17. Study on Reliability Assessment System of Composite Materials

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概要

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• The present paper aims at establishing a general judgement system to predict a decrease in reliability of composite materials due to cumulative damage. The main system is composed of stochastic static and dynamic failure process simulations of composite materials considering the effect of a scatter in strength of fibers, matrix and defects mixed in during a fabrication process, accompanied with a subsystem of statistical analysis. For this purpose, a new failure process simulation model of composite materials is introduced considering the effect of matrix shear failure as well as fiber breaks based on a shear-lag theory in which a failure can occur randomly not only in fiber elements but also in matrix elements: a stochastic static tensile failure process of unidirectional composite materials is simulated by means of a Monte Carlo method based on a repeated increment scheme using a finite difference technique. A Weibull analysis technique is applied to determine the design allowable properties of composite materials. This method is also applied to predict the damage tolerance level of various defect modes of composite materials. Then a new dynamic failure process simulation model is proposed in which an additional time variable is also incorporated by taking into account the mass of fiber and matrix elements. An exact time-dependent stress redistribution process in a composite failure model is evaluated by means of a finite difference scheme based on a time-increment method. A statistical analysis is made on the dynamic failure model and compared with the static one in terms of the different strength parameters. It is shown by the results of this analysis that the dynamic simulation gives a better estimation on the dispersion of strength data and on the actual failure pattern. Finally a macro model is proposed which is a new cumulative failure model composed of elements of micro models based on the previous dynamic failure process simulation models. This method is successfully used in estimating the statistical nature of strength properties of composite materials of actual size, and it is shown that the strength of composites depends clearly on the length but not on the width of a specimen.

• 社団法人日本船舶海洋工学会の論文

著者

• Ozaki Tsuyoshi

  Materials And Electronics Devices Laboratory Mitsubishi Electric Corporation

• Kimpara Isao

  Department Of Naval Architecture And Ocean Engineering The University Of Tokyo

• Kimpara Isao

  Department Of Environmental And Ocean Engineering University Of Tokyo

関連論文

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