The strength reduction of the composite structures due to damage and development of damage simulation method

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Fiber reinforced composite materials and their structures are susceptible to miner damage, such as matrix cracks and delaminations, due to various causes such as foreign object impacts, inadequate process controls, etc. The structural performance is often reduced by the damage. The damage problem is still a serious issue for the damage tolerant design of composite structures how to consider the effect of the damage on the strength and various properties. By using damage analysis tools we worked to investigate damage appearance and growth and identify the rupture strength of the composite laminates and structures. In the numerical analysis we studied on the problem occurring during the damage analysis using the cohesive damage model and stiffness reduction model. We worked particularly on the following four themes.・On failure of pressure vessel from the initial matrix damage and the guideline of pressure vessel design・Impact damage and reduction of compressive strength・Failure from the … More stress concentration area under compression load・Oscillating stress singularity and fracture mechanism of adhesively bonded dissimilar materials interfaceWe could publish 7 journal papers and present the findings at more than 20 conferences. To show the damage accumulation process and to predict the failure strength, an efficient and stable analytical tool is essential. We introduced a cohesive element with added Gauss points where the failure is judged at every Gauss point. This element also enabled us not only to determine the damaged portions depending on the stress distribution but also to define the initial damage independently of the finite element mesh. This is similar function as the extended finite element method. We also conducted the Gauss point base failure analysis using a solid damage element to simulate the compression failure problem. In the analysis we tried to use explicit solution method to overcome unstable damage growth problem. The result showed quite similar damage pattern to the experimentally observed one. Less