Study On The Preform Technology Of Hot Diaphragm Aimed At Carbon Fiber C-beam

With the development of composites,carbon fiber composite has been widely used in aerospace and other fields.The typical composite profile components,represented by C-beam,are increasingly widely used.How to realize the automatic manufacturing of composite profiles has become an urgent problem for aviation enterprises.Because of its easy operation,hot diaphragm preform has gradually developed into a very important low-cost manufacturing technology.In this paper,according to the technical requirements of an aviation enterprise,the preliminary research on the automatic hot diaphragm preforming method of carbon fiber composite C-beam is carried out.Firstly,the material model and mechanical properties of prepreg and diaphragm were studied by theoretical analysis and experimental test.According to the stress-strain relationship of orthotropic materials,the test methods of engineering constants in different directions are given,and the engineering constants,₁E andG₁₂,of prepreg under plane stress state are tested.The stress-strain relationship of the membrane material was tested by single tensile test,and the hyperelastic constitutive model of membrane was obtained by fitting.According to the C-beam,a three-dimensional simulation model of hot diaphragm forming process has been established by ABAQUS.The deformation process of the diaphragm,and the influence of pressure and temperature on the formability of C-beam were studied.The relationship between the maximum flange size and forming pressure was obtained.The friction coefficient between prepreg layers under the condition of temperature of 30⁶0?and pressure of 0.05⁰.08MPa were measured by the designed testing fixture,and the reasons of friction transformation was analyzed.Besides,a two-dimensional simulation model of hot diaphragm forming with multilayer prepregs was established,and the effect of the friction coefficient on the internal stress of preform was studied.In order to carry out relevant experiments and verify the results of the simulation,a experimental system of hot diaphragm preforming was designed and built,which included forming system,temperature control system and pressure control system.And the evaluation standard and detection methods of preforming quality were given.Based on the experimental system,the influence of pressure and temperature on the preforming parts were studied.Besides,suggestions have been provided for the hot diaphragm forming process of carbon fiber composite C-beam.