Experimentally validated models for the prediction of fatigue damage progression and failure of conventional and green polymeric composites in aerospace and biomedical applications

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The use of polymer matrix composites (PMCs) in modern airplanes has dramatically increased since 2005, leading to changes in aircraft performance and environmental friendliness that have proven to be transformative within the worldwide aerospace industry. Such rapid proliferation, while opening the door wide for many new applications such as the biomedical ones proposed herein, also calls, among other things, for the development of analytical models that can help in the prediction of the long term fatigue failure of those PMCs. The latter is the aim of the proposed research program which will also focus on their emerging biomedical applications. The research effort will aim to confirm the validity of the proposed models by conducting mechanical loading tests and comparing the obtained results with those predicted by the models. The research will focus on two classes of PMCs, namely synthetic fiber-reinforced PMCs used in structural load bearing aerospace applications and bio-based (green) PMCs with a focus on those reinforced with flax fibers. The latter further addresses a pressing need to develop more environmentally friendly PMCs. The specific objectives include the development of generalized micromechanical-based fatigue failure prediction models that combine the concepts of micromechanics with progressive continuum damage mechanics (CDM) and statistical considerations, the development of computational software to implement the proposed fatigue models into Finite Element solutions, and the experimental characterization of various PMC material systems in order to confirm the accuracy and generality of the proposed models. The general approach for modeling is to represent the basic laminate building block (the lamina) through a network of micromechanical representative volume elements (RVE), model the failure of the lamina based on the behaviour of RVE under loading, and predict the property degradation and ultimately failure of the laminate through a continuum damage mechanics scheme. For the flax fiber based composites proposed for use in biomedical applications, the general approach will include the experimental characterization of their unidirectional laminae mechanical response under temperature, moisture, and loading conditions representative of their intended biomedical application. The ability to use accurate predictive models and the availability of the large amount of test data that will be produced through the proposed research will generate the necessary confidence in PMCs performance and pave the way to their wider use in the light weight, fuel efficient and environmentally friendly airplanes of the future, as well as biomedical implants where the advances made through the proposed research program will take this class of advanced materials one step closer to a widespread usage in this burgeoning area of engineering materials application.