Fracture Of Composite Materials Research Articles

Stress Intensity Factor of E-Glass Fiber Reinforced Polyester Composites

In order to analyze the stress concentration impact, intensity close to the zone of the crack tip, this work examines the in-plane SIF(SIF) of composite plates utilizing measured crack tip opening displacement (CTOD). The test specimens' E-glass fiber mats were arranged in various ply configurations. The ASTM standards utilized for researching mode I fracture of composite materials served as the foundation for the compact tension (CT) specimen. The mode I, KI Stress intensity factor (SIF), and critical stress, c, were calculated for each specimen along the fracture length propagation based on the experiments. It was found that the SIF is directly proportional with fracture length, or a/W, for all E-glass fiber laminate cases tested. The KIC is often higher in thinner laminates. The presence of woven roving increases the SIF and hence the toughness of the laminate.

Enhancing Reliability and Safety in Industrial Applications: Assessing the Applicability of Energy b-Value to Composites.

This study investigates the fracture behavior of glass fiber-reinforced plastic (GFRP) under various loading conditions using acoustic emission (AE) testing. Using fracture tests and time series analysis of AE signals, parameters such as b-value, improved b-value (Ib-value), and energy b-value (be-value) were examined to understand crack initiation, growth, and structural failure. The stress-strain curve revealed distinct responses during tensile and step loading, and time series analysis highlighted variations in amplitude, AE energy, and Kaiser and Felicity effects. Under tensile loading, the Ib-value exhibited a linear decrease, while step loading introduced complexities, including the Felicity effect. The be-value, incorporating energy considerations, fluctuated, providing insights into micro-cracks and macro-cracks. Statistical analysis demonstrated a consistent decrease in the be-value, emphasizing its potential for long-term monitoring. This study provides a comprehensive technique for assessing composite material fracture behavior, enhancing understanding for critical applications in hydrogen storage vessels and pressure pipes as well as advancing reliability and safety in industrial sectors.

Influence of material microstructure on fracture development in deformable bodies

The problem of predicting the location and direction of local fracture and estimating the ultimate load of composite material is one of the practically important problems of fracture mechanics. With a wide variety of composite materials, it is natural to expect the presence of a large number of failure criteria, each of which should be valid for a certain class of materials and reflect most completely its physical and mechanical properties, structural defects, operating conditions, etc. The choice of effective assessment of the bearing capacity of modern composite material under extreme conditions is at present the main task of researchers. In this paper, the criterion of fracture of composite materials based on simple and quite effective theory of macrostresses by M.Ya. Leonov and K.M. Rusynka is preferred. The macrostress theory effectiveness is shown in the papers by V.V. Panasiuk, L.T. Berezhnytskyi, S.Ya. Yarema, L.V. Ratych, and M.H. Stashchuk. In our paper, we clarify and extend the advantages of macrostress concept criterion in comparison with other fracture criteria in deformable bodies. Examples of crack propagation in the process of body tension are given in this paper.

Enhancing interfacial adhesion of carbon fiber/poly(phthalazinone ether ketone) composites by the hybrid sizing agent of hydroxyapatite‐reinforced PAEK‐COOH

AbstractImproving the interfacial adhesion of carbon fiber (CF)/polymer composite is an urgent demand to enhance its mechanical properties. A kind of poly(aryl ether ketone) with carboxyl groups (PAEK‐COOH) was newly synthesized. PAEK‐COOH is similar to the thermal properties of PPEK matrix. Hydroxyapatite (HAp) was easily dispersed in an NMP solution containing PAEK‐COOH. Different kinds of hybrid sizing agents were obtained for preparing the prepreg through the solution impregnation. The hot‐pressing method was employed to produce the laminated composites. Flexural strength, flexural modulus and interlamellar shear strength (ILSS) of 0HP@CF/PPEK composites were improved by 8.8%, 17.3%, and 14.7%, respectively, in comparison to desized CF/PPEK. The interface bonding between CF and PPEK was improved by the addition of PAEK‐COOH sizing agent. Meanwhile, compared with desized CF/PPEK laminates, flexural strength, flexural modulus and ILSS of 5HP@CF/PPEK composites were enhanced by 63.5%, 87.4%, and 40.9%, respectively. The crack propagation path became dispersed and the stress was effectively absorbed when the sizing agent containing nano‐hydroxyapatite particles. By characterizing and reconstructing the transverse and longitudinal fracture in composite materials, the failure process of the composites under the action of stress was explained, and the interface theories of CF reinforced polymer were further explored.Highlights A kind of polyaryl ether ketone containing carboxyl functional group (PAEK‐COOH)was newly synthesized. HAp was distributed in the polymer sizing agent to obtain a HAp/PAEK‐COOH hybrid sizing agent. The interfacial adhesion of CF/PPEK composite was greatly improved by the hybrid sizing agent.

