Three-Dimensional Evolution of Mechanical Percolation in Nanocomposites with Random Microstructures

One mechanism that is expected to play a large role in the enhanced, and sometimes novel, mechanical properties of nanocomposites is the probabilistic formation of percolated or connected microstructures. The majority of the models used to describe mechanical percolation have the functional form of a power law and depend on prior knowledge of a percolation threshold or critical volume fraction. While these models have been fairly accurate predictors of electrical conductivity in composites, they do not take any microstructural mechanisms, other than connectivity, into consideration. Classic mean-field micromechanics models, however, do not capture the variability in effective properties due to a random microstructure. In this work, aspects of both modeling approaches, i.e. probabilistic events and micromechanics, are adopted. A computational unit cell model is used to calculate the effective composite properties of random microstructures based on principles of micromechanics. The influence of the spatial randomness is incorporated using Monte Carlo techniques to simulate microstructural realizations. In this way, the modeling paradigm is reversed. Instead of using a percolation threshold to predict mechanical properties, mechanical properties are used to demonstrate the location of apparent percolation thresholds. By observing the distributions and variations of the predicted effective properties, the evolution of microstructural events can be tracked. Microstructures were simulated for a model material system consisting of metallic particles in a polymer matrix. Effects of a matrix-particle interface, interfacial thickness and interfacial stiffness, were also considered. The influence of particle aspect ratio on the apparent percolation threshold was also explored

Creation of a CIP Method for the Heat Exchangers at Rolls-Royce

Rolls-Royce produces various engines which must be tested prior to their distribution to ensure a high-quality product. The manufacturing plant contains four test cells where the engines can be subjected to high levels of torque and extreme temperatures. A heat exchanger is necessary in this testing system and over time, unwanted waste accumulates on the system’s plates. The team is tasked with developing and implementing a system mounted on a mobile cart which can provide data to determine whether the plates need to be cleaned. For this cleaning system to work, it must fully saturate the heat exchanger in cleaning solution, making the choice of pump important to the planning process. Additionally, the pump must be able to handle liquid containing silt and other debris and possess a maximum flow rate allowing the plates to be saturated. The pump must have four connection points to the heat exchanger system, and the fitting nozzle to control the flow rate of the cleaning solution into the heat exchanger. The cleaning solution for the system must be strong enough to clean the waste from the heat exchanger, yet weak enough to not corrode the plates. Additionally, some cleaning solutions have standards regarding storage and disposal, which have considerable influence on the selection of an acceptable solution. The final design incorporates a workable pump, a suitable solution, and the supporting materials needed to sustain the system. Implementation of the design will include pressure testing and a cleaning system that will improve the life span and efficiency of the heat exchanger in each test cell