Matrix Failure Research Articles

Microstructure-based three-dimensional characterization of chip formation and surface generation in the machining of particulate-reinforced metal matrix composites

Particulate-reinforced metal matrix composites (PRMMCs) are difficult to machine due to the inclusion of hard, brittle reinforcing particles. Existing experimental investigations rarely reveal the complex material removal mechanisms (MRMs) involved in the machining of PRMMCs. This paper develops a three-dimensional (3D) microstructure-based model for investigating the MRM and surface integrity of machined PRMMCs. To accurately mimic the actual microstructure of a PRMMC, polyhedrons were randomly distributed inside the matrix to represent irregular SiC particles. Particle fracture and matrix deformation and failure were taken into account. For the model’s capability comparison, a two-dimensional (2D) analysis was also conducted. Relevant cutting experiments showed that the established 3D model accurately predicted the material removal, chip morphology, machined surface finish, and cutting forces. It was found that the matrix-particle-tool interactions led to particle fractures, mainly in the primary shear and secondary deformation zones along the cutting path and beneath the machined surface. Particle fracture and dilodegment greatly influences the quality of a machined surface. It was also found that although a 2D model can reflect certain material removal features, its ability to predict microstructural variation is limited.

Investigations of Strain Rate Effects on the Mechanical Properties of Hybrid Composite Laminate Under Varying Temperatures

The mechanical behavior of hybrid composite laminates under varying strain rates and temperatures was investigated in this study. The hybrid composite laminate is constituted as a sequential stacking sequence of plain-woven carbon-fiber-reinforced epoxy (CFRE) and plain-woven glass-fiber-reinforced epoxy (GFRE) laminates. Vacuum-assisted resin transfer molding (VARTM) process was used to fabricate the composite laminates. Hybrid composite laminates (HCGFRE) were tested under four different strain rates (0.05 min−1, 0.5 min−1, 2.5 min−1, 5 min−1) and three different temperatures (RT, 60 °C, 100 °C). Microstructure analysis was performed to observe the voids, fiber delamination and matrix failure occurring in the composite laminate. In numerical analyses, continuum damage mechanics material model (MAT 58) was utilized in LS-DYNA® explicit finite element program to simulate the mechanical properties of CFRE, GFRE and HCGFRE laminates. It was determined that the tensile strength of all composite laminates is increasing by increasing the strain rates in all temperatures. The continuous damage mechanics material model (MAT 58) was found to be suitable for simulating woven composite laminate under different strain rates and temperatures. In microstructural study, it was not observed significant changes in the microstructure of composite laminates by changing strain rates.

An effective finite element modeling approach for prediction of the behaviour of a jute fibre-reinforced composite tube under axial impact

The focus of the work reported here is on the prediction of the behaviour of a hollow cylindrical jute– polyester composite tube under axial impact using the explicit finite element analysis code, LS-DYNA. An efficient finite element modelling approach using a single shell element through the thickness of a thin-walled structural part has been chosen. Effective orthotropic material properties of a laminate which can be determined through standard ASTM tests have been used as input data for a popular constitutive model titled ‘Enhanced Composite Damage’ with the option of specifying either the Chang–Chang criteria or the Tsai–Wu criterion for failure. A unique feature of the current approach is to verify the modeling procedure initially for coupon-level tensile, compressive and flexural tests through a numerical design of experiments involving a set of physically meaningful fibre and matrix failure strain parameters, and then extend the same toward successfully predicting the mechanical behaviour of a jute composite tube subject to axial drop-weight impact. Theoretical predictions of peak responses for flexural and tube impact tests are also presented.

Continuum and cohesive zone damage models to study intra/inter-laminar failure of curved composite laminates under four-point bending

Matrix failure and delamination are the two dominant damage modes that govern the out-of-plane strength of the curved composite laminates. In this work, the out-of-plane failure behavior of curved CFRP laminates of different stacking sequences, namely, uni-directional [0]20, cross-ply [0/90]5s and multi-angle [45/0/-45/90/0]2s are studied experimentally and numerically. Digital image correlation and acoustic emission techniques are used for in situ monitoring of intra/inter-laminar damage modes under four-point bending load. A detailed fractography study is carried out to assess the damage modes and the failure mechanisms of the curved specimen. Subsequently, a finite element based progressive damage model (PDM) comprising of the 3D Hashin failure criteria and cohesive zone model is developed in Abaqus finite element software for simulating the intra/inter-laminar damages. The importance of combining matrix damage models with CZM and their synergy on the out-of-plane failure is studied and validated with experimental observations. The PDM model is then used to investigate the effect of stacking sequence, matrix tensile strength, and delamination strength on the failure of multi-angle curved laminates. This numerical study show insights to improve the out-of-plane strength of curved laminates by appropriate selection of laminate stacking sequence and matrix strength properties.