A phase-field lattice model (PFLM) for fracture problem: Theory and application in composite materials

In the present work, a phase-field lattice model (PFLM) is proposed to model fracture problems. The element deletion process and oversimplified failure criterion of the classical lattice model not only lead to a strong mesh sensitivity but also limit the method’s application to various materials and fracture modes. Hence, a smeared form of crack is introduced into the lattice model to deal with these problems. The model exploits discontinuous discrete methods to model the propagation of three-dimensional cracks by characterizing the crack with a phase-field variable. Moreover, by regarding the crack propagation process as a multi-field problem composed of a displacement field and a phase-field, a flexible and robust algorithm is established, in which the crack path can be obtained directly by resolving the governing equations. Numerical simulations were performed and compared with the experimental results and other numerical models. It is shown that the PFLM can capture the main features of the fracture for both brittle and quasi-brittle materials. To further demonstrate the performance of the model, a mesoscale system of cement composite generated by computed tomography scanning technology was examined. The result demonstrates that the fracture of composite materials can also be well predicted.

On the use of strength criteria of anisotropic materials

One of the distinctive properties of composite materials is their anisotropy, which allows, in particular, to use of their strength properties maximum. Thanks to new technologies, in particular 3-D printing, there are new opportunities for purposeful formation of the structure of composite materials and their properties. An important issue here is ensuring strength, which is determined depending on the structure of the composite as a whole and the mechanical characteristics of its individual components. The article reviews well-known strength criteria (Goldenblatt-Kopnov, Mises-Hill, Fisher, Hoffman, Tsai-Wu, and others), the relationship between them, and data on the reliability of their application under certain load conditions. Some of them assume the same properties of materials under conditions of compression and tension and are obtained by generalizing the classical theories of strength and plasticity of isotropic bodies. The criteria that take into account the different resistance of the composite material to tension and compression, which is inherent in many composite materials, have gained greater practical application. When choosing a strength criterion, from the point of view of structure, it is worth considering separately layered and reinforced composite materials, and from the point of view of load - the static or cyclic nature of its application. The criteria listed above do not take into account the damage accumulation in the material that occurs under the influence of external loads. The number of such known criteria is limited, because today there is no method for predicting the stage of scattered fracture of composite materials taking into account the anisotropy of mechanical properties, and the choice of the damage parameter is not justified. The perspective of developing such criteria for clarifying the received conclusions regarding the load-bearing capacity of products made of composite materials under different types of application of external loads is noted.

A novel SiC composite material infiltrated by basalt glass-ceramic with a high hardness

New high-performance materials for environments with high abrasive and erosive loads resistant are in a great demand for the modern industry. For the first time, a composite material obtained by infiltration of SiC porous oxide bonded preform with a basalt rock melt at a temperature of 1400 °C in air was proposed. The produced composite material significantly reduces porosity from 31.0 to 1.2%. Interestingly, an aluminosilicate phases crystallizes on the surface of SiC grains meanwhile the migration of Ca and Fe to the melt basalt volume due to atomic radii mismatch with the forming phases. The crystallinity of the basalt glass matrix obtained by petrurgical method is 66.9%. All together allows to improve hardness of the obtained composite material SiC/basalt glass-ceramics from 2.6 (preform) and 6.8 (basalt glass ceramics) to >9.6 GPa. The composite material fracture toughness (K1c ∼ 0.85 MPa·m1/2) also increases in comparison to a highly fragile basalt glass ceramics matrix. Thermal expansion coefficient value of the produced composite material is close to the dense polycrystalline SiC one and no sample destruction was observed caused by materials TEC mismatch.

