Damage Modes Research Articles

Acoustic emission characteristics of waste fiber‐reinforced recycled high‐density polyethylene composites under damage conditions

AbstractAcoustic 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.

Tube-to-tube impact wear damage mechanism and nonlinear ultrasonic detection method of alloy 690 tubes

Tube-to-tube impact wear is one of the prime reasons that cause the failure of alloy 690 tubes in nuclear steam generators. Therefore, it is of great importance to study the tube-to-tube impact wear damage mechanism and damage detection method of alloy 690 tubes. In this paper, the tube-to-tube impact wear experiments are conducted on alloy 690 tubes under different impact loads and cycle numbers. The impact wear damage mechanism of alloy 690 tubes is revealed by analyzing the macro and micro morphologies as well as metallographic structures of the wear scar. A nonlinear ultrasonic wave mixing (NUWM) method is proposed for damage detection of alloy 690 tubes. A detection device is developed to implement the NUWM method. A nonlinear modulation index is used to assess the damage degree of alloy 690 tubes. Experimental results indicate that, for an impact load lower than 100 N and a cycle number smaller than 2 × 105, the tube damage is mainly in forms of the surface plastic deformation and delamination. For a higher impact load or a larger cycle number, the fatigue cracking is the main tube damage mode. With increasing the impact load or cycle number, the tube damage degree increases, leading to an increase of the nonlinear modulation index. Therefore, the NUWM method is effective for detecting and assessing the damage of alloy 690 tubes.

Research on the Shear Performance of Cold-Formed Thin-Walled Steel-Glued Laminated Wood Composite Beams

This paper proposes a new type of composite box beam combined with cold-formed thin-walled steel and glued laminated timber to develop green building structures while improving the load-carrying capacity of a single steel girder and glued timber girder. Two composite beams composed of laminated timber and Q235 cold-formed thin-walled steel were designed and fabricated. Then, the shear performance test with quadratic loading was carried out to analyze the load carrying capacity, damage modes, and deformation characteristics of the test beams, as well as their influencing factors. Subsequently, a finite element model of the composite beam was established, and the loading mode was the same as that of the test to further study the parameters affecting the shear performance of the composite beam. The results of the study indicate that steel and glued timber in composite beams connected by adhesive bonding can work and deform together under load and each give full play to its material properties, especially the composite beams, which exhibit higher shear strength than a steel or timber beam. The effects of parameters such as steel cross-sectional area, shear span ratio, steel skeleton form, and steel cross-sectional strength on the shear capacity of the composite beams were observed, among which the shear span ratio had the greatest effect on the shear capacity of the composite beams. The shear capacity decreased by 14.3% and 19.5% when the shear span ratio was increased from 1.5 to 2.0 and 2.5, respectively. The shear capacity of the combined composite beams increased by 10.6%, 6.3%, and 5.8% when the thickness was increased from 1.5 mm to 2.0 mm, 2.5 mm, and 3.0 mm, respectively. When the combination of the steel cross-section was a box beam, the overall shear-bearing capacity could be increased by 12% compared with the “I” type composite beam, although its shear stiffness was close to that of the “I” section composite beam.

A conjugated bond-based peridynamic model for laminated composite materials

The bond-based peridynamic (BB-PD) theory is inadequate in describing the four independent engineering material constants of composite lamina, which results in fixed values its Poisson's ratios and shear moduli. This study presents a novel lamina conjugated BB-PD model encompasses not only the fiber bond and matrix bond, but also the transverse bond and conjugated bond pair. By defining these four basic PD bonds, the improved conjugated BB-PD model can overcome the restriction of material properties. The determination of the four basic PD micro-modulus parameters is achieved through the utilization of the equivalent relationship of strain energy density. In addition, the lamina conjugated BB-PD model is extended to deal with composite laminates with different stacking sequences. The present study validates the accuracy and applicability of the conjugated BB-PD model for composite materials by conducting simulations of the elastic deformation and progressive damage behavior of unidirectional laminae and laminates. Moreover, the proposed model provides an elucidation of the damage modes and failure mechanisms of laminated composite materials subjected to uniaxial loading.

