Calculation Of Residual Stress For Carbon Fiber Wound Composites During Curing Process

Carbon fiber wound composites are increasingly used in various field as ideal materials,such as aerospace,weapons,transportation,owing to their superior mechanical properties.The most common forming method for fiber wound composites is wet winding.And the mechanical properties of composites after curing depend on the curing process.One of the main factors affecting the mechanical properties of composites is residual stress,which is caused by the recovery of the temperature from a normal rise to a higher processing temperature during the curing process.Aiming at the formation process of curing residual stress and the influence of winding angles on the bearing performance of structures,this paper uses numerical simulation as the main research method to establish a numerical model for simulating the evolution of temperature,degree of cure,and residual stress during the curing process of composites.And the damage analysis of composites under tensile,bending,torsion,and combined loads,is carried out by strength criteria.The main work of this article is as follows:(1)Using the heat conduction equation,curing kinetics equation,curing deformation model and viscoelastic constitutive model,a finite element model for the simulation of temperature field,degree of cure field and the calculation of residual stress during the curing process of composites is established by the user subroutine.Firstly,AS4/3501-6 composite laminates are taken as an example to calculate the distribution of temperature and residual stress in the structure,and the results are verified.(2)A numerical model of carbon fiber wound composites is established.First of all,the distribution of temperature field and degree of cure field in the structure is obtained by thermochemical coupling analysis.And then in order to obtain the variation of residual stress in the structure during the whole curing process,the thermo-mechanical coupling analysis is carried out by taking the temperature field as the input variable.Next,the effects of curing process temperature,curing environment,structural configuration and fiber winding angle on the distribution of curing residual stress in the structure is analyzed.It is found that the temperature field and degree of cure field in the structure will change when the curing process temperature changes within a small range,which will affect the curing residual stress.The change of the thickness of lining material in the structure will obviously change the magnitude of stress in the composites,and the change of fiber winding angle will also affect the distribution of residual stress.(3)Based on Hashin’s criteria and a degradation model for material property,the damage analysis model of carbon fiber wound composites is established.So it can obtain the bearing capacity of the structure under tensile,bending,torsional and combined loads.Next,the influence of curing residual stress on the bearing capacity of the structure is also analyzed.The results show that the bearing property of the composites is determined by the fiber winding angle and the existence of curing residual stress can also affect the structural strength.