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The hydrogen embrittlement (HE) leads to severe steel degradation of mechanical properties. The hydrogen atoms diffuse into the steel and get posi- tioned into reversible and irreversible trap sites. The pipe to transport oil and gas needs to be welded to construct long-distance pipeline projects; thus, friction-stir welding (FSW) has proven an excellent alternative to joining these pipelines. Therefore, this work assessed and analyzed the influence of hydro- gen on the microstructure and fracture toughness of API 5L X70 steel welded by friction-stir welding. The in-service conditions were simulated by charging the specimen electrolytically in a 3.5% NaCl water solution with an intensity current of 2 mA cm 2 . According to fracture toughness tests, the base metal (BM) was more affected by hydrogen embrittlement than the friction-stir zone (SZ), with a fracture toughness reduction of 20% after hydrogen charging. The SZ fracture toughness did not statistically show changes in hydrogen charging by the used times; however, the fracture mechanism changed from ductile to brittle-like after 4 days of charging. The SZ depicted a better fracture toughness than BM due to the bainitic microstructure, a significant amount of irrevers- ible hydrogen trapping. The authors acknowledge the National Council for Scientific and Technological Development scholarship, CNPq - Brazil, grant number: 165065/2017-6. This research used facilities of the Brazilian Nanotechnology National Laboratory (LNNano), part of the Brazilian Centre for Research in Energy and Materials (CNPEM), a private non-profit organization under the supervision of the Brazilian Ministry for Science, Technology, and Innovations (MCTI). In addition, the author would like to thank the staff at the University of S ̃ao Paulo, specifi- cally in the Materials Engineering Department at the S ̃ao Carlos School of Engineering (SMM, EESC-USP), the Laboratory for Friction and Wear Technology (LTAD) at F I G U R E 1 3 Orientation maps showing the crack path at the stable crack propagation region during the CTOD test. (A, B) H-free samples from the BM and SZ and (C, D) H-charged samples from BM and SZ [Colour figure can be viewed at wileyonlinelibrary.com] 12 GIAROLA ET AL . the Federal University of Uberlândia (UFU), and the Multi-user Laboratory Complex (C-LABMU) ate the State University of Ponta Grossa (UEPG). The authors also acknowledge Gabriel Severino de Almeida for the sample preparation. H.C. Pinto is a CNPq fellow. J. A. Avila is a Serra Hunter Fellow and a CNPq fellow.

In engineering materials, defects, such as cracks, may occur during production and/or owing to various reasons. One of the aims of fracture mechanics is to determine the fracture toughness-based residual strength of structural members with cracks. A quasi-brittle material, such as concrete or rock, may include certain defects, such as voids and cracks, even before being exposed to loads. Experimental analyses on concrete members indicated that specimens’ nominal strength values decreased as their sizes increased while specimen geometry remained the same. In fracture mechanics, this condition is defined as the ‘size effect’ in both concrete and reinforced concrete units. In the literature, numerous theoretical and experimental studies have been conducted on beams, while compact split-tension specimens, particularly notched ones, are limited. In this study, six series of notched beams with three different sizes and notched square prismatic specimens with four different sizes were tested. According to the test results, the peak loads were analysed by using the fundamental theorem of the modified size effect law. In conclusion, two formulae were proposed to predict the flexural strength and the splitting strength of quasi-brittle bodies with cracks.

The combined effect of temperature and humidity on the fracture toughness of aluminium alloys has not been extensively studied, and little attention has been paid due to its complexity, understanding of its behaviour, and difficulty in predicting the effect of the combined factors. Therefore, the present study aims to address this knowledge gap and improve the understanding of the interdependencies between the coupled effects of temperature and humidity on the fracture toughness of Al–Mg–Si–Mn alloy, which can have practical implications for the selection and design of materials in coastal environments. Fracture toughness experiments were carried out by simulating the coastal environments, such as localised corrosion, temperature, and humidity, using compact tension specimens. The fracture toughness increased with varying temperatures from 20 to 80 °C and decreased with variable humidity levels between 40% and 90%, revealing Al–Mg–Si–Mn alloy is susceptible to corrosive environments. Using a curve-fitting approach that mapped the micrographs to temperature and humidity conditions, an empirical model was developed, which revealed that the interaction between temperature and humidity was complex and followed a nonlinear interaction supported by microstructure images of SEM and collected empirical data.

A WC-particle-reinforced nickel-based alloy surfacing layer was fabricated on 42CrMo ultra-high-strength steel. The microstructure and the mechanical and impact-damage behaviors of the surfacing layers at the evaluated temperatures were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and the Vickers hardness tester. Results showed that these WC particles gradually changed from elongated and crisscross needle-like phases to blocks with the increase in impact temperature. Numerous carbide phases (e.g., (Cr,Ni,Fe)23C6) and γ-Ni phases were formed in the substrate matrix. The surfacing layer showed a typical brittle fracture, and the impact energy decreased with the increase in temperature. Moreover, the surfacing layer showed a clear quasi-cleavage fracture morphology without dimples after a 600 °C impact test but exhibited a mixture of dimple fractures and cleavage fractures after the 200 °C and 400 °C impact tests. The Vickers fracture toughness test showed that the average hardness of the surfacing layer after a 600 °C impact test was 383 HV1.0, which is about 0.8 times that after the 200 °C impact test. In addition, the WC particles in the surfacing layer after the 600 °C impact test showed the highest fracture toughness, but the corresponding Ni40A binder phase possessed the lowest fracture toughness.

The production of alloys with high strength and toughness concurrently is still a difficult challenge. Here, we designed a simple solution-ageing heat treatment system to control the morphology and density of α in Ti-15Mo-3Al-2.7Nb-0.2Si via different heat treatment temperatures. The experimental results show that Ti-15Mo-3Al-2.7Nb-0.2Si exhibits a synergistic combination of tensile strength (1364 MPa), plasticity (7.8% elongation), and fracture toughness (101 MPa·m1/2) through solutions in the α/β biphasic region and duplex ageing. Notably, the strength of the alloy after the second step of the ageing process is increased by 15% compared with that after the first step of the ageing process. However, there is less than a 5% reduction in the fracture toughness. TEM observations show that the matrix continues to precipitate denser secondary α during duplex ageing, which causes the strength to increase significantly and causes the fracture toughness to weaken. Our work may provide a novel method to optimize the mechanical properties of alloys by controlling the precipitates.