Experimental and numerical research on the analysis methods for buckling and post-buckling of inclined stiffened panel under shear load

The purpose of this paper is to investigate the buckling and post-buckling behavior of inclined stiffened composite panels under shear load. Two types of stiffened composite panels were manufactured and tested. The buckling load, ultimate load and other required structural properties of the inclined stiffened composite panels were obtained. The test results show that the failure load of the two types of panels are 5.79 times and 11.2 times of the buckling load, respectively, indicating that such inclined stiffened panels have a large post-buckling capacity. The damage modes of the panel are tearing around the skin near the clamps and debonding of the stringers from the skin. The combination of Hashin failure criterion, Cohesive model and nonlinear connection of clamp was used to conduct finite element modeling, which effectively predicts the buckling, post-buckling and damage modes of the structure. The buckling and post-buckling behavior of stiffened panels with different stinger configurations were discussed based on finite element analysis. The results show that when the initial buckling occurs between the stringers, the buckling and failure load of the stiffened panel become larger as the equivalent skin thickness between the stringers become larger. The research in this paper can provide reference for aircraft structural design.

Temperature dependence of mechanical properties and damage evolution of hot dry rocks under rapid cooling

Understanding the differences in mechanical properties and damage characteristics of granitoid under high temperatures is crucial for exploring deep geothermal resources. This study analyzes the evolution of the acoustic emission (AE) characteristics and mechanical parameters of granodiorite and granite after heating and water cooling by uniaxial compression and variable-angle shear tests under different temperature gradients. We identify their changes in mesostructure and mineral composition with electron probe microanalysis and scanning electron microscopy. Results show that these two hot dry rocks have similar diagenetic minerals and microstructure, but show significantly different mechanical and acoustic characteristics, and even opposing evolution trends in a certain temperature range. At the temperatures ranging from 100 °C to 500 °C, the compressive and shear mechanical properties of granodiorite switch repeatedly between weakening and strengthening, and those of granite show a continuous weakening trend. At 600 °C, both rocks exhibit a deterioration of mechanical properties. The damage mode of granite is characterized by initiating at low stress, exponential evolutionary activity, and intensified energy release. In contrast, granodiorite exhibits the characteristics of initiating at high stress, volatile evolutionary activity, and intermittent energy release, due to its more stable microstructure and fewer thermal defects compared to granite. As the temperature increases, the initiation and propagation of secondary cracks in granodiorite are suppressed to a certain extent, and the seismicity and brittleness are enhanced. The subtle differences in grain size, microscopic heterogeneity, and mineral composition of the two hot dry rocks determine the different acoustic-mechanical characteristics under heating and cooling, and the evolution trends with temperature. These findings are of great significance for the scientific and efficient construction of rock mass engineering by rationally utilizing different rock strata properties.

Damage characterization and microscopic mechanism of steel slag-cemented paste backfill under uniaxial compression

The utilization of steel slag-cemented iron tailings for preparing mine backfill materials can effectively consume industrial solid waste generated from steel production and significantly reduce backfilling costs. The study analyzed the influence and mechanisms of steel slag (SS) content on the mechanical damage characterization of steel slag-cemented paste backfill (SS-CPB) through uniaxial compressive strength (UCS) tests and microscopic testing methods such as X-ray diffraction (XRD) and a scanning electron microscope (SEM). The engineering applicability and economic feasibility of the material were evaluated. The main conclusions were as follows: (1) With the increase of SS content, the strength of SS-CPB first increases and then decreases, with the highest strength observed at a 10% SS content. (2) The inclusion of SS in SS-CPB leads to higher peak strain and post-peak strength, demonstrating significant plastic deformation characteristics. (3) When the SS content increases from 30% to 60%, the Ca(OH)2 content in SS-CPB hydration products decreases by 20.2%, and internal micropores increase. (4) When the SS content reaches 30%, the damage mode of SS-CPB changes from purely splitting failure to a plastic combination of splitting and shear failure. These research findings provide a new application model for the collaborative utilization of steel slag, tailings, and other solid wastes.

