Research For Reliability Analysis Of Bolted Joint In Laminated Composites

Composite materials are widely used in the aerospace field.The mechanical joint is the key part and the weak link of the structural member.Once the mechanical joint goes wrong,it can cause very serious consequences.Due to the complexity of composite manufacturing processes,the mechanical properties of composite materials always display obvious scatter,and many other uncertainties exist.Therefore,the randomness of material properties must be considered in the design of mechanical joints.Because of randomness,it is necessary to reevaluate the safety and reliability of mechanical joints.According to the reliability theory and response surface method,the reliability of the bolted joints in laminated composites is studied by using the finite element model,which is valuable to the reliability design of the composite structure.In this paper,the three-dimensional finite element model of the joints structure is established,and the progressive damage analysis is carried out.The load is applied to the structure,then different failure criteria and associated degradation methods are used to analyze the ultimate strength,and the results are compared with the experimental values to verify the accuracy of failure criteria.Secondly,the reliability of the joints structure is analyzed.The material function parameters are taken as the basic random variables to establish the functional function of structural failure.Because of the implicit expression of the function,the response surface method is used to fit it as an explicit function.Then the reliability of the structure is calculated and the influence of the scatter of the basic random variables on the probability of failure is studied.Finally,static strength and failure probability of the three forms of composites bolted joints are calculated by three-dimensional finite element model and response surface method.The influence of material size and ply change on the ultimate strength and failure probability of structure is studied,and some suggestions are put forward.