Heat Transfer Handbook part 129. The Heat Transfer Handbook provides succinct hard data, formulas, and specifications for the critical aspects of heat transfer, offering a reliable, hands-on resource for solving day-to-day issues across a variety of applications. | PROCESSING OF POLYMER-MATRIX COMPOSITE MATERIALS 1277 Void Growth Microscopic Model In the regions outside the consolidation rollers the tow matrix melt is exposed to the ambient atmospheric pressure . pf patm . The reduced fluid pressure outside the voids combined with the high void pressures resulting from the high temperatures under the torches causes the voids to grow in size. Furthermore because the tow surfaces are unconstrained and the matrix melt is assumed incompressible the increase in void size leads to an increase in tow dimensions. The goal of the void growth analysis is flierofore that of determining the void fraction and tow thickness as a function of the axial location along the process y direction in Fig. . Because the fluid pressure is known ambient the macroscopic model equations need not be solved in the void growth analysis. The change in the void dimensions is given by the microscopic model eq. with pf replaced by patm and the corresponding density change is obtained from eq. . The volume change in the tow due to void growth will in general manifest itself in a dimensional change in the tow width and thickness. However owing to bonding of the contacted areas at the tow-substrate interface the tow is assumed to be constrained along its width. The void growth therefore directly translates to a thickness change in the tow. The relationship between tow thickness and the void fraction is obtained by noting that the volume ofthe incompressible matrix melt is constant in the tow during the process. The instantaneous tow thickness h is therefore related to the instantaneous width-averaged void fraction v as follows h 1 - v constant where R 3 v ------------- S 3 R 3 - 1 Interlaminar Bonding Interfacial bonding and development of bond strength during the process are attributed to the mechanisms ofintimate contact and healing at the tow-substrate interface. Theoretical models for the two mechanisms are now reviewed .