Fracture toughness determination is crucial for the design phase of pressure vessels, and, although ASTM E1820 and ISO 12135 fracture toughness standards have existed for some time, some differences have been reported in the determination of this property. This study investigates the ductile fracture behavior of ASTM A516 Gr.70 pressure vessel steel and assesses the differences in estimating both standards. The steel’s tensile properties and initiation fracture toughness (JIC) were evaluated, taking into account the parallel and perpendicular orientations to the rolling direction. The results reveal the properties’ dependence on the rolling direction, mainly attributed to perlite banding. Additionally, as for the JIC determination, the differences were associated with the different blunting line slope estimations on each standard, reinforcing the necessity of a work-hardening-based blunting line for each material assessed.

The fracture toughness of sand concrete is affected by aggregate characteristics. In order to study the possibility of exploiting tailings sand, available in large quantities in sand concrete, and find an approach to improve the toughness of sand concrete by selecting appropriate fine aggregate. Three distinct fine aggregates have been used. After characterizing the fine aggregate used, the mechanical properties were tested to characterize the toughness of sand concrete, the box-counting fractal dimensions were calculated to analyze the roughness of fracture surfaces, and the microstructure was tested to observe the path and width of microcracks and hydration products in sand concrete. The results show that the mineral composition of fine aggregates is close, but their fineness modulus, fine aggregate angularity (FAA) and gradation vary considerably; FAA has a significant impact on the fracture toughness of sand concrete. The higher the FAA value, the more resistant it is to crack expansion; with the FAA values of from 32 s to 44 s, the microcrack width in sand concrete was reduced from 0.25 um to 0.14 um; The fracture toughness and microstructure of sand concrete are also related to the gradation of fine aggregates, the better gradation can improve the performance of the interfacial transition zone (ITZ). The hydration products in the ITZ are also different because more reasonable gradation of aggregates reduces the voids between the fine aggregates and the cement paste and restrains the full growth of crystals. These results demonstrate that sand concrete has promising applications in the field of construction engineering.

Yttria-stabilized zirconia (YSZ) has been widely used in structural and functional ceramics because of its excellent physicochemical properties. In this paper, the density, average gain size, phase structure, and mechanical and electrical properties of conventionally sintered (CS) and two-step sintered (TSS) 5YSZ and 8YSZ are investigated in detail. As the grain size of YSZ ceramics became smaller, dense YSZ materials with a submicron grain size and low sintering temperature were optimized in terms of their mechanical and electrical properties. 5YSZ and 8YSZ in the TSS process significantly improved the plasticity, toughness, and electrical conductivity of the samples and significantly suppressed the rapid grain growth. The experimental results showed that the hardness of the samples was mainly affected by the volume density, that the maximum fracture toughness of 5YSZ increased from 3.514 MPa·m1/2 to 4.034 MPa·m1/2 in the TSS process, an increase of 14.8%, and that the maximum fracture toughness of 8YSZ increased from 1.491 MPa·m1/2 to 2.126 MPa·m1/2, an increase of 42.58%. The maximum total conductivity of the 5YSZ and 8YSZ samples under 680 °C increased from 3.52 × 10−3 S/cm and 6.09 × 10−3 S/cm to 4.52 × 10−3 S/cm and 7.87 × 10−3 S/cm, an increase of 28.41% and 29.22%, respectively.

Recently, many researchers in the semiconductor industry have attempted to fabricate copper with carbon nanotubes for developing efficient semiconductor systems. In this work, tensile tests of a carbon-nanotube-reinforced copper specimen were conducted using the molecular statics method. The copper substrate utilized in the tensile tests had an edge half-crack, with the carbon nanotube located on the opposite side of the copper substrate. Subsequently, the effects of carbon nanotube radius were investigated. The mechanical properties of the copper/carbon nanotube composite were measured based on the simulation results, which indicated that the atomic behavior of the composite system exhibited the blocking phenomenon of crack propagation under tension. The fracture toughness of the composite system was measured using the Griffith criterion and two-specimen method, while the crack growth resistance curve of the system was obtained by varying the crack length. This study demonstrated that the mechanical reliability of copper can be improved by fabricating it with carbon nanotubes.

Tungsten heavy alloys (WHAs) are candidates for use in fusion reactor divertors. Here, we characterize liquid-phase sintered WHAs with 90, 92.5, 95, and 97 (wt.%) tungsten (W), with a balance of a 0.7Ni–0.3Fe ductile phase. These WHAs show remarkable room temperature (RT) fracture toughness at the maximum load, KJm, ranging from ≈ 38 to 107 MPa√m, compared to a monolithic W toughness of ≈ 8 MPa√m. In most cases, the fracture of WHAs occurs through stable crack tearing. However, the 97W WHA has the lowest toughness and fracture elastically in all but the smallest specimens. As lower Ni contents are desirable for fusion application, we explore the potential for improving the ductility and KJm of WHAs using vacuum annealing at 1300 °C for 24 h. The microstructural observations reveal negligible changes in the WHA microstructure and constituent compositions. While annealing reduces the Vickers microhardness (HV), it does not significantly change the RT yield (σy) and ultimate (σu) strengths but results in beneficial increases in total elongation in the 95 and 97W WHAs by a factor of 2. RT tests on the precracked three-point-bend (3PB) bars show that annealing increases the KJm of these WHAs, and in the case of the 97W WHA, the increase is from 42 to 92%, depending on the size of the specimen. Toughening is due to enhanced crack tip process zone microcracking and dilatation.

The present paper is dedicated to the mechanical and fracture characterisation of a specific earthen material, that is, the shot-earth 772. Although such a material has been recently characterised from a microstructural, chemical and physical point of view, the knowledge of its mechanical and fracture properties (essential for extending its use in construction industry) is still lacking. Such characterisations are here performed both experimentally, through laboratory tests, and numerically, through a FE model. The experimental tests (i.e. flexural, compression and fracture tests) are carried out on shot-earth specimens according to Recommendations available for concrete and a method proposed by some of the present authors, named Modified Two-Parameter Model. The numerical analyses are performed by employing a micromechanical model (implemented in a non-linear 2D FE homemade code), which allows to simulate both flexural and fracture behaviour of the shot-earth examined. Finally, the obtained numerical results are compared with the experimental ones.

