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This article presents mechanical and thermal characterisation of unidirectional glass/epoxy (GE) and GE composites with graphene nanoplatelets (Gp-GE) fabricated using the hand lay-up method followed by compression moulding. The content of graphene nanoplatelets varied is 0.1, 0.3, 0.5 and 0.7 wt%. The obtained material properties are required to analyse the response of cylindrical shells under thermo-mechanical loads such as internal pressure and thermal loading in the thickness direction. The cylindrical shell models consist of multilayers of continuous fibre composites with varying Gp content in each layer. Tensile tests are performed to measure the longitudinal (E1), transverse (E2) and shear modulus (G12), as well as the modulus with 45° fibre orientation. The effective moduli of the Gp-GE composites are predicted using modified Halpin-Tsai and the Rule of Mixtures (RoM) and compared with the experimental data. The through-the-thickness thermal conductivity ($k$ k) and specific heat (${C_p})$ C p) are measured using Light Flash Apparatus (LFA). The increments in E1, E2 and G12 are 24%, 143.9% and 13.8%, respectively, and the properties $k$ k and ${C_p}$ C p improved by 11.7% and 13.4%, respectively, as compared to GE composites. Finally, empirical relations are established for different moduli, $k$ k , and ${C_p}$ C p as a function of Gp content. [ABSTRACT FROM AUTHOR]

This study investigates the repair of damaged curved glass/epoxy composite laminates through various adhesive reinforcements and adhesively bonded external patches. The experimental procedures involve fabricating laminates, conducting four-point bending tests, quasi-static indentation tests, and optimizing damaged areas. Results demonstrate the influence of repairs on curved beam strength and interlaminar tensile strength. Adhesive repairs with chopped fiber reinforcement outperform plain epoxy and particle fiber-reinforced repairs, preserving 51.28% of curved beam strength. Adhesively bonded external patches, both single and double, with chopped fiber reinforcement exhibit significant strength recovery 72.08% and 80.78% compared to virgin samples. The study emphasizes the effectiveness of adhesively bonded external patches, particularly those with chopped glass fiber reinforcement, in enhancing curved beam strength and interlaminar tensile strength. This research provides valuable insights for repairing angled structures, such as those in airplane components, showcasing potential applications of these techniques for structural maintenance. HIGHLIGHTS: Investigated adhesive reinforcements and bonded external patches for curved composites. Laminates fabricated, tested for bending, indentation, and optimized in damaged region Chopped fiber adhesive repairs preserve significant 51.28% strength. Adhesively bonded patches exhibit 72.08% and 80.78% strength recovery. [ABSTRACT FROM AUTHOR]

Laminated composite materials are susceptible to damage, such as delamination, due to poor out-of-plane properties and inadequate adhesion at the layer interface. Using the interlayering method is an effective way to enhance resistance against delamination in these materials. However, interlayer synthesis methods have been limited and sometimes very expensive. Therefore, this study investigates the impact of novel 3D-printed polyvinyl alcohol (PVA) interlayers on the mode II interlaminar fracture toughness in glass/epoxy laminated composites. Notably, the interlayers feature a geometrical structure consisting of square cell shapes, allowing the filament to have an equal volume percentage to the resin in the interlayer. To achieve this, end-notch flexure specimens (ENF) were prepared, and the mode II interlaminar fracture toughness was calculated using the compliance-based beam method (CBBM). The specimens' crack growth resistance curve (R-curve) analysis revealed that using the desired 3D-printed interlayer increases the mode II interlaminar fracture toughness by 73%. Furthermore, the behavior of crack growth resistance in laminated composites reinforced with 3D-printed interlayer shows an increasing trend. The mode II fracture surface analysis of reinforced specimens demonstrates the influence of square cell shapes in creating shear hackles, increasing surface friction at the interface of laminated composite layers, crack pinning mechanism, and changing the direction of crack growth, ultimately leading to increased resistance to crack growth. [ABSTRACT FROM AUTHOR]

