Jianjun Jiang

Effects of electrophoretically deposited graphene oxide coatings on interfacial properties of carbon fiber composite

Graphene oxide (GO) was utilized to improve the interfacial performance of carbon fiber (CF) and epoxy resin. In this work, a simple and an effective way, without complex chemical reactions and long processing time, is proposed to prepare GO/CF hybrid fiber via electrophoretic deposition (EPD). In this method, ultrasonically assisted EPD is employed to deposit GO on CF when oxidized carbon fibers are continuously immersed into GO aqueous dispersion. Surface functional group, surface roughness, and surface morphologies of carbon fibers were examined by Fourier transform infrared spectrometer, atomic force microscopy, and scanning electron microscopy, respectively. Surface free energy of the fiber was characterized by dynamic contact angle analysis. Results show that uniform GO coating with rough morphology can be formed on carbon fibers. Moreover, surface wettability of carbon fibers to epoxy resin is significantly improved by enhanced surface free energy due to the deposition of GO. Meanwhile, the introduction of GO in the carbon fiber/epoxy resin composites results in a 56.1xa0% enhancement in the interfacial shear strength which confirms the remarkable improvement in the interfacial adhesion strength of the composites. The interfacial fracture mechanism was also analyzed.

Effect of Nesting on the Out-of-Plane Permeability of Unidirectional Fabrics in Resin Transfer Molding

The nesting of layers has great effect on the permeability which is a key parameter in resin transfer molding (RTM). In this paper, two mathematical models were developed to predict the out-of-plane permeability of unidirectional fabrics with minimum and maximum nesting, respectively. For different zones of characteristic yarn arrangement in the unit cell, the local permeability was modeled as a function of geometrical yarn parameters. The global permeability was then modeled as a mixture of permeabilities of different zones with the electrical resistance analogy. The influences of local permeability of each zone on the global value of unit cell were deeply researched. In addition, two different fabrics were tested and a reasonably good agreement was found between the model predictions and experimental results. We also found that the permeability values were two orders of magnitude larger with minimum nesting than with maximum nesting. However, the differences between minimum nesting and maximum nesting decreased with increasing fiber volume fraction.

Non-uniform capillary model for unidirectional fiber bundles considering pore size distribution

Capillary rise affects void inclusion during the impregnation of fiber reinforcements in resin transfer molding. A new model of effective capillary radius has been developed to investigate the effect of pore size distribution on capillary flow in unidirectional fiber bundles. With the image analysis method, the statistical results showed that the pore size distribution could be very different even for the same fiber volume fraction. Then, the classical Washburn equation, in conjunction with different models for calculating effective capillary radius, was applied to predict the capillary rise rate. Compared with the experimental results, we found that the new model performed better than traditional models where the effective capillary radius was obtained using average pore radius or hydraulic radius.

Effect of layer shift on the out-of-plane permeability of 0°/90° noncrimp fabrics

Layer shift has a great effect on the permeability which is a key parameter in resin transfer molding. In this paper, nine different unit cells were modeled based on the range of layer shift and decomposed into zones of characteristic yarn arrangement, respectively. For each unit cell, a set of equations was derived allowing description of the local permeability of each zone as a function of geometrical yarn parameters. The overall permeability was then modeled as a mixture of permeabilities of different zones with the electrical resistance analogy. Excellent agreement was found between predictions and experiment. Both results indicated that the channel flow had a dominant role in the whole flow through the fabrics. And the permeability values reached maximum when the empty regions were interconnected between upper and lower layers. In addition, the effect of fiber volume fraction on the differences of two extreme cases was also investigated.

Effects of Resin Injection Speed on the Bubble Content of Glass Fiber Laminate

In order to eliminate the bubbles during composites manufacturing, a special performance was designed. And the effects of the speed of the resin injection on bubble content were investigated. The results demonstrate that the speed of resin injection has distinct effects on the bubble content. When the speed of resin injection is slightly higher than the speed of capillary injection, the bubble content of the test pieces with latitudinal fiber bundles is more than the test pieces without latitudinal fiber bundles. But when the speed of the resin injection is slower than the speed of capillary injection, the bubble content of the test pieces with latitudinal fiber bundles is less than the test pieces without latitudinal fiber bundles. These results will provide a reference for the design of RTM process parameters.

Algorithm Design of Four-Step Three-Dimensional Braided Composite Structures in Matlab Environment

For solving the problem of the geometric simulation of 3D braided composites, taking four-step rectangular 3D braided fabrics as an example, and based on the analysis of yarn moving regulation, the mathematical models between the braiding technique parameters and the geometric structures is established. By taking UG as the 3D display platform and MATLAB as the control core, 3D geometric simulation of the pre-modeling entity is realized. Such a simulation enables the users to observe the braid spatial structure and braiding moving process intuitively and modify them dynamically on the Internet. With this method, the design quality and efficiency of products will be raised remarkably.