| Project/Area Number |
63550057
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Aerospace engineering
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
KUROKAWA Tomoaki Kyoto Univ., Faculty of Engng., Asso. Prof., 工学部, 助教授 (80127076)
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| Co-Investigator(Kenkyū-buntansha) |
SHIROSHITA Sohei Kyoto Univ., Faculty of Engng., Instructor, 工学部, 助手 (80026252)
SHIMA Susumu Kyoto Univ., Faculty of Engng., Professor, 工学部, 教授 (70026160)
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| Project Period (FY) |
1988 – 1989
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| Project Status |
Completed (Fiscal Year 1989)
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| Budget Amount *help |
¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 1989: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1988: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Keywords | CFRP / composite laminates / stress wave / impact / delamination |
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| Research Abstract |
The following results were obtained for wave propagation in composite laminates and dynamic interlaminar strength of graphite/epoxy (T300/2500) composite.
1. Stress wave in unidirectional composites (1) The longitudinal bar velocity C_0 in fiber direction (0ﾟ) is four times higher than that in transverse direction (90ﾟ). The measured value of each velocity shows a good agreement with the predicted value by the formula C_0 ROO<E/rho>, using static Young's modulus. (2) The damping loss of the longitudinal wave in transverse direction (90ﾟ) due to internal friction is significantly greater than that in fiber direction (0ﾟ). The ratio of retardation time between 90ﾟ direction and 0ﾟ direction is approximately twenty.
2. Stress wave in composite laminates and interlaminar shearing strength For the longitudinal wave propagating in symmetric cross-ply laminate [0/90]_s with wave length sufficiently long compared with the thickness of the ply group, the following remarks were obtained. (1) The v
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elocity C_c of longitudinal wave propagating in cross-ply laminate is in agreement with the predicted value by the law of mixture. (2) The longitudinal wave generates the shearing stress acting on the interlaminar surface due to the difference of longitudinal wave velocities between ply groups. The amplitude of the shearing stress is proportional to the longitudinal strain gradient and the difference of longitudinal elastic moduli between ply groups. (3) A delamination crack grows when the shearing stress due to the longitudinal stress wave reaches to the critical value, which is significantly higher than the static value.
3. Transverse wave propagating along composite beam and delamination strength The transient delaminating configuration of thin composite laminates subjected to transverse impact is similar to the transverse wave propagation of thin strip. The value of dynamic interlaminar fracture toughness G_<Id> for T300/2500 in this study obtained by measurement of delaminating transverse wave ranged from 1000 to 2000 J/m^2, this is approximately 10 times higher than the static value. Less
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