The purpose of this study is to improve composite mechanical properties by reducing the degradation induced by seawater in glass fibre/epoxy composites. To do this, glass flakes (50 µm in size) were placed on the surfaces of the glass fibre/epoxy composite material using various ratios (5%–15%). Glass flakes were introduced into composite materials that were exposed to seawater for a period ranging from 0 to 12 months, and changes in bending, tensile, impact, compression, and compression after impact strengths were assessed. Flexural tests revealed that the gel coat and glass flakes increased their loads by up to 24% and 23% after 6 and 12 months of water immersion, respectively. Tensile tests indicated that lower tensile strength loss occurred as the glass flake ratio rose. As the immersion duration increased, the effect of glass flakes became more evident in terms of tensile strength. Composites containing glass flakes showed greater impact strength load values in both 20 and 30 J impacts compared to the control sample. The use of glass flakes improved the residual strength values because it prevented water penetration. The control sample retained up to 50% of its compressive strength, while the 15% glass-flake reinforcement promoted retention to 56%. [ABSTRACT FROM AUTHOR]

Investigation was performed to evaluate the puncture resistance of multi-walled carbon nanotubes (MWCNTs)/glass fibre epoxy laminate composites using different indenters (conical, elliptical, flat, and hemispherical). For the puncture tests, MWCNT weight percentage and indenter type were varied. Furthermore, the impact of MWCNT on tensile, flexural, and interlaminar shear strength was evaluated. Ultrasonic C-scan provided insights into the damage evolution and failure mechanisms of the laminates under puncture. The results indicate that the flat indenter exhibits prolonged indentation time and enhanced energy absorption, resulting in a disc-shaped failure pattern. On the other hand, the conical indenter demonstrates rapid penetration due to its smaller contact surface area. The elliptical indenter generates higher frictional energy, leading to bulging damage. The hemispherical indenter showed an even distribution of force across the impacted surface, minimizing force concentration and reducing the extent of damage. These findings shed light on the puncture mechanisms of MWCNT/Glass fibre epoxy laminate composites, paving the way for more precise glass fibre laminate composite design and optimisation in practical applications such as aerospace, automotive, and sporting goods, where puncture loading is a critical consideration.

This study investigates the influence of silane-treated aluminum hydroxide on the mechanical performance of flame-retardant composites. These composites have potential applications for luggage bags, as a replacement for conventional plastics, offering more durability and lighter weight. Glass fabric was used as the reinforcement, while epoxy was used as the matrix material. To impart flame retardancy, aluminum hydroxide nanoparticles were used as fillers in different weight % age (5%, 10% and 15%). As these are inorganic particles and have compatibility issues with the matrix material, silane-coupling agents (Dynasylan® 6490 and Dynasylan Glymo) were used to treat these filler particles. Both the silane-coupling agents fraction used for treatment and the fillers fraction added to the composites were varied to determine the most optimum combination. The mechanical properties of the developed composites such as tensile, flexural, and short beam shear strength were investigated. The best results were exhibited by 10% aluminum hydroxide fillers treated with 1% (by weight) coupling agent (Dynasylan Glymo). [ABSTRACT FROM AUTHOR]

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This work experimentally investigates the quasi‐static crush response and energy absorption of glass‐reinforced epoxy thin‐walled crash box filled with nano‐aluminum oxide (Al2O3). The effect of the triggering (45 ° edge chamfering) and the weight percentage (wt%) of Al2O3 on the crushing performance have been studied. Field emission scanning electron microscope (FE‐SEM) and energy‐dispersive X‐ray spectroscopy (EDX) were adapted to show the elemental composition of the fabricated samples' surfaces. To follow the fracture mechanism, visual inspection, and scanning electron microscope (SEM) were performed. Two‐parameter Weibull distribution function was employed to statistically analyze the experimental results. Failure probability curves were established to help the designers in selecting the suitable material for energy‐absorbing applications. Results indicated that for untriggered glass/epoxy composite crash boxes, the inclusion of 1, 2, and 3 wt% of nano‐Al2O3 leads to an increase of, respectively, 16.34%, 48.46%, and 68.70% in the absorbed energy (U). While there is a decrease of 32.72% in (U) when adding 4 wt% of nano‐Al2O3. An enrichment of 9.00%, 18.04%, 31.53%, and 11.30% in crush force efficiency (CFE) was reached by the inclusion of, respectively, 1, 2, 3, and 4 wt% of nano‐Al2O3. Triggering has a considerable effect on the crashworthiness parameters of the fabricated composite crash boxes. A decrease of 6.56%, 10.11%, 4.01%, 4.76%, and 11.62% in the initial peak load (Pip), an enrichment of 34.10%, 26.06%, 26.77%, 18.08%, and 28.97% in (CFE) and an improvement of 36.43%, 31.32%, 29.27%, 12.99%, and 52.47% in (U) were reported for composite crash boxes filled with 0, 1, 2, 3, and 4 wt% of nano‐Al2O3. It is obvious that glass/epoxy triggered composite crash boxes filled with 3 wt% of nano‐Al2O3 are appropriate to be used as energy absorbing device employed in vehicles due to their enhanced energy absorbing capabilities. [ABSTRACT FROM AUTHOR]

