Đang chuẩn bị liên kết để tải về tài liệu:
Heat Transfer Handbook part 128

Heat Transfer Handbook part 128. 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 1267 through application of an external pressure or vacuum cycle on the laminate. The process is influenced by the resin viscosity which is a function of the temperature and degree of cure in the laminate and the applied pressure. The resi n vs s co s t ty dec reuses initially with temperature however as the cross-linking reactions proceed the viscosity sharply increases near the gel point at which the viscosity is theoretically inflnite. Thus the cure pressure cycle is designed to take advantage of the wmdow during processing when the viscosity is low. Mathematically the consolidation process is described as that of resin flow through a porous bed formed by the reinforcing fibers. Models for the consolidation process have been presented by Springer 1982 Dave et al. 1987 and Gutowski et al. 1987 among others. The models by Dave et al. 1987 and Gutowski et al. 1987 consider the composite to contain a deformable fiber network in which resin flow in all directions is governed by Darcy s law. The fiber network also takes part in carrying the load due to the applied pressure or vacuum during processing. The total force a acting on the porous fiber bed is balanced by the sum ofthe force due to the springlike behavior of flee liber network p and the hydrostatic force due to the pressure of the resin in the layup P. The hydrostatic pressure is obtained as the solution of hie g ov nnig equation for consolidation ofa porous bed within a given time interval with three-dimensional flow and a one-dimensional confined compression condition no boundary motion in the x and y directions given by Dave et al. 1987 1 vm . d 9M d 9 d 9P dx x dx d y dy 9 z dz dP It 17.41 where p is the viscosity of the sm m the porous fiber bed kx ky and kz are the specific permeabilities in the x y and z directions which depend on the stress level t is time and mv is the coefficient of volume charigee which describes the stress-strain behavior of a body