Failure Mechanisms Of Materials Research Articles

Experimental Investigation into the Failure Mechanisms of Fabric Membrane Materials with Defective Flat Round Cracks

The emphasis of this study is placed on the investigation into the failure mechanisms of the fabric membranes when exposed to such defective cracks. This experimental study investigates the initial crack of a flat circle and conducts a uniaxial shear test on the membrane materials. The deformation of the membrane materials is obtained through an optical non-contact scanner. Our study has been conducted to assess the crack propagation of fabric membrane materials at different angles. The relationships between crack width and stress together with stress and strain are also obtained. Based on the results, a mechanic of failure on the membrane was proposed. Moreover, new findings into the ductility and energy absorption of the fabric membrane materials have been established to inform the failure mechanisms.

Introduction to the special issue on failure mechanism in advanced materials and structures

Introduction to the special issue on failure mechanism in advanced materials and structures

Representation of Thermomechanical Damage in Fiber-Reinforced Ceramic Composites at High Thermal Gradients

Ceramic matrix composites (CMCs) are the core strategic materials for the thermal structure of new-generation hypersonic aircraft. The unclear understanding of the cross-scale thermomechanical behavior and failure mechanism of materials and structures in high-temperature transient environments is a key scientific issue that restricts the reliable design and safe operation of hypersonic aircraft. In this study, a high-temperature test module in a supersonic wind tunnel with integrated various test systems was independently designed to systematically investigate the thermal mechanical damage evolution of CMCs used in astronautics applications under high-temperature transient conditions. Furthermore, a numerical method for fluid-heat-solid coupling based on an iterative solution strategy was developed and compared with an algorithm based on a wall modification strategy in terms of computational efficiency and accuracy. Besides, a comparative analysis was conducted with the temperature field distribution of the sample obtained in the hypersonic wind tunnel integration test to verify the correctness of the developed thermal-fluid-solid coupling calculation method. Finally, through thermoelastic coupling computational models, the high-thermal-gradient-induced thermomechanical damage mechanism of the CMCs was revealed, providing support for further optimizing the material system and thermal structure design of the CMCs.

Dynamic mechanical properties and failure mechanisms of rock-like materials containing main and auxiliary holes with various arrangement inclinations and spacing ratios

As a typical rock defect, circular holes significantly influence rock masses, diversifying their failure modes and ultimately weakening their bearing capacities. To study the effects of hole arrangement inclination and spacing ratio on the mechanical properties and failure mechanisms of rock-like specimens, dynamic uniaxial compressive tests were conducted by employing a modified split Hopkinson bar apparatus and digital image correlation. The results reveal a V-shaped trend in the peak stress, Young’s modulus, and absorbed energy proportion as the hole arrangement inclination increases from 0° to 90°. However, the peak strain is insensitive to changes in the hole arrangement inclination and spacing ratio. The hole spacing ratio has no significant effect on the Young’s modulus, but it causes a gradual reduction in the proportion of energy absorbed in the specimens. Moreover, shear and tensile cracks emanating from the main hole dominate the failure mode of specimens with main and auxiliary holes, as demonstrated by the resultant displacement and vertical strain contours. Rock bridges experience shear failure as the hole arrangement inclination increases from 15° to 75°, whereas the rock bridges of specimens with various hole spacing ratios tend to fail owing to tensile cracks. The interaction between main and auxiliary holes with an arrangement inclination of 0° is the weakest, suggesting that tunnel groups should be arranged perpendicularly to the direction of dynamic loading.

A numerical investigation of energy dissipation mechanism of visco-hyperelastic bimaterials subjected to low-velocity impact

Impact protection equipment typically relies on the material failure mechanism and is frequently discarded after the impact. A promising alternative emerges utilizing a foam-infilled lattice bimaterial with shape recovery trait and customizable impact protection capability. This study employs a numerical approach to elucidate the energy dissipation mechanism exhibited by the bimaterial under low-velocity impact condition. The experiment-based inverse method is used to characterize visco-hyperelastic models for two base materials. The investigation reveals that the interaction between the two base materials significantly amplifies the foam’s energy dissipation capability, resulting in an overall higher energy dissipation for the bimaterial. Besides, the study establishes a close correlation between the bimaterial’s effective viscoelastic properties and the enhancement in energy dissipation. Furthermore, the numerical design of experiments (DOE) analysis of base material properties indicates that there is an optimal region for selecting the critical foam material constants for a significant improvement of bimaterial energy dissipation. The results reveal that the combination effect of material interaction and material viscoelastic properties constitutes the fundamental elements of bimaterial energy dissipation mechanism. The insight derived from this study can inform the future design and material selection of a more complicated bimaterial across a wide range of impact protection applications.

