Japan Aerospace Technology Foundation
Advanced Composite Research Center, Institute of Aeronautical Technology, Japan Aerospace Exploration Agency (JAXA)
Advanced Composite Research Center, Institute of Aeronautical Technology, Japan Aerospace Exploration Agency (JAXA)
Structures Research Group, Institute of Aeronautical Technology, Japan Aerospace Exploration Agency (JAXA)
The load enhancement factor (LEF) approach is proposed as a fatigue acceleration test to demonstrate the fatigue strength of composite material structures. The objective of the LEF approach is to increase the applied loads in the fatigue spectrum so that the same level of reliability can be achieved with short test durations. Some fatigue tests on the full-scale composite structure are executed on the basis of this method. In the LEF approach, the probability distribution of residual strength and fatigue life is assumed to be a two-parameter Weibull distribution. LEF is defined as a function of shape parameters from the Weibull distributions. As a consequence, the uncertainty in residual strength and fatigue life greatly affects LEF assessment. For simplicity, modal values of the shape parameters are used in the Composite Materials Handbook (CMH-17). This study investigates the uncertainty in the shape parameters in more detail. First, the shape parameters are modeled as a probability distribution, by using Bayesian analysis to evaluate the scatter of the shape parameter. As the so-called parametric method, the unknown parameters of the distribution are estimated using the Bayesian method from the database. The Bayesian expected value of the LEFs is calculated from the estimated probability distribution of the shape parameter. When the uncertainty of the shape parameter is large and the assumption of the usual probability distribution is problematic, the non-parametric estimation method for the distribution is applied. The probability distribution approximation that uses the spline function is used here. Last, this paper presents two types of expected LEF values mentioned above and their comparison with already reported results in CMH-17.
内容記述
形態: カラー図版あり
内容記述（英）
Physical characteristics: Original contains color illustrations
複合材構造の疲労寿命実証試験における荷重設定について: ベイジアン・アプローチ
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