Optimization of Cure

We can, however, write a list of parameters for cure optimization. To limit the possible combinations, we assume that the composite composition is known (i.e., resin, fibers, geometry, etc., are given, and the mold design and mold material is known). This reduces the number of buttons for control of cure to the following  

Although we have limited the parameters to three, there is a larger number of degrees of freedom hidden inside these high-level parameters. 

The best would be to use all of the preceding actions to find the optimum conditions. Most often, however, the economical constraints and possibly the time put limits to the efforts that can be invested. Moreover the need to find optimum processing conditions may not be critical for many applications. Very often, however, the situation can be the opposite (i.e., the curing process generates material defects or takes too much time, hence actions must be taken to find solutions to these problems). 

The use of simulation tools (e.g., computer programs) to calculate curing conditions is an area of great interest and is increasingly used to optimize cure for several processes including LCM [32,35] however, there are some obstacles to the use of this advanced route, such as the need of  

In addition to the preceding points experience and good knowledge of processing is needed to evaluate the results from the simulation. 

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Potyrailo, R. A., Olson, D. R., Medford, G., Brennan, M. J., Development of combinatorial chemistry methods for coatings high-throughput optimization of curing parameters of coating libraries, Anal. Chem. 2002, 74, 5676-5680. 

Optimization of Cure Conditions During Processing of Acrylic Latex Coatings... 

Though sufficient experimental evidence is not presently available, the optimization of curing conditions should also play an important role in achieving maximum coherence in the network. 

One of the conveniences afforded by curing PPS is that a single uncured feedstock can give rise to an entire family of cured polymers. The flow rates, ie, the extent of cure, of the cured polymers are optimized for specific appHcations. Table 1 shows typical melt flow values of cured PPS polymers for various types of appHcations. 

Determination of mechanical properties like tensile strength, tear strength, modulus, and elongation at break are the most common methods adopted to determine the cured properties of short fiber-mbber composites. Murty and De [133] discussed the technical properties of short fiber-mbber composites whereas Abrate [8] reviewed the mechanism of short fiber reinforcement of mbber. Fiber concentration in the matrix plays an important role in the optimization of the required... 

Bose, A. B., Shaik, R., and Mawdsley, J. Optimization of the performance of polymer electrolyte fuel cell membrane electrode assemblies Roles of curing parameters on the catalyst and ionomer structures and morphology. Journal of Power Sources 2008 182 61-65. 

An optimization of the cure schedules and processing parameters consists of exploring the most favorable conditions, judged under specified criteria, that will lead to a product... 

Heat transfer models are a powerful tool for developing autoclave process cycles. They are especially useful in aiding tool designers in choosing tooling materials, thicknesses, and thermocouple locations. Models can also be used to determine if a tooling concept would be detrimental in a specific position in the autoclave and the types of tools that should be processed together to optimize the cure cycle. 

Process models are unfortunately often oversold and improperly used. Simulations, by definition, are not the actual process. To model the process, assumptions must be made about the process that may later prove to be incorrect. Further, there may be variables in the material or processing equipment that are not included in the model. This is especially true of complex processes. It is important not to confuse virtual reality with reality. The claim is often made that the model can optimize a cure cycle. The complex sets of differential equations in these models cannot be inverted to optimize the multiple properties they predict. It is the intelligent use of models by an experimenter or an optimizing routine that finds a best case among the ones tried. As a consequence, the literature is full of references to the development of process models, but examples of their industrial use in complex batch processes are not common. 

Joseph and Wu used a simulation to show that an ANN could be used to optimize the cure cycle for variations in raw material properties. The results were encouraging an 89 percent decrease in standard deviation for thickness and a 96 percent reduction in void size. The mean thickness was also closer to the target thickness for the neural network-optimized processes. They also used the ANN for in-process adjustment of the cure cycle [22]. 

In process design, the main objective is to optimize the cured properties of the finished product. To that end, the following conditions have to be established and quantified ... 

Effects of Curing Agent Type. Epoxide-Cured Propellant. Carboxyl-terminated polybutadiene is a linear, difunctional molecule that requires the use of a polyfunctional crosslinker to achieve a gel. The crosslinkers used in most epoxide-cured propellants are summarized in Table IV and consist of Epon X-801, ERLA-0510, or Epotuf. DER-332, a high-purity diepoxide that exhibits a minimum of side reactions in the presence of the ammonium perchlorate oxidizer, can be used to provide chain extension for further modification of the mechanical properties. A typical study to adjust and optimize the crosslinker level and compensate for side reactions and achieve the best balance of uniaxial tensile properties for a CTPB propellant is shown in Table V. These results are characteristic of epoxide-cured propellants at this solids level and show the effects of curing agent type and plasticizer level on the mechanical properties of propellants. 

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