Study on bearing capacity and damage mode of carbon fiber composite J-type structures in oilfield completion tool connections

Carbon fiber composite structures have a broad application prospect in oilfield completion tool module connection. However, the material failure mechanism is still unclear. In this paper, the mechanical properties and failure mode of T700/7901 composite J-type structure are investigated from experimental and finite element perspectives. Firstly, the load-carrying and failure properties of the structure were analyzed through typical mechanical property experiments such as tensile, bending, and compression, and the fiber, matrix damage, and delamination damage are the main reasons for the failure of the mechanical properties of the material. Secondly, a numerical model of the progressive damage ontological relationship of the composite material was established, and the accuracy of the model was verified by combining the experimental results. Based on the above study, this paper proposes the failure mechanism and optimization of composite J-type, which provides useful guidance for the design of fiber composite structures for oilfield completion tool types in the future.

Representative rupture stress-based parameter for characterizing the intensity of creep fracture constraint effect on creep crack growth rate

The introduction of creep fracture constraint parameter offers the possibility of accurately obtaining the CCG rate for specimens/structures subject to different constraint levels through the establishment of constraint-dependent CCG rate equation. However, experimental evidence indicates that the existing constraint-dependent CCG rate equation is generally material- and stress regime-dependent. It is noted that the dependencies may be attributed to the intrinsic difference in creep failure mechanisms of materials, which has not been fully considered by previous constraint parameters. To cope with the dependencies, a parameter, Kz, for characterizing the intensity of constraint effect is proposed in this work based on the representative rupture stress, which could better reflect the operative creep failure mechanism sustained by the material. To justify the parameter, finite element analysis is carried out for five different materials based on experimental data available in the literature. Results show that, compared to the existing constraint parameters, R* and Ac, the Kz is capable of characterizing the crack-tip constraint level under the influence of creep failure mechanism. Furthermore, a generalized constraint-dependent CCG rate equation is established based on the Kz, which overcomes the material and stress regime dependencies of the existing equation. Finally, to clarify the advantage of the Kz, further comparison between the new parameter and the existing parameters is made.

Static Behavior of a 3D-Printed Short Carbon Fiber Polyamide: Influence of the Meso-Structure and Water Content.

The knowledge of the mechanical behavior of a 3D-printed material is fundamental for the 3D printing outbreaking technology to be considered for a range of applications. In this framework, the significance, reliability, and accuracy of the information obtained by testing material coupons assumes a pivotal role. The present work focuses on an evaluation of the static mechanical properties and failure modes of a 3D-printed short carbon fiber-reinforced polyamide in relation to the specimen's unique meso-structural morphology and water content. Within the manufacturing limitations of a commercially available printer, specimens of dedicated combinations of geometry and printing patterns were specifically conceived and tested. The specimens' meso-structure morphologies were investigated by micro-computed tomography. The material failure mechanisms were inferred from an analysis of the specimens' fracture surfaces and failure morphologies. The outcomes of the present analysis indicate that each test specimen retained proper mechanical properties, thereby suggesting that they should be accurately designed to deliver representative information of the underlying material beads or of their deposition layout. Suggestions on the adoption of preferred test specimens for evaluating specific material properties were proposed.

Analyzing the Sound of Materials: Application of Acoustic Emission Technique for Monitoring Material Behavior

During the last years, some concerns have arisen in relation to the outcome of mechanisms of failure in composite materials according to its mechanical behavior. Such interest resulted in the development of new complex structures in order to enhance its mechanical resistance and the controlling of damage processes. Nevertheless, it is imperative to understand the degree of mechanical performance that these materials can achieve when under external stresses. In this regard, applying Acoustic Emission (AE) technique is widely known as a very effective technology for identifying and monitoring damage progression on different kind of materials and structures providing valuable information. AE is a non-destructive technique (NDT) capable of detecting micro damage initiation and propagation along several types of failure modes such as reinforcement/matrix interfacial debonding, matrix cracking, delamination, fracture, etc. This paper examines applications of AE regarding to composite materials where fracture processes are generally more complex and data interpretation is correspondingly more difficult. Finally, in order to continuously improve the reliability of this technique, several researches have advanced its trustworthiness through innovations in AE technology. Some perspectives are discussed.

