Study On Preparation Of Thick-Section Composites By RTM-Molding Process

The composite components prepared by the traditional RTM and its derivative process have usually low fiber volume fraction(generally 40%),and the porosity is difficult to be reduced effectively,which limits the full performance of the composite material and the popularization and application of the process,especially for thick-section main-bearing structural composites.High-fiber volume fraction of thick-section composite main bearing structural members.To this end,this paper proposes a new method that combines the advantages of RTM and molding process:RTM-molding process,analyzes the characteristics and performance requirements of the RTM-molding die,designs and fabricates molding die to study the three key parameters(compression pressure,reserved clearance,compression temperature)on the performance of RTM-molding process combining with the orthogonal experiments.The main conclusions are as follows:(1)The RTM-molding process requirements is analyzed to determine and choose suitable resin,Epoxy resin EP CYD-128/curing agent 70~#anhydride/accelerator2,4,6-tris(dimethylaminomethyl)phenol with mass ratio of 1000/700/8 resin system is chosen system as a matrix material which has a prominent advantage in that the viscosity at 25?is about 0.36 Pa·s and the low viscosity time can be maintained for more than 1000 minutes.(2)The performance requirements and structural stress characteristics of the mold for RTM-molding process are analyzed to optimize and prepare the mold for thick-section(flat and profiled)composite samples:The test orthogonal samples are prepared by RTM-molding process to investigate the influence of the parameters on the process performance and product-properties.The results show that the comprehensive mechanical-properties(flexural,compression,interlaminar shear performance)are optimal when the compression pressure,reserved clearance and compression temperature are 5MPa,3mm and 60?respectively.And the fiber volume fraction of the contrastive sample is 55.9%and its porosity is as low as 2.8%.When the compression pressure(MPa),the reserved gap(mm),and the compression temperature(?)are:5,4,40/5,4,40/7,3,80/7,3,60,the RTM-molded samples have the best indexes of porosity,flexural strength,compressive strength and interlaminar shear strength.(3)The profiled composite are prepared by RTM-molding process to investigate the influence of the plane angle on its mechanical properties.The results show that the porosity the flexural strength and modulus of the profiled composite decrease gradually with the increase of the plane angle(0°,30°,45°).While the compressive strength,compressive modulus and interlaminar shear strength gradually increases with the increasing plane-angle.However,the fluctuation of composite properties caused by angular changes is limited.Between 0°and 45°,the porosity varies by less than0.12%,the flexural strength and compressive strength vary by about 10MPa,and the interlaminar shear strength varies by less than 5MPa.The flexural modulus and the compressive modulus vary by less than 5 MPa.(4)The properties of the thick-section composites preparedly RTM-molding process are analyzed.The results show that compared with the traditional RTM,the composite material prepared by RTM-molding process has a porosity reduction of about1.3%,and the flexural strength,compressive strength,interlaminar shear strength,flexural modulus and compressive modulus are increased by 18.7%,11.7%,8.8%,47.6%,and 60.6%,And the fiber volume fraction of the RTM-molded sample reach55.9%.It indicates that the RTM-molding process can significantly improve the mechanical properties and fiber volume fraction of the composite component compared to the conventional RTM process.And it can effectively reduce the product porosity.