Response Mechanism Of Carbon Fiber Composite Laminates Under Ice Impact

The application of lightweight and high-strength carbon fiber composite materials has become an important direction for the improvement of high-speed train technology,due to the development strategy of PRC national "dual carbon" and powerful country in transportation.However,when the train body made of CFRP(Carbon Fiber Reinforced Polymer)laminates encounters impacts such as hail,ice falling from the line,and ice falling from the tunnel during the running of highspeed trains,the low delamination threshold may easily lead to potential safety threats to the CFRP train body.The delamination is visually undetectable and difficult to effectively predict.Its biggest challenge is rationally recognizing the damage and evolution law of CFRP laminates under the random and rate-sensitive ice impact.This study starts with three characteristics in terms of ice structure,ice constitutive and ice load distribution,and then systematically investigates the impact response behavior of ice,as well as the damage prediction of CFRP laminates under single ice impact and random ice impact using the methods including theoretical analysis,high-speed impact experiment and numerical simulation.In addition,the non-consistent deformation mechanism of composite delamination is revealed,and the delamination threshold of CFRP laminates under ice impact is predicted.The main research contents and innovative work include:(1)A pressure-dependent and strain-rate-sensitive ice constitutive model is proposed.According to the anisotropy of compression and tension and the three-dimensional stress-sensitive characteristics of ice materials,the ice failure criterion and constitutive model coupled with hydrostatic pressure and deviatoric stress are proposed,and thus the conventional ice constitutive model that only considers hydrostatic pressure is improved;On this basis,according to the strain rate sensitive phenomenon of ice,an ice constitutive coupled with compressive and tensile strain rate effect is proposed,which improves the conventional constitutive model that only considers the compressive strain rate effect;Through the ABAQUS VUMAT subroutine design,numerical simulation and experimental comparison,the prediction accuracy of pressure-dependent and strain-rate sensitive ice constitutive in terms of impact force,failure mode,crack propagation,etc.is validated;Based on the analysis of simulation and experimental results,the influence mechanism of hydrostatic pressure and strain rate effects during ice failure are clarified.(2)A non-consistent deformation analysis method of delamination mechanism of CFRP laminates is proposed.Through the self-designed experimental system of ice impacting on CFRP laminates,the experimental research on CFRP laminates subjected to ice ball impact is carried out.Using the C-scan non-destructive testing technology,the delamination results of CFRP laminates under different ice impact conditions are obtained,and the quantitative relationship between the delamination and impact conditions is statistically achieved;Based on the delamination morphology analysis,the law of delamination,i.e.,the delamination expansion along the fiber direction of the next ply of the adjacent plies,is obtained;Through the analysis of deformation process,the patterns of the non-consistent deformation area between adjacent plies is theoretically achieved,which is consistent with the experimental delamination results,and thus reveal the mechanism of delamination morphology and delamination expansion of CFRP laminates.(3)The delamination prediction model of CFRP laminates under ice impact is proposed.Based on the analysis of the impact mechanical response characteristics of CFRP laminates,a CFRP constitutive model containing anisotropic elasticity,failure and progressive damage is constructed.Combined with SPH(smooth particle dynamics)and finite element method,a meso-scale numerical model of CFRP laminates under ice impact is established,and the reliability is validated by experiments;According to the non-consistent deformation analysis method,a theoretical prediction model for delamination of CFRP laminates under ice impact is proposed,and the feasibility of the theoretical prediction method is validated by experiments.(4)A prediction method of CFRP laminates under random hail ice impact is proposed.According to the characteristics of random particles,a mathematical characterization model of stochastic particles including randomness of spatial position,attitude and speed is proposed,and the realization method of random particle field is established based on Monte Carlo stochastic algorithm;Through combining the statistical analysis of natural hail and random particle modeling method,the numerical simulation method of random hail ice impact is achieved using ABAQUS PYTHON,which breaks through the conventional method of using singleparticle or single-state repeated impact to approximate the random impact response;Based on the stochastic modeling and CFRP modeling methods,a numerical model of CFRP laminates impacted by random hail ice is established,and thus the interaction effect between random hail ice impact is obtained;Furthermore,a characterization method for the cumulative impact effect of CFRP laminates under random hail impact is constructed,and the distribution law of cumulative impact damage of laminates is predicted.(5)The safety assessment method of the CFRP train body impacted by random hail ice is established.Using the numerical simulation method of CFRP laminates under ice impact,the influence of random factors of natural hail on the delamination of CFRP laminates is analyzed,including random impact position,impact angle,hail shape and cumulative impact;According to the influence laws,an equivalent simplified analysis model for predicting the delamination of CFRP train body under natural random hail ice impact is established;From the perspective of engineering,taking the approximate configuration of the head,roof and side walls of highspeed trains with a speed of 350 km,400 km and 600 km per hour under natural random hail impact as examples,the typical structural damage of the above scenarios is calculated and safety assessment is carried out;On this basis,the reasonable CFRP thickness of the corresponding train body laminates under different speed conditions is given.In summary,this paper systematically recognizes the constitutive characteristics of ice,reveals the damage evolution law of composite laminates impacted by ice,and establishes a stochastic analysis method to characterize and predict the damage of CFRP laminates under hail impact.Finally,combined with engineering applications,the safety assessment method for high-speed train structures made of composite laminates under hail ice impact is developed,which provides theoretical reference and guidance for the CFRP train body under hail ice impact.There are 96 figures,30 tables and 308 reference literature in this doctoral thesis.