Life Prediction Of Composites Research Articles

Study on fatigue life prediction method of composite laminates

Advanced composites have been widely used in aerospace field and transportation field in ground due to their excellent mechanical properties. Fatigue damage and life prediction of composites have always been the important and difficult issues in the field of composite mechanics. In this paper, the maximum stress criterion and Puck criterion were extended to fatigue failure criterion, and the fatigue damage analysis model of composite laminates was established by combining the gradual degradation model of material properties, the regularized fatigue life analysis method and the fatigue damage accumulation theory. Then, the model was used to predict the damage evolution and failure mechanism of composite laminates, and the fatigue tests with three stress levels (55%, 60% and 65%) were conducted. The fatigue life and failure mode of the numerical results matches well with the test results. Under fatigue loadings, the fatigue damage initiated from free edges on both sides of the plate to the inside of the laminates. The matrix damage first appeared in the 90° plies on two free sides, then the matrix damage and fiber damage of 45° plies were induced. The fiber damage of 0° ply finally appears and rapidly spreads to the center of laminates until the damage covers the entire cross section.

Prediction of Remaining Fatigue Cycles in Composite Materials Under Uncertainty

In this paper, a stiffness-based model is initially assessed for fatigue damage simulation of composite materials. The model is evaluated with three sets of experimental data. A residual strength model is coupled to the choice model and a modified model is developed. Numerical results show that the modified model leads to a noticeable improvement of accuracy in fatigue life prediction of composites under two-stage loadings. In the second step of the research, an uncertainty analysis is conducted to evaluate the reliability of the achieved results. The fatigue life and strength are assumed as random variables and uncertainty analysis is done by the Monte Carlo (MC) approach. Reliability variations of predicted residual fatigue lives are studied as well. The results demonstrate that the fatigue life dispersion noticeably decreases the reliability of predicted remaining fatigue cycles.

A review of advances in fatigue and life prediction of fiber-reinforced composites

This contribution is an attempt to provide a thorough review of past and current research work on fatigue and life prediction of fiber-reinforced composites. In order to summarize and present a comprehensive overview of the current state-of-the-art published works, the reviews in this contribution are broadly summarized into four groups of review; (1) fatigue of fiber-reinforced composites, (2) composite damage mechanism, (3) composite failure criteria and, (4) composite fatigue modeling and life prediction. The review will begin with a discussion of inherent and environmental factors affecting the fatigue of composites. This is followed by a rather extensive description of the composite damage mechanism and a summary of commonly used failure criteria for life prediction. And towards the end, models and methods for fatigue and life prediction of composites are summarized and discussed.

MAE: An Integrated Design Tool for Failure and Life Prediction of Composites

An advanced strength and life prediction tool, MAE, was developed for the analysis and design of composite structures and components. The MAE integrates three theories and methods: micromechanics of failure (MMF), an accelerated testing method (ATM), and an evolution of damage (EOD). The MAE can serve as a useful tool to predict damage initiation, progression and life under various durability loading and environmental conditions. It can handle the inhomogeneous complex geometries and structural components such as open-hole, filled-hole, bonded/bolted joint, stiffened panel, textile, etc. Therefore, it can help select not only the material and laminates but also optimal geometrical configurations. The MAE modules were implemented and integrated with a commercial finite element software, Abaqus, for better reliability and maintainability. Several examples of strength and life predictions of open-hole and double-edge notched specimens demonstrated the capability of the MAE as an advanced tool for the composite durability design.

A two-stage theory on fatigue damage and life prediction of composites

Fatigue tests on unnotched and notched composite laminates under compressive cyclic loading have been carried out. The damage mechanism is discussed, and it is seen that the process of composites fatigue damage under the compression cycles loading appears at two different stages. A dual fatigue cumulative damage rule to predict fatigue damage formation and propagation of notched composites is presented according to the traditional phenomenological fatigue methodology and a modern continuum damage mechanics theory. Then a three-dimensional damage constitutive equation for anisotropic composites is established. A new damage evolution equation and a damage propagation σ a – σ m – N * surface is derived based on damage strain energy release rate criterion. Finally, the theoretically predicted results are compared with experimental results.

Fatigue life prediction of composites under two-stage loading

In order to predict the fatigue life under two-stage loading by formulating a cumulative fatigue damage rule for composite materials, the fatigue process in SiC–Al and glass-fibre reinforced plastics were investigated. A microcrack occurred within the composites which resulted in cumulative fatigue damage that increased linearly with the number of cycles. The mechanical conditions of damage growth and failure were determined by characterizing the microdamage governing the fatigue. The ultimate failure is shown to occur when the product of the stress amplitude ratio and microdamage density is beyond a critical value and an expression for the remaining fatigue life is derived.