Multi-barrier cleavage models consider cleavage fracture which is characterized by a series of microscale events. One of the challenges for multi-barrier cleavage models is the strong variations of cleavage parameters across different types of steels. The source and magnitude of the variations have not been studied systematically. In the current paper, cleavage parameters corresponding to fracture initiation at a hard particle and crack propagation overcoming grain boundaries are determined for three bainitic steels, a martensitic steel, and a ferritic steel, using a recently proposed model. It is found that the particle fracture parameter depends on particle morphology and composition, while the grain boundary cleavage parameter depends on the hierarchical grain structure. The determined values of cleavage parameters present a high degree of consistency among the five different steels, which allows the further application on microstructure design to control macroscopic toughness.

The energy for tearing is a classical measure of fracture toughness for elastic materials at finite strains. The prominent approach to quantify the tearing energy utilizes a tensile test on edge-cut thin rectangular specimens with low height-to-width ratio to determine the critical stretch at which a crack propagates from the tip of the cut. The analysis of the experiment, proposed by Rivlin and Thomas (1953), relies on the assumption that a large portion of the test piece is in a state of plane strain, and that the change of the total elastic energy is equal to the energy release due to the formation of new crack surfaces. While these assumptions are well justified for test pieces with sufficiently low height-to-width ratio, limitations in the availability and homogeneity of various sample materials have enforced the use of specimens with higher height-to-width ratios. In order to analyse the applicability of the classical theory and the corresponding errors, we investigate in the present work the influence of the sample's height-to-width ratio on the estimation of the tearing energy in mode I fracture tests. Exemplified with experiments and simulations for the elastomer Ecoflex 1:1, we show that reliable measurements can be obtained even for a quadratic sample geometry. For tough materials, however, significant overestimation of the tearing energy is expected already for a height-to-width ratio larger than 1/2. Surprisingly, in very brittle materials the tearing energy is vice-versa prone to be underestimated by up to 10% for ratios up to 1. The error also depends on the non-linear stress–strain characteristics, as illustrated by the use of different constitutive models. While a generally valid geometrical criterion cannot be defined based on the present results, our results suggest that the error hardly exceeds 10% for height-to-width ratios of up to 1/2., Engineering Fracture Mechanics, 287, ISSN:0013-7944, ISSN:1873-7315

Many failure and fracture studies of reactor pressure vessel material 20MnMoNi55 steel are performed in cryogenic conditions to study the scattered failure distribution property of the material in the lower self of ductile to brittle transition region. The experimental failure values of the RPV material are fitted with generalized extreme value (GEV) distribution and Weibull distribution through the commercial Statistical package R-i368 4.05 to study the nature of the distribution of fracture toughness in the lower self of ductile To brittle transition region. The nature of the distribution of fracture toughness of the RPV material 20MnMoNi55 steel is investigated from those experimental results. It is observed stochastically that the GEV distribution provides a better fit to the experimental failure data than the established Weibull distribution at least in the brittle portion of the DBT region of the tested material. This investigation is also supported by the two goodness of fit tests (Anderson–Darling test and Kolmogorov–Smirnov). Kolmogorov—Smirnov test results qualify Weibull distribution but indicated GEV as a better-fitted distribution of the experimental results. While Weibull distribution failed to qualify Anderson Darling test but GEV distribution qualifies the test. Therefore, GEV distribution can be thought, as a better option than Weibull distribution to capture the failure distribution for the RPV material in the lower self of the DBT region.

Hydroxyapatite (HA) has great potential as a reinforcing filler for poly (methyl methacrylate) (PMMA) denture base materials. Nevertheless, filler particles need to be homogeneously distributed throughout the PMMA particles to get the maximum benefit from using the filler. Therefore, the physical mixing of the powder components (PMMA and the filler) is strongly preferred to provide the required dispersion of the filler in the matrix. However, conventional techniques that have been tried, such as hand mixing and stirrer mixing techniques, were not effective. Therefore, the current study was designed to experimentally investigate the effect of different mixing times on the fracture toughness of PMMA/HA using a developed ball milling method. In this study, heat cured PMMA reinforced with 15 wt% HA ceramic powder was ground for different times (i.e., 10, 20, 30, and 40 min) via the technique of planetary ball milling (PBM). The ground powder mixtures were used for the fabrication of denture base testing samples. The particle size and distribution of the PMMA/HA composites after milling for several times were determined by the laser light scattering technique. The X-ray diffraction (XRD) patterns of the PMMA/HA composites were obtained. However, no new phase was observed. The effects of mixing time using the PBM technique on the fracture toughness were investigated. The effect of mixing time on the microporosity (voids) on the fractured surface of PMMA/HA was studied with field emission scanning electron microscopy (FESEM). Within the limitation of the current study, 30 min is considered the optimum mixing time for the tested PMMA/HA composite.

A powder metallurgy-based strategy to in situ construct a three-dimensionally interconnected hexagonal boron nitride (3Di-hBN) layers surrounding the grains of Cu-Ni matrix through metal–organic chemical vapor deposition process was utilized to fabricate 3Di-hBN-reinforced Cu0.7-Ni0.3 (3Di hBN-Cu-Ni) composite. The effect of 3Di-hBN on the mechanical properties of 3Di hBN-Cu-Ni composite was assessed by comparing with pure Cu-Ni alloy (without hBN) fabricated via powder metallurgy route under similar processing conditions. Uniaxial tensile investigations showed that 3Di-hBN positively influenced the mechanical properties of 3Di hBN-Cu-Ni composite; ∼16.3, ∼11.67, and ∼27.9% higher yield strength, UTS, and fracture toughness, respectively, compared to PM Cu-Ni alloy. The overall improved performance of 3Di hBN-Cu-Ni composite was attributed to the formation of 3Di-hBN layers at the interfaces of Cu-Ni grains, which enable the composite to withstand the applied load through the mechanisms of load transfer, dislocation strengthening, and grain refinement. In addition, thermal conductivity of 3Di hBN-Cu-Ni composite was found ∼10% higher than that of pure Cu-Ni alloy.

Using polylactic acid (PLA), polyamide (PA) and glass fiber–reinforced polyamide (GF/PA) as raw materials, samples with different printing temperature and speed were prepared. PLA samples were prepared by fused deposition modeling, and PA and PA/GF samples were prepared by selective laser sintering. The fracture toughness of 3D printed engineering plastics was characterized by three-point bending test. The results show that the process parameters have little effect on the fracture toughness of the specimen. With the change of printing temperature or speed, the fracture toughness of the specimen decreases by 4.9%. The raw materials have great influence on the fracture toughness of the specimens. The fracture toughness of PLA increases by 27.95% compared with PA and 58.71% with GF/PA. The results show that the fracture toughness of PLA is the highest among the three materials. Finally, the fracture surface of the specimen was scanned by scanning electron microscope, and the fracture microstructure was analyzed to reveal the influence of process parameters and raw materials on the fracture toughness of 3D printed engineering plastics.

