Composite Failure Research Articles

External validation of a risk model predicting failure of salvage focal ablation for prostate cancer.

To externally validate a published model predicting failure within 2 years after salvage focal ablation in men with localised radiorecurrent prostate cancer using a prospective, UK multicentre dataset. Patients with biopsy-confirmed ≤T3bN0M0 cancer after previous external beam radiotherapy or brachytherapy were included from the FOcal RECurrent Assessment and Salvage Treatment (FORECAST) trial (NCT01883128; 2014-2018; six centres), and from the high-intensity focussed ultrasound (HIFU) Evaluation and Assessment of Treatment (HEAT) and International Cryotherapy Evaluation (ICE) UK-based registries (2006-2022; nine centres). Eligible patients underwent either salvage focal HIFU or cryotherapy, with the choice based predominantly on anatomical factors. Per the original multivariable Cox regression model, the predicted outcome was a composite failure outcome. Model performance was assessed at 2 years post-salvage with discrimination (concordance index [C-index]), calibration (calibration curve and slope), and decision curve analysis. For the latter, two clinically-reasonable risk threshold ranges of 0.14-0.52 and 0.26-0.36 were considered, corresponding to previously published pooled 2-year recurrence-free survival rates for salvage local treatments. A total of 168 patients were included, of whom 84/168 (50%) experienced the primary outcome in all follow-ups, and 72/168 (43%) within 2 years. The C-index was 0.65 (95% confidence interval 0.58-0.71). On graphical inspection, there was close agreement between predicted and observed failure. The calibration slope was 1.01. In decision curve analysis, there was incremental net benefit vs a 'treat all' strategy at risk thresholds of ≥0.23. The net benefit was therefore higher across the majority of the 0.14-0.52 risk threshold range, and all of the 0.26-0.36 range. In external validation using prospective, multicentre data, this model demonstrated modest discrimination but good calibration and clinical utility for predicting failure of salvage focal ablation within 2 years. This model could be reasonably used to improve selection of appropriate treatment candidates for salvage focal ablation, and its use should be considered when discussing salvage options with patients. Further validation in larger, international cohorts with longer follow-up is recommended.

Physico-Mechanical Property Evaluation and Morphology Study of Moisture-Treated Hemp–Banana Natural-Fiber-Reinforced Green Composites

The development of many engineered product applications for automobiles and aircraft parts has initiated the search for novel materials as alternatives to metal matrix composites (MMCs). Natural-fiber-reinforced polymer composites offer distinct advantages such as biodegradability, eco-friendliness, flexibility, low density, and higher specific strengths, etc. This study focuses on natural-fiber (hemp and banana)-fabric-reinforced polymer composites suitable for exterior-engineered parts. The hand lay-up process is used to fabricate these hybrid composites. Exterior-engineered products are highly susceptible to moisture, which can deteriorate their mechanical performances, including their tensile and flexural strength, thereby affecting the durability of the hybrid composites. Therefore, the hybrid composites are subjected to water absorption tests, where samples are immersed in distilled water for week-long intervals. After each interval, the water-absorbed specimens are tested for their tensile and flexural characteristics as per ASTM D-3039 and ASTM D-790, respectively. The moisture treatment had a notable impact on the composite materials, causing a slight decrease in the tensile strength by 2% due to the diminished lateral strength in the interlaminar fibers. Contrary to expectations, the flexural strength of the composites improved by 2.7% after the moisture treatment, highlighting the potential of the moisture treatment process to enhance the elastic properties of such composites. The dimensions of the specimens changed after the water immersion test, resulting in increased longitudinal and decreased lateral dimensions. The surface morphologies of the composite failure samples showed fiber delamination, fiber breakage, voids, and matrix fractures.

Clinical Evaluation of Reasons for Immediate Composite Restoration Failure Placed by Dental Students: A Cross-sectional Study in Jordan

