Multiscale Modeling to Describe Free Surface Resin Flow around Fibers and within Fiber Bundle

Composite materials have been increasingly utilized for ballistic armor, in which they are subjected to high strain rates. The porosity of the composite as well as fiber-resin interface plays a key role in dissipating energy when subjected to high strain rates. This dissertation develops a suite of modelling tools capable of predicting the resin configuration within fiber tows across multiple length scales. Fiber tows consists of thousands of individual aligned fibers bundled together. Fiber tows are of the order of millimeters whereas the fibers are of the order of microns.;On the microscale, utilized model is developed to predict the wetting dynamics of resin on an individual fiber and within unit cells containing various arrangements of fibers. The model predicts the spreading of the resin between the fibers within the unit cell and can calculate the contact area between the fibers and the resin. This model is used to characterize the average capillary pressure of resin for various packing arrangements and the influence of imperfections and different surface treatments on the capillary pressure.;A novel mesoscale model that accounts for capillary pressure characterized from our microscale model to describe resin impregnation into fiber tows is developed. This model can account for non-uniformly spaced fibers within the tow. The mesoscale model allows for a stochastic fiber distribution which predicts formation of many microvoids within the tow as observed in manufacturing as opposed to the single void located in the center of the tow for traditional models which assume spatially uniform capillary pressure. The influence of air evacuation time, hybrid fiber tows, and capillary forces is explored with this model. The mesoscale model is extended to predict the wicking of finite resin volumes into a fiber tow, which allows for the design of composites with controlled resin distributions within individual fiber tows. The model should prove useful to optimize and tailor composite properties on a tow level for desired applications.