The SiC–Ti3SiC2–TiB2 composites herein were prepared in situ by reactive melt infiltration (RMI). The synergy mechanism between Ti3SiC2 and TiB2 on fracture toughness of SiC matrix was investigated. The phase composition and microstructure of SiC–Ti3SiC2–TiB2 composites were studied, and their mechanical properties, such as Vickers hardness, elastic modulus and indent fracture toughness, were compared to those of SiC ceramics and SiC–Ti3SiC2 composites. The crack propagation of SiC–Ti3SiC2–TiB2 composites was simulated via Extended Finite Element Method (XFEM), and the fracture behavior in laminated Ti3SiC2 grains was also evaluated. The results show that SiC–Ti3SiC2–TiB2 composites exhibit an indentation fracture toughness of 9.57 MPa m1/2, which is greatly higher than that of SiC ceramics and SiC–Ti3SiC2 composites. It was suggested that the main toughening mechanisms of lamellar Ti3SiC2 grains and columnar TiB2 grains are crack deflection, crack bridging, grain fracture, delamination and grain pull-out.

3D printing technologies offer numerous advantages and have attracted the attention of researchers recently. Yet, the most commonly preferred additive manufacturing system is the extrusion-based process that is called fused deposition modeling (FDM) as it is simple, low cost, and prone to customization. In this paper, the effects of the short-term aging of the additively manufactured PLA and ABS specimens were investigated experimentally. The test specimens were aged by keeping them at ambient temperatures of − 80, − 20, 60, 100 °C for 10, 20, and 30 days. Thermally aged specimens and the pristine specimens were forced to fracture with bending load at room temperature. Thus, the permanent effects of thermal aging of the specimens were investigated utilizing the load–deflection curve, plane-strain fracture toughness, and the morphologies of fracture surfaces. It was concluded that the printed PLA materials are more susceptible to the thermal aging than the ABS printed materials. The contraction and expansion of the fused polymer filaments affect directly the bonding strength between the adjacent layers. Therefore, plane-strain fracture characteristics of the FDM polymer materials exposed to thermal aging differ according to the filament orientation and the aging time.

It is desirable to fabricate an antifatigue gel for skin-mimicking sensors on the demand of long-term durability in practical usage. Here, we developed a physically cross-linked eutectogel based on a poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) binary polymer skeleton and a deep eutectic solvent (DES). In this eutectogel, uniformly distributed PVA crystalline domains acted as stable physical cross-linkers, and high-density hydrogen bonds possessed great reversibility. Such a polymer network structure was expected to endow this eutectogel with excellent mechanical strength, stretchability, and a self-recovery ability. Specifically, this eutectogel exhibited a superior tensile strength of 2.6 MPa, a fracture strain of 680%, and a fracture toughness of 8.39 MJ m-3. In cyclic stretching/releasing tests with a fixed strain of 100%, this eutectogel could recover its mechanical properties within a 600 s resting time. Based on this self-recoverable eutectogel, a reliable flexible sensor was fabricated, which possessed good sensitivity and stability over a wide strain range (1-300%). More importantly, the flexile sensor was able to maintain a highly repeatable response signal during 1000 consecutive stretching/releasing cycles, showing outstanding long-term durability. Given the excellent sensing performance, this eutectogel has promising potential in wearable electronics, human-machine systems, and soft robotics.

Summary The toughness of composite materials is size dependent below a critical load transfer length (lT). Fiber-reinforced viscoelastic polymers are uniquely suited to study the size-limited regime because the lT of these soft composites can be as high as several centimeters, in contrast to traditional composites where lT is extremely small, allowing a large window for macroscale characterization. In this work, we elucidate the parameters that influence the toughness of soft composites when failure is governed by a fiber pullout-induced matrix-fracture mechanism. We ultimately demonstrate three important points: (1) fiber-reinforced viscoelastic polymers can possess high toughness, even at dimensions well below lT, (2) significant toughness amplification occurs due to the presence of fibers, even when the fracture process consists solely of matrix rupture, and (3) the composite toughness in the fiber pullout region can be predicted from easily attainable component parameters.

A crack front straightness is one of the test result validity criteria for fatigue precracked static fracture toughness specimens. Actually, the ideally straight crack front cannot be reached due to the presence of residual stress. This is particularly actual for specimens cut out of welded joints containing the residual welding stress (RWS). One of the techniques allowing to lower the RWS effect is a local side compression of specimens. Its efficiency has been proved in physical testing however no quantitative assessments are known in the literature. This work comprises FEM simulation of welding, sampling and side compression processes. The effect of local compression on base metal containing no residual stress is also investigated.It has been found that in the course of local side compression the initial residual stress field caused by welding and specimen making is replaced by another field showing stress gradients more favourable for getting the fatigue crack shape meeting the validity criteria of test results as per approved test methods. The calculation results show that the complete removal of residual stress as in base metal as in welded specimens is not feasible in the range of actual practicable degrees of compression.

This study aims to develop a general model to examine the weathering-induced degradation of a polycarbonate/acrylonitrile–butadiene–styrene (PC/ABS) blend under various temperatures and UV irradiance levels. The carbonyl index (CI) was measured with respect to the diverse conditions by Fourier-transform infrared (FT-IR) spectroscopy. Then, a response surface model for the CI with respect to the temperature and UV irradiance was established. The glossiness, tensile properties, and Izod impact resistance were measured under various weathering conditions. The fracture properties were also tested using the essential work of fracture (EWF) method. The correlations between these properties and the CI were determined. The results show that the fracture toughness and crack growth resistance measured by the EWF tests were significantly reduced even at a low CI level, i.e., the early degradation stage, whereas the tensile properties and impact resistance did not noticeably change. Although the tensile properties and impact resistances maintained their initial properties until a certain CI value, the fracture characteristics degraded rapidly, even at the initial degradation level. The model was verified by comparison with samples weathered outdoors for four and six months in Seoul, Republic of Korea. It was confirmed that the model for the Izod impact strength (IZOD) with a CI function can predict the experimental IZOD data for the outdoor-weathered specimens using the predicted CI values, with an error of 5.6%.

