On the tension–tension fatigue behaviour of a carbon reinforced thermoplastic part I: Limitations of the ASTM D3039/D3479 standard

Abstract

Investigating the fatigue behaviour of a material often requires a lot of experiments in order to have statistically valid results. However, the number of successful fatigue experiments, meaning tab failure did not occur, can be significantly smaller than the total number of experiments. This manuscript studies the fatigue behaviour of a carbon fabric reinforced PPS using the specimen geometry proposed by the ASTM D3479/D3479M standard. As it turns out, all specimens failed in the tabbed section, meaning that fatigue life may be significantly underestimated and that the proposed geometry needs for improvement. Therefore, the main emphasis in this manuscript lies on the stiffness degradation and the permanent deformation of the material, rather than on the number of cycles till failure. It may be concluded that for the [(0°,90°)] 4s stacking sequence the material does not show significant stiffness reduction and that only limited permanent deformation is present. Furthermore, the material shows very brittle failure behaviour and the stress-span between infinite fatigue life and failure in a few dozen cycles is very narrow.

On the tension–tension fatigue behaviour of a carbon reinforced thermoplastic part II: Evaluation of a dumbbell-shaped specimen

“…Previous experiments with rectangular specimens, done by the authors yielded average failure stresses between 600 and 700 MPa, with occasionally a value higher than 700 [1,18]. However, in almost all cases, failure occurred in the tabbed section.…”

“…However, some materials, such as the carbon-fabric reinforced polyphenylene sulphide under study, do not have the tendency to narrow because of the very low Poisson's ratio and as such, failure is most likely to occur in the area of the stress concentration, underneath the end tabs. In the first part of this study [1], several combinations of adhesives, tab materials and tab geometries were examined under static loading conditions, but no acceptable failure was achieved. Furthermore, during tension-tension fatigue loading conditions, failure always occurred in the tabbed section.…”

“…Similar to the previous study [1], all fatigue tests here are done in load-controlled mode with a minimum stress of 0 MPa and a certain maximum  max. Furthermore, both 2 Hz and 5 Hz experiments are conducted.…”

Fatigue in Fiber-Metal Laminates for Small Wind Turbine Blades Application

“…Tension-tension constant amplitude fatigue tests were performed using MTS 810 servo-hydraulic testing machine and based on ASTM D3479 [17]. The maximum stress applied is from 80Mpa to 300Mpa at a stress ratio of R=0.05 and frequency of 5Hz on GLARE 3/2-[0°] 4 -0.4 samples.…”

Assessment of the interlaminar behaviour of a carbon fabric reinforced thermoplastic lap shear specimen under quasi-static and tension-tension fatigue loading

“…As the minimum of the displacement does not increase, there is no permanent deformation. Given the low uniaxial load levels, no permanent deformation of the adherends was expected [27,28], but this means that there is virtually no permanent deformation of the overlap area under shear loads. A little sliding of the specimen in the grips is present, as can be seen at the beginning of the test since the displacement starts at 0 mm, but increases slightly.…”