Structural Design And Manufacturing Technology Of New GRP Sandwich Pipe

As a kind of composite pipe,Glass Fiber Reinforced Plastics GRP pipe is widely used in water supply and drainage industry because of its light weight,high strength,good hydraulic performance and corrosion resistance.Due to the low elastic modulus of GRP,in order to improve the stiffness of GRP pipe,it is necessary to increase the thickness of the pipe wall,thus increasing the cost.Fiberglass reinforced plastic sand sandwich pipes use sand layer to increase the thickness of pipes,and increase the stiffness at a lower cost.However,due to the material difference between sand layer and inner and outer structural layer,it is easy to occur delamination or sand layer damage when subjected to impact or bending.In this paper,a new type of sandwich pipe structure is proposed based on the existing problems of GRP pipes.Its mechanical properties and design methods are studied,and a new manufacturing process is developed for sample manufacturing and test.The main contents of this paper are as follows:(1)A new type of GRP sandwich pipe is proposed.The sandwich pipe is composed of inner structure layer,outer structure layer and web connecting inner and outer structure layer.Compared with traditional GRP pipes,sandwich pipes do not have obvious interface problems.They have low cost and stronger design ability under the same stiffness level,and have broad application prospects.(2)The mechanical properties and design methods of sandwich pipeline are studied.According to the national standards,the pressure and stiffness grades of sandwich pipes under actual working conditions are determined.According to the failure strain,the pressure grade of sandwich pipes is determined,and the stiffness grade is determined by the equivalent section method.(3)The stability and design method of web are studied.Web plays an important role in sandwich pipeline structure,but because of its thin thickness,it is easy to lose stability when it is too high.A simplified model for web stability analysis is established.Based on Euler's formula,a formula for calculating the critical line load of web is proposed.The constraint coefficients in the formula are obtained by using finite element software Ansys.(4)A multi-stage winding process for sandwich pipes was developed.Samples were prepared by this process and tested.The maximum error between the experimental and theoretical values of ring stiffness is 9.53%.The failure mode is lamination failure of external structure.There are no web instability and delamination.The test results show that this process can produce sandwich pipes with excellent performance,and the reliability of the design method is verified.