Metal/CFRP hybrid thin-walled structures combine low-density and high-strength carbon fibre reinforced plastics (CFRP) with low-cost and stable failure form aluminium, which have drawn increasing attention in the transportation industry. A theoretical model was developed to predict the average crushing force of a hybrid multicell under axial compression. The model captures the main energy dissipation mechanism of the hybrid tube under axial compression, and the average crushing force is determined by a quasi-static compression test. The obtained results show that the average crushing force predicted by the theoretical model is in good agreement with the experimental results. However, the geometry size and configuration of multicell thin-walled structures have important effects on crashworthiness. Therefore, it is necessary to study the parametrization of hybrid multicell tubes. First, the simulation model of the multicell tube is established, and quasi-static experiments verify its accuracy. Second, finite element analysis was used to compare the effects of the geometric size of the cell and the multicell structure of different configurations on the energy absorption characteristics. It is clear that with the increase in the thickness of the large aluminium tube, the specific energy absorption (SEA) and crush force efficiency (CFE) both show an upward trend. In addition, with the increase in the ply number of the CFRP tubes, the SEA also shows a minor monotonic increasing trend. Finally, various hybrid tubes with different configurations are designed, and the C-C4-AL tube (the aluminium tube surrounded by four small-size CFRP tubes being placed inside a CFRP tube.) configuration has the most significant energy absorption (EA) and peak crushing force (PCF).

Carbon fiber reinforced plastics (CFRP) have the advantages of being light weight and having high strength, which means that they can be used to effectively realize the lightweight design of automobile components. In this paper, the original steel crossbeam of the twist beam rear axle of a passenger car is replaced by CFRP, and then the cross-section improvement design is implemented. The ply stacking sequence of the CFRP crossbeam is also optimized to enhance its structural performance. Considering the multiscale characteristics of CFRP, a multiscale analysis model of the CFRP crossbeam is established, and the effects of microscopic, mesoscopic and macroscopic structures and material parameters on the stiffness, maximum stress and vibration characteristics of the CFRP crossbeam are discussed. The multiscale propagation law of the random-interval mixed uncertain parameters of the CFRP crossbeam is studied by using the multiscale model. On this basis, the reliability optimization design model of CFRP crossbeam considering multiscale uncertainty is established, and the multiscale reliability optimization method of the CFRP crossbeam of twist beam axle based on approximate models, Monte Carlo simulation (MCS) and intelligent optimization algorithms is studied. The optimization method of the combination of the ply stacking sequence optimization and the multiscale reliability optimization of the CFRP structure is proposed, the mass is reduced by 46.96% while ensuring reliability, and other structural performances are improved. Meanwhile, a theoretical research basis and technical support for the design and development of CFRP suspension components are provided, and the application of CFRP in the automobile field is promoted.

To meet the lightweight design requirements of the control arm, an automobile suspension control arm with a carbon fiber reinforced plastics (CFRP)–aluminum foam sandwich structure was proposed, and the structure optimization design of the CFRP panel was performed. The accuracy of the cellular pore model of aluminum foam hexahedron was verified by the quasi-static compression test of aluminum foam. The performance parameters of carbon fiber reinforced plastics were obtained by the mechanical property test of CFRP. A suspension control arm composed of a CFRP–aluminum foam sandwich structure body and an aluminum alloy connector was designed, and the adhesive-bolted hybrid joint was used to connect the two. Based on this, the finite element model of the control arm of the CFRP–aluminum foam sandwich structure was established. The porosity of aluminum foam in the sandwich was 55%. The multi-level optimization method was used to optimize the layering of the CFRP panels. Free size optimization was used to obtain the layered shape of CFRP under four classical ply angles, during which the mass of the panel was reduced while its stiffness improved. Based on the regularization of the CFRP layer, the ply thickness was discretized into manufacturing thickness by size optimization. Simultaneously, the number of layers of the panel was determined, and its mass was further reduced as the stiffness of the composite material is also dependent on the ply angle. Therefore, the arrangement order of the classical ply angle was obtained by ply stacking sequence optimization, further improving the panel stiffness. The results show that compared with the steel control arm, the mass of the optimized sandwich structure control arm was reduced by 26%. Simultaneously, the maximum stress at the foam aluminum sandwich was reduced from 225.6 MPa before optimization to 151.2 MPa. The safety factor and the failure coefficient of the CFRP panel after optimization were 1.1 and 0.81, respectively, both meeting the strength requirements. From the stiffness perspective, the longitudinal stiffness of the optimized control arm increased by 54.7% compared to the initial control arm of the sandwich structure, 103.2% compared to the steel control arm, and the lateral stiffness increased by 37% compared to the initial control arm of the sandwich structure and 56% compared to the steel control arm, respectively. Thus, the stiffness improvement effect was obvious. The first-order modal frequency of the optimized control arm was 785 Hz, 573.1 Hz higher than that of the steel control arm, and the vibration performance was significantly improved.

