composite, composite material, ceramic matrix composites, inventor
I retired in September of 2011, but immediately prior, my research had been in the areas of ceramic matrix composite materials, and the development of exotic polymers. In that time a total of two patents describing new technologies in the field of materials science issued. United States Patent No. 6,447,840. This new intellectual property is an advanced polymer/ceramic matrix composite that provides significant improvements over prior art composite materials. Concurrently, several new intellectual properties were developed relating to environmentally friendly plastics and their application. My research into polymer chemistry really began in about 1990, and sometime in 1991 (I think..), I filed a patent application that later issued as U.S. Patent 5,186,990 in 1993.
I try to learn all that I can by reading, listening, observing, and most important, thinking critically. One of the concepts that I find extremely interesting is that which is commonly referred to as "the creative process", thus, my 2 cents worth: The term "process" is a misnomer, because it eludes to an event sequence that is, in essence, inherently analytical. Analytic thought is an exercise given to problem solving. While this endeavor is a noble cause, it is not analogous to "creating" or the act of "creation". Creativity, in its truest sense, occurs on a level that utilizes quintessential human consciousness, a phenomenon unencumbered by the restrictions indigenous to analytical thought. Simply stated, problem solving and creating are two separate, distinct, and uniquely human enterprises. Whilst sequential, analytical thought is not required to "create", creativity and an analytical mind are both required if one is to "invent" successfully.
Composite materials are exciting because they facilitate the development of advanced structural components as well as finished products. Being relatively new as materials go, composites first saw success in high technology applications, namely aerospace and military because engineers and designers were quick to embrace the unique qualities that composite materials provide. As a direct result of these successes, composite materials have gained the attention of pioneers in such areas as infrastructure and building construction.
To a great extent, the advancement of the state of the art of composite materials is a result of the availability of new and improved raw materials. Equally responsible, in my opinion, is the ability to virtually prototype new materials. Powerful desktop computers have made closed form analysis of proposed laminate schedules extremely quick and painless. Numerically intense analysis methods such as computational fracture mechanics (CFM) were, practically speaking, impossible without powerful computers. AFGROW (Air Force Grow) is a great CFM package that is available for Macintosh, UNIX, and Windows platforms. AFGROW's history can be traced back to the early 1980s when it began as ASDGRO. In 1985 ASDGRO was used as the basis for crack growth analysis for the Sikorsky H-53 Helicopter. Today, AFGROW is a very comprehensive CFM package, providing those involved in materials research and development a robust suite of tools for structural life analysis / prototyping.
Perhaps the most exciting prototyping / analysis technology is Finite Element Analysis or FEA. I have found FEA to be a superbly powerful tool. It allows me to "virtually prototype" composite materials by virtually testing material assumptions. Typically, I would first build a quasi-isotropic material model (if appropriate). For this task, I have written closed form analysis algorithms in Mathematica tm. which, when executed, generate the requisite mechanical properties, thereby providing the basis for a theoretical material model for later utilization within the finite element model . Alternatively, a anisoptropic material model is constructed during Finite Element modeling within the modeler/preprocessor. My FEM/FEA applications are ANSYS, Pro Mechanica, FEMAP and NASTRAN.
Here is an example of "virtually prototyping" with the aid of FEA. The figure below shows a model of a proposed composite shell panel. In this case, the client wanted a panel that could safely carry a static load of 154 pounds per square foot, normal to the exterior surface.
The composite material used in this construction is a polymer - ceramic matrix composite. For this particular formulation, Young's modulus is 1.75 msi and Poisson's ratio is .33. Our preliminary analysis called for a total laminate thickness of 0.125 inch. The client insisted on eliminating all reinforcement and half of the matrix material from the surfaces checked in red, thus, these areas had 0.625 inch of matrix only ( Young's modulus approximately 0.45 msi). Below is the result of physical testing conducted on the clients prototype panel. For this test, the client placed a load equal to 154 psf normal to the surface ( load vector represented by red arrow below).
The initial laminate schedule called for a stitched, biaxial reinforcement in this area (the surfaces checked in red above). In material science terminology we would call this "a no brainer", however, this is a prime example of how finite element modeling can effectively communicate what should have been intuitively obvious to the client, and especially his engineering personnel. The screen shot below shows the solid XY shear stress contour (modeled with FEMAP, output is NASTRAN) for the idealized panel section modeled as originally specified. In this model, I meshed the geometry as a solid, a technique that I consider "quick and dirty " for composite elements. In any case, the analysis was accurate enough to prove the point.
The screen shot below shows a yet smaller section of the panel. This model is highly idealized and was modeled as thin plates. Analysis in this case was performed with the classic "SAP" analysis code.
Below is yet another FEM of the idealized panel section, this time showing the plate bottom maximum shear stresses. In both of the SAP analysis, I used a course mesh, simply because employing a finer mesh would have been a purely academic exercise. The purpose of these three models was to graphically illustrate to the client, in general terms why his prototype failed.
Obviously, the use of FEM / FEA in this situation is gross overkill, and the examples provided do not begin to exploit the power of Finite Element Analysis, however, they do illustrate the applicability of the technology.
Copyright © 2006 - 2014 Brad Starcevich