Influence of Alkali Treatment and Stacking Sequence on Mechanical, Physical, and Thermal Characteristics of Hemp and Palmyra-Reinforced Hybrid Composites

ABSTRACT

Natural fibers are available in low cost, easily renewable and they are rich in cellulose. As the natural fibers possess impurities over the surface, poor wettability and interfacial bonding are the main drawbacks encountered during fabrication process. In the current research work, hemp (H) and palmyra (P) fibers were treated with different sodium hydroxide (NaOH) concentrations (2%, 4%, 6%, and 8%) for 5 hrat room temperature. The influence of stacking sequence (HHPPHH, HPHPHP and PPHHPP) and surface modification and on physical, mechanical, and thermal properties of hemp and palmyra fiber-reinforced epoxy composites were investigated with a 30 wt.% of fiber loading. The attributes such as water absorption, density, tensile properties, flexural properties, impact energy, hardness, and thermal conductivity were examined. From the experimental results, the 6% NaOH-treated composites compared with untreated fiber composites disclosed an increase of 19.34% for tensile strength, 16.77% for flexural strength, and 12.35% for hardness with stacking sequence of PPHHPP. The experimental thermal conductivity results show that there is a significant decrease in values after NaOH treatment of hybrid composites. The surface morphology of the untreated, treated reinforcements, and fracture surface of the tensile-tested hybrid composite specimens were examined by scanning electronic microscope.

摘要

天然纤维成本低，易于可再生，并且富含纤维素. 由于天然纤维表面含有杂质，润湿性差和界面结合是制造过程中遇到的主要缺点. 在目前的研究工作中，大麻（H）和棕榈（P）纤维在室温下用不同浓度的氢氧化钠（2%、4%、6%和8%）处理5小时. 研究了堆叠顺序（HHPPHH、HPHPHP和PPHHPP）和表面改性对纤维负载量为30 wt.%的大麻和棕榈纤维增强环氧树脂复合材料的物理、机械和热性能的影响. 测试了吸水性、密度、拉伸性能、弯曲性能、冲击能、硬度和热导率等属性. 从实验结果来看，与未处理的纤维复合材料相比，6%NaOH处理的复合材料的拉伸强度增加了19.34%，弯曲强度增加了16.77%，硬度增加了12.35%. 实验热导率结果表明，经过NaOH处理后，杂化复合材料的热导率值显著降低. 通过扫描电子显微镜检查了未处理、处理的增强材料的表面形态和拉伸测试的混合复合材料试样的断裂表面.

KEYWORDS:

• Alkaline treatment
• hybrid composite
• mechanical properties
• stacking sequence
• thermal conductivity

关键词:

• 碱性处理
• 混合复合材料
• 机械性能
• 堆叠顺序
• 导热系数

Highlights

• Preparation of hybrid composite materials reinforced with hemp and palmyra fibers.

• A comprehensive discussion on effect of alkali treatment on physical, mechanical, and thermal properties of hemp and palmyra fiber-reinforced composites.

• Improvement of mechanical and thermal properties of the elaborated materials.

Disclosure statement

No potential conflict of interest was reported by the authors.