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CHARACTERISTICS OF CFRP STRUCTURE OF BENDING STRENGTH AND RIGIDITY

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CHARACTERISTICS OF CFRP STRUCTURE OF BENDING STRENGTH AND RIGIDITY Powered By Docstoc
					                                                                                 J.H. Kim, J.Y. Jeong, J.M.Bang, J.H. Kim, and I.Y. Yang




                     CHARACTERISTICS OF CFRP STRUCTURE OF BENDING
                     STRENGTH AND RIGIDITY ACCORDING TO STACKING
                                 ORIENTATION ANGLE

                                                      J. H. Kim* and I. Y. Yang
                                  Department of Mechanical Design Engineering, Chosun University
                                                     J. Y. Jeong and J. M. Bang
                             Department of Advanced Parts and Materials Engineering Graduate School
                                              Chosun University, Chosun University
                                                             and J. H. Kim
                      Jung Ho Kim, Suite 811, Sunil-Technopia, Sangdaewon-dong, Jungwon-gu, Sungnam-si
                                                 Kyeonggi-do, Korea, 462-807




                                                                                                                                   :‫اﻟﺨﻼﺻـﺔ‬
          ‫ﻳ‬                            ‫ﺒ‬                       ‫ﻤ‬                                          ‫ﻮ‬
‫( ﺑﺎﻟﻤﻘﺎوﻣﺔ اﻟﻌﺎﻟﻴﺔ ﺑﺎﻟ ُﻘﺎرﻧﺔ ﻣﻊ اﻻﺳﺘﻘﺮار اﻟ ُﻌﺪي، وﺛﺒﺎت اﻟﺨﺼﺎﺋﺺ اﻟﻤﺎدّﺔ، واﻟﺸﺪة‬CFRP) ‫ﺗﺨﺘﺺ اﻟﻠﺪﻳﻨﺎت )اﻟﺒﻼﺳﺘﻴﻚ( اﻟﻤﻘ ّاة ﺑﻠﻴﻒ اﻟﻜﺮﺑﻮن‬
‫واﻟﺼﻼﺑﺔ، وﻣﻘﺎوﻣﺔ اﻟﺘﺂآﻞ. وﻟﺬﻟﻚ ﻳﺘﺴﻊ ﻣﺪى اﺳﺘﻌﻤﺎﻟﻬﺎ ﻓﻲ ﻣﺠﺎﻻت ﻣﺘﻌﺪدة ﻣﺜﻞ ﺻﻨﺎﻋﺔ اﻟﻄﺎﺋﺮات واﻷﺟﻬﺰة اﻟﻔﻀﺎﺋﻴﺔ، وﺻﻨﺎﻋﺔ اﻟﻤﻌﺪات اﻟﺘﺮﻓﻴﻬﻴﺔ‬
‫واﻟﺮﻳﺎﺿﻴﺔ، وﺻﻨﺎﻋﺔ اﻷﺟﺰاء اﻟﻌﺎﻣﺔ ﻟﻠﺘﺮآﻴﺒﺎت اﻟﻤﺨﺘﻠﻔﺔ. وﺟﺮى ﻓﻲ هﺬا اﻟﻤﺠﺎل ﻋﺪد ﻣﻦ اﻟﺪراﺳﺎت اﻟﻨﻈﺮﻳﺔ واﻻﺧﺘﺒﺎرﻳﺔ وذﻟﻚ ﻟﻠﺤﺼﻮل ﻋﻠﻰ أﺟﺰاء ﻣﻦ‬
                ‫ّ ﻤ آ‬                                        ّ        ‫ّ ﻤ ﺣ‬                                                  ‫ﺸ‬
CFRP ‫ ﻋﺎﻟﻴﺔ اﻟ ّﺪة واﻟﺼﻼﺑﺔ؛ إﻻ أن هﺬﻩ اﻟﺪراﺳﺎت ﺗﻘﺘﺼﺮ ﻋﻠﻰ اﻟﻤﻮاد اﻟ ُﻮ ّﺪة اﻟﺨﻮاص ﻓﻲ ﺟﻤﻴﻊ اﻟﻨﻮاﺣﻲ. وآﻐﻴﺮهﺎ ﻣﻦ اﻟﻤﻮاد اﻟ ُﺮ ّﺒﺔ ﺗﻈﻬﺮ‬CFRP
                                       ّ                                                                                 ‫ّﺪ ﺼ‬
‫ ذات زاوﻳﺔ ﺗﻮﺟﻴﻪ‬CFRP ‫اﺧﺘﻼﻓﺎ ﻓﻲ اﻟﺸ ّة واﻟ ّﻼﺑﺔ وذﻟﻚ ﻻﺧﺘﻼف اﻟﺨﺼﺎﺋﺺ ﻓﻲ آﻞ ﻣﻦ اﻟﻠﻴﻒ واﻟﻤﺎدة اﻟﺤﺎوﻳﺔ. وﻓﻲ هﺬﻩ اﻟﺪراﺳﺔ، ﺗﻢ ﺗﺼﻨﻴﻊ ﻋﻴﻨﺔ‬        ً
                   ً                  ِ ‫د ﻤ آ ﻤ‬                           ‫ﺜ‬                                                          ‫ﻜ‬
‫ﻣﺘﻐﻴﺮة ﻟﻠ ُﻮﻣﺔ آﺠﺰء ﻋﺎم ﻟﻼﺳﺘﻌﻤﺎل ﻓﻲ اﻟﺘﺮآﻴﺒﺎت وﺗﻢ ﻗﻴﺎس ﻣﻘﺎوﻣﺔ اﻟ ّﻨﻲ واﻟﺼﻼﺑﺔ ﻓﻲ اﻟﻤﺎ ّة اﻟ ُﺮ ّﺒﺔ اﻟ ُﻨﺎﻇﺮة. آﻤﺎ أﻧﻪ ﺗﻢ أﻳﻀﺎ وﺿﻊ أﻧﺒﻮب ﺗﻘﻮﻳﺔ‬
                     ‫ﻤ ﺑ‬                       ‫ﻤ‬               ً ‫ﺧ‬                        ً    ّ                    ‫ﻘ‬
‫ اﻟﻤﻀﻐﻮط َﻮاﺋﻴﺎ ﺑﻮﺳﺎﻃﺔ اﻟ ُﻮﺻﺪة ﻣﻊ أﻧﺒﻮب اﻟﺘﻘﻮﻳﺔ اﻟ ُﺮّﻊ ﻣﻦ اﻷﻟﻤﻨﻴﻮم وذﻟﻚ‬CFRP ‫. وﺗﻢ أﻳﻀﺎ ﺗﻘﻴﻴﻢ‬CFRP ‫ُﺮّﻊ ﻣﻦ اﻷﻟﻤﻨﻴﻮم ﻟﻤﻨﻊ اﻟ ُﺼﻮر ﻓﻲ‬        ‫ﻣ ﺑ‬
                                                                                                                      .‫ﻋﺒﺮ ﺗﻐﻴﻴﺮ زاوﻳﺔ اﻟﺘﻮﺟﻴﻪ‬



