Failure Modes Of Composites Research Articles

Stability Analysis of the Landfill Slope with an Engineered Berm Under Composite Failure Mode

In order to increase the capacity of landfills while ensuring a certain degree of stability of such structures, an engineered berm is typically constructed at the front slope of the landfill. For this type of landfill slopes, this paper primarily focuses on the construction and verification of stability assessment models for such structures. Initially, the calculation models of the safety factor were established, considering over and under berm failure modes separately. Subsequently, through error analysis, it was determined that it is feasible to evaluate the stability of this type of landfills by substituting the true safety factor with the average safety factor obtained from the calculation model. The analysis for parameters and slip surfaces was then conducted to investigate the impact of parameters associated with the engineered berm on the landfill slope stability. Finally, a visual comparison and brief discussion were conducted on the average safety factors under translational and composite failure modes. Thus, the critical failure modes under specific working conditions can be reasonably ascertained, which holds significant practical implications for enhancing the reliability of stability assessment of such landfill slopes.

Efficacy of carbon nanotube bucky paper for interlaminar damage sensing in composites and fiber‐metal laminates

AbstractDelamination between adjacent laminas and debonding at the fiber/metal interface are common failure modes in composites and fiber‐metal laminates (FMLs). During the initial stages, these flaws are difficult to detect because of their small size and limited applicability of existing damage‐sensing techniques due to the associated heterogeneity and anisotropy with composites and FMLs. Here, we demonstrate a feasible interlaminar damage‐sensing strategy in composites and FMLs using carbon nanotube (CNT) bucky paper (BP). The microstructure dependence of BP electrical conductivity allows it to sense the damage under varying loading conditions. The accuracy of strain sensing with BP is similar to the commercial 120 Ω strain gauge. The BP sensor accurately detects the interlaminar damage in composites (glass fiber/epoxy, carbon fiber/epoxy) and glass fiber–Al (GLARE) laminates. The delamination is marked by a steep rise in the electrical resistance of BP‐modified coupons. Moreover, the sensing capability of the BP sensor is found to be independent of the electrical conductivity of the tested coupons. Thus, the present approach is applicable to sense the interlaminar damage in a much wider class of structural composites and FMLs.Highlights Timely and accurate damage detection in composites is important to ensure their structural integrity. Electrical resistance of bucky paper (BP) varies with deformation. Performance of the BP sensor is comparable to the strain gauge at small strains. BP accurately captures interlaminar damage in composites and FMLs. BP is suitable for damage sensing in a wider class of layered materials.

Enhancement Effect of Phragmites australis Roots on Soil Shear Strength in the Yellow River Delta

Soil erosion is one of the causes of ecosystem fragility in the Yellow River Delta. Plant roots can improve soil shear strength and effectively prevent soil erosion. However, there are no studies on soil shear strength in the Yellow River Delta. In this study, Phragmites australis (PA) root–soil composites with different root area ratios (RARs) (RARs = 0%, 0.06%, 0.14%, 0.17%, 0.19%, 0.24%, 0.36%) were prototypically sampled from the Yellow River Delta. Direct shear tests of root–soil composites were performed by a ZJ-type (three-speed) strain-controlled direct shear apparatus. The normal stresses were 25, 50, 100, and 200 kPa, and the shear rate was 1.2 mm/min. The results showed that PA roots significantly increased soil shear strength and cohesion with maximum growth rates of 219.0% and 440.1%, respectively. An optimal RAR of 0.14% in the range of 0~0.36% maximized the shear strength and cohesion of the root–soil composites. The internal friction angles of root–soil composites with different RARs did not differ significantly from those of the rootless soil. This indicates that the increase in shear strength was mainly due to an increase in cohesion. In addition, overall shear failure was the primary failure mode of rootless soil, with the roots pulled out of the soil in the root–soil composite failure mode. It is important to note that the root is deflected during shear in the direction opposite to the direction of the shear stress. These findings deepen our understanding of the effect of vegetation roots on soil shear characteristics and provide a scientific basis for the protection of bank slopes, soil and water conservation, and vegetation restoration in the Yellow River Delta.

