Design And Optimization Analysis Of Composite Hat-joint Under Bending Load

Fiber reinforced composites(FRP)have become the ideal structural material for ship superstructures due to its high specific strength,high specific stiffness,corrosion resistance,design flexibility and ease of molding process.As composite materials are widely used in ship structures,design of composite joint is an indispensable key link in the design of composite structures.The design and optimization of joint structures broaden the application range of marine composite materials and have important engineering significance.Composite sandwich plate with stiffener is the analysis of basic plate frame of ship superstructures,including composite sandwich plate and stiffener.Based on the loading condition and structural scheme of the composite sandwich plate with stiffener,the composite hat-joint was designed with non-plane adhesive bond each other together.Employing of method of the equivalent section and equivalent engineering parameters,the bending stiffness of the sandwich plate with stiffener was calculated theoretically.The scheme dimensions of the hat-joint were calculated,which was based on the composite structure's design requirements of the bending stiffness and load carrying capacity.Composite hat-joint structure comprises three kinds of material systems,which include plain weave composite material,polyurethane foam(PVC)and epoxy resin adhesive.The connection form and material system are complex,and it is difficult to establish a theoretical formula to analyze the damage and failure process.The numerical simulation method was used to analyze the bending bearing capacity of the composite hat-joint structure,and simulate the deformation,stress and damage evolution process.Progressive damage model was used to simulate the damage initiation,damage evolution and failure of composite materials.In-plane failure and out-of-plane failure of plain woven composites were simulated by using modified Hashin failure criterion and Yeh criterion respectively.The damage evolution law of power function is used to simulate composite damage propagation and ultimate failure and the user subroutine VUMAT of this progressive damage model is programmed.The rationality and reliability of the progressive damage model were verified by the tensile test for the open-hole plain weave composite plate.The cohesive zone model is used to simulate the failure progress of the adhesive layer,in the meantime,the low-density foam model is adopted to analyze the failure of the foam core.Adopting different failure model in composite hat-joint is to obtain more accurate simulation results,which aided the optimization design of the composite hat-joint.A multi-objective optimization model is established for the composite hat-joint.Based on the Latin hypercube experimental design method,the influence factors of design variables on the optimization target are analyzed,and the key design variables of different optimization targets are identified.Non-dominated sorting genetic algorithm is used to solve multi-objective optimization model.Combining Abaqus with Isight to obtain the Pareto optimal solution set of multi-objective optimization model,and fitted the Pareto frontier curve to provide evaluation basis for optimization design.The optimization results show that the non-dominated sorting genetic algorithm is feasible and effective for analyzing the multi-objective optimization problem of composite joints.The optimized bearing capacity of the composite hat-joint structure under bending load has been significantly improved.