Anisomorphic constant fatigue life diagrams for quasi-isotropic woven fabric carbon/epoxy laminates under different hygro-thermal environments

Abstract

The effect of absorbed moisture on the fatigue strength of a plain-weave roving fabric carbon/epoxy quasi-isotropic laminate under constant amplitude loading at different stress ratios has been examined. First, constant amplitude fatigue tests are performed at room and high temperatures (HT), respectively, on the specimens immersed in hot water until saturation as well as on the specimens kept in a dry place. The results indicate that the fatigue lives of wet specimens are shorter than those of dry specimens, regardless of stress ratio as well as test temperature. The fatigue strength is reduced by about 11% due to water absorption at room temperature (RT), regardless of stress ratio. A similar reduction in fatigue strength can be seen in wet specimens at HT as well. Then, the full shapes of constant fatigue life (CFL) diagrams for the woven carbon fiber-reinforced plastic (CFRP) laminate in dry and wet environments are identified using fatigue test data obtained at different stress ratios and at different test temperatures. The results show that the experimental CFL diagrams are asymmetric and nonlinear, and the shape of CFL envelope gradually changes. Finally, the CFL diagrams for the woven CFRP laminate under uniaxial fatigue loading in different hygro-thermal environments are predicted using the anisomorphic CFL diagram approach for composites that was developed in an earlier study. Comparison with experimental results demonstrates that the anisomorphic CFL diagram approach is a promising step in predicting the CFL diagram for the woven CFRP laminate not only in a dry environment but also in a wet environment, regardless of test temperature.

Fatigue models for woven textile composite laminates

“…Finally, Kawai, Yagihashi, Hoshi, and Iwahori (2013) further developed their models discussed previously in Section 13.3.1 to include the combined effect of temperature and moisture. Constant fatigue life diagrams were derived for quasi-isotropic woven carbon/epoxy composites under dry and wet conditions.…”

The fatigue of carbon fibre reinforced plastics - A review

“…The hygrothermal conditioning of PEEK matrix CFRP is reported to have little influence on its T-T fatigue life compared to dry composites [214]. This is in stark contrast to epoxy matrix CFRP, which shows not only a strong decline in properties compared to dry composites, but are moreover highly sensitive to the loading regimen (R ratio) [215,216,217,218].…”

“…Many posit that these are bell-shaped curves, regardless of the types of carbon fibres and matrix resins used [239,241,242,247,243]. The CFL diagram for has been used for several different kinds of CFRP laminates [248,249,250,251,252,253,254]. Recently, it was shown by [255] that a unidirectional carbon/epoxy composite, under (T-T) loading (0 < R < 1) and (T-C) (R < 0) loading, has a steeper S-N curve slope than (C-C) loaded (R > 1) composites.…”

“…It was shown to be valid for the prediction of fatigue failure in non-woven carbon/epoxy laminates [302]. The approach was extended to predict the fatigue of woven composites for different temperatures in a later study [303]. Their approach involved using the critical stress ratio defined above as the ratio between compressive and static strength χ = σ C /σ T .…”

The effect of long-term exposure to high temperature atmosphere on weight change and damage progress in carbon fiber-reinforced polycyanate ester composites

“…[1,2] Some kinds of heatresistant polymer matrix-based composites (PMCs) (e.g. bismaleimide or polyimide resin systems) are currently being used on structures for both military and commercial aircraft.…”