| Fiber metal laminate is a hybrid composite material which combines the properties of with metal and resin matrix composite.With its structural characteristics,it has gradually become an ideal material for aerospace vehicles.However,due to the heterogeneity of the component materials,the fiber metal laminate has a heterogeneous interface problem during the hot-pressing curing process,which leads to the problem of curing residual stress caused by the mismatch of the thermal expansion coefficients of the component materials.On the one hand,the complexity of the stress-strain evolution during the curing process of the resin matrix composite in the fiber metal laminate leads to the complexity of the heterogeneous interface of the laminate,which increases the difficulty of predicting the curing residual stress of the fiber metal laminate;On the other hand,the determination of the curing process parameters of the existing fiber metal laminates refers to the curing process parameters of the prepreg resin system,while ignoring the incompatibility of the shape evolution caused by the heterogeneity of the laminate components,resulting in higher curing residual stress and defects of the laminate,which limits the exertion of the comprehensive performance advantages of the fiber metal laminate.In this paper,the multi-parameter coordinated on-line monitoring system for the curing and forming process of composite materials constructed by the laboratory is used to study and analyze the evolution process of the interface strain during the hot-pressing curing process of the fiber-metal laminates;The simulation modeling of hot pressing curing process of fiber metal laminate is carried out,and the evolution law of curing residual stress of laminate is analyzed;On this basis,the optimization research of the hot pressing curing process of the fiber metal laminate and the trial production of the scaled sample were carried out.The main research work and results of this paper are as follows:(1)Through the forming experiments based on resin system curing process and different curing processes for asymmetric fiber metal laminates,the experimental results show that compared with the laminates based on resin curing process,the demoulding springback curvature decreases by 26.9%,16.7% and 10.3% respectively,indicating that the curing process has a great influence on the residual stress distribution of fiber metal laminates;The multi parameter coordinated on-line monitoring system is used to monitor the evolution of interfacial strain in the curing process of fiber metal laminates.The experimental results show that the interface evolution in the curing process of fiber metal laminate is mainly affected by the curing temperature parameters,and under different hot pressing curing processes,the fiber metal laminate interface can effectively transfer the stress and strain between aluminum alloy and composite when the curing reaction of composite is carried out to 0.6.(2)By introducing resin layer to describe the evolution law of laminate interface properties in the curing process,a simulation modeling method for analyzing the interface residual stress in the hot pressing and curing process of fiber metal laminates is proposed.First,the interfacial properties of the fiber metal laminate aluminum alloy/carbon fiber composites were obtained by nanoindentation experiments.Combined with the viscoelastic constitutive of epoxy resin,the evolution model of interfacial properties during curing of fiber metal laminate was established.On this basis,by introducing the resin layer describing this evolution law,and secondary developing the user subroutine for its curing characteristics,combined with the finite element model of the hot-pressing curing process,the evolution law of interface residual stress in the curing process of fiber metal laminate is simulated.Taking asymmetric and symmetric fiber metal laminates as examples,the simulation prediction of curing deformation and residual stress distribution of fiber metal laminates under different curing process parameters is realized.The maximum error of comparative test results is 6.6%,which provides an important support for finding out the influence of curing process parameters on curing residual stress of fiber metal laminates and optimizing process parameters.(3)Based on the range analysis and variance analysis of orthogonal test and the combination of simulation and experimental research,the influence weight proportion of three process parameters of holding temperature,holding time and heating rate on the interlaminar shear strength and curing residual stress of fiber metal laminate is explored.The experimental results show that the influence weight of interlaminar shear strength is: holding temperature(63.7%)> holding time(31.5%)> heating rate(4.8%);The influence weight of residual stress is: holding temperature(46.6%)> heating rate(27.7%)> holding time(25.7%).In order to realize the manufacture of high-rise shear strength and low curing residual stress of fiber metal laminate,the hot pressing curing process of fiber metal laminate is determined as follows: holding temperature 140 ℃ + holding time 90 min + heating rate 1.5 ℃ / min + forming pressure 0.6MPa.Compared with the process scheme based on resin curing characteristics,the curing residual stress of fiber metal laminate under the optimized process scheme is reduced by 26.7%.(4)Combined with the simulation modeling method of fiber metal laminate hot press curing process established in this paper,the hot press curing process simulation and engineering trial production of typical curved parts of aircraft wing leading edge are carried out.The results show that the finite element simulation of fiber metal laminate curved surface part is consistent with the curing deformation trend of the experimental part.The maximum deformation of fiber metal laminate curved surface part predicted by the simulation model under the optimized process is 1.76 mm and the maximum deformation of the experimental part is 1.91 mm.The error between the simulation results and the experiment is 7.9%.Compared with the process based on resin curing characteristics,the deformation of laminate curved surface part under the optimized process is reduced by 19.4%,and the interlaminar shear strength increased by 3.7%.It provides a theoretical basis for the integrated shape and property manufacturing of fiber metal laminate components. |
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