Study On Bending And Low Velocity Impact Properties Of 2D Woven Basalt Fiber Composites

The social problems of energy shortage and environmental pollution are becoming increasingly prominent.The lightweight design of automobiles is an important means to increase cruising range and reduce environmental pollution.In the process of automotive lightweight design,using lightweight materials to replace steel components is a significant method.The characteristics of fiber composite materials are lightweight and excellent in performance,which provides many possibilities for automotive lightweight design.At present,carbon fiber composite materials are the most widely used.However,carbon fiber composite materials are brittle and easy to be damaged by stress concentration.Besides,the price of carbon fiber composite materials is relatively high.Taking those factions into consideration,finding fiber composite materials with excellent performance and low cost is becoming a hot issue in lightweight research.Basalt fiber is a natural,non-toxic,and environmentally friendly inorganic fiber with low cost and abundant reserves.It is called "the non-polluting green material of the 21 st century".Although the overall performance of basalt fiber is not as good as carbon fiber,compared with other fibers,basalt fiber has high strength,high modulus,stable chemical properties,high fracture toughness,and has good corrosion resistance and flame retardancy.In addition,basalt fiber’s extrusion process is simpler and more energy efficient than any other fiber process.The braided composite material is a composite material formed by the yarn through a certain weaving process,and then cured with the base material.Compared with unidirectional fiber-reinforced composite materials,composite laminates have great potential for improving interlayer and intralayer strength,providing better damage tolerance.On the other hand,it is easier to form by lower manufacturing costs.,with great competitiveness.This article takes plain weave basalt fiber as the research object.To improve the material’s bending performance and low velocity impact performance,optimize the braided structure and use interlayer hybrid carbon fiber,give full play to the advantages of braided structure and fiber hybrid,and finally strengthen the basalt-carbon hybrid composites are used in automotive B pillar outer panels for basic research.The specific research contentsare as follows:(1)Samples of basalt fiber laminates were made and relevant mechanical performance tests were performed.For details,a basalt fiber laminate composed of 6 layers of plain basalt fiber cloth was prepared,and tensile,compression,and shear tests were performed to obtain basic mechanical performance parameters.At last,a three-point bending test and a drop weight test were performed.(2)Establish a RVE model to predict the elastic properties of plain basalt fiber laminates,and establish an accurate macroscopic finite element model.First,a representative volume unit capable of accurately depicting a plain weave structure is established,and the elastic properties of the composite material are predicted based on the homogenization theory,and compared with the test results.Then,based on the continuous damage model,the bending and low-speed impact finite element model of the laminate is established,and the simulation results are compared with the test results.After comparison,it is verified that the meso-scale model can be used to predict the elastic properties of composite materials,and the continuous damage model can be used for macro-finite element modeling.(3)The effects of yarn width,yarn spacing,and yarn thickness on elastic properties were studied,and the combination of structural parameters was optimized.Based on representative volume units and elastic performance prediction methods,the effects of yarn width,yarn spacing,and yarn thickness on the elastic modulus and shear modulus were studied,and then the elastic modulus,shear modulus,and bending strength were studied.The optimization objectives are elastic modulus,shear modulus,maximum bending strength and minimum fiber volume fraction in the range.Multi-objective optimization design is performed using response surface method and genetic algorithm.The final optimized combination of the braided structure parameter is yarn width x1 = 0.8mm,yarn spacing x2 = 0.2mm,yarnthickness x3 = 0.35 mm.(4)The bending performance and low velocity impact performance of different hybrid ratios,different stress surfaces of the meta-carbon hybrid composites were studied.The basalt-carbon hybrid laminates and pure carbon fiber laminates with basalt-carbon hybrid ratios of 1: 1,2: 1,and 5: 1 were prepared,and the bending test and drop weight test were performed with the carbon fiber and basalt fibers as the stress surfaces(5J,10 J,15J),combined with the corresponding finite element simulation and comparative analysis of bending performance and impact resistance,it was concluded that the hybrid carbon fiber in basalt fiber can not only improve the bending performance of the laminate on the one hand,the bending modulus and bending strength are improved.And,with the increase of the number of carbon fiber layers,the bending performance of the carbon fiber layer placed on the compression side of the three-point bending is stronger;On the other hand,the impact peak force of the laminate after the hybrid carbon fiber is reduced,but the energy absorption is increased and the hybrid Laminates combine the advantages of good carbon fiber energy absorption and high basalt fiber peak force.Carbon fiber placed on the impact side has less damage,less energy absorption,and higher peak force than carbon fiber placed on the back side.(5)Based on the self-optimization results and the best hybrid ratio of basalt fiber,the reinforced basalt-carbon hybrid laminate is applied to the automobile B pillar,and compared with the steel B pillar under three-point bending,low-speed impact,and static conditions.The hybrid composite B-pillar can reach the rigidity and strength of the steel B-pillar.The intrusion amount and speed of the head,chest,and crotch are smaller than those of the steel B-pillar.After replacement,the weight of the outer plate of the B-pillar is reduced by 55%,and the weight reduction effect is obvious.It proves that basalt fiber reinforced composites can be used for lightweight design of B pillar of automobiles.