DOI QR코드

DOI QR Code

Low Cycle Fatigue Life Behavior of GFRP Coated Aluminum Plates According to Layup Number

적층수에 따른 GFRP 피막 Al 평활재의 저주기 피로수명 평가

  • Myung, Nohjun (Department of Mechanical Engineering, Graduate School, Hanyang Univ.) ;
  • Seo, Jihye (Department of Mechanical Design Engineering, Graduate School, Hanyang Univ.) ;
  • Lee, Eunkyun (Department of Mechanical Design Engineering, Graduate School, Hanyang Univ.) ;
  • Choi, Nak-Sam (Department of Mechanical Engineering, Hanyang Univ.)
  • Received : 2018.10.18
  • Accepted : 2018.11.28
  • Published : 2018.12.31

Abstract

Fiber metal hybrid laminate (FML) can be used as an economic material with superior mechanical properties and light weight than conventional metal by bonding of metal and FRP. However, there are disadvantages that it is difficult to predict fracture behavior because of the large difference in properties depending on the type of fiber and lamination conditions. In this paper, we study the failure behavior of hybrid materials with laminated glass fiber reinforced plastics (GFRP, GEP118, woven type) in Al6061-T6 alloy. The Al alloys were coated with GFRP 1, 3, and 5 layers, and fracture behavior was analyzed by using a static test and a low cycle fatigue test. In the low cycle fatigue test, strain - life analysis and the total strain energy density method were used to analyze and predict the fatigue life. The Al alloy did not have tensile properties strengthening effect due to the GFRP coating. The fatigue hysteresis geometry followed the behavior of the Al alloy, the base material, regardless of the GFRP coating and number of coatings. As a result of the low cycle fatigue test, the fatigue strength was increased by the coating of GFRP, but it did not increase proportionally with the number of GFRP layers.

섬유 금속 적층판(Fiber metal hybrid laminate, FML)은 금속재료와 FRP의 접합으로 기존의 금속 소재가 가지지 못했던 뛰어난 물성과 가벼운 무게로 경제적인 구조용 재료로 사용된다. 그러나 섬유의 형태와 종류, 적층조건에 따라 물성의 차이가 크며, 파괴거동을 예측하기 어렵다는 단점이 있다. 본 논문에서는 Al6061-T6 합금에 직조형태의 유리섬유 플라스틱(GFRP, GEP118)을 적층피막한 복합재의 파손거동에 대해 연구한다. Al합금에 GFRP 1, 3, 5 겹을 피막한 3가지 조건으로 성형하고, 피막의 적층수를 변수로 정적시험과 저주기 피로시험을 병행하여 파손거동을 분석하였다. 저주기 피로시험에서는 변형률-수명 해석, 전변형률 에너지밀도법을 사용하여 분석하고, 피로수명을 예측하여 하이브리드 재료에 대한 수명예측성을 분석하였다. 인장해석 결과, GFRP 피막으로 인한 강화효과는 없었고, 피로시험시 나타나는 히스테리시스 형상은 GFRP피막 유무와 피막 수에 상관없이 모재인 Al합금의 거동을 따랐다. 저주기 피로시험 결과 GFRP의 피막으로 피로강도가 증가하였지만, GFRP의 두께에 따라 비례하여 증가하지는 않았다.

Keywords

BHJRB9_2018_v31n6_332_f0001.png 이미지

Fig. 1. Sketching order of GFRP and adhensive film

BHJRB9_2018_v31n6_332_f0002.png 이미지

Fig. 2. Tensile test curves of aluminum alloy and Al/GFRP laminates

BHJRB9_2018_v31n6_332_f0003.png 이미지

Fig. 3. Nominal stress-strain curves of aluminum alloy at the cycle of half lives

BHJRB9_2018_v31n6_332_f0004.png 이미지

Fig. 4. Nominal stress-strain curves of aluminum alloy and Al/GFRP laminates at the cycle of half lives

BHJRB9_2018_v31n6_332_f0005.png 이미지

Fig. 5. Nominal stress-strain curves of Al + 3 plies at 1,2 and 600 cycles

BHJRB9_2018_v31n6_332_f0006.png 이미지

Fig. 6. Fatigue test results of aluminum alloy and Al/GFRP laminates

BHJRB9_2018_v31n6_332_f0007.png 이미지

Fig. 7. Description of the plastic and elastic strain energy densities

BHJRB9_2018_v31n6_332_f0008.png 이미지

Fig. 8. Total energy density method results of aluminum alloy and Al/GFRP laminates

BHJRB9_2018_v31n6_332_f0009.png 이미지

Fig. 9. Comparison at each specimen type between experimental life and predicted life by total strain energy density method

