| Advanced resin matrix composite features high specific strength and specific modulus,low density,high toughness,corrosion resistance,diversified craftsmanship and so on.It has been widely applied in national defense,military,aerospace,construction,chemical,transportation,energy,machinery and electronics,medical,sports and many other fields.Autoclave forming process is one of the methods commonly adopted by aerospace manufacturers to manufacture advanced composite components,in which the curing stage is the key link affecting the quality of components.The curing process of resin matrix composites has the characteristics of non-steady state,non-uniform and strong coupling.It is difficult to realize the goal of high-performance,low-defect and low-cost in integral forming of composites only based on traditional experience and test methods.Numerical simulation is an effective method commonly used in the field of composite material curing.In curing process,the mode,degree and integrity of coupling,simulation scale and materials constitutive equation have a direct impact on the validity and accuracy of simulation results.In this paper,the autoclave curing process of resin-based composites is taken as the research object,and a macro-scale simulation model for the curing process of composites was created which featured high integrity and intensive coupling.Furthermore,a new meso-scale calculation method was put forward for the simulation of composites’ curing behavior;and a meso-scale multi-field coupling simulation model for the curing process of composites was developed.The impacts of curing process and lay-up design on the curing behavior of composite materials were explored.In the meantime,the effect of the material constitutive model on the curing and deformation of composite materials was studied.The main work and conclusions were as follows:(1)A macro-scale simulation model for the curing process of resin-based composite materials was established featuring with high integrity and intensive coupling.Currently,most curing simulation models have the problem of incomplete physical field coupling and inadequate consideration of factors.In this paper,the impacts of temperature,pressure,fiber volume fraction,laminate thickness,material performance and other parameters were taken into account,and a macro-scale simulation model for the curing process of composites was established which highly integrated integrating heat conduction,curing kinetics,resin flow-compaction and solidification deformation.This provides a much effective method for comprehensively analyzing and controlling the curing behavior of composite materials.In the model validation,the evolution and variation of temperature,curing degree,resin viscosity and pressure,fiber volume fraction,laminate thickness,elastic modulus,thermal-chemical strain and residual stress for AS4/3501-6 prepreg during a typical curing process were calculated and analyzed.The results showed that the strength-weak coupling relationship between each physical field was represented effectively in the presented model,which could simulate the curing process of resin matrix composite completely,in real time and accurately.The calculated results of curing temperature,curing degree and internal stress of AS4/3501-6 prepreg were well in line with the literature.(2)A new meso-scale calculation method was proposed to simulate curing behavior of composite materials,and a meso-scale simulation model for the curing process of composite materials was established.The macro-scale material model did not distinguish between the calculation regions of the reinforcing fibers and the resin base in the calculation process;while it used the meso-mechanical equations and mixing rate formulas for the calculation in all the domains of composite materials.Therefore,the calculation results had relatively large errors.In order to improve the accuracy of calculation,in this paper,a new method for meso-scale calculation of curing simulation was put forward.In the model verification,the curing process of USN125 prepreg was numerically simulated and the calculation results were compared with those of the macro-scale model of the same size.The results showed that,compared with the macro-scale model,the meso-scale material model was more in line with the actual composite material structure,and obtained a more accurate calculation result;furthermore,the material temperature and strain values calculated were greatly close to those of the FBG sensor in the literature.(3)The impact of curing process and layup design on the curing behavior of composite materials was explored and analyzed.Curing process and layup design have a direct impact on the curing deformation and molding quality of components.Due to the limited factors considered by the model,the existing researches on the impact of curing process and layup design are not comprehensive and accurate.In this paper,a simulation model of the curing process for X850/T800 composite laminates was established.Also,three research schemes were designed to analyze the effect of the curing process and the laminate design.The calculation and analysis results showed that: the process temperature,the process pressure and the lay-up design have an important influence on the curing behavior and the curing quality of the composite materials.This study provides an effective method and basis for the optimization design of the curing technology and structure.And it’s of great significance in controlling curing deformation of components,as well as in improving the curing quality.(4)The effect of the material constitutive equation on the curing and deformation of composites was analyzed.The material constitutive equation was the main control equation of the curing deformation module,which exerted a direct impact on the prediction results of the residual stress and curing deformation during the curing process of the composite material.The comprehensive and accurate analysis and evaluation of the effect of material constitutive equations on the curing and deformation of composites are conducive to the correct use of the constitutive equations and the prediction of curing deformation.Linear elasticity,CHILE(Cure Hardening Instaneously Linear Elastic)and viscoelastic constitutive equations are three commonly used constitutive models.In this paper,the curing of AS4/3501 composites was taken as an example.Then the effects of these three constitutive equations on the thermal-chemical strain,residual stress and curing deformation of the composites were compared and analyzed.And the comprehensive evaluation was made from the three aspects of calculation accuracy,calculation time and memory occupancy.It’s found that the linear elastic model had large calculation error but short calculation time and less occupied memory.Though the viscoelastic model had high calculation accuracy,the calculation time was long and with a large amount of memory.In particular,the required experimental data were numerous so that it’s not conducive to execution.The overall efficiency of the CHILE model ranked between the other two mentioned above.Because these three constitutive models have their advantages and disadvantages,within the allowable error range,they may be selected based on the specific circumstances. |
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