Study On The Permeable Property Of Warp Knitted Fabrics With Thick-Section For Wind Blade And LCM Process

Liquid Composite Molding(LCM) is a close mold technology.As a well-known low-cost,environment friendly manufacturing technology,LCM is widely used in vessels,military,defense,transportation,aerospace industry, etc.The product has good quality and quality repeatability,on which the operator's skill has less effect.The permeability is a parameter to express the resistance of the fiber reinforcements to the fluid flow.Accurate permeability data is essential for the optimization of composite manufacturing process,arrangement of the inlet and outlet in the mold,which reduces the production time and improvement of the composite part quality.However,with the increasing number of lay-up up to 100 layers in the LCM process,particularly under the VARTM process,the permeable property through the thickness will play a critical role on the whole process.It is very important to use sensor and on-line monitoring to study flow front of the resin on the surface and through the thickness of the preforms.In this paper,according to the real wind blade lay-up,self-developed sensor and monitoring device system is used to detect flow front through the thick-section lay-up during LCM process.One-way flow method and radial flow method are used to study the permeable properties of thick-section reinforcements.The permeability of thick-section reinforcements was tested.The rules of the permeable properties have been investigated.The experimental results show that the permeability varies with the number of layers.Many experiments were conducted to explore the impact of high distribution media, the relationship of k_xx and k_yy,the permeability of thickness direction(k_zz),the impact of different test method on the testing results and the permeability of different fabrics.In this paper,on-line sensor and monitoring system was used to study the internal flow of test fluid in thick-section preforms during liquid composites molding process.The properties of the flow between layers were studied.The flow behaviors between layers with different number of layers,fabric structures,lay-up structures of the reinforcements were investigated. Different scenarios were studied,such as glass fiber reinforcement,glass fiber reinforcement with a distribution media on the top and glass fiber reinforcement with a distribution pure media on the top and strand mat in the layers.It is noticed that the distribution media should be introduced to improve the permeable property of the surface and the thickness direction in order to reduce the lead-leg between the top and bottom layer.It is very critical to have the right size of distribution media on the preforms to increase the productivity and ensure part quality.The combination of distribution media and strand mat can be used to increase the impregnation when the structure design allows.In this paper,the LCM process was also investigated.The experimental results show that the effect of the type of test fluid,the type of reinforced fabric and the injection pressure on the LCM process.The results will play an important role in optimizing the LCM process and improving the performance of product made by LCM process.