Due to the lightweight and excellent mechanical property, carbon fiber reinforced plastics (CFRP) are widely applied in vehicle components. In this paper, a reliability-based multi-level optimization method is proposed for the lightweight design of the crossbeam. The CFRP specimens were first fabricated to acquire the mechanical parameters. Then, based on the equal stiffness theory, CFRP was used to replace the material of steel beam and the section was improved. The optimal ply scheme of CFRP beams was determined by ply optimization. On this basis, considering the uncertainty of the ply thickness and the ply angle, the reliability-based multi-objective optimization of CFRP beams was carried out. Finally, entropy weighted grey relational analysis (GRA) was used to determine the lightweight scheme of the crossbeam. The results show that the crossbeam mass is reduced by 59.85 % under the premise of ensuring structural performance and high reliability after multi-level optimization.

The lightweight design of the control arm, as the unsprung mass of the automobile, could effectively improve the fuel economy and driving performance. The material of a steel control arm of the automotive suspension was replaced with carbon fiber-reinforced plastic (CFRP) because of its excellent mechanical properties and good designability. Additionally, considering that the design parameters of the CFRP control arm in the manufacturing process will produce inevitable errors, resulting in random fluctuations in structural performance, the uncertainty of the design parameters is considered in the design process to stimulate the excellent mechanical properties of CFRP. A multilevel optimization method including ply optimization and multiobjective reliability optimization was proposed to optimize the CFRP control arm in this study. First, the mechanical parameters of the materials were obtained through the mechanical property test of CFRP laminates. Second, ply optimization, including free-size optimization, size optimization and layer sequence optimization, was performed to obtain an optimum ply scheme for the CFRP control arm. Furthermore, considering the uncertainties in the ply angle and thickness, reliability optimization of the CFRP control arm was conducted to reduce the influence of parameter uncertainty on the optimization results. The results show that after reliability optimization, the standard deviation of each performance index of the CFRP control arm is reduced and that the reliability of the longitudinal stiffness and lateral stiffness are increased by 32.80 and 27.12%, respectively. The reliability of the mechanical properties of the control arm is greatly improved. Compared with the original steel control arm, the mass of the optimized CFRP control arm is reduced by 38.34% under the premise of ensuring the high reliability of the optimization results, which provides reference value for the optimization design of CFRP structures.

为提高混凝土搅拌运输车的燃油经济性和操纵稳定性,本文以混凝土搅拌车车架为例,基于混凝土搅拌车车架有限元模型,对混凝土搅拌车车架的结构性能及灵敏度进行分析.选取车辆满载弯曲、扭转、爬坡、制动、转弯5种工况进行车架强度分析,并分析了车架的自由模态.在模态分析基础上,以一阶扭转模态为约束,以车架质量最小为优化目标,建立车架灵敏度分析模型,并将车架灵敏度模型提交OptiStruct求解器运算,得到变量厚度对车架模态及车架质量灵敏度的影响.研究结果表明,车架质量灵敏度最高的4个变量分别是纵梁、内纵梁、横梁6和前台,而副纵梁和横梁2两个变量模态灵敏度较高,质量灵敏度相对较低;纵梁、内纵梁、横梁6和前台4个变量质量灵敏度较高,而模态灵敏度较低.该研究为混凝土搅拌车车架轻量化设计提供技术参考.

碳纤维增强复合材料(CFRP)具有轻质高强的特点,本文中基于抗撞性要求将某乘用车保险杠原钢制防撞梁替换为CFRP,并进行铺层优化设计.首先对CFRP层合板进行力学性能试验以获得材料参数,并通过三点弯曲仿真试验验证其准确性,然后根据等刚度设计原理,确定CFRP防撞梁的厚度,并通过保险杠低速碰撞有限元仿真对比分析两种材料防撞梁的抗撞性能.在此基础上,以质量、比吸能、最大侵入量和碰撞力峰值为目标,采用熵权TOPSIS方法对CFRP防撞梁进行铺层优化,确定出最优铺层方案.结果表明,在保证抗撞性能要求的条件下,优化后的CFRP防撞梁比原钢制防撞梁减轻了76.82％.

Thin-walled tubes have gained wide applications in aerospace, automobile and other engineering fields due to their excellent energy absorption and lightweight properties. In this study, a novel method of entropy-weighted TOPSIS was adopted to study the energy absorption characteristics of a thin-walled circular tube under axial crushing. Three types of thin-walled circular tubes, namely, aluminum (Al) tubes, carbon-fiber-reinforced plastics (CFRP) tubes and CFRP-Al hybrid thin-walled tubes, were fabricated. Quasi-static axial crushing tests were then carried out for these specimens, and their failure modes and energy absorption performance were analyzed. The CFRP material parameters were obtained through tensile, compression and in-plane shear tests of CFRP laminates. The finite element models for the quasi-static axial crushing of these three types of circular tubes were established. The accuracy of the finite element models was verified by comparing the simulation results with the test results. On this basis, the effects of the geometric dimension and ply parameters of a CFRP-Al hybrid thin-walled circular tube on the axial crushing energy absorption characteristics were studied based on an orthogonal design and entropy-weighted TOPSIS method. The results showed that Al tube thickness, CFRP ply thickness and orientation have great effect on the energy absorption performance of a CFRP-Al hybrid thin-walled circular tube, whereas the tube diameter and length have little effect. The energy absorption capability of a CFRP-Al hybrid tube can be improved by increasing the thickness of the Al tube and the CFRP tube as well as the number of ±45° plies.