Objective: The present study aims to investigate the reasons for the immediate failure of direct anterior and posterior resin composite restorations placed by dental students. Methods: A cross-sectional study on resin composite restorations placed by fourth- and fifth-year dental students (n=436). Variables included in the study were; the operative field isolation method, the time needed to complete the restoration after cavity preparation to polishing and finishing, and the plaque index of the patient. Restoration class distribution according to the type of tooth and cavity classification was examined and recorded. Restorations were clinically evaluated immediately after placement. It involved the assessment of the restoration’s mobility, marginal discoloration, and lack of anatomy. Results: A total of 233 direct anterior and posterior resin composite restorations which were placed by 127 students were diagnosed as failed restorations. The mode of failure was distributed as mobility/debonding (61.80%), marginal discoloration (29.18%), and lack of anatomy (9.02%). Cl III restorations demonstrated the highest failure on tooth type and cavity classification (30%), followed by Cl II restorations in molars (18.45%). Failure-associated factors were proper restoration manipulation, field isolation, and patients’ plaque index. Conclusion: In the current study, the most frequent reason for the immediate failure of resin composite restorations was the quick application of the restoration either as the only associated factor or coupled with other failure-associated factors. Failure to maintain proper field isolation and the poor oral hygiene of the patient were the other two failure-associated factors.

In-situ quantitative tracking of micro-crack evolution behavior inside CMCs under load at high temperature: A deep learning method

Micro-cracks play an extremely significant role in the failure of ceramic matrix composites (CMCs). In-situ quantitative tracking of micro-crack evolution behavior remains a great challenge. In this study, a deep learning micro-crack segmentation method based on the generative adversarial network was developed to quantitatively characterize the micro-crack evolution behavior of CMCs under tensile load at high temperature with in-situ X-ray computed micro-tomography (μCT). This method realizes a precise and robust segmentation of the micro-cracks in μCT images with low gray contrast and image quality caused by noise and artifacts. The crack parameters including crack opening area, crack opening displacement and crack volume of each micro-crack were obtained. For the most micro-cracks, the values of these parameters exhibited no obvious increase during the loading process. Noticeable increasing of crack parameters occurred in some large micro-cracks at high load levels. The evolution of each micro-crack was also tracked to further identify the critical damages dominating the eventual failure. The four largest cracks exhibiting a more dramatic volume evolution were captured as the main cracks. These main cracks all originated from the preexisting micro-cracks and were usually formed by the coalescence of adjacent small micro-cracks with increasing tensile loads. The ultimate fracture was demonstrated to take place near these main cracks.

Mechanical and Energy Evolution Characteristics of Sandstone under True Triaxial Cyclic Loading

To study the mechanical and energy evolution characteristics of sandstone under true triaxial cyclic loading, a sandstone mechanical test with different intermediate principal stress under true triaxial loading was conducted using the rock true triaxial disturbance unloading test system. The influence of axial load on the deformation, energy evolution, and macroscopic failure characteristics of sandstone under different intermediate principal stress in a true triaxial test was systematically analyzed, and the damage evolution law of sandstone under true triaxial cyclic load was revealed. Results showed that the failure mode of sandstone under true triaxial compression changed from tension–shear composite failure to tension failure. Grading cyclic load σ1 greatly influenced maximum principal strain ε1 and minimum principal strain ε3 but had little influence on intermediate principal strain ε2. Under the same σ2 condition, the input energy and elastic energy in σ1, σ2, and σ3 directions increased nonlinearly. Under different σ2 conditions, the dissipated energy in σ1, σ2, and σ3 directions decreased with the increase in σ2. With the increase in σ2, graded cycles σ1, ε2, and ε3 decreased considerably, and the failure mode changed from tensile failure to shear failure. When the cyclic loading rate increased, the σ1, ε1, ε2, ε3, and volume strain εv of sandstone failure decreased, but the expansion point increased. Under true triaxial grading cyclic loading and unloading, the total dissipated energy of sandstone increased exponentially. The larger σ2 was, the smaller the damage variable was.

Effects of Hybridization on Tensile, Flexural, and Damage Behaviors of Flax/Carbon Epoxy Composites

In recent years, the hybridization of natural fibers with synthetic fibers has received much attention. This paper conducted an experimental study on the tensile and flexural behavior of unidirectional carbon/flax fiber reinforced epoxy composites and single flax fibers. Four hybridization rates were considered for 16 reinforced layers in a symmetric staking sequence, with the carbon ply at the surface. The damage evolution under load increase was monitored using the acoustic emission (AE) technique. The Davies–Bouldin index and the K-means clustering algorithm were used to correlate the hybridization rates to the contribution of each damage mechanism to overall failure. AE monitoring of tensile and flexural behaviors showed that delamination and fiber breakage mechanisms dominate the composite failure, regardless of the hybridization rate.

