Faculty Mentor: Karen Yan
Students: Daniel Christiansen
A fiber reinforced composite (FRC) consists of two parts: high strength fibers and the resin that hold layers of these fibers together. The directional specific strength and relative lightweight nature of these materials are perfect for advanced applications such as aerospace and automotive engineering. While in most practical applications composite materials are treated as homogenous materials to simplify design and analyses, this approach has certain limitations in explaining failure phenomena and predicting failure since failures start at the microscopic level.
During the 2012 MUSE program, we generated a series of finite element models using a 9-fiber representative volume element (RVE) to better understand effects of microstructure failure. This model was first constructed in 3 dimensions but was later replaced by a simple 2 dimensional model due to its low computational time and fine meshing characteristics. After gathering a base line for comparison, defects of varying size were individually introduced in several locations around the center of the RVE. Qualitative and quantitative data on the area and magnitude of these stress concentrations was analyzed and graphed according to size and location. The combination of graphs and stress maps give a detailed look into the behavior of the material under this transverse loading.
The data gathered in this research shows that, even with a large stress concentration, the homogenized material properties of a composite material can remain virtually unchanged, while such stress concentration could initiate failure locally. It also shows an indirect correlation between defect size and maximum stress concentration, but a direct correlation between defect size and region of elevated stress. These findings are important in predicting local defect interface and macroscopic failure. The effects of multiple defects and varying shapes will be the focus of this project going forward.