Fatigue Degradation in Centrally Notched Quasi-Isotropic Laminates

Abstract

The aim of this research is first to model the degradation of the elastic modulus of quasi-isotropic [0/90/ ±45] 2 s graphite/epoxy centrally notched composite laminates subjected to tension-tension ( T-T ) fatigue tests. Then we can predict the fatigue life in terms of elastic modulus as a non-destructive parameter of failure criterion and express the residual strength by using the elastic modulus degradation model. Extensively, the concept of cumulative damage is adopted to expand these models for wide applications to any sequence of loading spectrum instead of the constant stress amplitudes. These models have been modified from the existing models, they possess the features of accuracy, simplicity and applicability. Basically, part of them are verified satisfactorily in comparison with the experimental data. They still have sound theoretical bases and simply applicable to engineering problems.

Experimental study on flexural fatigue behavior of glass fibers/epoxy hybrid composites with statistical analysis

“…The failure criterion of the flexural fatigue used in the present study is defined as: the specimen fails when the residual stiffness of the specimen (EI)/(EI) 0 reaches 80% of its initial stiffness value. 14 In the present work, the elastic modulus degradation model proposed by Jen et al 15 was used to illustrate the relationship between the stiffness reduction ratio, (EI)/(EI) 0 , and the number of cycles (N) as follows:…”

“…14 In the present work, the elastic modulus degradation model proposed by Jen et al. 15 was used to illustrate the relationship between the stiffness reduction ratio, ( EI )/( EI ) 0 , and the number of cycles ( N ) as follows: where A i and B i are constants depending on the test specimen material and are calculated from the fatigue experimental data.…”

Flexural fatigue and failure probability analysis of polypropylene-glass hybrid fibres reinforced epoxy composite laminates

“…The elastic modulus degradation model proposed by Jen et al. [28] was employed to define the relation between the stiffness ratio and the number of cycles as follows: where and are constants, which can be calculated from the fatigue experimental data. These constants depend on many factors, such as the constituent materials, fibre volume fraction and fibre orientation.…”

“…This ratio was adopted by many authors [14,[25][26][27]. The elastic modulus degradation model proposed by Jen et al [28] was employed to define the relation between the stiffness ratio and the number of cycles as follows:…”