Load-Frequency Effect on Fatigue Life of IMP6/APC-2 Thermoplastic Composite Laminates

A probabilistic model for estimating the fatigue life of laminated composite materials considering the uncertainty in their mechanical properties is developed. The uncertainty in the material properties is determined from fatigue coupon tests. Based on this uncertainty, probabilistic constant life diagrams are developed which can efficiently estimate probabilistic ɛ-N curves at any load level and stress ratio. The probabilistic ɛ-N curve information is used in a reliability analysis for fatigue limit state proposed for estimating the probability of failure of composite laminates under variable amplitude loading cycles. Fatigue life predictions of unidirectional and multi-directional glass/epoxy laminates are carried out to validate the proposed model against experimental data. The probabilistic fatigue behavior of laminates is analyzed under constant amplitude loading conditions as well as under both repeated block tests and spectral fatigue using the WISPER, WISPERX, and NEW WISPER load sequences for wind turbine blades.

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Development of a High Cycle Fatigue Life Prediction Model for Thin Film Silicon Structures

Journal of Electronic Packaging ◽

10.1115/1.4040297 ◽

2018 ◽

Vol 140 (3) ◽

Cited By ~ 2

Author(s):

Chia-Cheng Chang ◽

Sheng-Da Lin ◽

Kuo-Ning Chiang

Keyword(s):

Thin Film ◽

Fatigue Life ◽

Life Prediction ◽

Microelectromechanical Systems ◽

Fatigue Testing ◽

Mesh Size ◽

Prediction Equation ◽

Frequency Effect ◽

Element Analysis ◽

Solution Type

The fatigue characteristics of microelectromechanical systems (MEMS) material, such as silicon or polysilicon, have become very important. Many studies have focused on this topic, but none have defined a good methodology for extracting the applied stress and predicting fatigue life accurately. In this study, a methodology was developed for the life prediction of a polysilicon microstructure under bending tests. Based on the fatigue experiments conducted by Hocheng et al. (2008, “Various Fatigue Testing of Polycrystalline Silicon Microcantilever Beam in Bending,” Jpn. J. Appl. Phys., 47, pp. 5256–5261) and (Hung and Hocheng, 2012, “Frequency Effects and Life Prediction of Polysilicon Microcantilever Beams in Bending Fatigue,” J. Micro/Nanolithogr., MEMS MOEMS, 11, p. 021206), cantilever beams with different dimensions were remodeled with mesh control technology using finite element analysis (FEA) software to extract the stress magnitude. The mesh size, anchor boundary, loading boundary, critical stress definition, and solution type were well modified to obtain more correct stress values. Based on the new stress data extracted from the modified models, the optimized stress-number of life curve (S–N curve) was obtained, and the new life-prediction equation was found to be referable for polysilicon thin film life prediction under bending loads. After comparing the literature and confirming the new models, the frequency effect was observed only for the force control type and not for the displacement control type.

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