1993 Fiscal Year Final Research Report Summary
Micro Mechanical Study on Fatigue Damage Mechanism of Composite Materials
| Project/Area Number |
03452192
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
船舶構造・建造
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| Research Institution | The University of Tokyo |
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Principal Investigator |
KIMPARA Isao University of Tokyo Faculty of Engng.Professor, 工学部, 教授 (50011101)
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| Co-Investigator(Kenkyū-buntansha) |
OHSAWA Isamu University of Tokyo Facult.of Engng.Assis.Res., 工学部, 助手 (00143389)
SUZUKI Toshio University of Tokyo Facult.of Engng.Assis.Res., 工学部, 助手 (20010895)
KAGEYAMA Kazuro University of Tokyo Facult.of Engng.Asso.Prof., 工学部, 助教授 (50214276)
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| Project Period (FY) |
1991 – 1993
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| Keywords | Composite Materials / Carbon Fibers / Polymer Materials / Fracture / Fatigue / Delamination / Ultrasonic C-Scan / Acoustic Emission |
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| Research Abstract |
Computer aided testing system was developed for measuring damage accumulation of composite laminates under cyclic load. Stiffness reduction and energy assumption in the stress versus strain diagram are monitored as a function of cycle numbers. A master curve of stiffness degradation of fatigue damage is obtained for glass, carbon, aramid and their hybrid fibers reinforced plastic. Hybrid effect and design criteria were discussed.
Static and fatigue tests were carried out for unidirectional, cross plied and quasi-isotropic carbonepoxy composite laminates, and their S-N diagrams and stiffness degradation curves were discussed with special consideration on propagation behavior of delamination and matrix cracks.
A model of delamination growth model under cyclic load based on the fracture mechanics approach. Stress and strain concentration at delamination was measured by energy release rate. Effect of elastic moduli on fatigue strength was well explained by the model based on the energy release rate. In order to measure the accurate behavior of fatigue delamination growth, end notched flexur (ENF) test was carried out under constant crack shear displacement rate. A power raw relation between mode II energy release rate and delamination growth rate was obtained.
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