| Vacuum Assisted Resin Infusion (VARI) is a composite material molding technology and draw lessons from the method of vacuum bag on the basis of the Resin Transferring Molding (RTM). VARI technology is an advanced low cost composite molding technology, and VARI technology has many advantages, such as low fiber porosity, good product performance, flexible process, etc. VARI technology is suitable for production of aircraft, ships and other large size products. Due to the VARI technology adopted a rigid mould and a vacuum bag membrane structure, molding products through this technology with the characteristics of rough and smooth on both side. VARI technology is very suitable for the production of square which requests higher surface roughness of appearance and lower internal surface roughness. The purpose of this project is to design a large square sandwich structure conformed to the actual requirements by using composite materials. The layer structure of square is fiber layer-PVC foam-fiber layer. Using the PAM-RTM simulation software have a molding simulations on square produced by using VARI technology. The main factors influencing the forming simulation of large square is the viscosity of the resin system, the composition of fiber layer, the layer of the way, the injection gate, the extrusion gate, port settings, and so on. This paper study these factors by using the experiment and simulation, and optimize the corresponding process parameters, come up with a large square VARI molding process which has a strong guiding significance.Firstly, systematic study has been done on the rheological properties of epoxy resin in the large square, combining with the analysis of isothermal viscosity properties and dynamic viscosity properties. After the analysis of the result by the Origin and fitting processing, the viscosity’s model of epoxy resin system is concluded which can provide data support for the final computer simulation and analysis gelation temperature、curing temperature of the epoxy resin system by DSC.Secondly, the permeability of carbon fiber and glass fiber fabric reinforced material used in the large square has been targeted research. Experimental research is conducted on the permeability of the single axial to glass fiber, biaxial glass fiber and biaxial carbon fiber glass fiber. This paper proposes a new method for calculating the equivalent permeability through discussion of calculation method of sandwich structure and the method of finite element modeling, and simplifies the square model to 2D shell element model. At last, the value of equivalent permeability of sandwich structure is calculated through the experiment. This paper uses the reference of the military square general specification requirements and relevant technical standards. The square of the solid model is designed and established by Solidworks software, then simplifies solid model into 2D shell element model. Square model has been divided into finite element by using Visualmesh.At last, analysis the structure and shape of square and design six different molding scheme, resin filling process simulation of VARI technology molding process of square has been done through PAM-RTM software. the influence of settings of the injection gate and the extrusion gate on square molding process and result is analysized by resin flow cloud animation, resin filling pattern and molding pressure profile. In order to more in line with the actual situation of mold filling process, the scheme is optimized considering the influence of gravity and vacuum pressure to the mold filling process. The optimal mold filling scheme is:injecting resin by the long axis of top’s surface, injecting resin by four horns at the bottom, extraction of vacuum pressure under a standard atmospheric pressure, one straight down gravity direction, using gravity to promote resin’s injection from top to bottom. The character of the optimized molding scheme is shortly mold filling time and the uniformed distribution of molding pressure. |
PDF Full Text Request