Maraging steels are precipitation hardened steels with high-strength and excellent toughness. Maraging steels being the key player in the strategic sector, demands welding of thick sections up to 12 mm for critical applications. They are readily weldable in the soft solution-annealed condition and further strengthened by post-weld heat-treatment (PWHT). However, welding of thick sections, on the other hand, necessitates a longer welding time, more number of passes and a higher heat input. This paper elucidates the influence of different PWHTs on the metallurgical and mechanical behavior of 12-mm-thick plates of MDN 250 grade maraging steel by using multi-pass gas metal-arc welding (GMAW). The different PWHTs adopted for the study include; Direct Aging (DA), Solutionizing + Aging (SA) and Homogenizing + Solutionizing + Aging (HSA). The microstructures of the fusion zone (FZ) with DA and SA condition reveal the presence of reverted austenite (RA) along the cell boundaries. However, in the weldment with HSA treatment was free from RA. Metallographic analysis of the as-welded FZ showed nickel, molybdenum and titanium segregation along the cell boundaries. This resulted in the formation of RA on subsequent aging. The SA treatment was not effective in complete elimination of reversion. The HSA treatment, on the other hand, had completely eliminated both elemental segregation and reversion. The welded joint with HSA treatment had an ultimate tensile strength (UTS) of 1582 MPa and a fracture toughness of 92.9 MPa√m, respectively. HSA treatment also shows a remarkable improvement in fracture toughness compared to other PWHTs. The present study underscores the fact that multi-pass GMAW with HSA treatment provides optimal mechanical properties.

Nanoceramic composites exhibit superior properties over their microcounterparts due to their microstructural differences. However, achieving grain size reduction in these composites through grain suppression is limited. Therefore, the use of nanopowders (both matrix and reinforcement) at the starting level itself and an attempt to further reduce the grain size may yield extraordinary properties. Thus, the present research aims to investigate the tribological and mechanical properties of ZTA nanocomposites reinforced with nano-MgO/MWCNT. The composites were developed separately through spark plasma sintering (SPS) and microwave sintering. The experimental results showed that with increase in the normal load and sliding velocity, the COF decreases, while the wear rate increases. Further, both the COF and wear rate increased with increase in the normal load and sliding velocity beyond a certain point. Moreover, when the normal load is increased beyond 65N, the wear rate of the composites increases rapidly irrespective of the sliding velocities. The addition of MgO increased the hardness through a secondary phase and pinning effect of the composites, while the addition of MWCNTs increased their fracture toughness through crack branching. The wear rate and the COF of the SPS composites were better than their MW-sintered counterparts.

This research investigated the effects of multi-walled carbon nanotubes (MWCNTs) on the chemistry, microstructure, phase distribution, and fracture response of potassium-based metakaolin geopolymers at the microscopic scale. We formulated novel protocols to cast geopolymers reinforced with 0.3, 0.6, and 1.5 wt% MWCNTs. We studied the chemistry using XRD, FTIR, and solid state $$^{29}$$ Si NMR. We characterized the microstructure and dispersion state of MWCNTs geopolymers using microscopic imaging and high-resolution scanning electron microscopy. We assessed the fracture behavior and mechanical properties using scratch tests and indentation tests. We used cluster analysis of indentation results to study the phase distribution. MWCNTs were well dispersed with an average accumulated area less than 8.9 $$\mu \hbox {m}^{2}$$ . XRD showed that MWCNTs preserved the amorphous phase. NMR showed that the addition of MWCNTs decreased $$\hbox {Q}^{4}$$ (Al2) fraction, but increased $$\hbox {Q}^{4}$$ (Al3) fraction. We observed a densification of the microstructure and a reduction in porosity. The microstructure showed that MWCNTs acted as bridges for fracture surfaces and connections for pores. The addition of 0.6 wt% MWCNTs increased the strength by 3.2%, and stiffness by 11.1%. Meanwhile, the addition of 1.5 wt% MWCNTs addition increased the fracture toughness by 10.5%. An inner strengthening effect was observed as MWCNTs reduced the microporosity, resulting in an increase in the indentation modulus and hardness for the dominant microphase. Therefore, MWCNTs promote the geopolymerization reaction, strengthen the geopolymer skeleton, affect the pore structure, and improve mechanical characteristics.

Nanoindentation is one of the methods that allows for determining the fracture properties of brittle materials. In this article, the authors present the possibility of the fracture toughness coefficient calculation of ceramic-based coatings doped by metal (W, Cr) by using the nanoindentation method with the Berkovich diamond indenter. The mechanical properties of selected coatings, such as hardness and Young’s modulus, were investigated from nanohardness experiments. We analyzed the brittle fracture, which includes changes in hardness (H), Young’s modulus (E), plasticity index H/E and resistance to plastic deformation H3/E2, enabled the concentration of tungsten and chromium. Due to the size of the indentation and the size of the initial cracks, it is necessary to use Scanning Electron Microscopy (SEM) to observe and measure the indentations made and the generated cracks. For evaluation of the fracture toughness in mode I, the Laugier model was chosen experimentally. The fracture toughness analysis showed that doping with concentrations of 10% W and 10% Cr causes an increase in the fracture toughness for KIc = 4.98 for TiBW (10%) and KIc = 6.23 for TiBCr (10%).

High-performance composites suffer from fatigue crack propagation during service. Traditional repair methods can be expensive and time-consuming. Therefore, research on composites with self-healing capabilities has considerably increased in the past decade. The aim of this work is to develop a polyamide 6 (PA6) matrix with self-healing properties. Polycaprolactone (PCL) was used as healing agent and melt compounded with PA6. PCL caused a decrease of the mechanical properties of PA6, due to its immiscibility and low mechanical properties. Nevertheless, acceptable fracture toughness values in quasi-static mode were obtained. Samples were thermally mended at 80 and 100 °C, and the healing efficiency was assessed by comparing the fracture toughness of virgin and repaired samples both in quasi-static and in impact mode. The blend with a PCL content of 30 wt% showed limited healing efficiency values (up to 6%) in quasi-static mode, while an interesting repair capability (53%) was detected under impact conditions. This discrepancy was explained through microstructural analysis and correlated to a different fracture morphology. In fact, under quasi-static mode, the PA6 matrix was severely plasticized, while under impact a brittle fracture surface was obtained. This morphology favored the flow of PCL during the thermal healing process.