Mathematical modeling and experimental investigation of a composite beam failure - Case study

Composite materials have been extensively employed in the aviation industry in recent years. The application of new materials enables significant weight savings with improved mechanical characteristics. This is also very important in the field of development of unmanned aerial vehicles (UAV). In the design phases, it is necessary to perceive all the aspects that are important for the structure and consider different load cases. The relationship between weight and strength proved to be important. This means that detailed strength analyses of each structural part are indispensable. In particular, primary load-bearing structures must sustain all types of loads without fail. Failure of the structure can affect the motion of the UAV during the mission or lead to a crash and significant losses. This paper presents the research performed on the failure analysis of a composite beam of a novel UAV. During the testing phase, under an unpredictable load condition followed by a crash landing, failure of the structure occurred on a beam element. The study was performed to determine the cause of the failure of certain layers of the composite laminate, because the previous calculation showed that it met the criteria for which it was dimensioned. Based on the telemetry data and the impact load that was registered, a complementary numerical and experimental analyses were performed to determine what happened and why. Composite test specimens were extracted from the beam and subjected to standard tensile tests, in order to determine the actual mechanical characteristics of the layered material. The paper presents in detail the comparison of the results as well as the methodology used in this research.

Particle flow simulation of Brazilian splitting failure characteristics of layered shale

Shale reservoir is the research hotspot in the development of unconventional oil and gas resources. The properties of bedding plane have an important influence on the mechanical behavior of shale. According to the fracture characteristics of layered shale under Brazilian splitting load, the effects of bedding angle, bond strength ratio and natural fractures on the tensile strength and fracture pattern of layered shale in Brazilian splitting test were studied by particle flow code. The evolution mechanism of meso–macro fracture of shale is analyzed by combining the dynamic change process of particle mesoscopic force chain and crack. The results show that three types of fracture patterns are observed: splitting tensile failure of shale matrix, splitting tensile failure along bedding plane and tensile–shear composite failure along shale matrix and bedding plane. Mesoscopic cracks initiate at the top and bottom loading points of the disk. After the peak load, mesoscopic cracks propagate through and appear dense force chains until macroscopic failure occurs. The bond strength ratio of bedding plane affects the failure pattern and peak strength of the specimen. With the increase in bedding angle, the tensile strength decreases gradually. Considering the influence of natural fractures, the tensile strength of shale is lower, and the crack propagation is more complex. The research model and results provide theoretical basis for the mechanical properties evaluation and fracture pattern analysis of shale.

Enhancement of high-performance structures with sustainable seashell filler-based GFRP composites in static loading

Research on reinforcing airplane structures while reducing their weight by employing sustainable materials is currently challenging. In this study, damage mechanisms, mechanical characteristics, and failure behavior of laminates made of plain-woven glass fiber/epoxy and Glass Fiber Reinforced Polymer (GFRP) with sea shell filler under low-velocity impact static loading conditions are experimentally investigated. The bi-directional GFRP type E-glass laminates with 10 plies and a total thickness of 3.35 mm are created by hand lay-up process using an epoxy matrix. Comparing GFRP with an effective ratio of sea shell filler of 5% under various impact loading, composites are characterized in accordance with ASTM standards to assess the progressive damage and failure of GFRP composite. The findings of the experiment indicate that GFRP with seashell filler composites outperforms GFRP composites in terms of impact strength, outstanding flexural strength, and tensile strength. The findings show that adding seashell filler to GFRP increased the composite’s ability to sustain various impact loads. The sample with seashell infill has a drop weight impact that is 25.26% lower than GFRP. Moreover, the flexural test demonstrated a 59.6% increase in bending over GFRP. Seashell filler outperformed GFRP in the longitudinal strength test by 33.12%, according to the results of the tensile test. Finally, the compression after impact test (CAI) manifested a remarkable increase in transverse strength by 78.23%.

Investigation on structural failure of filament reinforced barrel containment

During the launching process of a composite railgun, some working conditions may lead to the structure failure of its filament reinforced barrel. For instance, the instantaneous electric power impact caused by the unexpected large pulse current and surge from the pulse-forming network, which inspires the electrodynamic response beyond the safety limit of the barrel. More importantly, the alternating load after a long-term working causes damage accumulation and failure in the composite structure. For the railgun, considering that the radial deformation of the barrel has special effect on the contact state of the rail and armature in bore, it is necessary to focus on whether the radial stiffness of the barrel is affected even if the strength of the barrel does not decrease significantly by hidden injuries in the fiber wraps. In this study, based on the common used method of progressive failure theory, the radial stiffness attenuation process of the barrel is analyzed. The fiber fracture and composite delamination failure modes are found to be the main factors for radial stiffness attenuation of railgun barrel containment as persistent deformation will generate after these damage propagation. In addition, the loss of prestress in the fiber containment is evaluated based on structural analysis for the barrel in service and in manufacturing time. The research has found that optimized preloading seems important for improving the strength performance of the barrel.