Evaluation for tensile failure process of NOL rings based on infrared thermography

This paper presents a new method for evaluating the failure and processing technology of fiber-winding composites based on infrared thermography. Firstly, infrared thermography was used to monitor the surface temperature evolution during the loading of Naval Ordnance Laboratory (NOL) rings. Secondly, the mechanical and temperature data were recorded simultaneously until the failure of the NOL rings occurred. Thirdly, the mechanical results were compared with the monitoring results obtained from infrared thermography concerning the failure of the NOL rings. Lastly, an evaluation was conducted regarding the capability of infrared thermography to elucidate the failure of the NOL rings. The experiment results demonstrated that infrared thermography can characterize the failure process and failure modes of fiber-winding composites with limited mechanical or optical technology. Besides, this testing technology provides a significant advantage when comparing fiber volume fractions, particularly in situations where professional testing devices are unavailable. This work provides a new reference for the application of infrared thermography within the domain of fiber-winding composites.

Study on mechanical degradation of Ferrite/ martensite and austenitic steels in high-temperature supercritical carbon dioxide environment

The mechanical degradation mechanism of T91 ferrite/martensite steel at 500 °C and 316NG austenitic steel at both 500 °C and 600 °C in supercritical carbon dioxide were investigated in detail by slow strain rate tensile tests and first-principles calculations of the adsorption and dissociation of CO2. In high-temperature CO2 atmosphere, CO2 could spontaneously dissociate into CO and O, and the spontaneously and partially dissociated O atoms exhibited a strong interaction with Cr. As the temperature was increased to 600 °C, the partial dissociation of CO2 occurred more rapidly and the ultimate tensile strength and total elongation of 316NG steel decreased significantly as well. Furthermore, a composite failure mode with intergranular brittle fracture and ductile fracture was investigated.

Internal shear damage evolution of CFRP laminates ranging from −100 °C to 100 °C using in-situ X-ray computed tomography

Carbon Fiber Reinforced Polymer (CFRP) composites have been widely used in aerospace due to their high specific stiffness, strength, and fatigue properties. However, the ambient temperature significantly influences CFRP's mechanical properties and damage evolution, deriving from the temperature effect on the microstructural behavior and the mesoscopic damage evolution. In this study, the temperature-dependent in-plane shear failure behavior of CFRP composites was investigated. In-situ X-ray Computed tomography (CT) tensile experiments of laminates ([45°/-45°]2s) at RT, −100 °C, and 100 °C were carried out to study the in-plane shear failure mechanisms. The 3D fracture morphology was extracted with internal damage evolution process estimated and quantified. The in-situ 3D deformation fields of critical regions were acquired using the Digital Volume Correlation (DVC) method. The effect of temperature on strain field and the correlation between the high-strain region and the fracture location were analyzed. The results revealed the temperature correlations and failure mechanisms of CFRP's mechanical characteristics and internal damage evolution process. Compared to room temperature (RT), the delamination damage area of the sample increased by 80 % at 100 °C. Meanwhile, the shear modulus of CFRP decreases by 78.4 % from −100 °C to 100 °C, and the fracture strain increases by 95 % from RT to 100 °C. The DVC results indicated a dispersion of high-strain regions at −100 °C, reflecting the brittle damage characteristics, while an extensive ductile deformation region was captured at 100 °C. Fiber-matrix debonding is the dominant failure mode of composites under shear loading, whereas significant matrix cracking was observed at −100 °C and partial fiber pullout occurred at 100 °C.

Failure modes and non-destructive testing techniques for fiber-reinforced polymer composites

Prognostics and health management (PHM) is an enabling technology essential for the safe operation and conditional maintenance of any engineering system. Over the past two decades, the use of fiber-reinforced polymer (FRP) composites has increased to develop high-strength, lightweight, and durable composite structures. PHM technology has been widely adopted in the composites industry to address challenges such as damage detection, localization, remaining useful life (RUL) prediction, and maintenance scheduling. However, implementing PHM technologies for FRPs necessitates a thorough understanding of their failure modes and the non-destructive testing (NDT) techniques commonly used to assess their health condition. Therefore, this review provides a comprehensive discussion on the failure modes of FRP composites based on practical loading conditions, examines several NDT techniques employed on FRP composites, detailing their advantages and limitations, and highlights the current challenges while providing future directions for the use of NDT techniques in PHM of composite structures. Thus, the review aids practitioners, the scientific community, and new researchers in understanding the failure modes of FRP composites and exploring recent advancements in NDT techniques to address the current challenges and limitations in PHM of composite structures.