Cross-scale data-based damage identification of CFRP laminates using acoustic emission and deep learning

Damage characterization of laminated composites has undergone extensive research, leading to the development of several damage models that incorporate acoustic emission (AE). However, feature extraction from AE data will cause the loss of certain information in the construction of damage models, which manifestly falls short of feature analysis in the frequency domain. In this study, a novel cross-scale data-based damage identification methodology for carbon fiber-reinforced polymer (CFRP) laminates is proposed by combining the AE technique with deep learning approach. Elementary experiments involved with single damage mode are designed to avoid blind inference, and the cross-scale correlation of AE features between component materials and CFRP laminates is established by wavelet packet transform (WPT). The time–frequency spectrums of AE signals of CFRP laminates by continuous wavelet transform (CWT), which adequately preserve the frequency domain information, are adopted as inputs to the convolutional neural network (CNN) model. The proposed methodology achieves a high accuracy of 96.3% in detecting and classifying damage modes (i.e., matrix cracking, matrix/fiber debonding, and fiber breakage) in unidirectional CFRP laminates.

Enhancing performance of hybrid carbon/glass textile-reinforced composites: Theoretical prediction and experimental characterization

Multi-scale analysis is of great interest to calculate the final response of hybrid textile-reinforced carbon/glass epoxy (TRCG) composites based on micromechanical tests and geometrical properties. A novel multi-scale model and experiments are utilized to enhance the performance of TRCG composites. Experiments are conducted on TR glass/epoxy, carbon/epoxy, and 7 hybrid TRCGs. The model integrated viscoplastic-material and nonlinear-geometry properties and damage initiation-propagation mechanisms to address stress–strain curves that incline with experimental data with less than 11 % deviation. The microscopic scanning is utilized to study the fracture mechanisms and delaminated areas of specimens. The tensile curves and delaminated-area of TRCG composites are affected by the local glass/carbon mixed ratio and stacking arrangement. Alternative arrangement, H3:[G/C/G/C]S, provides better mechanical properties and a lower isotropy-mismatch effect and delaminated area compared to H1:[2G/2C]S, and H2:[2C/2G]S, and H4:[C/G/C/G]S. H5:[G/2C/G/C]S with the highest possible properties provides the lowest delaminated-area, because of bridging-glass layers to mitigate brittleness and primary failures of carbon, yet is low enough to restrict premature delamination. H6:[4G/2C/4G] and H7:[2G/2C/G]s with high isotropy-mismatch hustle premature failure and fail to deliver expected performance. The fracture mechanisms of TRCG composites are utilized to propose two 10-layer composites with alternative arrangements, which they are experimented afterwards to study the damage modes. It is concluded that H8:[G/C/G/C/G] laminate has the highest mechanical properties and energy absorption amongst TRCG composites. In which with highest integrity, the delaminated area is limited to the vicinity of fracture zone.

Different effects of interfacial properties on the tensile and compressive damage mechanisms of 3D woven composites: Multiscale damage model and numerical comparative study

A multiscale damage model is proposed based on a micro-mesoscale bridging model and a multiscale kinking model, which can predict the damage development processes of 3D woven composites (3DWCs) under different loading conditions using only few material parameters. At the microscale, the various mesoscopic damage modes of yarns, including tensile fiber breakage, compressive fiber kinking and transverse inter-fiber crack, can be simply divided into matrix- and fiber-dominated damage. Using this multiscale damage model, a numerical comparative study is conducted to investigate the effect of interfacial properties on the mechanical performances and damage mechanism of 3DWCs. The numerical results indicate that the interfacial properties exhibit different effects on the tensile and compressive strengths and damage mechanisms of 3DWCs. The interaction of different damage modes controls the overall trend of the tensile strength of 3DWCs. There is an optimum point for the tensile strength of 3DWCs at different interfacial fracture toughness. Beyond the optimum point, the tensile strength of 3DWCs is negatively correlated with interfacial properties. Unlike the tensile loading case, the better the interfacial properties, the later fiber kinking occurs, resulting in higher compressive strength of 3DWCs.