ASTM E1921 is a testing standard to determine the fracture toughness for ferritic steels in the ductile-to-brittle transition range. If the crack front curvature criterion in the standard is not fulfilled, the result is invalid, and more testing is required. However, previous investigations do not focus on quantifying the effect of curvature on Master Curve reference temperature, T0. The numerical and experimental analyses done in this study indicate that, for increasing crack front curvatures, the effect of curvature on T0 is marginal and the obtained T0 tends to provide a conservative estimate. Future investigations on large experimental data sets with the methods provided in this study would help to quantify the trends more in detail. The results contribute to the development of more cost-efficient testing methods and impact long-term operation of nuclear power plants.

With the rapid growth in the miniaturization and integration of modern electronics, the dissipation of heat that would otherwise degrade the device efficiency and lifetime is a continuing challenge. In this respect, boron nitride nanosheets (BNNS) are of significant attraction as fillers for high thermal conductivity nanocomposites due to their high thermal stability, electrical insulation, and relatively high coefficient of thermal conductivity. Herein, the ambient plasma treatment of BNNS (PBNNS) for various treatment times is described for use as a reinforcement in epoxy nanocomposites. The PBNNS-loaded epoxy nanocomposites are successfully manufactured in order to investigate the thermal conductivity and fracture toughness. The results indicate that the PBNNS/epoxy nanocomposites subjected to 7 min plasma treatment exhibit the highest thermal conductivity and fracture toughness, with enhancements of 44 and 110%, respectively, compared to the neat nanocomposites. With these enhancements, the increases in surface free energy and wettability of the PBNNS/epoxy nanocomposites are shown to be attributable to the enhanced interfacial adhesion between the filler and matrix. It is demonstrated that the ambient plasma treatments enable the development of highly dispersed conductive networks in the PBNNS epoxy system.

Two 4,4′-(hexafluoroisopropylidene)diphthalic anhydride-based thermosetting polyimide formulations with varied amounts of crosslinking sites were compared to understand the influence of crosslinking density on fracture toughness, glass transition temperature and thermal oxidative stability. The thermal and mechanical properties of both materials were investigated through a series of single-edge notched beams, differential scanning calorimetry, dilatometry, weight loss, light optical microscopy and nanoindentation experiments. It was found out that the reduced crosslinking resulted in slightly increased fracture toughness but decreased the Tg of the material. No significant difference could be observed in the thermal oxidative stability with the experimental techniques considered.

The reinforcements represented by graphene nanoplatelets, graphite, and carbon nanotubes have demonstrated the great potential of carbon materials as reinforcements to enhance the mechanical properties of TiO2. However, it is difficult to successfully prepare TiO2-diamond composites because diamond is highly susceptible to oxidation or graphitization at relatively high sintering temperatures. In this work, the TiO2-diamond composites were successfully prepared using high-pressure sintering. The effect of diamond on the phase composition, microstructure, mechanical properties, and tribological properties was systemically investigated. Diamond can improve fracture toughness by the crack deflection mechanism. Furthermore, the addition of diamond can also significantly reduce the friction coefficient. The composite composed of 10 wt.% diamond exhibits optimum mechanical and tribological properties, with a hardness of 14.5 GPa, bending strength of 205.2 MPa, fracture toughness of 3.5 MPa∙m1/2, and a friction coefficient of 0.3. These results enlarge the family of titania-based composites and provide a feasible approach for the preparation of TiO2-diamond composites.

Excellent thermal and mechanical properties and high chemical resistance with low shrinkage of epoxy resins open a wide window of various industrial applications, including coatings, paints, adhesive, etc. Despite their excellent properties, epoxy resins are brittle and have a low resistance to the initiation and growth of cracks. To overcome this drawback, different kinds of reinforcements, including liquid rubbers, core–shell rubber particles, dendritic polymers, block copolymers, thermoplastics, rigid particles, etc., have been used to improve the fracture toughness of epoxy resin systems. This paper briefly introduces each reinforcement separately and mainly presents an in-depth review of the progress of the last decade in the field of toughening of epoxy resins using core–shell rubber particles. This review paper also refers to the results of the research papers published on the effect these rubber particles on the mechanical properties of epoxy resins, as well as explains different toughening mechanisms of epoxy resins. Researchers first focused on the use of core–shell rubber particles containing different cores and shells. They then used core–shell rubber particles along with rigid fillers such as silica to offset the slight diminish in mechanical properties, as well as the glass transition temperature. In recent years, some research teams have used core–shell rubber particles and block copolymers simultaneously and have achieved fascinating results.

In this paper, the compression behavior of four lattice topologies with body-centered and face-centered structures was first analyzed numerically based on the material model of 3D printed polylactic acid (PLA). To enhance the interface bonding properties between the AZ31B Mg face sheets and the PLA lattice cores, the skin-core interface was preprocessed by 3D printing microgrooves on PLA pre-pregs. The interface parameters of the heterogeneous bonding layer were then obtained through DCB and ENF experiments. The impact simulation by using ABAQUS/Explicit with a self-written VUMAT subroutine for the enhanced interfacial layer was finally carried out for the hybrid Mg alloy skin and PLA lattice-core sandwich panels with high energy absorption characteristics under static compression. The results have shown that the BCCZ and F2CCZ lattice configurations with Z-direction pillars exhibit better quasi-static compression characteristics compared with the BCC and F2CC structures. Interlayer fracture toughness values GIC and GIIC of the skin-core interface can reach up to 0.63 and 7.02 kJ/m2, respectively. Under low-velocity impact, the hybrid sandwich panels with F2CCZ lattice cores exhibit better impact resistance and energy absorption capacity than those of the BCCZ lattice sandwich panels.

Zirconium based alloys, as refractory metallic materials, can be fabricated into brittle zirconium hydride by hydrogen charging and can then be used as neutron moderators in the nuclear industry. In this study, the fracture toughness of bulk e zirconium hydride was attempted to be estimated by means of Vickers microhardness indentation. Several representative semi-empirical formulas based on Palmqvist and half-penny crack models were adopted, and relevant parameters including Young’s modulus, Vickers hardness, indentation dimension, and crack length were respectively determined. It was observed that cracks began to nucleate at impression corners and peripheries when the load was higher than 500 gf. Crack length at 1000 gf was measured and used to estimate the fracture toughness. The results showed similar values to previous reports obtained from conventional experimental means, indicating that Vickers microhardness indentation is an available method for estimating the fracture toughness of e zirconium hydride.

