and the effective shell stiffness appeared to considerably affect the dynamic impact response of curved shells. Under the same impact energy level, the maximum contact force increased with the decreasing radius of curvatures, with reaching 1.5 times that for plates at the radius of curvature of 50 mm. Since the maximum contact force is directly related to the impact damage, curved laminates can be more susceptible to delamination and less resistant to the low-velocity impact damage. The distribution of delamination along the thickness direction of curved laminates are also different from that of flat plates. Delamination was distributed rather even]y at each interface along the thickness direction of curved laminates. This implies that the effect of curvatures has to be considered for the design of a curved composite laminate.

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Vibration Characterization of Cross-ply Laminates Beam with Fatigue Damage (피로 손상을 입은 직교 복합재료 적층보의 진동 특성)

  • 문태철;김형윤;황운봉;전시문;김동원;김현진
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.1-4
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    • 2001
  • A new non-destructive fatigue prediction model of the composite laminates is developed. The natural frequencies of fatigue-damaged laminates under extensional loading are related to the fatigue lift of the laminates by establishing the equivalent flexural stiffness reduction as a function of the elastic properties of sublaminates. The flexural stiffness is derived by relating the $90^{\circ}$-ply elastic modulus reduction, and using the laminate plate theory to the degraded elastic modulus and the intact elastic modulus of other laminate. The natural frequency reduction model, in which the dominant fatigue mode can be identified from the sensitivity scale factors of sublaminate elastic properties, provides natural frequency vs. fatigue cycle curves for the composite laminates. Vibration tests were also conducted on $[\textrm{90}_{2}\textrm{0}_{2}]_s$ carbon/epoxy laminates to verify the natural frequency reduction model. Correlations between the predictions of the model and experimental results are good.

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A Progressive Failure Analysis Procedure for Composite Laminates II - Nonlinear Predictive Finite Element Analysis (복합재료 거동특성의 파괴해석 II - 비선형 유한요소해석)

  • Yi, Gyu-Sei
    • Journal of the Korean Society for Advanced Composite Structures
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    • v.5 no.4
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    • pp.11-17
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    • 2014
  • A progressive failure analysis procedure for composite laminates is completed in here. An anisotropic plastic constitutive model for fiber-reinforced composite material is implemented into computer program for a predictive analysis procedure of composite laminates. Also, in order to describe material behavior beyond the initial yield, the anisotropic work-hardening model and subsequent yield surface are implemented into a computer code, which is Predictive Analysis for Composite Structures (PACS). The accuracy and efficiency of the anisotropic plastic constitutive model and the computer program PACS are verified by solving a number of various fiber-reinforced composite laminates with and without geometric discontinuity. The comparisons of the numerical results to the experimental and other numerical results available in the literature indicate the validity and efficiency of the developed model.

Matrix Cracking and Delmaination in Laminated Composite Plates Due to Impact (적층복합판의 충격에 의한 모재균열 및 층간분리에 관한 연구)

  • Kim, Moon-Saeng;Park, Seung-Bum
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.21 no.2
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    • pp.317-326
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    • 1997
  • An investigation was performed to study the matrix cracking and delamination in laminated composite plates due to transverse impact. A model was developed for predicting the initiation of the matrix cracking and the shape and size of impact-induced delamination in laminated composite plates resulting from the ballistic impact. The model consists of a stress analysis and a failure analysis. A transient finite element analysis which was based on the higher-order shear deformation theory was adopted for calculating the stresses inside the laminated composite plates during impact. A failure analysis was used to predict the initial intraply matrix cracking and the shape and size of the interface delamination in the laminates. As a results, a shear matrix cracking which was governed by the transverse interlaminar shear stress occured at the middle layer near the midplane of laminates and a bending matrix cracking which was governed by the transverse inplane stress occured at the bottom layer near the surface of laminates. In a thick laminates, a shear matrix cracking generated first at the middle layer of laminates, but in a thin laminates, a bending matrix cracking generated first at the bottom layer of laminates.

