Abstract
Two implicit progressive fatigue damage models that rely on new equivalent-damage and equivalent-stress criteria are presented for the prediction of various failure modes of the composites. The criteria are coupled with lamina-based and representative-volume-element-based damage progression approaches. The common concepts of residual strength and residual stiffness are revisited and modified. A fatigue life assessment algorithm that incorporates the strain-rate-dependence of the fatigue strengths and stiffnesses, and random and asynchronous changes of the stress components, distinct mean values, and phase shifts of the stress components is employed. New ideas and new post-processing procedures are employed in the current research. It is the first time that the significant impacts of the strain-rate-dependence of the properties of the composites on stress and fatigue life analyses are investigated. Results of the proposed fatigue criteria are first implemented to a composite plate with a complex lamination scheme under a random transverse load and the predicted fatigue lives are verified by the experimental results. Then, these criteria are implemented to a composite chassis frame of an SUV car under realistic random road inputs and the theoretical results are verified by the experimental results. Results confirm the significant role of the strain-rate-dependence effects on the fatigue lives.
Highlights
M odern composites have been used extensively in durable and ultra-safe engineering structures
Fewer researches have taken into account the influence of the stress ratio on the fatigue analysis results
The current article is concerned with the suggestion of new ideas for the development of two categories, i.e., lamina-based and phase-based, progressive-damage fatigue life assessment criteria that can be employed for composites with arbitrary lamination schemes under loads with arbitrary time-variations patterns
Summary
M odern composites have been used extensively in durable and ultra-safe engineering structures. Passipoularidis et al [7] presented a progressive damage fatigue modeling algorithm in ply level for variable-amplitude loads, utilizing Puck’s failure criterion, residual strength, and gradual/sudden stiffness degradation methodologies. Yang et al [9] presented a short review on the phenomenological and progressive damage models of the fatigue life prediction of the fiber-reinforced ceramic-matrix composites under, thermomechanical loadings. A limited portion of the original ideas of these criteria has already been proposed by the author [11], the employed concepts, the modeling procedure (especially, the RVE-based one), and incorporation of the ideas of the strain-ratedependence of both the material properties and fatigue strengths (S-N and T-N curves) are novel and the life assessment algorithm is new.
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