铝合金-碳纤维增强聚丙烯混合帽型梁热成形数值模拟

Numerical simulation of hot forming of aluminum-carbon fiber reinforced polypropylene hybrid hat-shaped rail

铝合金(Aluminum alloy,Al)-碳纤维增强聚丙烯(Carbon fiber reinforced polypropylene,CF/PP)混合材料通过热模压工艺可快速成形为车身薄壁构件,在汽车轻量化设计中应用前景广阔。然而,在热模压中Al主要以塑性变形为主,而CF/PP则以织物拉伸/剪切变形为主;此外,Al-CF/PP混合材料具有明显的热力耦合力学特性,为其数值模型的发展及热成形特性的研究带来了巨大挑战。本文首先通过热模压工艺制备8层(Al与CF/PP交替对称铺放)Al-CF/PP混合帽型梁试样,并采用X射线扫描断层(X-ray computed tomography,X-ray CT)手段对纤维夹角变化进行逐层表征。结果表明:Al-CF/PP中织物发生了明显的剪切变形;然后分别对Al片材和CF/PP片材在不同温度条件下开展单轴拉伸和偏轴拉伸实验,并构建了与温度相关的Al-CF/PP材料本构模型;在ABAQUS中构建了Al-CF/PP帽型梁的热模压有限元模型,仿真预测的纤维夹角变化与实验结果基本吻合;结果表明热模压过程中所有Al片材均出现了厚度减薄,CF/PP片材均经历了明显的剪切变形,Al-CF/PP层间材料则发生了显著的失效损伤。

Aluminum alloy(Al)-carbon fiber reinforced polypropylene(CF/PP) hybrid materials can be quickly formed into thin-walled components of the vehicle body by the hot press molding technology,and has broad application prospects in the lightweight design of automobiles.However,the Al mainly exhibits plastic deformation while the CF/PP mainly exhibits fabric tensile/shear deformations during the hot pressing process;In addition,the Al-CF/PP hybrid materials exhibit significant thermo-mechanical coupling characteristics,which bring huge challenges to numerical model developments and hot forming characteristic studies.The 8-layer(Al and CF/PP are alternately and symmetrically laid) Al-CF/PP hybrid hat-shaped rail specimen was prepared by the hot pressing technology,and the fiber angle variations were characterized through the X-ray computed tomography(X-ray CT)layer-by-layer,and the results indicate that the fabrics in Al-CF/PP undergo significant shear deformations;Then,the uniaxial and biaxial tensile experiments were conducted for Al sheets and CF/PP sheets under different temperature conditions,and the temperature-dependent material constitutive model of Al-CF/PP was constructed;And the hot press molding finite element model of the Al-CF/PP hat-shaped rail was developed in ABAQUS,and the predicted fiber angle variations by the simulation are basically consistent with the experimental results.The results indicate that all Al sheets occur thickness reductions,all CF/PP sheets undergo obvious shear deformations and interlayer materials between Al and CF/PP occur significant failure damages during the hot press molding process.