One unique property of a Machine Augmented Composite (MAC) is its ability to convert a compressive force into a shear force, and vice versa, simply by the geometry of its angled sidewalls. We have discovered that a non-spinning ball dropped at a normal angle onto the MAC’s surface rebounds from that surface at an angle different from the normal and develops a significant rotational velocity. The MAC can be designed so that the spin imparted on the ball is either clockwise or counterclockwise and tailored so that the ball’s oblique angle rebound is either positive or negative from its normal angle. Through finite-element analyses and experiments, the magnitude and direction of the spin can be precisely controlled by tailoring the stiffness of the MAC through the properties and dimensions of its constituent materials.
We have recently demonstrated that composites with unique properties can be manufactured by embedding many small simple machines in a matrix instead of fibers. We have been referring to these as Machine Augmented Composites (MAC). The simple machines modify the forces inside the material in a manner chosen by the material designer. When these machines are densely packed, the MAC takes on the properties of the machines as a fiber-reinforced composite takes on the properties of the fibers. In this paper we describe the Machine Augmented Composite concept and give the results of both theoretical and experimental studies. Applications for the material in clamping mechanisms, fasteners, gaskets and seals are presented. In addition, manufacturing issues are discussed showing how the material can be produced inexpensively.
Composite materials are being used for bridge column seismic retrofits and to rehabilitate other concrete structures. There are three different manufacturing methods for applying composites to concrete columns which are outlined in this paper. Each method has the potential for creating debonds at the composite-concrete interface and within the composite itself. Thermography is a non-destructive evaluation technique which can be used to image debonds below the composite surface. Background fundamentals of the thermographic technique are discussed. Data from thermographic tests of a variety of retrofit applications, which include examples for each of the three aforementioned manufacturing processes, are then presented. The paper concludes with a list of issues which need to be addressed when performing a thermographic inspection in the field.
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