This article presents a review of the kinetic studies on the cure reactions of thermosetting resins. The emphasis is placed on those conducted using the thermal analysis by differential scanning calorimetry. Two important categories of kinetic models are discussed and some existing parameter estimation techniques are presented. A variety of factors affecting the cure reactions, including the formulation of cure and process variables, are discussed. At the end, two different approaches in modeling the chemoviscosity of polymeric reactive systems are presented and some existing chemorheological models developed based on these approaches are briefly reviewed.

As new developments are brought to the group of manufacturing processes for composite parts known as liquid composites molding (LCM), the compaction behavior of the textile reinforcements is increasingly seen as an important parameter of the definition of these processes. The evolution of the permeability tensor of the reinforcements with time, the general kinetics of the manufacturing operations, and the modelization of these processes depend on a large extent on the compaction behavior of the reinforcements used, especially in flexible‐wall RTM and autoclave molding. Also, more research efforts are devoted toward the development of a complete analytical model of the properties of heterogeneous textile reinforcements. In this paper the published experimental data related to the compaction and relaxation of random mats and woven reinforcements are gathered. Observed parameters are defined, which allow numerical comparisons of the experimental curves to be made, as well as the identification of general trends seen with most tested reinforcements. The effects of various processing parameters are identified, and relations to published analytical models of the mechanical properties of fibrous assemblies are discussed.

The application of dynamic mechanical analysis (DMA) for quantifying interfacial interactions in composites is briefly reviewed. Carbon fiber/epoxy composites with fiber volume fractions of 12, 17, 38 and 61 vol% were subjected to flexural deformation on a Dupont DMA 983 instrument. The dependencies of dynamic mechanical properties of the composites on experimental parameters such as oscillation mode, amplitude, frequency, and temperature were investigated. As opposed to the storage modulus, the loss modulus is found to be sensitive to all parameters. In a fixed multiple frequency mode, the loss modulus of the composites increases with oscillation amplitude and decreases with frequency and the number of tests. The information produced in the resonant mode is more reproducible. An additional damping at the interfaces, apart from those of the constituents, suggests a poor interface adhesion in these composites. A linear relationship between the excess damping at the interfaces and the fiber volume fraction shows a similar interface quality for these composites having different fiber volume fractions. The detection of interfacial properities was found to be more sensitive in the flexural deformation mode than in the torsional mode. At temperatures higher than the glass transition temperature of the matrix, the effective volume fraction of the matrix is reduced. Such a reduction can be interpreted from the mismatch of thermal expansion of the matrix and the fibers.

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As large components of fiber reinforced composite materials are being more frequently produced by Resin Transfer Molding (RTM), a computer simulation of the injection process can help the mold designer to accomplish three important tasks: (1) to ensure a complete filling of the mold through adequate positioning of the injection ports and of the air vents; (2) to verify the integrity of the mold during the filling process through knowledge of the pressure distribution; and (3) to optimize the production cycle using information about the filling time. The resin impregnation is usually modeled as a flow through a porous medium. It is governed by Darcy's law, which states that the flow rate is proportional to the pressure gradient. In our model, Darcy equation is solved at each time step inside the saturated part of the mold using nonconforming finite elements. This method was chosen because the approximated flow rates, contrary to conforming finite elements, satisfy locally the important physical condition of resin conservation across inter-element boundaries. This permits simplification of the numerical procedure. It is no longer necessary to resort to a control volume approach to move the flow front forward. The resin pressure distribution and the resin front positions are obtained by the computer simulation and calculated results for selected mold geometries are compared with experimental observations. Molds with inserts, multiple injection ports, and the case of anisotropic preforms can be analyzed by the computer program.Sons, Inc.-

The objectives of this series of papers are to describe the mechanical behavior of textile reinforcements under normal load and to quantify the effects of diverse processing parameters on that behavior. In the first and second papers of the series, experimental compaction and relaxation results were reported; general trends were identified and the effects of changes in the processing parameters were analyzed. In this paper, the results of sequences of successive compaction cycles applied to dry textiles and to textiles saturated in distilled H2O and silicone oil are presented. The reinforcements investigated are produced by assembling tows or rovings following different patterns; it is shown that the resulting heterogeneity, or regular variation of the local fiber volume fraction, can be associated to some particular elements of the mechanical behavior of the reinforcements. The reorganization of the fiber network and the effect of friction at the fiber contacts are demonstrated. Different stages in the reorganization process are identified; each stage is controlled by different parameters and corresponds to a precise behavior. Successive compaction cycles applied to a preform can reduce the void content of the final part.

Previous analysis of published experimental results on compaction and relaxation of textile reinforcements allowed the effects of some processing parameters on the mechanical behavior of the reinforcements to be identified. However, a limited number of relaxation results are available; also, the effect of some parameters on compaction received limited attention, and the behavior observed with fluid-saturated reinforcements has not been investigated. In this paper, the results of a structured experimental program of compaction and relaxation performed on three woven reinforcements are reported. In half the trials, a relaxation period was imposed on the samples. In the other half, samples saturated with distilled H, O were compacted. The selection of the processing parameters was found to be as important as the selection of the reinforcement itself for the definition of a manufacturing operation. The processing parameters governing the compaction and relaxation were seen not to be the same, and the fiber reorganization that occurs during the compaction phase was found to have a different effect on successive compaction cycles than the reorganization occuring during the relaxation. (1)Darcy's empirical law was generalized for the case of high speed flows (2, 3) to be known as Forchheimer's (Lv K -VPJ = -*Corresponding author.

Continuous fiber reinforced polymer composites can be produced by the injection of a reactive fluid into a mold with preplaced reinforcement. Mold filling modeling softwares such as our RTMFLOT software are being developed to help design and production engineers meet their requirements for part production. The utilization of accurate permeability values is an absolute necessity for relevant mold filling simulation. This paper presents permeability results for several reinforcements. Experimental techniques being used to measure the permeability are also discussed. Several points are highlighted and suggestions are made to help the investigator in the search for reliable permeability data.