Karuppannan Gopalraj Sankar, Kärki Timo
Fiber Composite Laboratory, Department of Mechanical Engineering, LUT University, P.O. Box 20, 53850 Lappeenranta, Finland.
Polymers (Basel). 2021 Sep 21;13(18):3192. doi: 10.3390/polym13183192.
Recycled carbon fibre-reinforced epoxy (rCF/EP) composites and recycled glass fibre-reinforced epoxy (rGF/EP) composites were numerically investigated to examine their mechanical properties, such as uniaxial tensile and impact resistance, using finite element (FE) methods. The recycled composites possess unidirectional, long and continuous fibre arrangements. A commercially available Abaqus/CAE software was used to perform an explicit non-linear analysis with a macroscale modelling approach, assuming the recycled composites as both homogenous and isotropic hardening. Five composite types were subjected to a numerical study based on the recycled fibre's volume fraction (40 and 60%) of rCF/EP and rGF/EP, along with (100%) fibreless cured epoxy samples. The materials were defined as elastoplastic with a continuum ductile damage (DUCTCRT) model. The experimental tensile test results were processed and calibrated as primary input data for the developed FE models. The numerical tensile results, maximum principal stress and logarithmic strain were validated with their respective experimental results. The stress-strain curves of both results possess a high accuracy, supporting the developed FE model. The numerical impact tests examined the von Mises stress distribution and found an exponential decrease in the stiffness of the composite types as their strength decreased, with the 60% rCF/EP sample being the stiffest. The model was sensitive to the mesh size, hammer velocity and simulation time step. Additionally, the total internal energy and plastic dissipation energy were measured, but were higher than the experimentally measured energies, as the FE models eliminated the defects from the recycled process, such as a poor fibre wettability to resin, fibre bundle formation in rCFs and char formation in rGFs. Overall, the developed FE models predicted the results for a defect-free rCF/EP and rGF/EP composite. Hence, the adopted modelling techniques can validate the experimental results of recycled composites with complex mechanical properties and damage behaviours in tensile and impact loading conditions.
采用有限元（FE）方法对回收碳纤维增强环氧树脂（rCF/EP）复合材料和回收玻璃纤维增强环氧树脂（rGF/EP）复合材料进行了数值研究，以考察它们的力学性能，如单轴拉伸性能和抗冲击性能。回收复合材料具有单向、长且连续的纤维排列方式。使用商用Abaqus/CAE软件，采用宏观尺度建模方法进行显式非线性分析，假设回收复合材料为均匀且各向同性强化材料。基于rCF/EP和rGF/EP回收纤维的体积分数（40%和60%）以及（100%）无纤维固化环氧树脂样品，对五种复合材料类型进行了数值研究。材料被定义为具有连续延性损伤（DUCTCRT）模型的弹塑性材料。将实验拉伸测试结果进行处理和校准，作为所开发有限元模型的主要输入数据。数值拉伸结果、最大主应力和对数应变与各自的实验结果进行了验证。两种结果的应力-应变曲线具有很高的精度，支持了所开发的有限元模型。数值冲击试验考察了von Mises应力分布，发现随着复合材料强度的降低，其刚度呈指数下降，其中60% rCF/EP样品最硬。该模型对网格尺寸、锤击速度和模拟时间步长敏感。此外，还测量了总内能和塑性耗散能，但由于有限元模型消除了回收过程中的缺陷，如纤维对树脂的润湿性差、rCF中纤维束的形成以及rGF中炭的形成，所以这些能量高于实验测量值。总体而言，所开发的有限元模型预测了无缺陷rCF/EP和rGF/EP复合材料的结果。因此，所采用的建模技术可以验证回收复合材料在拉伸和冲击载荷条件下具有复杂力学性能和损伤行为的实验结果。