Influence of cyclic loading on lightweight self-compacting concrete double-skin tubular columns

Self-compacting concrete (SCC) has gained prominence in recent decades due to its inherent qualities, particularly its ability to compact autonomously. SCC proves invaluable in scenarios where traditional compaction is challenging due to placement conditions or the presence of close space reinforcement. This study focuses on evaluating the structural performance of lightweight self-compacting concrete (LWSCC) columns confined with glass fiber-reinforced polymer (GFRP) and steel tube (ST) subjected to cyclic loading. The LWSCC columns, denoted as LWSTC, are designed with inner steel tubes and outer GFRP tubes, imparting corrosion resistance and reduced weight alongside enhanced ductility. Through quasi-static loading, five fabricated LWSTC columns were subjected to assess their structural response under dynamic effects. The investigation delves into three key variables: axial load ratio, reinforcement ratio, and the replacement ratio of coarse lightweight expanded clay aggregate (LECA) in the fabricated LWSTC columns. A comprehensive analysis of various parameters, including skeleton curves, ductility, hysteretic cycles, damage modes, dissipation of energy capacity, stiffness behavior, strain spreading, and strength reduction, was conducted on the LWSTC columns. The findings reveal that the replacement of LECA with natural aggregates has an insignificant impact, whereas varying the axial load ratio significantly influences the structural behavior of LWSTC. Notably, LWSTC exhibits a remarkable 121% higher horizontal load capacity compared to counterparts using natural aggregate. Furthermore, LWSTC demonstrates superior axial strength and enhanced capability for energy dissipation.

Study on post-fire resistance of ceramsite foamed concrete sandwich composite slabs

The ceramsite foamed concrete sandwich composite slab has the characteristics of light weight and good heat insulation performance. At present, there are few research on the fire resistance of ceramsite foamed concrete sandwich composite slab at home and abroad, and the damage mechanism of ceramsite foamed concrete sandwich composite slab under fire is not clear. To fill this gap, constant load-temperature rise fire test and static loading test on five slab specimens are conducted by varying the parameters such as sandwich layer thickness, reinforcement pattern, shear span ratio and construction method. Based on the test, the results are studied, including the temperature distribution and deformation characteristics under fire, load–displacement curves, crack pattern and damage mode, residual bearing capacity of the slab after fire. The results show that ceramsite foamed concrete sandwich composite slab has good thermal insulation performance, the overall working performance, flexural bearing capacity and deformation ability of the slab is mainly affected by the slip at the composite surface. The integrity of the slab and the residual bearing capacity and ductility after fire could be significantly improved by the configuration of truss rebar. It is suggested to decrease the time difference of concrete placement at the composite surface or set shear keys and truss rebar to improve the cooperative working ability between the surface layer and the sandwich layer. Moreover, Finite Element analysis is carried out by ABAQUS software and the results show good agreement with experiment results. A new compositeness degree analysis (CDA) method for calculating the residual bearing capacity of ceramsite foamed concrete sandwich composite slab after fire considering different compositeness degree is proposed, which could be used for the practical engineering design.

Stab resistance mechanism of lightweight PLA/CFRP hybrid composite structures

The preparation of lightweight and high-performance material is of great significance for developing stab-resistant clothing. This paper proposes a stab-resistant composite structure combining lightweight polylactic acid (PLA) and carbon fiber reinforced polymer (CFRP). The effect of stacking sequence and filling density on the puncture resistance of composite structures was investigated by dynamic puncture and quasi-static puncture. Puncture load, energy and depth are studied as key parameters of puncture resistance. This paper investigated composite structures' failure process and damage morphology using high-speed camera photography and microscopic imaging techniques. The results show that the composite structure exhibits the strongest puncture resistance when CFRP is designed on the top layer of PLA. The higher the filling density, the lower the puncture depth of the composite structure, but the increase in the overall weight eventually leads to a decrease in the puncture specific energy (PSE). The introduction of the bottom PLA delays the penetration point of the composite structure and increases the absorption of the penetration energy by the CFRP before penetration. The final damage modes of composite structures include fiber fracture, slip and pull-out, matrix fracture and peel damage, as well as fracture damage and plastic deformation of PLA materials.