Self-healing interface of carbon fiber reinforced composites based on reversible hydrogen-bonded interactions

The microscopic interfacial damages of carbon fiber reinforced composites (CFRCs) are difficult to repair and tend to initiate composites failure. Fortunately, the emergence of self-healing methods could effectively address this challenge. Herein, we report a self-healing interface based on the reversible hydrogen-bonded interactions in carbon fiber/polyvinyl alcohol (CF/PVA) composites system. By surface functionalization with dopamine (DA) containing active functional groups (e.g., –NH2 and –OH), the obtained polydopamine-functionalized CF (CF-PDA) possesses multiple reversible hydrogen bonds between PDA and PVA at the interface. The CF-PDA/PVA composites presented significantly higher interfacial bonding force (33%) than that of CF/PVA composites when hydrogen bonds were reconnected by thermal treatment. After five interfacial self-healing cycles, CF-PDA/PVA composites could recover a relatively high self-healing efficiency (∼73.6%). Moreover, the self-healing mechanism is further discussed by molecular dynamics simulation. The strategy of reversible hydrogen-bonded interactions is promising for developing high-performance self-healing carbon fiber reinforced composite materials.

Evaluation of multi-directional compression behaviors and failure of three-dimensional orthogonal woven composites via liquid nitrogen temperature

Three-dimensional orthogonal woven composites (3DOWCs) are extensively employed in structural engineering applications for their lightweight, high designability, and excellent interlayer performances. This work constructed two 3DOWCs with different fiber volume contents, and their multi-directional compression properties and damage mechanisms at room and liquid nitrogen temperatures (RT and LNT) were thoroughly investigated and evaluated. Temperatures, fiber volume contents, and loading directions all had a significant influence on behaviors. The stress-strain curves presented ductility at RT and gradually decreased after reaching the maximum load, whereas they were brittle and rapidly decreased at LNT. Compared to the compression properties at RT, the compression strength of 3DOWC40-LNT and 3DOWC50-LNT increased by 22.6% and 9.3% in the warp direction, 11.8% and 29.0% in the weft direction, as well as 32.9% and 24.6% in the Z direction. Additionally, edge yarn stripping and shear cracking were the primary fracture patterns for 3DOWCs under RT, while they exhibited interface layering, yarn fracture, shear cracking, and interfacial debonding at LNT, especially the deformation along the warp direction was more pronounced under Z direction compression.

FEM-SPH Coupling Approach for Impact Response Analysis of Composite Plates with Brick-and-Mortar Structure

Bioinspired nacre-like composites have attracted increasing research interests recently. They are typical composites with brick-and-mortar structure and usually employ a combination of hard material and soft material to achieve a good balance between stiffness and toughness. Impact response analysis of such composites is difficult due to their complex structure and interface. In this work, an effective finite element method-smoothed particle hydrodynamics (FEM-SPH) coupling approach is developed for impact response analysis of composite plates with brick-and-mortar structure. In the approach, hard material taking up the bulk of the composite plate is modeled with the SPH method, and soft material forming thin layer structures in the composite plate is modeled with FEM. A coupling algorithm considering failure behavior is proposed to model bonding interfaces between FEM parts and SPH parts. A particle-to-particle SPH contact algorithm is employed to handle contacts between SPH parts, and a penalty-based FEM-SPH contact algorithm is implemented to treat contacts between FEM parts and SPH parts. The developed coupling approach is used to calculate stress wave propagation in two bonded plates of the same material and different materials and a composite plate with brick-and-mortar structure. The accuracy of the coupling approach is validated by comparing the calculated results with those of analytical method and FEM. The coupling approach is then used to simulate the effects of some factors on the impact damage of composite plates with brick-and-mortar structure. The coupling approach can conveniently model the complex structure and bonding interface of the composite plates and is capable of capturing interface failure and fragmentation of the major composition of the composite plates during impact events. It provides a promising alternative for the impact response analysis of brick-and-mortar composite structures.

