Cured Deformation Behavior Of Glass Fiber Reinforced Aluminum Laminate

Fiber metal laminate(FML)inherits the advantages of traditional composite and metal material at the same time.Because of their excellent fatigue resistance and damage tolerance properties,FMLs have been widely used in the field of aerospace and become a new type of aeronautical material.However,during the manufacturing process of FMLs,due to the mismatch of thermal expansion coefficient of component materials,the chemical shrinkage of resin matrix and the interaction between components and mould,complex residual stress field will be generated inside the laminate after the end of curing cycle.For unsymmetrical hybrid composite laminates,the internal stress is unbalanced along the thickness direction and produces bending moment,which results in warpage and springback deformation of the laminates.This seriously affects the shape stability of FML.Therefore,it is of great significance to accurately predict the cured shape of FML and effectively control its geometry size for ensuring the structural assembly tolerance requirements,improving the quality of components and reducing costs.Based on the experimental results,an analytical model is established to predict the equilibrium configurations of FML at room temperature,and the curing deformation behavior of FML under thermal stress is investigated.The cured shape of FML is accurately predicted and the influence of geometry parameters on the curing deformation behavior of laminates is given,which provides theoretical guidance for the configuration control of hybrid composite laminates in the preparation process.For the hybrid composite laminate structure,the metal layer and the prepreg layer are not completely bonded and the thermal strain is incompatible during the heating process,resulting in the phenomenon of bonding/slip at the interface.The slippage effect at the interface is the key factor to restrict the prediction accuracy of the equilibrium configuration of hybrid laminates.In this paper,the plane deformation coordination relationship between the metal layer and the prepreg layer during curing is analyzed.The mathematical expressions of interface slippage strain in the metal layer and the prepreg layer are obtained,and the curing deformation law of FML considering the slippage effect is given.On this basis,based on the nonlinear classical lamination theory and the minimum potential energy principle of Rayleigh-Ritz,an analytical model considering slippage effect is established.The equilibrium configurations of cross-ply FML after curing are accurately predicted.In addition,by using spring element to simulate the interfacial interaction of hybrid laminates,a finite element analysis model considering slippage effect is established.The correctness and rationality of the prediction model are verified by comparing the prediction results of the analytical and the finite element model with the experimental data.The different fiber orientations of the prepreg in the hybrid composite laminate show different mechanical properties.Based on the prediction results of cross-ply FML,the analytical model considering slippage effect is extended to predict the cured shapes and warping displacements of arbitrary angle-ply [Al/-? /? /Al] FML.In view of the important influence of geometry parameters on the curing deformation behavior of angle-ply laminates,the influence of laminate size,aluminum layer thickness,aspect ratio and ply orientation angle on the cured stable configuration is studied by using the established prediction model.At the same time,the relationship between the principal curvature direction and the equilibrium configuration of [Al/-45/45/Al] laminates is given.The contribution of thermal strain energy and slippage strain energy to the total potential energy is determined by strain energy analysis of laminates with different ply angles.When the slippage effect of the interface is considered,the prediction accuracy of the analytical model is increased by about 10%.Through the parameter sensitivity analysis of the laminates with different ply angles,the sensitive parameters affecting the cured equilibrium configuration of the laminates are determined.It is found that the Young's modulus of component materials,coefficients of thermal expansion,thickness of aluminum layer and temperature difference have significant influence on the cured shapes of laminates.Considering the fact that most of the FML components are complex curved surface structures in practical applications,an analytical model for predicting the equilibrium configuration of FML with initial curvature is proposed.In this model,the interfacial slippage effect is considered,and the initial and final shapes of the laminates are described by the sixth-order out-of-plane displacement function polynomials.The final shape function coefficients are solved by using Rayleigh-Ritz method.The FMLs with initial curvature have relatively complex deformation modes after curing.By analyzing the stress and the change trend of the potential energy and potential energy barrier,the curing deformation mechanism of FML with initial curvature is analyzed form the perspective of stress and strain energy.In addition,the distributions of residual stress along the thickness direction at the center and boundary points of the typical specimen are given by analytical calculation.Finally,the influence of laminate size,stacking sequence and initial curvature radius on the cured stable configuration of curved FMLs is analyzed by using the established analytical and finite element prediction model.In this paper,combined with the practical engineering problems,the finite element model considering slippage effect is used to predict the equilibrium configurations of the leading edge components after curing.The forming mould of leading edge component is made by roll bending technology.The leading edge components with two kinds of layup [Al/0/90/Al] and [Al/90/0/Al] are manufactured by autoclave curing process.The equilibrium configurations at room temperature are measured using a 3D laser scanner.The experimental data are in good agreement with the finite element simulation results.According to the simulation results of curing deformation of leading edge component by the finite element model,the compensation design of the mould surface is carried out by using the compensation algorithm based on the node deformation.The method and flow of mould surface design are summarized.Through the compensation research of the mould surface,the preparation precision of the dimension and shape of the component after curing deformation is effectively controlled.The goal of eliminating or reducing the deformation of components is achieved.