Forming Epoxy Coatings on Laser-Engraved Surface of Aluminum Alloy to Reinforce the Bonding Joint with a Carbon Fiber Composite

This study designed laser engraving and resin pre-coating (RPC) treatments on an aluminum alloy (AA) surface to construct through-the-thickness “epoxy pins” for improving the bonding strength with carbon fiber reinforced polymer (CFRP). A laser engraving treatment was used to create a pitted structure on the AA surface; higher wettability was acquired and greater vertical spaces were formed to impregnate epoxy resin, resulting in stronger mechanical interlocking. The RPC technique was further used to guide high-viscosity epoxy resin into pits to form the epoxy coatings and to minimize defects between the resin and the substrate. The bonding strength of the specimen treated with both laser engraving with a unit dimension of 0.3 mm and RPC increased up to 227.1% in comparison with that of the base. The failure modes of the hybrid composites changed from the debonding failure of the AA surface to the delamination-dominated failure of the laminated CFRP composites. It was confirmed that laser engraving is a feasible and effective method when combined with RPC for treating AAs to improve the bonding strength of AA-CFRP composites, which provides a reference for preparing high-performance hybrid composites with metals.

A semi-analytical method for determining the mode-I delamination R-curve and fiber bridging traction-separation law of Double-double laminates

Delamination, as one of the most prevalent failure modes of composites, was significantly influenced by the interface angles. In contrast to the limited combinations of interface angles found in traditional laminates, DD laminates, with unique sequence [±Φ/±Ψ]rT and diverse interface angles , urgently required extensive experiments and high-precision simulation analyses to delve into the complexities and unique properties of their interlayer performance. However, the calculation process of current method for determining the R-curve and the bridging traction-separation law was time-consuming. This study proposed a simplified semi-analytical method based on the Euler–Bernoulli beam theory that only required recording initial crack length, final crack length, initial compliance and final compliance. The method validation showed that the deviation between the results obtained from the semi-analytical method and the MBT method averaged no more than 2%. In addition, a tri-linear cohesive zone model based on the delamination fracture micro-mechanism was developed combining semi-analytical method. Both the initial load and ultimate load errors between the simulation and experimental results were within 5 N, showing the accuracy of the model and the semi-analytical method. This method provided a simple and effective way to study the delamination propagation behaviors of DD laminates.

A phase-field framework for modeling multiple cohesive fracture behaviors in laminated composite materials

This work proposes a phase-field (PF) framework to characterize the multiple fracture behaviors and quasi-brittle failure mechanisms in fiber reinforced laminated composites. The multi-phase field model considering the distinct failure mechanisms of composites is first derived based on thermodynamic principles. A hybrid PF formulation is proposed through the reasonable definition of the energy functional for each field, and a PF regularized cohesive zone model (CZM) combined with Hashin failure criteria is achieved for the typical failure modes in composites. The proposed PF-CZM is endowed with a linear softening behavior and is proven to be independent of the internal length scale parameter. The multiple fracture modeling of composite laminates is achieved by coupling the PF model for intralaminar failure with the cohesive interface element for interlaminar one. The model’s validation is demonstrated by several representative numerical examples, and results show that both the intralaminar fiber/matrix fractures and the induced interlaminar delamination, as well as their complex interactions, are well captured by the proposed model.