ABSTRACT
    Carbon fiber reinforced plastics (CFRP) have high strength in comparison with dimensional stability,
invariability of material property, high strength and rigidity, corrosion resistance. Therefore, CFRP is widely used in
various fields including space and aviation industries, sports and leisure industries, and general structural members
and parts. To achieve structural members of CFRP with high strength and rigidity, theoretical approaches are limited
to isotropic material, and empirical studies have been conducted. As with other composite materials, CFRP shows
different rigidity and strength due to differences in properties in fiber and matrix material. In this study, a CFRP
specimen with changing stack orientation angle was manufactured as general structural application, and bending
strength and rigidity of the corresponding composite was measured. In addition, square aluminium tube
reinforcement is applied to prevent the shortcoming of CFRP. Vacuum compressed CFRP via autoclave with square
aluminium tube reinforcement material (Hybrid) was evaluated by changing the orientation angle.
Key words: carbon fiber reinforced plastics, composite materials, rigidity, strength and hybrid




*Corresponding Author:
E-mail: kjh@chosun.ac.kr

This paper was presented at the Advanced Manufacturing Processes and Technologies (AMPT) Conference held in Bahrain on
November 2–5, 2008.



June 2009                                                     The Arabian Journal for Science and Engineering, Volume 34, Number 1C              21
     J.H. Kim, J.Y. Jeong, J.M.Bang, J.H. Kim, and I.Y. Yang




           CHARACTERISTICS OF CFRP STRUCTURE OF BENDING STRENGTH AND
               RIGIDITY ACCORDING TO STACKING ORIENTATION ANGLE

