Reliability Analysis for Composites (the 1 st paper)

摘要

Glass-reinforced plastics (GRP) are used for vessels or storage tanks of various chemical substances. In the meantime, test method for corrosion-resistance of GRP is prescribed in JIS K 7070; 1992, 'Testing method for chemical resistance of fiber reinforced plastics'. Also, JIS K 7020 1998 (ISO 10928:1997, Glass-reinforced thermosetting plastics (GRP) pipes and fittings-Method for regression analysis and their use) presents a method to estimate 50 years performance from 10,000 hours test data.JIS K 7020 provides three estimation methods, the first of which is method A; covariance method, the second, method B; regression with time as independent variable, the third, method C; second order of polynominal expression. All threemethods induce equation by putting time' as independent variable. It is reasonable to take time' as a major factor for deterioration but we can not conclude the effect of time', without condition, to have the 1 St order, the 2 nd order, another more higher order or their mixtures. Also, coefficients vary for every estimation by degree because of the dependence among variables.In order to avoid these weakness, it is useful to apply calculation by development of orthogonal polynominal expression (Chebishev's orthogonal function). The calculation requires more accurate statistical analysis of sum of squares by each factor. This paper forcuses an example of reliability analysis for GRP corrosion-resistant immersion test results to representative acid and alkali substances conducted through 1990-91 in accordance with JIS K 7070 test method.