Application research in multi-objective constrained optimization of composite wing structure

In order to explore the optimization of composite wing structure, this paper reviews the past research works of optimization of composite wing structures worldwide and in China. It concludes that most optimization methods and calculations are useful but only applied with specified theoretic model. Then relevant composite optimization theories and strength constraints with composite lamination failure criteria, stability, aeroelasticity are sorts out. Optimizing algorithm and applied solution rounding strategy are also listed. Concentrating on weight-reduction analysis on the thickness, sequence, and angle of the composite stacking under multiple constraints, a practical model of a composite wing structure example with a large aspect ratio is completed, and the calculation is based on the finite element analysis tool Nastran and the genetic algorithm Matlab program. Two optimal solutions are given with detailed differences and the comparison of the composite structure parameters before and after calculation is also recorded. The application example indicates the feasibility of the optimization method and quadratic rounding process, the detail structure performance improvements with skin lamination change under the calculation are illustrated at the same time.

Multiscale characterization of the fracture mechanics of additively manufactured short fiber-reinforced composites

We present a multiscale characterization approach to experimentally investigate the influence of architectural features, namely pores, weakly bonded filaments’ interfaces, and layer stacking, on the failure of composites manufactured by fused filament fabrication. Combining standard approaches, such as tensile and flexural tests, with contactless techniques, we identified the local phenomena driving the damage of 3D-printed short carbon fiber-reinforced polyetheretherketone specimens. The elastic and fracture tests highlighted the process-induced anisotropy and the incomplete interface adhesion resulting in the transverse tensile modulus drop to around 20% of the longitudinal value. Equivalent fracture toughness was measured for a crack propagation along filaments’ and layers’ interfaces, while the stress intensity factors doubled for a crack propagation involving the filaments’ breakage, when compared to the interface failure. The displacement and strain contours obtained by digital image correlation emphasize the influence of the stacking (i.e., 0°–90°, ±45°) on the preferential crack propagation at the layers’ and filaments’ interfaces. The specimen inspection by scanning electron microscopy and by X-ray tomography further highlighted the influence of the printed composites’ meso and microscale architecture on the fracture mechanisms, such as the simultaneous damage of parallel ±45° oriented layers’ interfaces or the zig-zag crack propagation for specimens with ±45° stacking undergoing intralayer delamination. The elastic and fracture properties, together with the full-field measurements, provide the tools to guide the design of complex and reliable components for high-performance applications (e.g., aerospace, automotive) and benchmark for damage prediction models.

Post‐curing and fiber hybridization effects on mode‐II interlaminar fracture toughness of glass/carbon/epoxy composites

AbstractFailure by delamination is one of the primary concerns in laminated composites. The development and progression of the delamination results in the degradation of composite stiffness affecting its structural integrity and may ultimately result in composite structure failure. Therefore, knowledge of the evolution of delamination resistance and the factors which affect the delamination in composites is of utmost importance for the selection of materials. This study investigates the effect of fiber hybridization and post‐curing on mode‐II interlaminar fracture toughness (GIIC) of Glass/Carbon/Epoxy (GCE) composites. Carbon/Epoxy (CE), Glass/Epoxy (GE), and GCE composite laminates were molded employing the process of hand layup technique and post‐cured at different temperatures. GE laminates exhibited a superior load for delamination and deformation compared to CE and GCE laminates. The hybrid GCE laminates exhibited higher interlaminar fracture toughness compared to non‐hybrid GE and CE laminates, which can be attributed to the synergetic effect of Carbon and Glass fibers. The laminates post‐cured at 180°C exhibited higher fracture toughness in their corresponding groups. The delaminated surfaces of CE, GE, and GCE laminates were further examined under Scanning electron microscopy (SEM) to understand the effect of post‐curing and fiber hybridization on mode‐II interlaminar fracture toughness.

Theoretical calculation of bending capacity of a steel beam - ultra high performance concrete slab composite girder

The composite girder, which combines a steel beam with an ultra-high-performance concrete (UHPC) slab, has gained significant attention in recent years as a new type of bridge structure. However, accurately estimating the bending capacity of such girders remains a challenge, as practical methods are limited. In this article, the authors propose a theoretical approach based on the Euler-Bernoulli beam theory to determine the bending capacity of composite girders. This approach considers the assumptions of plane sections remaining plane and infinitesimal strains during bending. By applying this theoretical approach, the authors derive a formula that allows engineers to calculate the bending capacity of the composite girder. The formula takes into account the dimensions and properties of both the steel beam and the UHPC slab. The derived formula serves as a valuable tool for evaluating the structural behavior and performance of composite girders. To validate its accuracy, the authors compare the results obtained from their calculations with numerical simulations of composite girder failures caused by bending. The close agreement between the theoretical calculations and the numerical simulation results confirms the reliability and applicability of the proposed formula. This research significantly contributes to the field of composite girder design by providing a practical and reliable method for estimating the bending capacity of steel beam-UHPC slab composite girders. The proposed theoretical approach, validated through numerical simulations, offers valuable insights for the design and optimization of these composite girders in various engineering applications.