BHJRB9_2018_v31n6_332_f0010.png 이미지

Fig. 10. Fractography of GFRP-coated Al specimens at the tensile test

BHJRB9_2018_v31n6_332_f0011.png 이미지

Fig. 11. Fractography of GFRP-coated Al specimen at the fatigue test

Table 1. Thickness of specimen and GFRP fraction

BHJRB9_2018_v31n6_332_t0001.png 이미지

Table 2. Tensile test results of rolling direction of Al6061-T6 plate

BHJRB9_2018_v31n6_332_t0002.png 이미지

Table 3. Average of the internal area of the hysteresis loop at half life

BHJRB9_2018_v31n6_332_t0003.png 이미지

Table 4. Experimental constants in total strain energy density method

BHJRB9_2018_v31n6_332_t0004.png 이미지

Table 5. Experimental constants in total strain energy density method

BHJRB9_2018_v31n6_332_t0005.png 이미지

References

  1. (International Journal) Lin, C.T., Kao, P.W., and Yang, F.S., "Fatigue Behaviour of Carbon Fibre-reinforced Aluminium Laminates," Composites, Vol. 22, Issue 2, 1991, pp. 135-141. https://doi.org/10.1016/0010-4361(91)90672-4
  2. (Proceeding) Yoon, H.K., Lee, K.B., Park, W.J., and Hue, C.W., "A Study on Characterisitcs of Tensile Strength and Fatigue Life with Hybrid Composite Materials for Aircraft," Proceedings of the KSME 1995 Conference, 1995, pp. 213-217.
  3. (International Journal) Vogelesang, L.B., and Vlot, A., "Development of Fibre Metal Laminates for Advanced Aerospace Structures," Journal of Materials Processing Technology, Vol. 103, Issue 1, 2000, pp. 1-5. https://doi.org/10.1016/S0924-0136(00)00411-8
  4. (International Journal) Cortes, P.W., and Cantwell, J., "The Fracture Properties of a Fibre-metal Laminate Based on Magnesium Alloy," Composites Part B: Engineering, Vol. 37, Issue 2-3, 2005, pp. 163-170. https://doi.org/10.1016/j.compositesb.2005.06.002
  5. (International Journal) Kawai, M., and Kato, K., "Effects of Rratio on the Off-axis Fatigue Behavior of Unidirectional Hybrid GFRP/Al Laminates at Room Tamperature," International Journal of Fatigue, Vol. 28, Issue 10, 2006, pp. 1226-1238. https://doi.org/10.1016/j.ijfatigue.2006.02.020
  6. (Proceeding) Monfared, A., Soudki, K., and Walbridge, S., "CFRP Reinforcing to Extend the Fatigue Lives of Steel Structures," Fourth International Conference on FRP Composites in Civil Engineering(CICE2008), 2008, pp. 1-6.
  7. (International Journal) Rhee, H.W., and Kim, S.H., "Fatigue Crack Growth Behavior of the Thin-to-thick Type Stiffened Panels with Bonded Patch," Journal of Ocean Engineering and Technology, Vol. 22, No. 3, 2008, pp. 89-95.
  8. (International Journal) Khan, S.U., Alderliesten, R.C., and Benedictus, R., "Post-stretching Induced Stress Redistribution in Fibre Metal Laminates for Increased Fatigue Crack Growth Resistance," Composites Science and Technology, Vol. 69, Issue 3-4, 2009, pp. 396-405. https://doi.org/10.1016/j.compscitech.2008.11.006
  9. (International Journal) Ergun, E., Tasgetiren, S., and Topcu, M., "Fatigue and Fracture Analysis of Aluminum Plate with Composite Patches under the Hygrothermal Effect," Composite Structures, Vol. 92, Issue 11, 2010, pp. 2622-2631. https://doi.org/10.1016/j.compstruct.2010.03.015
  10. (Korean Journal) Lee, S.H., Kim, H.J., Chang, Y.W., and Choi, N.S., "Bending Performances and Collapse Mechanisms of Light-weight Aluminum-GFRP Hybrid Square Tube Beams," Journal of the Korean Society for Composite Materials, Vol. 20, No. 3, 2007, pp. 8-16.
  11. (Korean Journal) Yoon, H.K., Park, W.J., and Hur, C.W., "A study on Fatigue Crack Retardation Using NDT Test in a Hybrid Composite Material Reinforced with a CFRP," Journal of the Korean Society for Composite Materials, Vol. 12, No. 3, 1999, pp. 1-7.
  12. (International Journal) Coffin, L.F., "A Study of the Effects of Cyclic Thermal Stress on a Ductile Metal," Trans. ASME, Vol. 76, 1954, pp. 931-950.
  13. (International Journal) Halford, G.R., "The Energy Required for Fatigue," Journal of Materials, Vol. 1, No. 1, 1966, pp. 3-18.
  14. (International Journal) Ellyin, F., and Kujawski, D., "An Energybased Fatigue Failure Criterion," Microstructure and Mechanical Behavior of Materials, Vol. 2, 1985, pp. 541-600.
  15. (International Journal) Basquin, O.H., "The Experimental Law of Endurance Tests," American Society for Testing and Materials Proceedings, Vol. 10, 1910, pp. 625-630.