Residual strength and failure mechanism of CF/PPS composites with delamination damage

AbstractDelamination is one form of damage in composite laminates. The effects of delamination damage locations (thickness direction of laminates) on the residual compressive strength and failure mechanism of carbon fiber/polyphenylene sulfide (CF/PPS) composites are studied by damage morphology, full‐field strain and finite element simulation. The closer the delamination is to the center of the composite, the lower the residual compressive strength. The failure mode of composites is dominated by 0° fiber fracture, which is divided into bulging, delamination propagation, and fracture. The delamination locations significantly affect the first two stages.Highlights Constructing delamination damage in composites by interlayer preset defects. Simulation and damage analysis to reveal the mechanism of compression failure. The relationship between delamination depth and damage stage is revealed.

Effect of salt–fog spray environment on bending fatigue properties of 3D woven composites

In this study, the effect of salt–fog spray corrosion environment on bending fatigue properties of three-dimensional (3D) woven composites was investigated. Three test environmental conditions, namely a normal environment, two cycles of salt–fog spray corrosion environment, and four cycles of salt–fog spray corrosion environment, were designed. In addition, the salt–fog spray corrosion mechanism, the bending fatigue properties, damage mechanisms, and failure modes of 3D woven composites were studied. The results showed that the bending strength and bending modulus decreased by 5.5 and 9.3%, and 2.27 and 3.45% after two and four salt–fog spray cycles, respectively, compared with that of the normal environment. The bending fatigue properties of 3D woven composites were related to the applied stress and salt–fog spray cycles. The salt–fog spray environment was responsible for the degradation of the interface bonding strength. The maximum reduction ratio of bending fatigue life after salt–fog spray treatment exceeded 70%. The brittle fracture characteristics of 3D woven composite yarn were more pronounced with an increase in salt–fog spray aging cycles.

Nonlinear analysis model of the progressive damage of aluminum–wood sandwich structures under high-speed impact conditions

The impact responses of various protective structures composed of 2A12 aluminum alloy and wood laminates were studied experimentally. The experiments were conducted using different impact energies. By varying the sandwich material thickness and using two different bullet shapes, the effects of the sandwich material’s damage process and the core layer thickness on the protective performance were studied. The multilayer structure’s core layer failure condition was determined using the improved 3D Hashin criterion and a finite element model was established using Abaqus software. Tensile and three-point bending tests were conducted and the progressive damage model was verified statically. The model was then verified dynamically using the Hopkinson bar test. The mechanical properties of the materials under high dynamic strain rates were obtained through action loading testing of the specimens at different loading rates. The loading waveform was analyzed and a stress-strain relationship diagram was drawn at various strain rates. By verifying the experimental data, a numerical model that could capture the deformation and failure details during crushing was established, and the composite target plate impact failure mode and the trajectory change law were described. This study could lead to use of a new impact damage prediction method for laminates.

Effect of warp yarn paths on the symmetrical cyclic bending fatigue properties of 3D woven composites

AbstractIn this study, the symmetric cyclic bending fatigue properties of three‐dimensional (3D) woven composites under the condition of R = −1 were investigated. Three types of 3D preform structures with different warp yarn paths were designed, and a bending fatigue testing fixture suitable for 3D woven composites under R = −1 conditions was developed. In addition, the bending fatigue properties, damage mechanisms, and failure modes of three composites were studied. The results showed that the warp yarn paths were responsible for the differences in quasi‐static bending properties. The bending fatigue properties were related to the warp yarn paths and applied stress. Satin woven (SW) structure had the highest bending fatigue failure strain value, followed by the twill woven (TW) structure, and the plain woven (PW) structure had the lowest. The bending fatigue limits of PW, TW, and SW structures were 40% (136 N), 40% (210.5 N), and 16% (119.4 N) stress levels, respectively. The bending fatigue failure mode of 3D woven composites was softening failure under the condition R = −1.Highlights The warp yarn paths significantly affects the quasi‐static bending properties. A symmetrical cyclic bending fatigue testing fixture was developed. The symmetrical cyclic bending fatigue life of 3D woven composites was obtained. SW composites have the highest bending fatigue failure strain value. The symmetrical cyclic bending fatigue failure modes were softening failures.