     1.   INTRODUCTIONS
         Applications of composite materials in various engineering fields have been extended significantly. Various
     researchers can modify the rigidity and strength characteristics of composite material according to structures and
     materials, they want. The design parameters, material systems, stacking direction, thickness, stacking sequence, etc
     are available. Strength and rigidity by parameters should be important to determine during the design of composite
     material. In this study, CFRP, which has been widely used in space/aviation industries, sports/leisure, and general
     structural applications due to dimensional stability, invariability of material property, high strength and rigidity,
     corrosion resistance, etc., was selected. For automobile application, integration, complex features, safety, and
     environmental issues have been improved. To meet this demand, structural members and parts should be light-
     weight including high strength and rigidity.
         To achieve structural members of CFRP with high strength and rigidity, theoretical approaches are limited to
     isotropic material, and empirical studies have been conducted. As with other composite materials, CFRP shows
     different rigidity and strength due to difference in properties in fiber and matrix material. Structural members receive
     not only compression but also bending and torsion. Therefore, respective studies should be conducted. Studies on
     compression have been extensively made, but studies on torsion and bending are lacking. Among the numerous
     design parameters, orientation angle is selected to find optimal condition for strength and rigidity for manufacturing
     CFRP square tube. In addition, square aluminium tube reinforcement is applied to prevent the shortcoming of CFRP,
     strength reduction under FOD.
        For the mechanical properties like bending strength and rigidity, vacuum compressed CFRP via autoclave with
     square aluminium tube reinforcement material was evaluated by changing the orientation angle. Stacking thickness
     and sequence among design parameters refers the one in previous study.
     2.   EXPERIMENTALS
     2.1. Specimen
         Stacking thickness and sequence for CFRP, which showed the highest compressive strength and energy
     absorption in compression test, was used as design parameter. Orientation angles, design parameter in this study, are
     [+0°/-0°]4, [+15°/-15°]4, [+45°/-45°]4, [+90°/-90°]4, [90°/0°]4, and [0°/90°]4. Stacking sequence is A, B, A, B, A, B,
     A, B (denoted as [A/B]4). CFRP for test was CFRP prepreg sheet (HANKUK carbon, CU125NS, Carbon Fiber uni-
     direction 125g/m2), and square aluminum for hybrid was Al6063 with 1 mm thickness. Its width and length was
     30mm. To determine the mechanism of orientation angle in CFRP, a bending plate was prepared. The CFRP plate
     was made at a 60:1 ratio of length to thickness to eliminate the effect of shear strength in bending test. In addition,
     width was ¼ of length. Therefore, thickness was about 2 mm, width was 40 mm, and length was 120 mm. CFRP was
     produced with vacuum compression autoclave forming at 130°. For square shape of the CFRP specimen, release film
     was wound on mandrel (cross-section: 28x28), and 8 ply of CFRP prepreg sheet was wound to form square tube. For
     hybrid specimen, surface of square aluminum (Al6063, t=1, cross-section: 30x30) was treated with metal finishing
     method, and foreign bodies were removed with methanol. After that, aluminum was laminated on CFRP prepreg
     sheet. Specimens were supported by jig as Figure 2 and processed with autoclave forming. Every specimen was cut
     with a diamond saw to prevent residual stress. (According to a previous study, 8 ply of stacking thickness showed
     the highest compressive strength and energy absorption.)
     2.2. Experimental Apparatus
         Dimension of width and length for general bending test specimen is specified according to thickness in KS
     standard. For ASTM, thickness and length of specimen (support span) should be 1:16, and width and length should
     have more than a ¼ ratio. However, a test sample for several anisotropic composites should be made by ASTM
     standard to minimize the effect of shear strength for determining bending strength and rigidity.
        Among bending tests, a 3-point bending test is the easiest and the most widely used method. In this study, a 3-
     point bending test device is prepared as shown in photo 1 according to standard. The diameter of the support span is
     30mm, and it is freely moved to prevent slip. The diameter of the nose span jig was 10mm in semi-spherical shape.
     The nose span jig is positioned at the center of the test specimen. The support span is 120mm for the CFRP plate and
     450mm for the square specimen.




22   The Arabian Journal for Science and Engineering, Volume 34, Number 1C                                         June 2009
                                                                    J.H. Kim, J.Y. Jeong, J.M.Bang, J.H. Kim, and I.Y. Yang




            z      y

                                                                   CFRP prepreg sheet (A)
                        x




                                                                  CFRP prepreg sheet (B)


                                    Figure 1. Schemation view of fabrication
                                                          Vaccum pack


                                                            Jig




                   Release Film

                                            Jig                                   Jig
                                                           Specimen
                Bag sealant tape




                                   Figure 2. Configuration of the test specimen




                              Photo 1.       Three point bending test device




June 2009                                         The Arabian Journal for Science and Engineering, Volume 34, Number 1C       23
     J.H. Kim, J.Y. Jeong, J.M.Bang, J.H. Kim, and I.Y. Yang




