| Since the beginning of the 21st century,Chinese car ownership has grown rapidly,and the problems of energy and environmental pollution caused by it have become increasingly serious.Studies have shown that automobile fuel consumption and carbon emissions are directly related to the weight of automobile.For every 1% decrease in automobile weight,fuel consumption will decrease by 0.7%,and carbon emissions will decrease by 0.4%.Lightweight design of cars is one of the most effective ways to reduce fuel consumption and environmental pollution.At the same time,relevant laws and regulations put forward higher requirements for the safety performance of cars.At the same time,the relevant laws and regulations have placed higher requirements on the safety performance of automobiles,therefore,there is an urgent need to realize the lightweight design of automobiles while satisfying the safety performance.By consulting a large number of domestic and foreign literature and statistical data of road traffic accidents,it is found that side impacts are the most common form of collision that causes personal and property losses.In side impacts,the B pillar structure is the most important load-bearing structural component and plays a vital role in protecting the occupants.In this research,by combining two advanced lightweight methods in the automotive industry,one is the tailor rolled blanks(TRB)technology,also known as differential thickness plate technology;the other is the application of lightweight and high strength carbon fiber composite materials,the aim of the paper is to optimize the design of a new super-hybrid composite B pillar structure that can meet both safety performance and achieve good lightweight effect.Taking a certain car as the research object,a finite element model of the side impact of the whole vehicle was established according to the US new car evaluation regulations,and the simulation results were compared with the actual vehicle test results to verify the accuracy of the model.The results show that,in the event of a side impact,the intrusive speed and intrusive amount of the vehicle’s B pillar structure corresponding to the occupant’s head and chest position measurement points are large,which is not conducive to occupant protection.The performance of the B pillar needs to be further improved.The performance of the B pillar needs to be further improved.In the subsequent optimization process,the structural form and material distribution of the B pillar is systematically optimized to make the stiffness distribution more reasonable and improve the impact performance as well as reduce the weight of the B pillar.In order to reduce the computational cost,the B pillar structure was extracted separately and the equivalent static load qualitative analysis was performed.The aim is to design a carbon fiber reinforced composite(CFRP)-differential thick steel plate(TRB)composite B pillar structure.That is to say,the traditional reinforcing plate in the middle of the B pillar is removed.The B pillar outer plate is designed as TRB,and CFRP is locally applied on the inner side for reinforcement.Based on Optistruct,the thickness distribution of the inner and outer plates of the hybrid composite B pillar and the layup sequence and layup thickness of the composite material were systematically optimized.Finally,the results of the simulated side impact of the whole vehicle show that under the conditions of meeting the requirements of the manufacturing process,the new super-hybrid composite B pillar structure has achieved a weight reduction of 22.6%,and at the same time,the side impact performance has also been improved.Finally,under the condition of the vehicle’s side impact,the multi-disciplinary optimization platform Hyperstudy combined with the finite element software Ls-Dyna were employed for joint optimization.In which,the thickness of each area of the B pillar outer plate and the inner plate are used as design variables,the mass is used as the optimization target,and the intrusive amount and intrusive velocity peaks of the key points are used as design constraints.The Hammersley sampling with uniform spatial distribution is used for sampling,then the moving least square method is used to construct the approximate model,and finally the genetic algorithm is used for optimization design.The optimized design of the super hybrid B pillar structure is compared with the initial B pillar structure,which achieves a weight reduction of 24.9%,and the optimized structure has better impact resistance and a more favorable deformation pattern for occupant protection.At the same time,compared with the B pillar structure design scheme using only TRB,the super hybrid composite B pillar structure reinforced with carbon fiber composite has better weight reduction effect and better crash performance,reflecting the superiority of the super hybrid composite structure.This study will provide some reference for future applications of carbon fiber composites and super hybrid composite structures on automotive load-bearing structural parts. |
