1990 Fiscal Year Final Research Report Summary
Holographic Interferometry Measurement and Theoretical Analysis of Deformations of Composite Laminates due to Interlaminar Stresses
| Project/Area Number |
01420019
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| Research Category |
Grant-in-Aid for General Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
Aerospace engineering
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| Research Institution | University of Tokyo |
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Principal Investigator |
KONDO Kyohei Univ.of Tokyo, Faculty of Engineering, Professor, 工学部, 教授 (20011190)
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| Co-Investigator(Kenkyū-buntansha) |
KOYAMA Kazuo Univ.of Tokyo, Faculty of Engineering, Lecturer, 工学部, 講師 (60010906)
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| Project Period (FY) |
1989 – 1990
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| Keywords | Composite materials / Laminate / Interlaminar stress / Delamination / Free edge / Transverse crack / Holographic interferometry / Finite element method |
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| Research Abstract |
Deformations due to the interlaminar stresses in the composite laminates subjected to the uniform mechanical and hygrothermal loadings were investigated in order to understand the mechanism of the delamination which is one of the most frequently observed fallure modes of the laminates.
By the quasi three-demensional finite element method, the deformations in the vicinity of the free edges or the transverse crack tips were analyzed assuming that the stresses do not vary along the direction of the free edge or the transverse crack. The superposition method was proposed where the free edge problem and the transverse crack tip problem are transformed to the superpositions of the infinite laminate under uniform stresses and the configurations with external loads applied on the free edge surface and the transverse crack surface, respectively. The superposition technique can eliminate the deformations not resulting from the interlaminar stresses.
By the holographic interferometry, the deformations of the graphite-epoxy laminates coupons under the pure bending moment or the uniform tensile load were measured. The delaminations were introduced by the cyclic tensile loading at the free edges. The overall deformations by the bending moment coincided with the theoretical predictions for the deformations of the infinite laminates based on the classical lamination theory. The deformation near the free edges due to the interlaminar stresses could not be detected since they were small compared to the overall bending deformations. The deformation near the free edges due to the interlaminar stresses in the laminates under the tensile loads were observed for the coupons with delaminations, verifying the numerical results by the finite element method.
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