               σ fm : Max Bending Stress
               E B I : Stiffness Coefficient
                                                                      σ fm = (3PL / 2bd 2 )[1 + 6(D / L )2 − 4(d / L )(D / L ]   (1)
               P : Load
               L : Span Length
               b , d :W idth and Depth
               D : rL 2 / 6d (r = 0.05)                                        M   6d 2 PL
                                                                      σ fm =     =                                               (2)
               δ : Displacement                                                Z 4(d 24 − d14 )
               M : Bending Moment
               I : Moment of Inertia of Area                                       PL3
                                                                      EB I =                                                     (3)
               Z : Section Modulus                                                 48δ
         Between load cell and actuator of universal testing machine (UTM), the nose span and support span device is
     installed. The specimen is placed on top of the support span, and the nose span is moved by 5 mm/min and 10
     mm/min to loading direction. After the bending test, load-displacement is measured using Equation (1) for CFRP
     plate and Equation (2) for square tubes (CFRP and hybrid). Stiffness coefficient is calculated by Equation (3).
         The following figure shows load-displacement of aluminum, CFRP plate, CFRP square tube, and hybrid tube.
     Every specimen except aluminum showed steep reduction in load due to fracture after having maximum load. This is
     originated from interlayer fracture in mode II by shearing force. Energy up to this point is regarded as absorption
     energy.
     3.   RESULTS AND DISCUSSION
        Figures 4 and 5 show the strength and rigidity of the CFRP plate. For the strength of the CFRP plate, [+15/-15]4
     showed the highest value, and the following are [+0/-0]4, [0/90]4, and [90/0]4 in sequence. For rigidity, [+15/-15]4
     and [+0/-0]4 displayed the highest in sequence as shown in strength. Therefore, the best strength and rigidity can be
     achieved with [15/-15]4 of orientation angle for CFRP plate.
         Figures 6 and 7 showed the strength and stiffness of the square CFRP tube after the bending test. For strength,
     [0/90]4 was the highest, but others had similar value with consideration of error except [+90/-90]4. For rigidity, [+0/-
     0]4, [0/90]4, and [90/0]4 exhibited almost same value. The effect of orientation angle did not show in square
     specimen different than CFRP plate.
         Figures 8 and 9 show the strength and stiffness of the hybrid tube after the bending test. From the reinforcement
     of aluminum, overall strength and rigidity was improved. To prove this, aluminum itself was bended to evaluate
     strength and rigidity. Therefore, the hybrid tube showed the higher value than the sum of the CFRP tube and
     aluminum reinforcement.
         The strength of the hybrid tube showed almost similar value between [+0/-0]4 and [+15/-15]4, but [+15/-15]4 had
     the slight edge. For rigidity, [+0/-0]4 and [+15/-15]4 displayed similar value, but [+0/-0]4 had the edge on the
     contrary. From the overall view on strength and rigidity, [+0/-0]4 and [+15/-15]4 of orientation angle was the best for
     the hybrid square tube.

                                                          6
                                                                                             Aluminum
                                                          5                                  Flat of CFRP
                                                                                             Square of CFRP
                                                                                             Square of Hybrid
                                                          4
                                               Load[kN]




                                                          3

                                                          2

                                                          1

                                                          0
                                                              0   3            6         9          12          15

                                                                      Displacement[mm]

                                      Figure 3. Load-displacement diagram by three points bending test




24   The Arabian Journal for Science and Engineering, Volume 34, Number 1C                                                       June 2009
                                                                                         J.H. Kim, J.Y. Jeong, J.M.Bang, J.H. Kim, and I.Y. Yang




                                                      3
                                              4.0x10




                  Flexural StrengthMax[MPa]
                                                      3
                                              3.5x10
                                                      3
                                              3.0x10
                                                      3
                                              2.5x10
                                                      3
                                              2.0x10
                                                      3
                                              1.5x10
                                                      3
                                              1.0x10
                                                      2
                                              5.0x10
                                                    0.0
                                                          [0]     [15]    [45]    [90]     [0/90]    [90/0]

                                                                    Stacking Angles

            Figure 4. Flexure bending strength of CFRP plate by three bending test

                                              3.0

                                              2.5
                  Stiffness Coefficient




                                              2.0

                                              1.5

                                              1.0

                                              0.5

                                              0.0
                                                    [+0/-0] [+15/-15][+45/-45][+90/-90] [0/90]      [90/0]

                                                                 Orientation Angle

            Figure 5. Flexure bending stiffness of CFRP plate by three bending test

                                          180
                  Bending Strength[MPa]




                                          150


                                          120


                                               90


                                               60


                                               30
                                                    [+0/-0] [+15/-15][+45/-45][+90/-90] [0/90]      [90/0]