An extended peridynamic model for analyzing interfacial failure of composite materials with non-uniform discretization

This work presents an extended ordinary state-based peridynamic model and approaches to analyze the fracture behavior of composite materials considering interfacial failure. An interface force term is introduced to characterize the interaction among different compositions in composite materials, which enables naturally the non-uniform discretization to be conveniently adopted, especially where sharp interfaces exist. The calculation of force states in different compositions is independent of each other, and the use of non-uniform discretization can improve computational efficiency significantly. Further, inspired by the cohesive zone model (CZM), the deformation coefficient and degradation behavior of interface bonds are derived by using the traction-separation law, and a mixed-mode fracture criterion for interface bonds based on the bond energy density is established as well. Validation of the proposed model and approach is established through a classical rectangular plate example, and then the proposed model is employed to analyze the failure of typical composites including laminated glass and concrete. The results show good agreement with corresponding experimental observations and it indicates that the proposed extended peridynamic model can accurately and efficiently capture and describe the fracture of composite materials with sharp interfaces.

Preface

Due to recent pandemic, the 2022 International Conference on Automation and Space Science and Technology (ASST 2022) was held virtually online during January 14-16, 2022. The decision to hold the virtual conference was made in compliance with many restrictions and regulations that were imposed by countries around the globe. Such restrictions were made to minimize the risk of people contracting or spreading the COVID-19 through physical contact. There were 60 individuals who attended this online conference, represented many countries including Malaysia, India, Japan, Pakistan, and China.China has stepped into the era of rapid development of space science applications, in which automation as a basic support discipline provides key theoretical and technical support. With the goal of the application of space science engineering, the 2022 International Conference on Automation and Space Science and Technology (ASST 2022) integrates the principles and achievements related to automation and intelligent systems, and intend to provide a new platform for communication and discussion in interdisciplinary fields and advance the further integration and development of automation and space technology.During the conference, the conference model was divided into three sessions, including oral presentations, keynote speeches, and online Q&A discussion. In the first part, some scholars, whose submissions were selected as the excellent papers, were given about 5-10 minutes to perform their oral presentations one by one. Then in the second part, keynote speakers were each allocated 30-45 minutes to hold their speeches. In the second part, we invited three professors as our keynote speakers. Prof. Quanxin Zhu, Hunan Normal University, China. His current research interests in Markov process, Stability and Control Theory and Application of Stochastic Systems, and a series of important developments have been made. And then we had Prof. Li Na, Xidian University, China. Her main research direction is high precision electronic equipment error theory, new system antenna structure design and optimization. Assoc. Prof. Fengnan Guo, our finale keynote speaker, from Dalian University of Technology, China. His current research interests focus on thermal fracture of composite materials, design of advanced astronautis propulsion and structural integrity analysis. Their insightful speeches had triggered heated discussion in the third session of the conference. Every participant praised this conference for disseminating useful and insightful knowledge.The proceedings are a compilation of the accepted papers and represent an interesting outcome of the conference. Topics include but are not limited to the following areas: Space detection technology, Air-ground joint technology, Automation in the application of space technology and more related topics. All the papers have been through rigorous review and process to meet the requirements of International publication standard.We would like to acknowledge all of those who supported ASST 2022. The help and contribution of each individual and institution was instrumental in the success of the conference. In particular, we would like to thank the organizing committee for its valuable inputs in shaping the conference program and reviewing the submitted papers.We sincerely hope that the ASST 2022 turned out to be a forum for excellent discussions that enabled new ideas to come about, promoting collaborative research. We are sure that the proceedings will serve as an important research source of references and knowledge, which will lead to not only scientific and engineering findings but also new products and technologies.List of Committee member are available in this pdf.

A Semi-theoretical criterion based on the combination of strain energy release rate and strain energy density concepts (STSERSED): Establishment of a new approach to predict the fracture behavior of orthotropic materials

