Strain and Damage Assessment of Treated and Untreated Luffa Mat Composite Using Acoustic Emission and Digital Image Correlation

ABSTRACT

In this work, acoustic emission and digital image correlation were applied to three different composites reinforced with treated (2% and 5% NaOH) and untreated luffa fibers during tensile testing, to follow the evolution of the different damage modes and determine strains and Poisson’s ratio. The tensile test results showed that alkaline treatment of 5% improved Young’s modulus and tensile strength. In comparison, the 2% treatment showed the most outstanding improvements in mechanical properties. The K-means clustering methodology identified four types of damage: matrix cracking, fiber pull-out, delamination, and fiber breaking. The 5% treated composite had lower cumulative energy and hits than the untreated and 2% treated composites, implying that the T5% composite suffered less damage. The DIC results showed that the longitudinal strains found by the extensometer are very approximate to those found by DIC, this technique also allows us to find the transverse strains of the composites UT (0.324), T2% (0.295), and T5% (0.207%). It is shown that the 5% alkaline treatment leads to the decrease of Poisson’s ratio (0.2378) compared to 2% treated (0.3113) and untreated (0.3120) composites. Based on AE, DIC results, and mechanical properties, the T5% composite is the most successful.

摘要

在这项工作中, 在拉伸试验期间, 将声发射和数字图像相关应用于三种不同的复合材料, 用处理过的 (2%和5%NaOH) 和未处理的丝瓜纤维增强, 以跟踪不同损伤模式的演变, 并确定应变和泊松比. 拉伸试验结果表明, 5%的碱处理提高了杨氏模量和拉伸强度. 相比之下, 2%的处理在机械性能方面表现出最显著的改善. K-均值聚类方法确定了四种损伤类型:基体开裂, 纤维拉拔, 分层和纤维断裂. 与未处理和2%处理的复合材料相比, 5%处理的复合材料的累积能量和命中率更低, 这意味着T5%的复合材料受到的损伤更小. DIC结果表明, 引伸计测得的纵向应变与DIC测得的纵向应变非常接近, 该技术还允许我们测定复合材料的横向应变UT (0.324%), T2% (0.295) 和T5% (0.207%). 结果表明, 与2%的处理 (0.3113) 和未处理 (0.3120) 复合材料相比, 5%的碱处理导致泊松比 (0.2378) 降低. 基于AE, DIC结果和机械性能, T5%复合材料是最成功的.

KEYWORDS:

• Luffa fiber/epoxy composite
• acoustic emission (AE)
• damage
• digital image correlation (DIC)
• strains
• poisson’s ratio

关键词:

• 丝瓜纤维/环氧树脂复合材料
• 声发射
• 损坏
• 数字图像相关
• 菌株
• 泊松比

Highlights

• Alkaline treatment’s effect on the mechanical performance and damage of luffa/epoxy laminates was studied.

• Identified the cumulative energy and number of hits and evaluated the damage modes caused during tensile testing by acoustic emission (AE).

• The damage mentioned with acoustic emission (AE) was identified by scanning electron microscopy (SEM) analysis.

• Poisson’s ratio, longitudinal, and transverse strain fields analysis of treated and untreated natural fiber reinforced composite was performed using digital image correlation (DIC).

Acknowledgments

The authors would like to thank the Laboratoire de Mécanique et Éco-Matériaux (LMEM) of the department of mechanical engineering, Université du Québec à Trois-Rivières, Quebec, Canada.

Disclosure statement

No potential conflict of interest was reported by the author(s).