Investigation of the impact of fiber incorporation on the properties of high belite cement

In contrast to ordinary portland cement (PC), the manufacturing process of high belite cement (HBC) boasts superior resource utilization, reduced energy consumption, and diminished greenhouse gas emissions. Additionally, HBC exhibits notable strengths in terms of durability and mechanical properties. This study delves into the thermal characteristics of hydration, mechanical behaviour, and failure mechanisms of HBC materials, both with and without fiber admixtures, employing a multifaceted approach encompassing hydration heat experiments, uniaxial compression tests, Brazilian tensile tests, alongside advanced techniques such as acoustic emission (AE) and digital image correlation (DIC). The results indicate that HBC has lower hydration heat release, contributing to a reduction in hydration temperature rise, offering advantages in large-scale structural construction. In terms of strength development, HBC exhibits compressive and tensile strengths similar to PC, while the strength of basalt fiber-reinforced HBC is notably lower than both. In terms of failure modes, both HBC and PC undergo shear failure in uniaxial compression tests, whereas basalt fiber-reinforced HBC experiences splitting failure. In Brazilian tensile tests, HBC and PC exhibit single-direction cracking, while basalt fiber-reinforced HBC shows synchronous cracking at the top, middle, and bottom. Due to the crack-arresting effect of basalt fibers, basalt fiber-reinforced HBC displays a bimodal feature on the stress-strain curve and features a stress plateau on both the stress-strain and strain energy development curves.

Superior mechanical and ballistic performance of carbon nanotube‐reinforced phenolic/aramid fabric composites via a two‐roll pressing process

AbstractIn this study, aramid fiber (AF)/phenolic resin prepreg was fabricated by impregnating low content carbon nanotube (CNT)‐reinforced phenolic resin with aramid fabric through a two‐roll pressing process. Both non‐functionalized and carboxylic‐functionalized CNTs (CNTs and CNTs‐COOH) were used for comparison study. For each of the formulations, composite laminate was made by a hot‐pressing process with a number of the prepregs stacked together. Mechanical properties and ballistic performance of the laminates and material failure mechanisms were evaluated and analyzed. Both non‐functionalized and CNTs‐COOH can effectively improve the mechanical and ballistic performance of the laminates. With CNTs‐COOH reinforcement, better results were achieved. As compared with the laminate without CNT reinforcement, 1.0 wt% CNTs‐COOH‐reinforced laminate showed 19.41%, 22.29%, and 45.83% improvement in tensile, flexural, and adhesion shear strength, respectively. The ballistic test results showed that the V50 and the specific energy absorption (SEA) were increased by 5.77% and 13.44%, respectively. The correlation between mechanical and ballistic performance of the composites was analyzed and conducted.

Atomistic Investigation of Grain Boundary Fracture in Alumina.

Grain boundary (GB) fracture is a major mechanism of material failure in polycrystalline ceramics. However, the intricate atomic arrangements of GBs have impeded our understanding of the atomistic mechanisms of these processes. In this study, we investigated the atomic-scale crack propagation behavior of an α-Al2O3 ∑13 grain boundary, using a combination of in situ transmission electron microscopy (TEM) and scanning TEM. The atomic-scale fracture path along the GB core was directly determined by the observation of the atomic structures of the fractured surfaces, which is consistent with density functional theory calculations. We found that the GB fracture can be attributed to the weaker local bonds and a smaller number of bonds along the fracture path. Our findings provide atomistic insights into the mechanisms of crack propagation along GBs, offering significant implications for GB engineering and the toughening of ceramics.

Failure Mechanism and Residual Stress Analysis of Crystal Materials for the Thermal Battery