In this study, an experimental investigation has been performed to understand the electromagnetic interference-shielding effectiveness (EMI-SE) of glass fiber/epoxy laminated composites embedded with carbon nanotubes (CNTs) and Fe3O4 nanoparticles, reinforced with micro carbon fibers along the thickness direction. Micro carbon fibers were reinforced along the thickness direction between the laminates using an electro-flocking process and a vacuum infusion process used to fabricate the composites. The EMI-SE of the composites was measured in the X-band frequency range (8-12 GHz). The effect of carbon fibers of three different lengths (80 μm, 150 μm, and 350 μm) with two different fiber densities (1000 and 2000 fibers/mm2) and two different amounts of Fe3O4 nanoparticles (0.5 and 1 wt.%) on total SE, absorption, and reflection was investigated. Due to the synergetic effect of Fe3O4 nanoparticles, CNTs, and carbon fibers, the final EMI shielding of the composites was mainly dominated by the absorption process. The absorption was more pronounced in the composites of longer carbon fibers with improved electrical conductivity. The presence of Fe3O4 nanoparticles also enhanced total SE values with improved magnetic permeability. The composite with micro carbon fibers of 350 μm length and 2000 fibers/mm2 density with 1 wt.% of Fe3O4 nanoparticles showed the maximum value of total SE. [ABSTRACT FROM AUTHOR]

In the present research, effects of applying strain rate on the mechanical behavior of single-lap glass/CNF/epoxy composite bolted joints including, damage initiation bearing stress, 2% offset bearing strength, ultimate bearing strength, bearing chord stiffness, ultimate bearing strain, and energy absorption were studied. To this end, a comprehensive experimental program was conducted. The protruding head bolt was used, the clearance was considered to be near fit and a finger-tight bolt condition was applied to all joints. The dimensions of joints were chosen to promote the bearing failure mode based on the ASTM standard. Four types of single-lap bolted joints (SLJs) with lay-ups of [–45/0/45/90]s and [90/–452/45]s with and without CNFs were tested at strain rates in the range of 0.0048 s−1 to 0.89 s−1. Unlike the available experimental results, the results obtained by the present experiments showed that the strain rate has a significant effect on all the above-mentioned mechanical parameters of SLJs. Also, it was shown that employing CNFs improved the mechanical parameters of SLJs under quasi-static and dynamic strain rates. [ABSTRACT FROM AUTHOR]

The main objective of this research is to find experimentally the effect of impact damage on the flexural strength of glass fiber/epoxy laminated composite materials at two different test conditions. The other objective is to determine the critical buckling load of laminated composite material after impact loading. Thus, the loss of flexural and buckling performances of the damaged material has been established by comparison with the undamaged material. Initially, angle-ply laminated composite plates with rectangular shaped have been subjected to impact load at different energy levels by using a dropweight testing machine and impact damage has been created. To find the residual flexural strength, four-point bending tests have been carried out. Four-point bending specimens have been cut from the damaged area of the middle of the laminated plates and have been positioned in two different ways according to the face subjected to the impact. For buckling tests, a unidirectional compression load has been applied to the impacted specimens with the size of 100 mm x150 mm. According to the four-point bending test results, the flexural strengths of the specimens subjected to impact at 10 J and 30 J have decreased approximately 25 and 42%, respectively. Similarly, the reductions in critical buckling loads of specimens subjected to impact at 10 J and 40 J are approximately 16 and 32%, respectively. Consequently, the impact load significantly reduces the flexural and buckling performances of laminated glass/epoxy composites. Furthermore, the positioning of the four-point bending test specimen affects the flexural strength. [ABSTRACT FROM AUTHOR]

In this research, the effect of adding clay Nanoparticles on increasing the lifetime of glass/ epoxy composites under hydrothermal conditions has been investigated. For this purpose, samples containing 3 Vol.% of clay Nanoparticles and samples without clay Nanoparticles in resin epoxy has been manufactured for the fabrication of specimens of the tensile test using hand lay-up and vacuum bag. The specimens were placed under the hydrothermal condition of 90% humidity and 75 °C temperature for 500 hours in the incubator and were tested for tensile properties. The results show that addition of clay Nanoparticles decreases the strength of the composite by 21.39% in the newly produced samples while in a long time, these particles slow down the process of composite degradation, so that in the same environmental conditions, the strength of specimens containing clay Nanoparticles is 9% higher than the specimens without clay Nanoparticles. [ABSTRACT FROM AUTHOR]