Motivated by previous research performed by the authors assessing the fracture behavior in orthotropic materials under mixed-mode I/II loading, this article aims to propose a novel Semi-theoretical criterion for desired crack-fiber angles to assess the fracture of composite materials. Contrary to all previously proposed fracture criteria, in this criterion a mid-point experimental data related to the mixed-mode I/II loading is employed instead of mode I fracture toughness. Utilizing an arbitrary combination of mixed-mode I/II experimental data leads to a significantly simple and accurate fracture assessment criterion. More accurate estimation is achieved using more experimental data in mixed-mode I/II. For the first time, due to the importance of providing a fracture criterion, a Semi-theoretical criterion based on a combination of Strain Energy Release Rate (SER) and Strain Energy Density (SED) criteria, namely STSERSED, is adopted for more accurate anticipating of the fracture of orthotropic materials. Using SED criterion, mode I fracture toughness is theoretically derived and substitutes in the equations of maximum strain release rate. Furthermore, fitting mid-point experimental data into the presented criterion compensate the portion of wasted energy due to the creation of Fracture Process Zone (FPZ) and therefore more accurate fracture estimation is possible. With the passage of pure mode I and the emergence of mode II, the effects of FPZ increase, so changing the critical point from pure mode I to mid-point experimental data makes the extracted fracture behavior closer to the experimental data. Due to using experimental data and the relevant theoretical criterion simultaneously, this criterion can be used in engineering applications to extract the crack behavior of orthotropic materials. The verification of the STSERSED criterion is evaluated by comparing the fracture limit curves (FLC’s) with the available experimental data. The extracted results based on the proposed criterion highlight the achievement of this criterion to assess the fracture of orthotropic materials.

On microscopic analysis of fracture in unidirectional composite material using phase field modelling

The demand for composite materials is higher than ever before. Effective and reliable modelling techniques allowing for better understanding of their failure are critical for designing future optimised light-weight structures. However, failure of composite at the microscopic level is a complex phenomenon and it has often been analysed using empirical approaches. A promising alternative, that instead takes a physics-based approach, is the phase-field model (PFM). This approach has been applied comprehensively to homogeneous materials and has briefly been extended to composite laminae, as modelled by Kanninen's local heterogeneous region (LHR). Despite this progress, a systematic investigation of the implications and requirements of using PFM for studying fracture in composite materials seems incomplete and missing links between the physical and the numerical aspects. This work aims to fill that gap and discusses in detail the role of the critical parameters in a PFM analysis of fracture, including length-scale interactions and concerns on convergence. The present analysis is framed around the problem of toughening of composites by weakening the matrix/fibre interface. Here, the PFM proves very efficient tool allowing recognition of multiple failure modes.

Multiple-phase-field modeling for fracture of composite materials

Fracture behavior of composite materials is a challenge in numerical simulations due to the heterogeneity introduced by reinforcements. Based on the phase-field fracture model, a multiple-phase-field ductile fracture model is developed by using different phase field descriptors to characterize multiple cracking behaviors, involving different fracture mechanism such as brittle fracture and ductile fracture for composite materials. A novel degradation function is introduced to couple different fracture mechanism, i.e., brittle damage and ductile damage. We also extended the proposed multiple-phase-field ductile fracture model to a general formulation which can incorporate with different constitutive models. The main findings of this article are three folds: (1) accuracy and robustness of the proposed model are guaranteed by comparing the present results and previous work; (2) plastic localization and accumulation is the main reason for crack initiation and propagation; (3) enhanced load carrying ability and ductility are obtained in composite structures with hard/tough inclusions.

Mode-II interlaminar fracture of composite materials in the presence of randomly distributed defects

Mode-II interlaminar fracture of composite materials in the presence of randomly distributed defects

The effect of T-stress on mixed mode I/II fracture of composite materials: Reinforcement isotropic solid model in combination with maximum shear stress theory

Due to the existence of cracks and defects in composite materials during the manufacturing process, damage and crack growth in these materials must be anticipated before application. In the present research, an efficient theoretical mixed mode I/II fracture criterion is proposed for fracture investigation of orthotropic materials considering the effects of non-singular stress term in William’s series expansion. This criterion is developed combining the maximum shear stress (MSS) theory with reinforcement isotropic solid concept (RIS) as a superior material model. RIS is based on the fact that cracks in orthotropic materials generally propagate along the fibers in the isotropic matrix media regardless of initial crack-fiber orientation. According to this fact, RIS offers to employ an isotropic stress field around the crack tip with defined stress reduction coefficients as fiber effects. This criterion is applicable for two cases wherein crack is placed both along and across the fibers. A comparison between available experimental data for two wood species and the results of the proposed criterion shows that this criterion can accurately predict both crack initiation and crack propagation direction and is in full compliance with the fracture nature of composite materials.

