Research On Cumulative Damage Performance Of Full-wound Composite Cylinders

Composite gas cylinders have light weight,high strength and good safety performance,and are widely used in various fields of aerospace and civil production.In recent years,there have been endless researches on composite gas cylinders.However,most of the current researches only focus on the static compressive strength of the gas cylinders.There are insufficient researches on the impact,fatigue and other cumulative damage that may occur during the use of composite gas cylinders..In response to the above problems,this paper uses numerical analysis combined with experimental research to explore the cumulative damage of composite gas cylinders.The main work and research results are as follows:(1)Based on the transient dynamics theory,a composite gas cylinder impact damage analysis model was established,and part of the experimental verification was carried out.On this basis,the layup sequence of the composite gas cylinder winding layer was optimized by the genetic algorithm to improve the gas cylinder Impact resistance.The results show that the impact test is carried out with the transition section of the gas cylinder and the middle of the cylinder body as the impact point.The error between the measurement results of the remaining burst pressure of the gas cylinder and the numerical calculation results after impact is within 5%,which can verify the impact damage analysis model in this paper.accuracy.After optimization by genetic algorithm,the impact resistance of the composite gas cylinder is significantly improved,the rupture area and the number of rupture layers of the matrix after the impact are significantly reduced,and the remaining burst pressure of the gas cylinder is significantly increased.(2)By testing the damage degree of composite gas cylinders under different impact positions and impact energy,combined with numerical analysis methods,the internal damage behavior of the composite winding layer under different impact conditions was studied,and the relationship between impact and residual strength was obtained.The results show that the outermost part of the fiber winding layer is the most severely damaged after impact,the innermost part is secondly damaged,and the middle part is the least damaged.With the increase of impact energy,the rupture area of each layer of the matrix and the fiber rupture area gradually increased,and the remaining burst pressure gradually decreased.Comparing the measurement results of the impact cylinder and the transition section of the impact cylinder,when impacting the transition section of the cylinder,the fiber rupture area is less,the matrix rupture area is more,and the pit depth is shallower.Comparing the measurement results of the square impact hammer and the cone impact hammer,the rupture area of the matrix after the square impact hammer is only 34.8% of the cone impact,and the pit depth is21.2% of the cone impact.Perform hydraulic blasting on the cylinder after impact.At the same impact position,the remaining burst pressure of the cylinder after 90 J energy impact is118.13 MPa,and the remaining burst pressure of the cylinder after 60 J energy impact is124.94 MPa,an increase of 5.8%.(3)Based on the residual strength theory and residual stiffness theory,the fatigue damage analysis model of composite gas cylinders was established,and the fatigue damage process simulation of composite gas cylinders during service was realized.The damage degree of composite gas cylinders under different fatigue times was studied and carried out.Fatigue test verification.The results show that after 11000 fatigue tests,the difference between the measurement result of the remaining burst pressure of the gas cylinder and the fatigue damage analysis result is 0.96%,which verifies the accuracy of the fatigue analysis model.During the fatigue process,the strength performance of the composite material layer gradually degrades.In the early stage of fatigue,the strength of the composite material degrades quickly,and the degradation rate gradually slows down in the later stage.After11000 cycles,the calculated remaining burst pressure of the gas cylinder is 125 MPa,which is11.3% lower than the calculated burst pressure of the original gas cylinder.The remaining burst pressure of the gas cylinder measured by the test is 123.8 MPa,which is compared with the test measurement of the original gas cylinder.The pressure has dropped by 11.3%.(4)Based on the above analysis model,the fatigue-impact cumulative damage performance of composite gas cylinders is studied by the method of numerical calculation combined with experimental research.The results show that the damage of impact after fatigue cycle is more serious than that of direct impact.Through numerical calculation,the rupture area of the matrix after the fatigue test is carried out under the impact energy of 60 J on the cylinder body increases by 16.2% compared with the rupture area of the matrix after the direct impact test.The depth of the pits after the fatigue test is more The depth of the pits subjected to the impact test increased by 7.4%.Compared with the original cylinder,after11000 times of fatigue-impact cumulative damage,the remaining burst pressure of the cylinder under 60 J impact energy is reduced by 19.9%,and the remaining burst pressure of the cylinder under 90 J impact energy is reduced by 21.3%.