Nb-Mo5SiB2 (T2)-based composites with Ti and Si additions were prepared by mechanical alloying followed by hot pressing. The phase analysis revealed that element additions induced the phase composition change. In the Ti-added Nb-T2 composite, Ti was distributed in the grain boundary as sub-micron Ti-rich oxide particles due to insufficient oxidation. The addition of Si turned the Nb-T2 into a complete intermetallic composite by forming Nb-silicide. The mechanical properties showed that Ti- and Si-co-added Nb-T2 composite had the highest hardness (1939 HV) and compressive strength (3445 MPa), while the Ti-added Nb-T2 composite exhibited the best toughening effect, and the fracture toughness reached 13.37 MPa m1/2, which were about 31% and 300% higher than that of Nb-T2 and pure polycrystalline T2, respectively. Although the Nb and Ti had excellent toughening effect on the T2 phase, it worsened the oxidation resistance of the composites.

Zirconium diboride (ZrB2) is a credible candidate for hypersonic aerospace applications owing to magnificent characteristics such as higher melting point temperature, higher hardness, higher thermal conductivity, moderate oxidation, and ablation resistance. The influence of MgO (1–3 vol%) on mechanical and ablation characteristics of ZrB2–SiC composites sintered via microwave sintering was investigated in the present study. The microwave sintering was performed at 1800 °C under the heating rate of 15 °C/minute and holding time of 40 min at maximum temperature. The MgO addition not only reduced the sintering temperature but also enhanced the fracture toughness of developed composites. The maximum relative density and microhardness were observed at 2 vol% MgO. The maximum fracture toughness was achieved at 3 vol% MgO. The prominent toughening mechanisms (crack bridging, crack deflection, and particle pull out) enhanced the fracture toughness. The ablation resistance was improved with the addition of MgO and composites containing 2 vol% MgO exhibited the highest ablation resistance. The developed composites have applications in the rocket nozzles, nose caps, and leading edges of aerospace hypersonic carriers.

A comparative study was carried out on the synthesis of ZrB2-25 vol.% SiC-(5, 10 and 15 vol.%) TiC composites through microwave sintering (MS) and spark plasma sintering (SPS). The effects of TiC inclusion on sinterability, microstructures, phase analysis and mechanical characteristics of ZrB2-SiC composites processed through MS and SPS were examined and compared. The structural integrity of ZrB2-based composites was enhanced by TiC addition due to generation of lower tensile residual stresses in the matrix phase and higher compressive residual stresses in the reinforcement phase. The composites developed by SPS exhibited higher relative density, hardness and compressive strength, whereas higher fracture toughness was observed for composites developed by MS. Results indicated that SPS sintered Z25S10T composite exhibited maximum relative density, microhardness, compressive strength and minimum open porosity of 99.38 ± 0.26%, 24.78 ± 1.06 GPa, 349.01 ± 16.72 MPa and 0.37 ± 0.11%, respectively. The maximum fracture toughness of 6.36 ± 0.296 MPa m1/2 along with maximum critical energy release rate of 93.275 ± 4.64 J/m2 was obtained for Z25S15T composite developed through MS. The higher fracture toughness of microwave sintered composites could be attributed to the activation of several strengthening mechanisms like deflection, bridging and impeding of cracks.

Bending fatigue tests of carburized gear in high cycle fatigue life regime were performed under stress ratio of 0.04. All the crack sources of the broken teeth are originated from the stress concentration on the surface of teeth root. By considering the effects of surface residual stress, notch effect, stress gradient and crack size, the predicted initiation life model of carburized gear is established by dislocation energy method. Meanwhile, based on the Paris Equation, the crack length a corresponding to fracture toughness and real crack propagation path, the predicted growth life model of carburized gear can be established. Finally, based on the behaviors of crack initiation and propagation, the whole life prediction model of carburized gear can be constructed, and the prediction accuracy of the model is within three times of the test life, which can be used to predict the bending fatigue life of carburized gear.

In this study, first, the microstructure and mechanical properties of AZ80 magnesium alloy and SiC/AZ80 nanocomposite were compared. Then, the effects of 1, 3, and 5 passes of repeated upsetting (RU) process performed at 300 °C on the nanocomposite were investigated. According to the optical microscopy images, the average grain size in AZ80 alloy is 60.3 μm, which has decreased to 30.6 μm as a result of adding SiC nanoparticles. After the fifth pass of RU process, the average grain size reaches its minimum value as 4.5 μm with a homogenous structure. The shear punch test was run to measure the shear strength of the samples. The results showed shear yield stress and ultimate shear strength, which were 111.2 and 145.2 MPa in AZ80 alloy, respectively, increasing to 150.6 and 181 MPa in nanocomposite after five passes of RU process. Also, mixed-mode fracture tests show that fracture toughness in mode I and the mixed-mode significantly increased as a result of adding the SiC nanoparticles and RU process. Following a decrease in grain size and improvement in strength, the surface hardness was elevated from 79.9 HV in AZ80 alloy to 96.2 HV in RUed nanocomposite. These results indicate that the RU process, which is capable of manufacturing thick samples, can improve the microstructure, shear strength, fracture toughness, and hardness of SiC/AZ80 nanocomposite.

In this study, the effect of minor (5 vol.%) addition of Al–10Si–0.2Mg (composition in wt.%) pre-alloyed powder on densification, microstructure and mechanical behaviour of spark plasma-sintered ZrB2-20 vol.% SiC composite has been investigated. The sintered composite records a relative density of 99.83% despite being processed at a relatively low temperature (1700 °C) in argon atmosphere. Interestingly, ZrB2–20SiC–5AlSiMg composite does not undergo any shape distortion though the liquidus temperature of this metallic alloy additive is quite low (~ 592 °C). Extensive phase and microstructure analyses by appropriate techniques indicate that no free or unreacted AlSiMg is detected in the sintered composite. Thermodynamic analysis suggests that AlSiMg serves as a reducing agent for ZrO2 oxide scale and forms respective high-melting oxide phases. Raman analysis confirms that incorporation of 5 vol.% AlSiMg enhances residual compressive stress of SiC grains. Furthermore, the addition of AlSiMg is found to enhance the thermal shock resistance of the composite. In brief, this new AlSiMg additive results in better densification (99.83%) and hence an attractive combination of useful mechanical properties like Vickers microhardness (17.63 ± 0.54 GPa), nano-hardness (18.62 ± 1.23 GPa), indentation fracture toughness (7.21 ± 1.13 MPa $$\sqrt {\text{m}}$$ ), elastic modulus (432.64 ± 32.90 GPa) and flexural strength (659.25 ± 32.40 MPa) in the AlSiMg-added ZrB2-20SiC composite.

