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Acoustic emission (AE) technology provides a novel approach for studying the damage and fracture behavior of wood‐plastic composites (WPCs) during their application process. This method allows rapid and precise analysis of the mechanical properties of materials, which is a significant advancement for the emerging WPC industry. Hence, a blend of waste floor sanding powder (FSP) and rice husk (RH) reinforced recycled high‐density polyethylene (Re‐HDPE) was prepared by the extrusion method. The AE technique, scanning electron microscopy, and finite element method (FEM) were used to analyze the damage and fracture behavior of the composite materials under a three‐point bending test. The results indicated that the bearing capacity of RH/Re‐HDPE composites was slightly higher than that of FSP/Re‐HDPE composites. The AE technique can better illustrate the damage evolution and fracture process of composites and determine the damage degree and mode. Matrix cracking and deformation were more pronounced in the FSP/Re‐HDPE composites. Fiber breakage and delamination were more prominent in the RH/Re‐HDPE composites. In addition, repeated loading caused irreversible damage to the composite. The increase in temperature led to the attenuation of the AE signal and a decrease in matrix strength. However, when the temperature reached a certain point, the cumulative AE ringing count increased again because the higher temperature improved the fiber–matrix interface strength, which partially canceled out the negative effect. In addition, Abaqus was used for simulation analysis, and the running results coincided with the experimental value. Highlights: RH/Re‐HDPE and FSP/Re‐HDPE are sustainability and low‐cost composites.AE can determine the degree and mode of damage of WPC at different temperatures.The AE curves of RH/Re‐HDPE and FSP/Re‐HDPE all pass through four stages.Heating reduced the matrix strength and improved the interface strength of WPC.The results of FEM were consistent with the experimental results. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The damage and fracture of fiber reinforced polymer composites are vital constraints in their applications. To understand the mechanism of damage of wood fiber (WF) reinforced high density polyethylene (HDPE) composites, we used waste WF and recycled HDPE (Re-HDPE) as the raw materials and prepared high-filled WF/Re-HDPE composites via extrusion. The damage and fracture mode and failure mechanism of the composites with different WF contents (50%, 60%, and 70%) was studied under a three-point bending test by combining the acoustic emission (AE) technique and scanning electron microscope (SEM) analysis. The results show that AE technology can better assist in understanding the progress of damage and fracture process of WF/Re-HDPE composites, and determine the damage degree, damage accumulation, and damage mode. The damage and fracture process of the composites presents three main stages: the appearance of initial damage, damage accumulation, and destructive damage to fracture. The matrix deformation, fiber breakage, interface delamination, fiber-matrix debonding, fiber pull-out, and matrix cracking were the dominant modes for the damage of high-filled WF/Re-HDPE composites under bending load, and the AE signal changed in different damage stages and damage modes. In addition, the WF content and repeated loading had a significant influence on the composite's damage and fracture. The 50% and 60% WF/Re-HDPE composites produced irreversible damage when repeated load exceeded 75% of the maximum load, while 25% of the maximum load could cause irreversible damage for 70% WF/Re-HDPE composites. The damage was accumulated owing to repeated loading and the mechanical properties of the composites were seriously affected. [ABSTRACT FROM AUTHOR]

• Digital image (DI) can reflect wood-plastic composites (WPCs) apparent crack growth. • Finite element method does not reflect the late fracture process of WPCs well. • Acoustic emission (AE) can reflect the internal damage and crack growth of WPCs well. • The R-square of the crack growth model based on AE cumulative count of WPCs is 0.97. • Change trend of AE cumulative count highly agrees with the crack growth rate of WPCs. To evaluate non-destructive methods for the characterization of highly-filled wood-plastic composites (WPCs), current work investigates the damage and crack propagation of highly-filled WPCs during three-point bending using digital image correlation (DIC), acoustic emission (AE), and finite element method (FEM). Herein, DIC can assess crack propagation, whereas FEM cannot provide insights into the late fracture process. Furthermore, AE shows that the WPCs crack propagation rate is closely related to the AE signal. Especially it is highly consistent with the slope changes of the strain-cumulative ringing count curve, indicating that AE can accurately evaluate the damage and crack propagation evolution within a material. [ABSTRACT FROM AUTHOR]