Experimental investigation of interlaminar mechanical properties on carbon fiber stitched CFRP laminates

  • Iwahori, Yutaka;Ishikawa, Takashi;Watanabe, Naoyuki;Ito, Akira;Hayashi, Yoichi;Sugimoto, Sunao
    • Advanced Composite Materials
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    • v.16 no.2
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    • pp.95-113
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    • 2007
  • Experimental investigations of interlaminar mechanical properties for carbon fiber reinforced plastic (CFRP) laminates were carried out using aramid fiber ($Kevlar^{(R)}$-29 1000d) and carbon fiber (TR40-1K 612d, Mitsubishi Rayon) stitching. Various carbon fiber (CF) stitch densities were used to prepare a number of CF stitched CFRP laminates for double cantilever beam (DCB) tests. An insert tongue-type loading fixture, developed by the Japan Aerospace Exploration Agency (formerly the National Aerospace Laboratory of Japan), was also employed in the DCB test. Interlaminar tension tests were carried out under an out-of-plane directional loading using a single CF stitch thread in the CFRP laminates. The DCB test results clarified that the relationship between the volume fractions of the CF stitch thread ($V_{ft}$) and mode I critical energy release rate ($G_{Ic}$) showed a mostly linear function with a higher gradient than that of the $Kevlar^{(R)}$ stitched CFRP laminates. The CF stitched CFRP tension test results indicated that the consumption energy per unit area ($E_i$) was larger than that of $Kevlar^{(R)}$ stitched CFRP laminates.

Mechanical behavior of the composite curved laminates in practical applications

  • Liu, Lonquan;Zhang, Junqi;Wang, Hai;Guan, Zhongwei
    • Steel and Composite Structures
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    • v.19 no.5
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    • pp.1095-1113
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    • 2015
  • In order to determine the mechanical behavior of the curved laminates in practical applications, three right-angled composite brackets with different lay-ups were investigated both experimentally and numerically. In the experimental, quasi-static tests on both unidirectional and multidirectional curved composite brackets were conducted to study the progressive failure and failure modes of the curved laminates. In the numerical modeling, three-dimensional finite element analysis was used to simulate the mechanical behavior of the laminates. Here, a strength-based failure criterion, namely the Ye criterion, was used to predict the delamination failure in the composite curved laminates. The mechanical responses of the laminate subjected to off-axis tensile loading were analyzed, which include the progressive failure, the failure locations, the load-displacement relationships, the load-strain relationships, and the stress distribution around the curved region of the angled bracket. Subsequently, the effects of stacking sequence and thickness on the load carrying capacity and the stiffness of the laminates were discussed in detail. Through the experimental observation and analysis, it was found that the failure mode of all the specimens is delamination, which is initiated abruptly and develops unstably on the symmetric plane, close to the inner surface, and about $29^{\circ}$ along the circumferential direction. It was also found that the stacking sequence and the thickness have significant influences on both the load carrying capacity and the stiffness of the laminates. However, the thickness effect is less than that on the curved aluminum plate.

Failure Criterion for Notched Composite Laminates (놋취가 있는 복합적층판의 파손기준)

  • Kim, Sung-Joon;Jeong, In-Oh;Choi, Ik-Hyeon;Ahn, Seok-Min
    • Aerospace Engineering and Technology
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    • v.7 no.2
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    • pp.21-26
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    • 2008
  • This study reviews several fracture models for predicting the notched strength of composite laminates. Representative experimental results on the notched strength of composite laminates containing a large notch subjected to static uniaxial tensile loading have been collected from open literature. Notched strength data for T300/5208 are analyzed. and the various parameters associated with the fracture models have been determined for laminates. Notched strength data sets are compared with fracture models and the applicability of the different fracture models in predicting the notched strength of composite laminates is discussed.

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