Experimental Study on Mechanical Properties and Deterioration Mechanism of Red Sandstone from the Panjiatuo Landslide under Action of Acidic Drying−Wetting Cycles

Due to frequent water level fluctuations and complex hydrochemical environments, rock slopes in reservoir areas progressively deteriorate and become unstable. This study investigated the coupling effect of drying−wetting cycles and acidic solutions on the physical and mechanical properties, strain field evolution, failure mode, and micro-mechanism of red sandstone using a series of laboratory experiments (wave velocity tests, uniaxial compression tests, the digital image correlation method, scanning electron microscopy, and X-ray diffraction). The results showed that with increasing drying−wetting cycles, the mass, P-wave velocity, elastic modulus, and uniaxial compressive strength decreased monotonically, while the water absorption and apparent strain in the strain localization band increased. Moreover, the failure mode transitioned gradually from tensile failure to shear failure or tensile-shear composite failure. The decrease in the solution pH values aggravated the changes in the physical and mechanical parameters and contributed to an increase in the secondary cracks and the occurrence of shear behavior. In addition, the coupling effect of drying−wetting cycles and acidic solutions accelerated the worsening of the microstructure and the dissolution of minerals, resulting in a loose structure with well-developed pores and fissures. These changes provide a favorable explanation for the mechanical property deterioration of red sandstone subjected to acidic drying−wetting cycles.

Enhanced Open-Hole Strength and Toughness of Sandwich Carbon-Kevlar Woven Composite Laminates.

Fiber-reinforced plastic composites are sensitive to holes, as they cut the main load-carrying member in the composite (fibers) and they induce out-of-plane stresses. In this study, we demonstrated notch sensitivity enhancement in a hybrid carbon/epoxy (CFRP) composite with a Kevlar core sandwich compared to monotonic CFRP and Kevlar composites. Open-hole tensile samples were cut using waterjet cutting at different width to diameter ratios and tested under tensile loading. We performed an open-hole tension (OHT) test to characterize the notch sensitivity of the composites via the comparison of the open-hole tensile strength and strain as well as the damage propagation (as monitored via CT scan). The results showed that hybrid laminate has lower notch sensitivity than CFRP and KFRP laminates because the strength reduction rate with hole size was lower. Moreover, this laminate showed no reduction in the failure strain by increasing the hole size up to 12 mm. At w/d = 6, the lowest drop in strength showed by the hybrid laminate was 65.4%, followed by the CFRP and KFRP laminates with 63.5% and 56.1%, respectively. For the specific strength, the hybrid laminate showed a 7% and 9% higher value as compared with CFRP and KFRP laminates, respectively. The enhancement in notch sensitivity was due to its progressive damage mode, which was initiated via delamination at the Kevlar-carbon interface, followed by matrix cracking and fiber breakage in the core layers. Finally, matrix cracking and fiber breakage occurred in the CFRP face sheet layers. The specific strength (normalized strength and strain to density) and strain were larger for the hybrid than the CFRP and KFRP laminates due to the lower density of Kevlar fibers and the progressive damage modes which delayed the final failure of the hybrid composite.

Strengthening and failure of iron-graphene composites: A molecular dynamics study

In order to contribute to the understanding of advanced materials with improved mechanical properties we investigate strengthening and failure processes in iron-graphene composites using molecular dynamics simulations. Graphene sheets are embedded in {110} planes of bulk iron. Tensile tests and shear tests are conducted and evaluated with regard to the orientation of the graphene sheet. It is found that two different failure mechanisms involving interfacial fracture and dislocation nucleation can occur due to tensile load. The shear tests revealed three mechanisms of dislocation-obstacle interaction. The highest strengthening was found for graphene sheet orientations which normal vectors are not orthogonal to the Burgers vector of the interacting dislocation.