Fitting Models to Composite Materials Fatigue Data

Abstract

A new procedure for fitting fatigue models (consisting of a deterministic equation defining the shape of the S-N curve and a probabilistic description of the data scatter) is presented. The procedure consists of (1) transforming the fatigue data into equivalent static strength data by using the deterministic equation in the fatigue model with unknown parameters, (2) obtaining the maximum-likelihood estimates for the parameters of the (two-parameter Weibull) distribution describing the equivalent static strength data, and (3) repeating Steps 1 and 2 until the largest maximum-likelihood estimate of the shape parameter is obtained. The procedure can handle runouts and tab failures through progressive censoring. Finally, the procedure is well defined when small fatigue data samples are available.

Fatigue models for woven textile composite laminates

“…Regarding the characterization of the SeN behaviour of composite materials, Sendeckyj (1981) advises taking into account three assumptions:…”

Phenomenological fatigue analysis and life modeling

“…An example is the formulation proposed by sendeckyj [19], who generates an s-N curve based on the concept of a direct correlation between strength and fatigue data (the 'strength-life-equal-rank assumption'), and allows for the inclusion of residual strength data in the construction of an s-N curve, as in where S e = equivalent static value of S S a = amplitude of S S r = residual S after N cycles D = fitting parameter for the high-cycle region E = fitting parameter for the low-cycle region.…”

Environmental effects on fatigue behavior of adhesively-bonded pultruded structural joints

“…All fatigue data sets were subjected to statistical analysis according to the wear-out model proposed in [13]. The wear-out model assumes that the stronger specimen in fatigue should also be the stronger one under quasistatic loads and that therefore a relationship exists between the equivalent static strengths and cyclic stresses and number of cycles to failure.…”

“…This process is performed iteratively for different values of S and C, until the maximum value of the shape parameter, a f, is obtained [13].…”