Performance of delaminated CFRP composite under pure bending using two-dimensional digital image correlation

ABSTRACT Delamination is an interlaminar damage which may be pre-existing in multilayered fibre reinforced polymer composite parts due to manufacturing imperfections or generated by out of plane loading during service life. Its existence leads to significant reduction of structural integrity, strength and stiffness of the material. Hence, to study the effect of induced delamination on the performance of a composite under pure bending, a circular polytetrafluoroethylene (PTFE) film was introduced between the second and third plies of a sixteen layered carbon/epoxy laminate during fabrication. The bending tests were conducted in displacement control mode. The displacements and strains were measured through the thickness of the composite using two-dimensional digital image correlation. The damage modes were captured using CCD camera and the causes were explained. The flexural strength and modulus of composite were 329.74 MPa and 104.58 GPa respectively. The delaminated composite behaved as a single member without any crack within the elastic range. The existence of PTFE drastically reduced flexural stiffness of composite beyond the stress at 75.81% of its ultimate strength. The ± 45º plies offered low mechanical performance against the induced off axis loading. Hence, in these plies fibre breakage was higher. In the portion of PTFE, the strains were higher due to larger outward displacements produced by local buckling.

Influence of bolt dynamic installation on topography characteristics and mechanical behaviors of CFRP interference-fit bolted joints

As the controlled research of Dynamic Installation (DI) and Static Installation (SI), a new interference installation method was developed based on electromagnetic loading to enhance the mechanical properties of composite structures. Four different interference-fit sizes were considered, ranging from a net fit to 2.0%. The experiments were conducted to evaluate the installation resistance and the mechanical behavior of the joint under external loads. Meanwhile, an FEA model to model the stress distribution and damage behavior of the bolt-hole contact interface was established. The load–displacement curve and damage modes of experiments were used to verify the FEA results. The results show that the installation resistance during DI process was remarkably lower than that of SI process corresponding to all interference-fit sizes, and the stress amplitudes induced by interference were larger and widely distributed. The damage of the hole wall was positively correlated with interference fit size, but DI can significantly reduce the damage compared to SI. In performance tests, DI enhanced the static bearing capacity and extended longer fatigue life of the joints than SI. DI methods can be an effective way to achieve highly reliable interference joints in composite structures.

Experimental investigation on dynamic response behavior of PC beam-column sub-assemblages under middle-joint drop-weight loading

The dynamic response of frame structure in progressive collapse has been investigated by some scholars by removing the column suddenly. However, the research cannot exhibit the effect of blast load on the dynamic response of the structure. Especially in a close-field explosion, a large axial tension force may occur in the cross-section of the column suffered from the blast load directly. It is the main factor causing dynamic response and subsequently leading to progressive collapse. This paper experimentally studied the dynamic response behavior of prestressed precast concrete sub-assemblage (PCS) through middle-joint drop-weight loading, and the tension force caused by the failed column was applied downward on the top of the middle joint of sub-assemblage through drop hammer impact. The same loading condition was also applied to the reinforced concrete sub-assemblage (RCS) to compare the dynamic response behavior. The results showed that all the sub-assemblages exhibited flexural damage mode. Compared with RCS, more serious damage occurred concentratedly at the beam-column interface in PCS, but no prompt damage appeared in the beams. The sub-assemblage went through local dynamic response and global dynamic response stages in succession. Reverse arch action (RAA) emerged during the local response stage due to the pronounced inertial action at the middle joint, and it became more significant with increasing impact velocity. Compared with RCS, the pretension of steel strands may enhance the effect of RAA in PCS. Compressive arch action (CAA) emerged during the global response stage with the energy transferring from the kinetic energy to strain energy when middle joint displacement (MJD) increased continuously. With increase of impact velocity, the contribution of steel strands tension in resisting collapse increased significantly. The damage mode of the beam end in PCS at the peak MJD was almost the same as that under quasi-static loading at the same MJD, and the strain energy was also approximately identical to that under quasi-static loading. Based on the premise of flexural damage mode of PCS, the peak MJD can be determined according to the vertical resistance of PCS under pushdown loading using the work-energy principle.

A Study on Damage of T800 Carbon Fiber/Epoxy Composites under In-Plane Shear Using Acoustic Emission and Digital Image Correlation.