                                                                 Orientaion Angle
                                                                 Orientation Angle
             Figure 6. Flexure strength of CFRP square tube by three bending test




June 2009                                                        The Arabian Journal for Science and Engineering, Volume 34, Number 1C             25
     J.H. Kim, J.Y. Jeong, J.M.Bang, J.H. Kim, and I.Y. Yang




                                                                      600

                                                                      500




                                              Stiffness Coefficient
                                                                      400

                                                                      300

                                                                      200

                                                                      100

                                                                        0
                                                                             [+0/-0] [+15/-15][+45/-45][+90/-90] [0/90]     [90/0]

                                                                                           Orientation Angle

                                     Figure 7. Flexure stiffness of CFRP square tube by three bending test

                                                                      300

                                                                      270
                                            Bending Strength[MPa]




                                                                      240

                                                                      210

                                                                      180

                                                                      150

                                                                      120

                                                                             [+0/-0] [+15/-15] [+45/-45] [+90/-90] [0/90]   [90/0]

                                                                                           Orientation Angle
                                   Figure 8. Flexure strength of hybrid square tube by three bending test

                                                                      2400

                                                                      2100
                                         Stiffness Coefficient




                                                                      1800

                                                                      1500

                                                                      1200

                                                                       900

                                                                       600

                                                                             [+0/-0] [+15/-15][+45/-45][+90/-90] [0/90]     [90/0]

                                                                                           Orienation Angle
                                                                                           Orientation Angle
                                     Figure 9. Flexure stiffness of hybrid square tube by three bending test


     4.    CONCLUSIONS
        Strength and rigidity of the CFRP plate and the CFRP square tube, and reinforcement with aluminum were
     evaluated by changing the orientation angle of the composite material.
          1.   Strength and rigidity of the CFRP plate was shown to be the best at [+15/-15]4.
          2.   For the CFRP square tube, orientation angle did not significantly affect rigidity except [+90/-90]4. However,
               [0/90]4 and [90/0]4 showed the highest.
          3.   Strength and rigidity of the hybrid square tube showed the higher value than the sum of aluminum support
               and CFRP square tube.
          4.   The hybrid square tube exhibited the highest value in rigidity and strength for [+0/-0]4 and [+15/-15]4, which
               was the best condition to prepare.


26   The Arabian Journal for Science and Engineering, Volume 34, Number 1C                                                           June 2009
                                                                  J.H. Kim, J.Y. Jeong, J.M.Bang, J.H. Kim, and I.Y. Yang




REFERENCES
[1]   C. S. Cha, K. S. Lee, S. H. Kim, J. O. Ching, and I. Y. Yang, “Axial Collapse Characteristics of Aluminum/CFRP
      Compound Circular Tube”, Key Engineering Materials, 297–300(2005), pp. 166–171.
[2]   J. H. Kim, I. Y. Yang, and J. K. Sim, “Evaluation of Fracture Toughness of Dynamic Inter-Laminar for CFRP
      Laminate Plates by Resin Content”, KSMTE, 12(4)(2003), pp. 43–49.
[3]   Y. N. Kim, K. H. Im, J. W. Park, and I. Y. Yang, “Experimental Approach on the Collapse Mechanism of CFRP
      Composite Tube”, Reviews of Progress in QNDE, (2000), pp. 369–376.
[4]   K. C. Shin, J. Lee, K. H. Kim, M. C. Song, and J. H. Huh, “Axial Crush and Bending Collapse of an
      Aluminum/GFRP Hybrid Tube and its Energy Absorption Capability”, Composite Structure, 57(2002), pp. 279–
      287.
[5]   A. G. Mamalis, D. E. Manolakos, M. B. Ioannidis, and D. P. Papapostolou, “Crashworthy Characteristics of
      Axially Statically Compressed Thin-Walled Square CFRP Composite Tube: Experimental”, Composite Structure,
      63(2004), pp. 347–360.
[6]   M. J. Robert, “Crushing Characteristics of Continuous Fiber-Reinforced Composite Tubes”, Journal of Composite
      Materials, 26(1)(1992).
[7]   Standard Test Method for Flectural Properties of Unreinforced and Reinforced Plastics and Electrical Including
      Materials, ASTM D6272-02 American Society for Testing and Materials (2003).
[8]   B. S. Almir, N. Santos, and C. L. R. Lebre, “Flexural Stiffness Characterization of Reinforced Plastic (FRP)
      Pultruded Beams”, Composite Structures, 81(2007), pp. 247–282.




June 2009                                         The Arabian Journal for Science and Engineering, Volume 34, Number 1C     27

				
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