Mechanical behavior of bio‐inspired composites made of co‐continuous geopolymer and 3D‐printed polymer

AbstractGeopolymers (GPs) are emerging, low‐density ceramic materials that are simple to manufacture, with high elastic modulus and strength, albeit with low toughness. Fiber reinforcements have been used to achieve varied ductile behaviors, but little is known about the GP addition to polymeric frame structures. Thus, drawing inspiration from the nanostructure of bones, this paper investigated an interpenetrating, co‐continuous composite consisting of a GP as the stiff but brittle phase, and a 3D‐printed polymer (PA12 White) as the soft and deformable phase. The composite mechanical properties and failure modes were studied experimentally using uniaxial compression and four‐point bending tests. The co‐continuous network constrained brittle cracking within the GP and reduced strain localization in the polymer. The results showed that the composite had higher strength (56.11 ± 2.12 MPa) and elastic modulus (6.08 ± 1.37 GPa) than the 3D‐printed polymer and had higher toughness (5.98 ± 0.24 MJ/mm3) than the GP for the specific geometries examined. The shape effect study demonstrated that cubic structures had higher elastic modulus and strength but at the expense of lower toughness when compared to rectangular prism structures. The study of scale effects indicated that increasing the number of periodic unit cells while maintaining consistent bulk dimensions led to augmented strength and toughness, albeit without statistically significant alterations in elastic modulus. Thus, this paper presents an experimental realization of a novel, bio‐inspired, interpenetrating, GP–polymer composite design, offering improved strength and toughness. It also provides valuable insights into the shape and size effects on the mechanical properties of this new composite.

Manipulating interfacial bond for controlling load transfer in 3D printed fiber reinforced polymer composites

The fiber/matrix interface is a critical item that affects Fiber Reinforced Polymer (FRP) composites mechanical performance due to its control of the load transfer mechanism. Partially bonded interfaces have been shown to affect the failure mode of FRP composites. This article examines the significance of manipulating the fiber/matrix interfacial bond in 3D printed FRP composites on the mechanical performance of multilayer 3D printed FRP composites. Three designs are investigated with different fiber stacking sequences, fiber orientation, and interfacial bond configurations. The designs have a low coefficient of variation in load fractions between layers to enable a gradual load transfer and progressive failure. Utilizing 3D printer chamber temperature changes, a composite with a controlled bond configuration is achieved using thermal blocks. It was observed that the controlled bond configurations resulted in promoting progressive failure and increased the strain at failure of 3D printed FRP composites. The observations of direct tension tests were supported with interlayer shear strength and interfacial adhesion tests which explained the weakened load transfer in the thermal block configurations. Using the interface manipulation strategy with thermal blocks in 3D printed specimens, a 25% lower interlayer shear strength and a 65% lower interfacial adhesion was achieved compared with un-modified interfaces. These changes attribute to the altered load transfer mechanism in 3D printed glass fiber reinforced composites and high strain to failure of up to 5% using high strength high stiffness fiber orientations. This work does not incorporate any new materials into the thermoplastic-fiber 3D printed structure which has been the strategy of past work to modify mechanical performance. Alternatively, a unique approach by using chamber and print bed temperature characteristics to modify the interfacial bond has been adopted that has shown to promote progressive failures and improve ductility in FRP composites. This study furthers the development of ductile designs in FRP composites with 3D printing technology in aerospace, wind, infrastructure, and automobile applications.

Fractographic analysis of fiber‐reinforced polymer laminate composites for marine applications: A comprehensive review

AbstractIn the past decade, polymer‐based glass fiber‐reinforced laminate composites have gained significant popularity in various mass transit applications, including marine, aircraft, and automotive industries. However, it is crucial to consider the degradation and potential failure of these materials, especially in mass transit networks. To address this concern, fractographic analysis has emerged as a valuable approach for investigating fracture surfaces, extracting vital information, and facilitating the development of new materials. Furthermore, it sheds light on the underlying physical mechanisms that contribute to composite failure. This paper primarily focuses on examining flaws, failure modes, and performing fractography analysis on fiber‐reinforced polymer (FRP) laminate composites subjected to various loading conditions such as tension, compression, flexure, impact, shear, and fracture. Fractography, as an indispensable method, plays a pivotal role in the comprehensive development of composite structures and has become a reliable tool for composite engineers. The outcomes of this study are expected to serve as a foundation for identifying areas that require further investigation in terms of fracture analysis and failure modes specific to FRP composite materials, particularly those used in marine applications.Highlights Introduction to FRP laminate composites in marine structures. Concise analysis of failure modes in FRP laminate composites. SEM fractography review of FRP laminate composites under varied loading conditions. Comprehensive study on tensile, flexural, impact, compression, shear, and fracture toughness failure modes. Summarization of identified defects in FRP composites.