In this research, delamination in an asymmetric double cantilever beam (ADCB) has been studied. The ADCB specimen is one the most proper samples for testing and calculating the mixed mode I/II fracture. First, a semi-empirical relation for calculating the total strain energy release rate (SERR) and the values of mode I and II of this parameter has been extended. Moreover, the total SERR of a laminated composite is determined using the virtual crack closure technique (VCCT). Furthermore, by the use of this method fracture toughness of ADCB specimen and its modes can be calculated by testing of a unidirectional DCB specimen. Therefore, testing of ADCB samples is not required. Also, for verifying results obtained by the semi-empirical relation of the total SERR, experimental, analytical and numerical methods are used. By modeling of the mentioned specimen in ABAQUS/Standard, values of mode I and II SERR are calculated. This method can be used for assessment of the semi-empirical relation. Finally, it was observed that results of the semi-empirical relation are in very good agreements with the experimental, analytical and numerical results. This method reduces the volume of calculations of numerical methods and costs of experimental tests significantly.

Abstract The main goal of the present work is to study the mechanical response of glass/epoxy composites when exposed to cement and geopolymer (metakaolin) mortars, as it happens in Civil Engineering applications. For this purpose, specimens were embedded into mortar followed by a period of curing, which was done under the air laboratory environment. For cement, curing was also performed inside a container filled with water. The specimens were removed from the mortars after 30, 60 or 90 days of curing and then tested. Three point bending (3 PB) tests, tensile and transverse impact tests were carried out. The degradation was evaluated, both by the residual mechanical properties and by the failure damage mechanisms. In terms of 3 PB, and comparatively to the control samples, decreases around 29.5%, 31.3% and 37.9% were found after 90 days of exposure to cement, cement with water and metakaolin mortar, respectively. The same comparison for the impact strength reveals decreases about 39%, 40.1% and 44.3% for impacts in tensile mode, while these values are 7%, 11.6% and 63.1% for impacts in transverse mode, respectively. Therefore, the exposure to both cementitious and geo-polymeric matrices affects significantly the mechanical properties, but their effects are strongly dependent of the exposure time. Finally, it was possible to conclude that the worst results are obtained with the metakaolin mortar. [ABSTRACT FROM AUTHOR]

Among the failure modes of composite materials, delamination is the most striking one. It may result in the reduction of stiffness and long-term performance of composite materials. The initiation stage is very crucial in delamination. This is because initiation stage requires higher amount of force, and after this stage, there is a stable propagation of delamination that requires little force and causes the failure of the structure. Initiation of delamination consists of two main stages including minor initiation and major initiation. These two stages are vital stages in the delamination process. Understanding the delamination behavior and their internal micro events in these stages may lead to better design and result in enhanced strength against crack initiation. This article proposes a combined method to discriminate various fracture mechanisms in the initiation of delamination. The combination of sentry function analysis and frequency analysis of acoustic emission (AE) waveforms are used to analyze crack initiation and to discriminate its internal micro failures during mode I delamination. Discrimination process is derived from the power spectrum density of AE waveform in distinct frequency intervals. Scanning electron microscopy (SEM) observation was used to determine different fracture mechanisms and associate these observed fracture mechanisms and their equivalent AE signal frequency range. It is shown that this combined method is a powerful device to study the behavior of the initiation of delamination. [ABSTRACT FROM AUTHOR]

The effect of through-thickness compression on in-plane tensile strength of glass/epoxy composites with random microstructure was investigated experimentally. The studied composite laminates were manufactured with a self-regulating Resin Transfer Moulding device. Their mechanical behaviour was assessed in pure in-plane tensile and through-thickness compressive tests, followed by biaxial tests combining both loading modes; indenters with a radius ranging from 5 to 25 mm were used to impose a compressive mode. The obtained results demonstrate a nonlinear decreasing trend for the in-plane tensile strength under the growing through-thickness compressive stress. All the failed specimens showed catastrophic brittle failure with a specific fracture orientation that mainly exhibited a tensile mode of fibre fracture for smaller radii of indenters and a combination of matrix crack, fibre fracture and typical shear failure for larger radii. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we used a homogenization method to estimate the equivalent properties of composite material, which depend on a microstructure and behavior of constituents (fiber and matrix). The estimated results conform well to the results of the rule of mixtures, which is a conventional method for estimating equivalent properties of composite materials. In addition, to assess the uncertainty of the equivalent properties of the composite materials according to the variability in the basic properties of the constituents, a probabilistic analysis using a homogenization-based Monte Carlo simulation was carried out. In this way, the variation of basic properties of the constituents was identified to have a significant effect on the uncertainty of the equivalent properties of composite materials. Moreover, a sensitivity of the properties of the constituents on the equivalent properties was assessed through a correlation and regression analysis. [Copyright &y& Elsevier]