This paper investigates the thermal battery as a research topic. We conducted an in-depth analysis of various thermal battery aspects, such as the cathode material CoS2 and electrolyte material morphology, crystal type, and interface state changes before and after service. The aim was to explore the core reaction and main failure mechanisms of the thermal battery. Prior to the reaction, the thermal battery cathode and electrolyte material consisted of pure-phase CoS2 and a composition of MgO-LiF/LiBr/LiCl. After service, the cathode and electrolyte of the single thermal battery exhibited significant morphological alterations caused by the presence of a molten state. The cathode transformed from CoS2 to Co3S4 and Co9S8 together with the presence of a marginal quantity of Co monomers visible throughout the discharge process, which was confirmed by means of XRD and XPS analyses. After the reaction, the electrolyte material was primarily made up of LiF, LiBr, and LiCl while the crystal components remained largely unaltered, albeit with apparent morphological variations. As was deduced from the thermodynamic analysis, the cathode material’s decomposition temperature stood at 655 °C, exceeding the working temperature of the thermal battery (500 °C) by a considerable margin, which is indicative of outstanding thermal durability within the thermal battery’s operational temperature range. Furthermore, the discharge reaction of the positive electrode was incomplete, resulting in reduced CoS2 residue in the thermal battery monomer after service. The reaction yielded a combination of Co3S4, Co9S8, and small amounts of Co monomers, indicating possible inconsistencies in the phase composition of the pole piece during the reaction process. In this study, we examine the distribution of residual stress in the thermal battery under various operating conditions. The simulation results indicate that exposure to a 70 °C environment for 2 h causes the maximum residual stress of the battery, which had an initial temperature of 25 °C, to reach 0.26 GPa. The thermal battery subjected to an initial temperature of 25 °C exhibited a maximum residual stress of 0.42 GPa subsequent to a 2-hour exposure to a temperature of −50 °C.

A continuous-discontinuous deformation analysis method for research on the mechanical properties of coarse granular materials

The mechanical properties of coarse granular materials play a crucial role in the safety of rockfill dams. From a mesoscopic viewpoint, the macroscopic mechanical properties of these materials are a result of the interactions between particles and the progression of particle breakage. Traditional continuum-based numerical methods struggle to accurately analyze the mechanical properties of coarse granular materials. Discontinuous deformation analysis (DDA) is a more suitable algorithm for studying these properties due to its significant benefits in block displacement mode and open-close iteration for contact handling. In this paper, a continuous-discontinuous deformation analysis method (CDDA) based on the conventional DDA is developed for the numerical investigation of coarse granular materials' mechanical properties. This method incorporates critical kinetic damping, multi-stageloading, stricter displacement convergence criteria and particle breakage simulation. It can provide a comprehensive representation of deformation, particle breakage, force chain, shear zone, and stress–strain curve evolutions. The CDDA results are found to be consistent with indoor test results and can more effectively disclose the deformation and failure mechanism of coarse granular materials. Furthermore, CDDA is employed to examine the impacts of particle size and end friction, leading to valuable insights regarding these effects.

Effect of graphene nano-platelets on the low-velocity-impact and compression-after-impact strength of the glass fiber epoxy composite laminates

Detecting the low-velocity impact damage on the FRP composite structures can be challenging because the visible signs on the surface may be subtle. Mitigating the effects of BVID (Barely Visible Impact Damage) is crucial in ensuring the safety and reliability of composite components, especially in industries where these materials are commonly used, such as aerospace and automotive. This article explores the experimental investigations of the impact and post-impact damage propagation under compression in the Graphene Nano-Platelets (GNPs) infused glass fiber epoxy composite laminates. A comparative study of varying the percentage of the nano-platelets (0, 0.25, 0.5, and 0.75%) in the matrix material of the composite laminate is presented. The impact tests at low energies (15 J, 20 J, and 25 J), followed by the quasi-static compression tests, are carried out as per the procedures mentioned in the ASTM D7136/D7137. The digital image correlation technique (DIC) is used to measure strains and plot the strain field on the impacted face of the specimen under compression. Damage envelopes of the impact and compression tests are studied using X-ray CT scans. Micro-level failures are observed through Scanning Electron Microscopy (SEM) to get better insights into the failure mechanism of the composite materials under impact and compression loadings. Upon completing the study, it is found that the addition of the GNP into the matrix materials not only increased the impact performance but also increased the load-carrying capacity of the laminate under compressive loading. A decrement of 2–21% in the energy absorbed in the damage formation is seen with the incorporation of GNPs into composite materials. A maximum increment of 17% in the compressive strength is observed for the composite laminates with the 0.75% GNPs. However, for a particular percentage of the GNP, the compressive strength of the laminate is reduced with an increase in impact energy compared with its virgin counterpart. From X-ray CT scans, it is seen that the laminate under the compression tests fails due to excessive ply-splitting and the delamination at the damage site created during the impact. Fiber breakage, fiber brooming, matrix cracking, fiber-matrix debonding, etc., are some of the other failure modes observed in SEM studies.

