Acoustic Emission-Based Study to Characterize the Crack Initiation Point of Wood Fiber/HDPE Composites.

Yong Guo,Yuxia Chen,Shiliu Zhu,Dagang Li,Dian Liu

doi:10.3390/polym11040701

Yong Guo, Yuxia Chen + Show 3 more

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https://doi.org/10.3390/polym11040701

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Abstract

The crack initiation point can be regarded as a sign of composite failure and plays a vital role in the evaluation of fracture toughness. Wood-plastic composites (WPCs) are viscoelastic materials and the evaluation of fracture mechanism and toughness has a great significance in their applications. Therefore, we used the acoustic emission (AE) technique to measure the crack initiation point of the WPCs and evaluate their fracture toughness. The results show that the novel AE-based methods were more effective than the conventional standard methods for characterization of the crack initiation point. Using the relationship of cumulative AE events with time and load, the critical failure load was quickly determined, and then the critical stress intensity factor and fracture toughness were calculated. The fracture toughness of the WPCs increased with an increase in the wood fiber content.

Highlights

Fracture toughness is an inherent property of a material which depends on its composition and structure and can be employed to characterize the ability of a material to resist crack propagation [1,2].The fracture behavior of polymer composites consists of processes starting from microscopic damage to crack initiation and propagation, leading to complete failure
acoustic emission (AE) signal does not utilize the P–V curve and is not affected by its nonlinearity. These results suggest that the use of AE technology to determine the critical load and calculate the fracture toughness has a clear physical meaning which can reflect the true mechanical properties and fracture resistance of the
The fracture toughness of wood-plastic composites (WPCs) increased with the increasing wood fiber content, and the variable coefficient of the three groups of experiments was small. These results indicate that the fiber-supporting effect of the fiber in the WPCs was enhanced with the increasing wood fiber content, and the ability to resist fracture increased

Summary

Introduction

Fracture toughness is an inherent property of a material which depends on its composition and structure and can be employed to characterize the ability of a material to resist crack propagation [1,2].The fracture behavior of polymer composites consists of processes starting from microscopic damage to crack initiation and propagation, leading to complete failure. The preferred structure can be obtained by adjustment of the raw material (including the additives like coupling agent), formulation design, molding, and processing techniques, leading to enhancement of the fracture toughness of the polymer composites and improvement of the bearing capacity of the cracked structural components. Stress analysis highlights that the critical state of crack propagation is determined by the critical stress intensity factor (KI ), while the energy analysis emphasizes the critical strain energy release rate (GIc ) when the crack propagates [1]. These are primarily used as the fracture failure criteria for linear elastic fracture mechanics. The wood-plastic composites (WPCs) are nonlinear viscoelastic materials [3,4], and still, no uniform standards exist for testing their fracture toughness

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