Abstract: This paper investigates the influence of char-forming, flame-inhibiting and intumescent surface coatings on the post-heat flexural behavior of glass fibre-reinforced epoxy composites exposed to one-sided radiant heating. The fire performance of glass/epoxy laminates surface-coated with varied formulations was evaluated using a cone calorimeter under various external heat fluxes (25, 50 and 65kW/m2). Self-sustained ignition was significantly delayed for fire-protected laminates relative to the control. The peak heat release rates and the time to reach this event were significantly reduced in thermally-protected laminates. In addition to the chemical nature of flame retardant chemicals present in the coatings, the time to reach the peak heat release rate and the magnitude of the total heat release were influenced by the quantity and morphology of the char formed by each type of surface coating. The post-heat flexural performance of heat-damaged laminates was determined via three-point bending. There was a significant improvement in the post-heat flexural moduli retention in thermally-protected glass/epoxy laminates. This may be due to the flame retardation efficacy of the coatings and the ability of the charred structures to reduce the heat transfer into the substrate thereby protecting the underlying composite and its mechanical integrity. [Copyright &y& Elsevier]

Abstract: This paper investigates the efficacy of varied (non-intumescent and intumescent) polymer-based surface coatings in providing fire protection to glass fibre-reinforced (GFR) epoxy composites exposed to one-sided radiant heating. In addition to an intumescent surface coating, two other non-intumescent surface coatings are considered – one that is active in the condensed phase and promotes surface char formation and another that is active in the gaseous phase and inhibits flaming combustion. The fire resistance of surface-coated GFR epoxy composite laminates is evaluated using the cone calorimeter at incident heat fluxes of 25, 50 and 65 kW/m2. For all tests conditions considered, there is a significant improvement in the fire performance of surface-protected GFR epoxy laminates relative to their unprotected counterparts. The intumescent surface-coated laminate showed the most significant variations in fire reaction properties with changes in irradiance. [Copyright &y& Elsevier]

Because of applications of composites in space and in low temperature equipment, low temperature mechanical properties of glass fiber-reinforced epoxy have to be assessed. Experimental or analytical investigation on the tensile failure behavior of glass/epoxy laminated composite with/or without stress concentration subjected to thermo-mechanical static loadings at low temperatures has not been done yet. In the present work, a model was developed to perform the progressive failure analysis of quasi isotropic composite plates at low temperatures. The initial failure load is calculated by means of an elastic stress analysis. The load is increased step by step. For each given load, the stresses are evaluated and the appropriate failure criterion is applied to inspect for possible failure. For the failed element, material properties are modified according to the failure mode using a non-zero stiffness degradation factor. Then, the modified Newton-Raphson iteration is carried out until convergence is reached. This analysis is repeated for each load increment until the final failure occurs and the ultimate strength is determined. The present method yields results in a reasonable agreement with the experimental data at room temperature and −60°C. The effect of low temperature on the failure mechanism of the plates was also determined. [ABSTRACT FROM AUTHOR]

Effects of ultraviolet radiation and condensation on the static and dynamic compressive properties of composites with and without nanoclay were investigated. Specimens were exposed to ultraviolet radiation (UV), and alternate ultraviolet radiation and condensation (UC) conditions for 5, 10, and 15 days, respectively. Compression test results showed an increase in strength and modulus with increase in strain rate and nanoclay weight percent loading. However, properties degraded upon conditioning with nanoclay infused systems showing less degradation. Scanning electron micrographs of fractured samples show better interfacial bonding in nanoclay infused composites in 2 wt. % system showing best properties. [ABSTRACT FROM AUTHOR]