Research on damage evolution mechanisms under compressive and tensile tests of plain weave SiCf/SiC composites using in situ X-ray CT

Abstract To investigate the damage evolution and failure mechanisms of fiber-reinforced composite materials under complex conditions, this study conducted in situ X-ray computed tomography (CT) compression and tensile tests on plain weave two-dimensional woven SiC/SiC composite materials. The obtained CT in situ image data captured the behavior of materials during loading and after failure. Using the image reconstruction of CT data, the actual microstructure and damage evolution of the material under six consecutive loading levels were accurately revealed. Three-dimensional visualization models of the composite material were established using image processing software to analyze the damage evolution under compression and tension, and the failure mechanisms were compared. The results showed that the compression and tension failure mechanisms of SiC/SiC composite materials were similar, with the transverse cracking of the matrix being the first mode of damage, followed by delamination between layers and longitudinal matrix cracking of fiber bundles. Specifically, in terms of compression failure, the strength of the fiber bundle itself has a greater influence, and fiber fracture is the main cause of ultimate material failure. On the other hand, the primary cause of tensile failure is the presence of porosity defects generated during material fabrication. Consequently, the tensile material fails earlier and can withstand lower loads.

Molecular Dynamics Investigation of Shock-Induced Deformation Behavior and Failure Mechanism in Metallic Materials

Molecular Dynamics Investigation of Shock-Induced Deformation Behavior and Failure Mechanism in Metallic Materials

The Material Heterogeneity Effect on the Local Resistance of Pultruded GFRP Columns.

Pultruded GFRP (glass fiber-reinforced polymer) materials are widely used in structural engineering because of their lightweight, corrosion immunity, and electromagnetic transparency. However, the design of load-bearing components facing substantial compressive stresses, e.g., columns, must be more stringent than steel structures due to excessive deformability, material heterogeneity, and vulnerability to stress concentration. This manuscript investigates the failure performance of locally produced GFRP materials, focusing on the material heterogeneity effect on the mechanical resistance of a support joint of a pultruded tubular GFRP column. This experimental campaign employs relatively short rectangular profile fragments to isolate the support behavior and verify a simplified numerical finite element model, which neglects the nonlinearity of GFRP material. This work determines the material failure mechanisms behind the mechanical performance of pultruded profiles subjected to longitudinal compression for various column lengths.

An enhanced constitutive model to predict plastic deformation and multiple failure mechanisms in fibre-reinforced polymer composite materials

Spurious damage modes in continuum damage mechanics models for fiber-reinforced polymer composite materials based on the effective stress tensor can be generated when large strains occur. A methodology to prevent this spurious phenomenon is developed in the present work. The longitudinal damage activation functions are based on the effective stress tensor, however, nominal stresses are used on the transverse damage activation functions. The proposed method can be straightforwardly implemented on previously-developed constitutive models which use the effective stress tensor, an explicit implementation of the proposed constitutive model is presented. The enhancement of the predicted failure mechanisms obtained from the present constitutive model, with respect to the models which use the effective stress tensor, is demonstrated. The proposed constitutive model presents a good agreement of the predicted failure pattern obtained from open-hole compressive experimental tests, as well as on the predicted failure strength.

Structural response of steel sandwich panels with PUR foam core subjected to edgewise compression: Experimental, numerical, and analytical considerations

With the objective of leading to innovative lightweight structural components in the construction sector using sandwich panels with polyurethane foam and steel face sheets, different studies were conducted on such structures, including experimental, numerical, and analytical campaigns. The experimental campaign includes the mechanical characterisation of the constituent materials and the edgewise compressive test of small-scale sandwich panels. The test protocols are detailed, and their influence on the results is assessed. Through the use of digital image correlation recordings, deformation patterns and failure mechanisms in the constituent materials and the composite structure are identified. Material constitutive models are calibrated based on the experimentally obtained results. The accuracy of such models is first evaluated against the stress–strain curves recorded during the experiments. In the second stage, the response of the sandwich panels subjected to edgewise compressive loading is simulated. A parametric analysis on the sensitivity of the numerical models to the initial geometrical imperfections is shown to be fundamental to capturing the behaviour of the sandwich panels. Furthermore, the experimental and numerical results are compared to analytical solutions of the problem of the edgewise compression of sandwich panels. Finally, a thorough discussion of the obtained experimental, numerical and analytical results is presented, along with comparisons to results available in the literature.