Nowadays research in the biopolymers is prominent area for research in medical fields. The metallic implants are used in many numbers for the orthopaedic surgeries. But some unavoidable issues are ...

We report a length-scale-controlled Brittle-Ductile Transition giving rise to significant toughening of a commonly brittle material. Using quantitative in-situ Transmission Electron Microscopy (TEM) fracture experiments at room temperature on single crystal Silicon, we find that large samples fracture concordant with the brittle bulk behavior at a stress intensity K I C ~ 1 M P a . m 1 / 2 . Below characteristic dimensions of about 250 nm, however, the fracture toughness strikingly increases inversely with size to at least triple. As evidenced from advanced in-situ TEM nanoscale strain mapping the stresses at the crack tip approach the theoretical strength. At the same time, below this critical transition length nucleation and propagation of dislocations was observed, shielding the crack tip and enabling the unprecedented rise in fracture toughness. These first time in-situ TEM observations in nanoscale Silicon at room temperature open new strategies to simultaneously strengthen and toughen indispensable yet brittle functional materials solely by geometrical miniaturization.

We prepared samples of composites based on tungsten carbide and cobalt with different concentrations (0–10 wt %) of chromium diboride, 10 mm in diameter and 8 mm in thickness, by cold pressing followed by vacuum hot pressing. A comprehensive study of composites using conventional methods of testing mechanical properties, combined with digital optical microscopy, transmission microscopy, and scanning atomic force microscopy, revealed stable correlations between the concentration of CrB2 additive with the average WC grain size and microstructure parameters, hardness, and fracture toughness of the composites. A coarse-grained structure is observed in WC–6Co (wt %) composites, with direct contact of WC grains and large regions of a cobalt binder. The introduction of CrB2 into the composite, on the contrary, ensures the formation of thin (~100 nm) and extended layers of a cobalt binder, even between fine WC grains. The CrB2 additive yields a finer-grained structure, the parameters of which can be purposefully controlled by changing the additive concentration. The addition of 4 wt % of CrB2 into the composite leads to a more than twofold increase in fracture toughness, that is, from 4.4 to 9.8 MPa m1/2, with a slight decrease in hardness from 15.1 to 13.0 GPa. With a further increase in the CrB2 concentration from 4 to 10 wt %, fracture toughness and hardness gradually decrease.

Hydroxyapatite (HAp) with good mechanical properties is a promising material meant for a number of useful bids in dentistry and orthopedic for biomedical engineering applications for drug delivery, bone defect fillers, bone cements, etc. In this paper, a comprehensive review has been done, by reviewing different literatures related to synthesis techniques, mechanical properties and property testing, method of calcination and characterization of hydroxyapatite which are product of catfish and bovine bones. The discussion is in relations of the obligatory features vital to attain the best properties for the envisioned bid of bone graft. The process approaches that are capable of fabricating the essential microstructure and the ways to advance the mechanical properties of natural mined HAp are reviewed. The standard values for tensile strength were found to be within the range of 40–300 MPa, compressive strength was 400–900 MPa, while Elastic modulus was 80–120 GPa and fracture toughness was 0.6–1 MPa m1/2 (Ramesh et al. in Ceram Int 44(9):10525–10530, 2018; Landi et al. in J Eur Ceram Soc 20(14–15):2377–2387, 2000; Munar et al. in Dent Mater J 25(1):51–58, 2006). Also, the porosity range was 70–85% (Yang et al. in Am Ceram Soc Bull 89(2):24–32, 2010), density is 3.16 g/cm3 and relative density is 95–99.5% (Ramesh et al. 2018; Landi et al. 2000; Munar et al. 2006). The literature revealed that CaP ratio varies in relation to the source and sintering temperature. For example, for bovine bone, a CaP ratio of 1.7 (Mezahi et al. in J Therm Anal Calorim 95(1):21–29, 2009) and 1.65 (Barakat et al. in J Mater Process Technol 209(7):3408–3415, 2009) was obtained at 1100 °C and 750 °C respectively. Basic understanding on the effect of adding foreign material as a strengthening agent to the mechanical properties of HAp is ground factor for the development of new biomaterial (Natural hydroxyapatite, NHAp). Therefore, it is inferred that upon careful combination of main parameters such as compaction pressures, sintering temperatures, and sintering dwell times for production natural HAp (NHAp), mechanical properties can be enhanced. Graphic abstract

Influence of Equal Channel Angular Pressing on mechanical properties and fracture toughness of Al-Zn alloy were studied in present investigation. Samples are successfully processed using the ECAP technique for up to a four passes by using route A. Al-Zn alloys were heated to a solid solution treatment temperature at 550 °C for 2 h prior to ECAP, this treatment introduces the precipitates which were capable of obstructing motions of dislocation and improves the refinement of the grain during ECAP process Finally, artificial aging was performed at a temperature of 190 °C for 0-20 hours with an interval of 2 h and specimens were cooled at room temperature with natural air. Fracture toughness was found experimentally for ECAP processed samples using SE (B) specimens according to ASTM E399 standard. This study revealed the enhancement in mechanical properties such as yield strength, ultimate strength and microhardness after four passes by route A technique. The improvement in the fracture toughness properties of artificially aged ECAP samples can also be due to dislocation strengthening, grain boundary strengthening, and the creation of much finer UFG grains, according to the results. Despite the increased tensile strength after ECAP, the ductility behavior has decreased due to the precipitation of GP zones and dispersion of η, ή, T and E within the Aluminum matrix, Furthermore, scanning electron microscope (SEM) micrographs revealed that ductile fracture with large dimples occurred in the artificial aged samples after the ECAP procedure.

Delamination and fiber pull-out remain significant problems with carbon fiber-reinforced epoxy composites due to the brittle nature of epoxy and weak fiber–matrix interface. The present study approaches overcome these problems by fabricating a multiscale carbon fiber-epoxy composites laminated composite with graphene nanoplatelets reinforced matrix, using a vacuum-assisted resin infusion method. Incorporation of 0.2 wt.% graphene nanoplatelets in carbon fiber-reinforced epoxy composites enhances fracture toughness by ~ 35% and ultimate tensile strength by ~ 22%, owing to significant adhesion between fiber and matrix. Thorough fiber–matrix interfacial characterization revealed improved modulus gradient across the interface, ~ 38% more energy absorption during delamination, and ~ 42% higher fiber pull-out strength from the matrix.