Research On Diaphragm Mechanical Behavior In Composite Material Hot Diaphragm Forming

Composite material has been widely used in aerospace field,such as aircraft structural part for its superior mechanical property.The development of aerospace technology makes higher requests for the forming technology of composite material.Poor efficiency of traditional hand lay-up molding limits its application and the mechanized lay up method is not suitable for complex composite material part.In this circumstance,the hot diaphragm forming method springs up and turns out to be an ideal method for manufacturing aircraft structural part,such as the wing.This paper researched the mechanisms of hot diaphragm forming of carbon fiber composite beam with C-shaped structure by the combination use of experiment and finite element method(FEM).Special focus was placed on mechanical behavior of the diaphragm,which was precisely the foundation of hot diaphragm forming as well as the relevant finite element simulation.Tensile property of the diaphragm was tested at various temperatures and strain rates.The hyperelastic constitutive relation was established based on the continuum mechanics and hyperelastic constitutive theory.The built constitutive equation was implemented in ABAQUS through user subroutine UHYPER,serving as material model in the follow-up simulation of hot diaphragm forming.Experimental system of hot diaphragm forming has been designed and set up,including the mold,heating system and vacuum air-removed system,according to the dimension of C-type beam.Deformation experiments of diaphragm were presented under the vacuum negative pressure and this procedure was simulated in ABAQUS.The good agreement between simulation results and experimental consequences demonstrated the accuracy and rationality of the established constitutive equation for describing mechanical behavior of the diaphragm.