Study On Process Parametric Effect On Voids And Mechanical Properties Of Composite Wound Riser

Composite winding forming technology is an effective method for the fabrication of composite risers.It can design the winding patterns of the structure according to the performance requirements of the pipes,allowing the fibers to fully exert their mechanical properties.The fabricated components have the advantages of high specific strength,high reliability,and low density.However,the underwater environment becomes exceptionally complex,imposing higher demands on the quality and performance of composite pipes as offshore oil and gas exploration goes deeper.Therefore,improving the quality of winding products,reducing fabrication defects,and obtaining excellent and stable mechanical properties have become the focus of research on composite winding risers.This is of great significance for promoting the application of lightweight and high-strength composite components in the field of marine engineering and the effective utilization of marine energy resources.However,the quality and mechanical properties of composite wound components are not only affected by the characteristics of the materials themselves,but also by the fabricating method and the selection of fabricating process parameters.During the composite winding process,unreasonable process parameters can lead to a large number of component defects,uneven distribution of the internal structure of the winding product,weakened local performance,and increased occurrence of crack initiation or stress concentration phenomena,which will reduce the overall performance of the product.Therefore,exploring the inherent relationship between composite fabricating process parameters,porosity,and mechanical properties is the key to improving the performance of composite products.Based on this,this thesis starts with the marine riser winding process,and conducts experimental research in several aspects such as microstructure morphology,microscopic structure,and performance testing,with product defects and structural compression performance as the targets.This thesis focuses on revealing the relationship between the winding process parameters of composite riser and porosity,and axial compression performance.Then,based on global multi-parameter sensitivity and local single-parameter sensitivity analysis methods,a stable process parameter domain associated with them is obtained.This thesis mainly carries out the following work:(1)Developing the preparation and experimental design of composite wound risers.Firstly,the liner,experimental materials and apparatus of the composite riser were selected.Then,the experimental combination under the influence of winding process parameters was designed based on the BBD method,and the winding riser was prepared by fiber winding machine.Finally,the OLYMPUS microscope DSX1000 was used to characterize the microstructure morphology of the void content in the cross-section of the winding riser.Besides,the compression performance testing experiment of the riser was carried out by electro-hydraulic servo-hydraulic universal testing machine to provide data basis for studying the relationship between the winding forming process parameters and the void content and mechanical properties of the products.(2)Establishing the relationship between composite wound process parameters and voids.Firstly,based on the experimental data of the composite winding test and void test,an empirical model of the coupling between process parameters and void was constructed using the response surface method.Finally,the sensitivity of void content to winding process parameters was obtained using global sensitivity analysis and local sensitivity analysis.(3)Establishing the relationship between the influence of the composite wound process parameters on compressive strength.Firstly,based on the experimental data of composite wound test and axial compression test,the failure strength of riser under compression load was analyzed.Moreover,the empirical model between winding process parameters and axial compression strength was constructed by multivariate nonlinear regression method.Then,based on this multivariate nonlinear regression model,the single parameter influence and parameter coupling influence of winding tension,feeding speed and curing time on the axial compression performance of wound riser was further revealed.Finally,the sensitivity of axial compression performance to winding process parameters was obtained using global sensitivity analysis and local sensitivity analysis.(4)Optimization of winding process parameters based on void content and compression strength.Firstly,based on the local single-parameter sensitivity analysis of void content and axial compression performance of composite wound riser,a new multi-dimensional interval division method was used to obtain the stable domains of process parameters for void content and axial compression performance respectively.Then,the void content and axial compression performance stability domains were integrated to obtain a stable process parameter domain satisfying the dual objectives.Furtherly,the grey wolf particle swarm optimization algorithm was used to optimize the process parameters under the multi-objective to obtain the optimal process parameters.Finally,the grey wolf particle swarm optimization algorithm was used to optimize the process parameters under the multi-objective to obtain the optimal process parameters.Moreover,the random sampling test results showed that the stability of void content and axial compression performance produced by the parameter set within the optimized range were better than those outside the optimized range.The optimal results were: winding tension was 51.7448 N,feeding speed was 14.8607m/min,and curing time was 6.3741 h.Under these conditions,the void content and the maximum axial compression load were 2.3278% and 88.4074 KN,respectively.