Comparison of two progressive damage models for predicting low-velocity impact behavior of woven composites

This research focuses on comparing the two progressive damage models available in the explicit nonlinear finite element software LS-Dyna. To explore the prediction capabilities in terms of mechanical response and dominating failure modes in S2 glass woven composites, low velocity impact response at four different energies ranging from 27.9 J to 109.7 J were considered in this study. A macro-homogeneous solid element formulated finite element model was simulated to understand the response and failure mechanics in the laminate under low-velocity impact. The material modeling was carried out utilizing the MAT 55 and MAT 162 material models. An effort has been made for robust calibration of the various physical and non-physical parameters in both material cards for accurate predictions. The prediction capabilities of the models were then examined by comparing them against the experimental results, which fall within the deviation of ∼11%. The results show that MAT 162 yields a better resemblance with the damage morphology patterns and the delamination for the accounted impact zone, due to inclusion of strain-rate effect. Overall, this paper provides insight into the limitations and advantages of both material models, which establishes the route for the selection of the appropriate material model for simulating impact behavior in woven composites.

Interfacial characteristics of fiber asphalt mastic and aggregates: Impact on mixture crack resistance performance

The interfacial characteristics between fiber-modified asphalt mastics and aggregates play a crucial role in the performance of asphalt mixtures. To explore these interfacial interaction characteristics, three types of fibers (basalt, glass, and polyester), five levels of fiber content (ranging from 0.1% to 0.5% by mixture mass), and two types of aggregates (limestone and basalt) were selected, and an optimal mixture design was established. Contact angle tests, binder bond strength tests, and disk-shaped compact tension tests were conducted to investigate the impact of fiber type, fiber content, and aggregate type on interface characteristics. The results indicate that the addition of fibers can enhance the interfacial strength, with basalt fibers exhibiting superior reinforcement effects. As fiber content increases, the influence of aggregate type on interfacial strength decreases. Under ambient conditions, a composite failure mode was observed, while at low temperatures, cohesive failures dominated. The incorporation of fibers led to an increase in interfacial cohesion strength. The interfacial interaction strength between fiber asphalt mastic and aggregates exhibits a favorable linear correlation with the fracture energy and peak crack mouth opening displacement of the asphalt mixture. Overall, this study elucidates the microscopic mechanisms involved in fiber asphalt mixtures, laying the foundation for further in-depth research.

Seeding ductile nanophase in ceramic grains.

Transgranular brittle fracture is the dominant failure mode of brittle materials, including ceramics and ceramic matrix composites. However, strengthening these materials without sacrificing their toughness has been a big challenge. In this study, an innovative approach is proposed to achieve coordinated strengthening and toughening of ceramics-based composites by introducing specific ductile coherent nanoparticles into ceramic grains. As an example, the WC-Co cemented tungsten carbides were used to demonstrate how this brittle material can achieve ultrahigh strength without losing toughness by seeding metallic nanoparticles inside WC grains. The mechanisms for inducing the formation and modulating the amount, size, and distribution of such nanophase within the ceramic grains were disclosed. The fraction of transgranular ruptures of the brittle ceramic phase was reduced significantly due to the presence of the ductile coherent in-grain nanoparticles. Both the strength and strain limit of the cemented carbides were remarkably increased compared to their counterparts reported in the literature. The coordinated strengthening and toughening strategy proposed in this work is applicable to a broad range of ceramics and ceramic matrix composites to obtain superior comprehensive mechanical properties.