Dimensions rheological analysis

An appropriate cure cycle was established based on the results obtained from the thermal analysis and cure rheology studies of the resin and cured BCB bar and dogbone shaped samples were fabricated for testing. Bar shaped specimens had the dimensions of 3.5 x 0.5 X 0.125 and were used to stake compact tension specimens for fracture toughness studies and for dynamic mechanical analysis of a torsion bar. Dogbone shaped specimens for tensile tests had a gauge area of 1 x 0.15 and were approximately 0.040 thick. 

Figure 7.18. Microstructural analysis Rheological determination of fractal dimension (D) and exponential term (A) for milk fat (A) slowly (0. l°C/min) or (B) rapidly cooled (5.0°C/min) to 5°C.

The analysis of mould filling requires rheological and thermal data for the plastic, and the mould dimensions. Polymer manufacturers usually provide shear flow curves at a range of temperatures these can be approximated by a power law relationship over a limited range of shear strain rates. In the days before computer analysis, flow lengths of short shots were determined in spiral test cavities, as a function of the injection pressure. However, the geometry of this constant cross section mould differs so much from most other moulds that the flow lengths in the two types of mould do not correlate well. 

Computer flow-analysis programs used throughout the plastics industry worldwide utilize two- and three-dimension models in conjunction with rheology equations. Models range from a simple Poiseuille s equation for fluid flow to more complex mathematical models involving differential calculus. These models are only approximations. Their relational techniques, coupled with the user s assumptions, determine whether the findings of the flow analysis have any real validity. What actually happens is determined after processing the plastic. See flow, Poi-seuille. 

Table 1 Fractal Dimension Calculated Via Image Analysis Compared to Fractal Dimension Calculated Via Rheology Using the Weak-Link Theory ... 

Fat system Fractal dimension from image analysis Fractal dimension from rheology (weak-link regime) Percent deviation Fractal backbone dimension x... 

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