In addition to measuring the strain, stress, and Young's modulus of materials through tension and compression, in-plane shear modulus measurement is also an important part of parameter testing of composites. Tensile testing of ±45° composite laminates is an economical and effective method for measuring in-plane shear strength. In this paper, the in-plane shear modulus of T800 carbon fiber/epoxy composites were measured through tensile tests of ±45° composite laminates, and acoustic emission (AE) was used to characterize the damage of laminates under in-plane shear loading. Factor analysis (FA) on acoustic emission parameters was performed and the reconstructed factor scores were clustered to obtain three damage patterns. Finally, the development and evolution of the three damage patterns were characterized based on the cumulative hits of acoustic emission. The maximum bearing capacity of the laminated plate is about 17.54 kN, and the average in-plane shear modulus is 5.42 GPa. The damage modes of laminates under in-plane shear behavior were divided into three types: matrix cracking, delamination and fiber/matrix interface debonding, and fiber fracture. The characteristic parameter analysis of AE showed that the damage energy under in-plane shear is relatively low, mostly below 2000 mV × ms, and the frequency is dispersed between 150-350 kHz.

Steam oxidation performance of Yb2Si2O7 environmental barrier coatings exposed to CMAS

Environmental barrier coatings (EBCs) are necessary for use of SiC/SiC ceramic matrix composites (CMCs) in gas turbine engines. Due to the complex operational environments, it is increasingly important to understand the interplay of damage modes to project the durability of the EBC/CMC system. Two life-limiting failure mechanisms of EBCs are steam oxidation and molten calcium-magnesium-aluminosilicate (CMAS) attack. Steam oxidation results in the formation of a thermally grown oxide (TGO) that acts as a weak interface and CMAS/EBC interactions cause thermomechanical and thermochemical changes that compromise coating integrity. EBCs consisting of a Yb2Si2O7 topcoat and a silicon bond coat were subjected to low (2 mg/cm2) loadings of two CMAS compositions prior to steam oxidation at 1316 °C for up to 300 h. Exposure to CMAS reduced the TGO thickness and the low CaO content glass resulted in the thinnest oxide scales. However, glass exposure had mechanical consequences that caused premature coating delamination.

Performance of round-ended recycled aggregate CFST stub columns after fire exposure

The post-fire performance of round-ended recycled aggregate concrete-filled steel tubular (RE-RACFST) short columns has been investigated experimentally and numerically. The test parameters included cross-section aspect ratios, recycled aggregate replacements and steel ratios. Twelve short columns were first heated for 90 min following ISO 834 standard fire, followed by natural cooling. Subsequently, axial compressive tests were performed to obtain the damage mode, load versus axial deformation, and strain development of the columns. The test results revealed that a higher level of recycled aggregate content resulted in decreased bearing capacity and elastic stiffness of RE-RACFSTs, and an earlier onset of the confining effect. Furthermore, finite element (FE) models were established and benchmarked against the experimental results. Parametric investigations were then conducted to study the effects of key factors on the residual load-carrying capacity. Finally, according to the experimental and FE results, a simplified formula was proposed to estimate the post-fire residual capacity of RE-RACFST stub columns.

Characterizing fatigue damage evolution in asphalt mixtures using acoustic emission and Gaussian mixture model analysis

The identification and investigation of fatigue crack evolution and damage modes in asphalt mixtures are crucial for understanding the corresponding mechanisms and characteristics of fatigue failure. In this study, the four-point bending fatigue tests were performed on the asphalt mixture specimens with precast joints using the acoustic emission (AE) technique to analyze the damage evolution. The failure modes of the asphalt mixtures were identified using the Gaussian mixture model (GMM). The results revealed that the fatigue damage of the asphalt mixtures can be categorized into four stages: Stage I (void compaction), Stage II (microcrack initiation and stable propagation), Stage III (crack aggregation and unstable propagation), and Stage IV (complete fracture). This division was defined based on the inflection points of the axial displacement curves, the cumulative number of AE events, and the cumulative ringing counts. The evolution of the AE b value was found to be correlated with the crack propagation. The rapid decline in the b value in Stage III was considered a harbinger of the eventual complete fracture in the asphalt mixtures. The GMM clustering analysis indicated that the fatigue damage of the asphalt mixtures primarily involved tensile damage (90%), and shear damage made a small contribution of 10%. Existing AE studies have focused on the quantitative evaluation of AE parameters, while research on clustering identification algorithms for these parameters is scarce. The analytical methods and findings of this study enable an effective identification of fatigue damage in asphalt mixtures at the laboratory scale and offer insights into the fatigue damage mechanisms of asphalt mixtures.