Modeling And Dynamic Response Prediction Of Composite Beams With Uncertainty Parameters

Constructing an accurate finite element model plays a key role in the field of design and analysis of structural dynamics.The accurate model can be used in dynamic response prediction,the mechanics environment prediction,damage detection and optimization design.In practical engineering applications,the macroscopic mechanical properties of fiber braided composites have heterogeneity characteristics which affect the accuracy of composite structure mechanical models.The heterogeneous parameters of the composite material are identified,so that the superior property of the composites can be fully utilized in the structural design and mechanical analysis.It is of great theoretical significance and application value to carry out stochastic modeling and dynamic response prediction of composites which considering the heterogeneity of parameters.In this paper,the stochastic modeling and dynamic response prediction method of composites have been studied.The main research work has carried out in the following aspects.Firstly,the heterogeneous parameter identification of composite materials is studied based on the experimental data and the sensitivity analysis.The method takes into account the advantages of the finite element method and the experimental,and is capable of providing a more complex model of composite material parameters.Furthermore,numerical simulations on an Euler-Bernoulli cantilever beam is conducted to verify the correctness of the identification method;And then,experimental studies are further carried out on the modal test.The acceleration frequency response function is calculated as input data and the modulus field of the composites is obtained by the proposed method.Results show that the frequency response functions of each measuring point on the beam calculated by the identified elastic modulus field agree well with the experimental values,and the proposed method is feasible when the measurement dynamic responses are contaminated noise.The identification method is also robust to the measurement noise.Secondly,in practical engineering structure,the elastic parameters of the composite are continuously distributed.However,in the above method,the heterogeneity of the spatial distribution of composites parameters is characterized by the difference of elastic parameters between different units.This does not exactly correspond to the actual continuous distribution.In order to reduce the effect,an equivalent distributed parameter identification method of composite material based on generalized orthogonal polynomials is proposed.A continuously distributed parameter is identified by the response measured at limited points.The identification of heterogeneous parameter is transformed to the identification of orthogonal polynomial coefficients with the distributed parametric model represented by Legendre orthogonal polynomials.Numerical simulations on an Euler-Bernoulli beam model are carried out to verify the feasibility of the identification method.The correctness and applicability of the proposed method are further verified by comparing the results in different boundary conditions.Then,a stochastic model of uncertain parameters of composite materials is conducted by spectrum decomposition and probability statistics based on the limited sample data,Such a model is set up to account for both random uncertainties related to the heterogeneity of the macroscopic mechanical properties,as well as epistemic uncertainties due to insufficiency of the sample data.The spectrum decomposition method is used to discretize the measured data.The uncertainty problem is transformed into a deterministic problem,which greatly reduces the difficulty of the stochastic problem.Bayes theory combines the prior information and can get more accurate results when the test data is not easy to obtain.Finally,the prediction of the stochastic response of the structure is studied based on the spectral stochastic finite element model conducted by the stochastic model of uncertain parameters used the measured samples.The composite beams from the same batch are used to carry out the vibration test.Comparing with the statistical characteristics of stochastic dynamic response samples,the correctness of the prediction method for the stochastic dynamic system response with the uncertain parameters is verified.