Study on properties of bamboo fiber composites with different fiber morphologies based on vacuum-assisted resin transfer molding
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摘要: 为探索不同形态竹纤维(BF)对真空辅助树脂传递模塑成型(VARTM)过程中环氧树脂(EP)浸渍纤维效果及BF/EP复合材料性能的影响,采用经机械碾压2次、3次、4次得到3种不同形态的BF(BF-2、BF-3和BF-4),通过湿法层铺工艺将BF制作成竹纤维毡(BFM),再利用VARTM制备出纤维含量为45wt%的复合材料BF-2/EP、BF-3/EP和BF-4/EP。采用ESEM、超景深显微镜、力学试验机、TG、DMA和Micro-CT对BF、BFM和BF/EP复合材料性能进行表征。研究结果表明:随纤维长度减小、纤维分离度增加,导致湿法层铺成型的BFM蓬松度降低,树脂注射难度增大,BFM-4在树脂注射时会发生纤维堆积,BF-3/EP复合材料吸水率最低。BF-2的长度较长、分离度低,虽保持了BF束自身结构与性能,但是与树脂界面结合性能差,长度与分离度适中的BF-3制备的复合材料力学性能最佳,弯曲强度、弹性模量、剪切强度和冲击韧性分别为97.90 MPa、7.2 GPa、17.01 MPa和8.11 kJ/m2。BF加速了BF/EP复合材料的热解,BF-4/EP复合材料因BF-4中半纤维素含量少,热解温度有所提高。BF能够提升EP的刚性,BF-3与树脂界面结合最佳,孔隙体积占比仅为0.04%,BF-3/EP复合材料储能模量最大值高达5198 MPa。使用VARTM制备BF/EP复合材料时,BF尺寸与分离度是影响纤维与树脂界面结合性能和BF/EP复合材料性能的关键因素。Abstract: The aim of this research was to explore the effect of different morphologies of bamboo fiber (BF) on epoxy resin (EP) impregnation in vacuum-assisted resin transfer molding (VARTM) process and the properties of BF/EP composites. Three types of BF with different morphologies (BF-2, BF-3 and BF-4) were obtained by mechanical rolling with 2, 3 and 4 times, respectively. The BF were made into bamboo fiber mat (BFM) by wet layering process, and then produced into BF-2/EP, BF-3/EP and BF-4/EP composites with fiber content of 45wt% by VARTM. The properties of BF, BFMs and BF/EP composites were characterized with ESEM, ultra-depth-of-field microscope, mechanical testing machine, TG, DMA and micro-CT. The results show that the fluffy degree of BFMs by wet layering decreases and the difficulty of resin injection increases when the fiber length decreases and the fiber separation increases. The fiber accumulation occurs during resin injection of BFM-4, and BF-3/EP composite has the lowest water absorption. The BF-2 with longer length and lower dispersion can easily lead to poor interfacial bonding with resin, although it can maintain the structure and properties of BF. The mechanical properties of the composite prepared by BF-3 with moderate length and separation are the best, and the flexural strength, flexural modulus, shear strength and impact toughness are 97.90 MPa, 7.2 GPa, 17.01 MPa and 8.11 kJ/m2, respectively. BF accelerates the pyrolysis of BF/EP composites. The BF-4/EP composite has a higher pyrolysis temperature because BF-4 has lower hemicellulose content compared with other BF. BF can improve the rigidity of EP. The interface bonding between BF-3 and resin is the best, and the proportion of pores volume is only 0.04%. The maximum storage modulus of BF-3/EP composites is 5198 MPa. When BF/EP composites are prepared by VARTM, the appropriate BF size and separation degree are the key factors that affect the interfacial bonding and properties.
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Key words:
- bamboo fiber /
- wet layering process /
- VARTM /
- fiber morphology /
- bamboo fiber composites
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表 1 不同纤维形态竹纤维(BF)的尺寸
Table 1. Size of bamboo fiber (BF) with different morphologies
Material Length/cm Diameter/mm Aspect ratio Average Range Average Range BF-2 23.97 (7.04) 11.20-41.00 0.50 (0.24) 0.19-1.14 479 BF-3 3.43 (0.75) 1.94-5.37 0.37 (0.21) 0.10-1.17 93 BF-4 2.54 (1.03) 1.28-6.02 0.25 (0.12) 0.13-0.55 102 Note: Standard deviation in brackets. 表 2 不同纤维形态BF/EP复合材料密度
Table 2. Densities of BF/EP composites prepared with different fiber morphologies
BF/EP composite EP BF-2/EP BF-3/EP BF-4/EP Density/(g·cm−3) 1.210 1.245 1.259 1.251 -
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