1995 Fiscal Year Final Research Report Summary
Mechanism of Compressive Strength Reduction due to Impact damage in Composite Laminate and Material Design
| Project/Area Number |
06650765
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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 |
Composite materials/Physical properties
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| Research Institution | Sophia University |
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Principal Investigator |
SUEMASU Hiroshi Sophia Univ., Dept of Mechanical Engineering, Professor, 理工学部, 教授 (20134661)
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| Co-Investigator(Kenkyū-buntansha) |
GOZU Katsuhisa Sophia Univ., Dept of Mech. Eng., Research associate, 理工学部, 助手 (40178439)
MAJIMA Osamu Sophia Univ., Dept of Mech. Eng., Research associate, 理工学部, 助手 (90053678)
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| Project Period (FY) |
1994 – 1995
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| Keywords | Composite Material / Delamination / CAI / Buckling / Post buckling / Fracture mechanics / Rayleigh-Ritz method / Finite Element Method |
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| Research Abstract |
A research work is conducted under the title of "Mechanism of Compressive Strength Reduction due to Impact damage in Composite Laminate and Material Design". The present work is made of three parts, that is, Approximate theory, numerical simulation of fracture behavior by finite element method and experiment of the plate with multiple circular delaminations which is an ideal model of impact damage.
In the Experiment, the buckling and postbuckling behaviors are studied and final failure of the specimen with multiple delaminations is caused by the delamination propagation in transverse direction to the load. It means that the inter-laminar toughness of the composite laminate is important for the CAI problem and a fracture mechanics approach should be conducted.
The approximate analysis is conducted through the Rayleigh Ritz method. Through a parametric study done by this method with respect to the size, number and shape of the multiple delaminations, we obtained various interesting phenomena on the buckling strength reduction due to the impact damage. But postbuckling analysis is found to be necessary to explain the final failure behavior of the damaged plate. The finite element analysis conducted needed huge numerical efforts, because not only a three dimensional analysis is done but also a contact problem must be considered. The results explain well the buckling, post buckling and failure behaviors observed in the experiment.
The buckling loads obtained through Rayleigh-Ritz agree well with those obtained through both experiment and finite element method. Considering its efficiency, the present method is useful to explain global phenomena.
In order to solve the CAI (Compression After Impact) problem, the strength reduction must be studied relating the damage accumulation process during impact response.
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