Curing of Epoxy Matrix Composites

Abstract

ABSTRAGT Models were developed which describe the curing process of composites constructed from continuous fiber-reinforced, thermosetting resin matrix prepreg materials. On the basis of the models, a computer code was developed, which for flat-plate composites cured by a specified cure cycle, provides the temperature distribution, the degree of cure of the resin, the resin viscosity inside the composite, the void sizes, the temperatures and pressures inside voids, and the residual stress distribution after the cure. In addition, the computer code can be used to determine the amount of resin flow out of the composite and the resin content of the composite and the bleeder. Tests were performed measuring the temperature distribution in and the resin flow out of composites constructed from Hercules AS/3501-6 graphite epoxy prepreg tape. The data were compared with results calculated with the computer code for the conditions employed in the tests and good agreement was found between the data and the results of the computer code. A parametric study was also performed to illustrate how the model and the associated computer code can be used to determine the appropriate cure cycle for a given application, which results in a composite that is cured uniformly, has a low void content, and is cured in the shortest amount of time.

Optimization of curing cycle in carbon fiber-reinforced laminates: Void distribution and mechanical properties

“…Thus resin flow in each ply was anisotropic and mainly occurred along the fiber direction, in agreement with the higher permeability factor in this direction. The dominant resin flow along the fibers led to the formation of a channel-type structure (also reported in previous studies ( [7,16])) and facilitated the transport and coalescence of voids along the fibers.…”

“…The external pressure drives the excess resin and air bubbles out of the laminate. The mechanics of prepreg compaction in autoclave was pioneered by Springer and co-workers [6,7] starting from the consolidation theory developed for soil mechanics [8], These authors described the resin flow through the composite following Darcy's flow theory in a porous medium, and determined the laminate compaction sequence. The external pressure was first supported by the resin and, as bleeding progressed through the surfaces, pressure was transferred to the fiber bed.…”

Method to determine thermoelastic material properties of constituent and copper-patterned layers of multilayer printed circuit boards

“…The heat provided by the hot press is required for initiating and maintaining the chemical reactions in the resin, which cause the desired changes in molecular structure. High pressure makes sure the resin flows between the copper features and exposed laminates [12]. As the crosslinking reaction completes, a high degree of cure that bonds the layers together is achieved.…”

A fiber optic temperature sensor based on the combination of epoxy and glass particles with different thermo-optic coefficients

“…temperature during curing, and therefore, the curing properties [30,31]. Figure 5 shows the temperature and the voltage U M (for a wavelength of 460 nm and 650 nm) with respect to the time for sensor elements with different lengths and a particle size of d 50.3 =43 m.…”