Studies were carried out on RT-cured glass/epoxy composite specimens, subjected to different post-cure schedules (50, 60, 70, and 85°C and durations) and immersed until saturation in distilled water at 50°C. The effects of different post-cure schedules, on the moisture diffusion characteristics of the composite were studied. Results showed that the saturation moisture levels decreased with increased post curing, a trend attributed to increased matrix cross-linking, as evidenced by the increase in Tg (glass transition temperature) values with extent of post cure. The diffusion parameter-like composite diffusion coefficient (Dc) and time of saturation (tm) showed either insignificant or marginal changes, within the range of post-cure schedule considered in these studies. [ABSTRACT FROM AUTHOR]

Polymer composite materials have received increased attention for applications in a cryogenic environment because of their light weight and unique properties. The research presented in this article is an effort to understand the interlaminar fracture behavior of glass/epoxy composite laminates at cryogenic conditions and at different loading rates. This study uses a three-point flexural test to qualitatively assess such behavior for 50wt% E-glass fibers reinforced epoxy composites during cryogenic and ambient conditions. The specimens were tested at a range of 2-500 mm/min crosshead speed to evaluate the sensitivity of mechanical response during loading at these conditions. The mechanical performances of the laminated specimens at cryogenic conditions were compared with room temperature properties by using SEM photographs. Phenomenological behavior of these materials may be attributed to polymer relaxation, low-temperature hardening, matrix cracking, and misfit strain due to differential thermal coefficient of the constituent phases, and also by an enhanced mechanical keying factor by compressive residual stresses at cryogenic temperatures. [ABSTRACT FROM AUTHOR]

The transverse mechanical and failure behavior of unidirectional S2-glass/epoxy composites are investigated and reported for a wide range of strain rates from 10-4 to 104s-1 under multiaxial compressive loading conditions. The effect of stress multiaxiality is explored using the confining sleeve technique to impose varying degrees of lateral confinement. The lateral confinement has been found to significantly increase both the maximum attainable stress level and the strain to failure. Scanning electron microscopy (SEM) observations on recovered specimens reveal that the transverse failure occurs within localized shear bands through multiple fiber-matrix interface failure at the micro-scale. Based on the orientation of shear bands a Mohr-Coulomb type failure criterion is suggested to represent the transverse failure of unidirectional S2-glass/epoxy composites. [ABSTRACT FROM AUTHOR]

Studies were conducted on the degradation of ILSS and compression strength properties of glass/epoxy composite specimens painted and unpainted that were subjected to immersion in a water bath maintained at 323 K.It is found that both ILSS and compressive strength of the composite degraded more in the case of unpainted specimens (coded L0) compared to the painted ones (L1 or L2). Further, the specimens with a thicker paint coat (L2) degraded less than those with a thinner paint coat (L1). [ABSTRACT FROM PUBLISHER]

Moisture diffusion behaviour of glass/epoxy composites coated with a polyurethane base paint and those without the paint were studied on immersion in water at 323 K. Neat resin castings of the epoxy resin system were also studied for comparison. The composite specimens with paint showed lower moisture absorption values than those of the unpainted specimens subjected to the same immersion conditions. The diffusion parameters obtained from the experiment conducted up to saturation limits agreed well with the data computed using moisture absorption programme (M8 gain) proposed by G. S. Springer. The mixture rule for moisture absorption was also verified for the weight fraction studied. Further, Fickian correlation was found to exist in all the cases. [ABSTRACT FROM PUBLISHER]

• The acoustic evolution and infrared thermal imaging techniques were used to study the defect evolution mechanism of glass/epoxy composites under tensile load. • The damage mode of the defective Glass/Epoxy composites is identified by k-means and principal component analysis. • The effects of different defects on the structural strength of Glass/Epoxy composites are analyzed. In this paper, a combination of acoustic emission and infrared thermal imaging technology is used to study the defect evolution mechanism of Glass/Epoxy composites with bubbles and delamination defects under the single-shot tensile load. The analysis of the acoustic emission signal consists of the k-means method and principal component analysis (PCA). According to the clustering method, the amplitude and peak frequency of the AE signal are clustered. The results show that the AE signal can be divided into four clusters during the tensile loading process, which correspond to four different damage modes: matrix cracking, fiber/substrate stripping, delamination and fiber breakage. The characteristic frequency range of each damage mode was determined by cluster analysis. The effects of bubble defects and delamination defects on the structural strength of the composites were analyzed by experiments. In addition, the combination of acoustic emission and infrared thermal imaging technology can effectively monitor the defect location and damage trend of composite materials. [ABSTRACT FROM AUTHOR]