Research Activities - 110 EES
Aluminum Composites (NSF sponsored)
Aluminum alloys are widely used for structural components, especially in the aerospace industry where weight is a critical concern. The stiffness (resistance to elastic deformation) of aluminum, which is about 1/3 that of steel, can be significantly improved by the addition of ceramic reinforcement. Either particles or continuous fibers can be used to improve the stiffness, wear resistance, and strength of aluminum. We are investigating behavior of these improved materials so that future aircraft, spacecraft, and ground vehicles can perform better, be more efficient and environmentally friendly, and yet be affordable.In the case of particle reinforcing, where the particles are irregularly shaped and 1-50 ?m in size, parts are primarily made by traditional metal forming operations. However, the ceramic particles constrain plastic deformation of the aluminum making the composite less ductile than unreinforced aluminum. A less ductile material is typically more susceptible to fatigue and fracture, so we are conducting experiments to understand the constraint provided by the ceramic particles as well as running computer simulations using finite element analysis in an attempt to improve the mechanical behavior of the composite. Continuous fiber reinforcement aligned in one direction makes the material properties very direction dependent.
aluminum composite
aluminum microstructure
These composites are manufactured using much different, more expensive, techniques, making their properties radically different. We are conducting experiments to understand material behavior and strength when the material is subjected to complex loads.
Titanium Composites (NASA GRC sponsored)
Titanium alloys are excellent choices for applications that require high specific strength and corrosion resistance. One such application is the aerospace industry, where titanium alloys are used extensively in propulsion systems. Continuous fiber titanium matrix composites (TMCs) have been and continue to be developed for advanced propulsion systems as well as for airframe components of next generation hypersonic vehicles. However, deployment of TMCs has proved challenging, in part because the thermomechanical response of titanium alloys is very sensitive to chemical composition and microstructure, which are affected by the presence of ceramic fibers and the thermal conditions required to process the composite material (titanium is highly reactive). While the mechanical behavior of TMCs in the fiber direction is dominated by fiber properties, in the transverse direction the matrix properties dominate the response. Thus, the matrix must be characterized in order to understand – and be able to predict – the behavior of TMCs. We are characterizing the cyclic deformation and life of the titanium matrix for use in micromechanical model development.steel sample with visible beach marks
from fatigue loading.