FFT phase-field model combined with cohesive composite voxels for fracture of composite materials with interfaces

A framework for damage modelling based on the fast Fourier transform (FFT) method is proposed to combine the variational phase-field approach with a cohesive zone model. This combination enables the application of the FFT methodology in composite materials with interfaces. The composite voxel technique with a laminate model is adopted for this purpose. A frictional cohesive zone model is incorporated to describe the fracture behaviour of the interface including frictional sliding. Representative numerical examples demonstrate that the proposed model is able to predict complex fracture behaviour in composite microstructures, such as debonding, frictional sliding of interfaces, crack deviation and coalescence of interface cracking and matrix cracking.

Acoustic Emission at Properties Change of Composite Destructed by von Mises Criterion

The results of theoretical studies influence the parameter characterizing the composite properties on acoustic emission signals parameters during composite material fracture by a shear force using von Mises criterion are considered. It has been determined that with increase of influencing parameter, there is decrease the maximum amplitude and duration of generated acoustic emission signals. In this case, a decrease the maximum amplitude of acoustic emission signals is ahead of decrease in their duration. It has been determined that the regularities of acoustic emission signals maximum amplitude and duration decrease with an increase the parameter characterizing the composite material properties are well described by power functions.

Effects of randomly distributed defects on Mode-I interlaminar fracture of composite materials

Effects of defects on the mode-I interlaminar fracture behavior of composite materials are studied using computational fracture mechanics. Cohesive-zone Finite Element (FE) models of both the Interlaminar Tension (ILT) and Double Cantilever Beam (DCB) test configurations are simulated where randomly distributed defects are explicitly modeled on a critical fracture plane. The effective interlaminar tensile strength and the effective mode-I fracture energy are derived by matching the simulation results with appropriate homogenized models that do not consider the defects explicitly. The results from the computational parametric studies show that both the effective ILT strength and the effective mode-I fracture energy are quite sensitive to defects, scaling linearly with the defect area fraction on the critical fracture plane. The effects of defect size on the mode-I fracture behavior are also studied. It is shown that, for a fixed area fraction of the defects, the ILT strength is not sensitive to the defect size. On the other hand, the mode-I fracture propagation behavior is sensitive to the defect size especially when the defect size is greater than the fracture process-zone size of the delamination crack.

Perspective Composite Material Made of Volume Fabric - Experimental Tests

In all industries, composite materials with a multilayer structure are widely used. Each layer of the composite material is a directional fiber impregnated with a binder polymer. Layered composite materials, possessing unique properties and high manufacturability, have a significant drawback - the presence of interlayer defects in material, which reduces the scope of their application. One of the perspective directions for reducing the process of interlayer fracture in composite materials is the use of bulk textile material, which is the reinforcement of the entire multilayer material. This article presents an overview of some researches that provide basic information about the creation of perspective composite material made of volume fabric and materials based on them. We provided open information about manufacturers of 3D fabric materials. We carried out experimental tests with composite materials, which showed that material with transverse threads is 30-35% stronger during end impact than a composite material without reinforcement.

Model of elastic modulus degradation and fracture of composite materials under cyclic loading

The aim of the work is to numerically simulate the degradation of elastic properties of carbon-fiber-reinforced polymers based on the previously developed model of damage in solids with mesoscopic defects. The paper presents a mathematical statement of cyclic loading of a representative volume of composite material with regard to damage accumulation. An analytical solution of the problem has been obtained, which made it possible to describe both the degradation of elastic properties and the Wöhler curve (fatigue curve). An identification procedure of unknown model constants has been performed. Comparison of modeling results with experimental data of other authors showed good agreement.

An anisotropic phase‐field model at finite strains for composite fracture

AbstractPhase‐field modeling has been intensively studied and demonstrated to appropriately capture complex fracture evolutions. Experimental evidence indicates that the fracture evolution is largely relying on the constitutive relations of the engineering materials, e.g. anisotropic properties. In general, anisotropic failure characteristics are governed by the mechanical response and the fracture evolution simultaneously. The work at hand introduces an anisotropic phase‐field modeling for composite material's fracture, which uses only one phase‐field variable to evaluate the fracture status of the matrix and the fiber materials simultaneously. As a result, an equivalent crack surface energy density function is established. Furthermore, the constitutive laws are consistently derived by a straightforward variational principle. Consequently, an interesting numerical example is shown to demonstrate the capabilities of this approach.