Acoustic Emission Analysis for Damage Mechanism in Fiber Reinforced Polymer Composite under Torsional Behaviour

In this study the torsional behaviour of fiber reinforced polymer (FRP) composite rods of different matrix materials like PEEK, Aqua bond, Epoxy are studied and different types of failures are observed. The FRP composite rods are fabricated by using Vacuum Assisted Resin Transfer Moulding (VARTM) method as per the standards. FRP composite rods are tested in the digital torsion testing machine (MTS100NM). The Acoustic Emission (AE) sensors are used to analyse the nature of the cracks. The defects in FRP composite rods are identified, like surface micro cracks, matrix failure and reinforcement failure. After getting AE signals based on different AE Parameters like Time, Frequency, AE hits and AE energy from the obtained results the failure initiation and crack propagation are identified, Hence the AE method is best suitable technique for identify the micro failures.

Drug release from magnesium aluminium silicate-polyethylene oxide (PEO) nanocomposite matrices: An investigation using the USP III apparatus

This work investigated the use of the USP III apparatus in discriminating simulated fed and fasted conditions as well as ionic strength on veegum-polyethylene (PEO) (called clay-PEO matrices hereafter) matrices. The successful formulations were characterised using differential scanning calorimetry (DSC) and evaluated for their physical properties. Isothermal calorimetry (ITC) was used to evaluate the thermodynamics of the complexation processes. The effect of agitation sequences on the matrices as evaluated from the USP III suggested an increase in polymer content to significantly decrease the burst release experienced using diltiazem hydrochloride (DILT) as a model cationic drug. The manufacturing methods showed superior performance in relation to a decrease in burst release over the physical manufactured counterparts. The clay-PEO matrices also showed robustness (no matrix failure) in up to 0.2 M ionic strength solutions mimicking the upper limit experienced in the GI tract. ITC results revealed that the binding between DILT and PEO was enthalpy and entropy-driven. Furthermore, the binding between veegum and DILT in the presence of PEO was shown to be enthalpy-driven and entropically unfavourable, which was also the case for the binding between veegum and PEO thus giving insights to how the matrices were performing on a molecular level.

First-order anisotropic beam model and failure criterion for flexural parallel bamboo strand lumbers

To investigate the anisotropic behavior of parallel bamboo strand lumbers (PBSLs), flexural properties of seven kinds of PBSL beams with different fiber orientations were tested. It is found that the bending strength and stiffness decreases with the increase of the angle between the fibers and the beam axis. When the fibers are not parallel to the beam axis, the PBSL beam has an interfacial failure judged from the crack evolution. To reveal the coupling effect between the shear deformation and the axial tension/compression deformation induced by the anisotropy, first-order anisotropic beam model is proposed. Based on the tensile-shear failure of fibers or matrix, composite failure criteria for PBSLs were proposed to predict the ultimate load. The research also suggests a method to get material properties of PBSLs based on flexural experiments and failure analyses.

Predicting the strength of carbon nanotube reinforced polymers using stochastic bottom-up modeling

It is intended to predict the strength of carbon nanotube reinforced polymer. For this purpose, a sequential multi-scale modeling technique is developed taking into account effective parameters at various scales of micro, meso and macro. CNT-polymer interaction, CNT orientation and CNT waviness are considered at the scale of micro, while formation of CNT aggregates is captured at meso-scale. The occurrence of failure in the form of either matrix failure or CNT and polymer debonding is considered in the modeling as the two prominent failure mechanisms under tensile loading. At the uppermost scale of macro, the investigated material region is partitioned into constitutive blocks using regular tessellation technique accounting for inhomogeneous material behavior. The induced uncertainties during the processing of carbon nanotube reinforced polymers necessitate stochastic modeling. The experienced inconsistencies consisting of CNT length, orientation, waviness pattern and intensity of agglomeration are captured using random parameters. Therefore, the constitutive behavior of each block at macro-scale is randomly picked from the outputs of the conducted modeling at lower scales and full stochastic modeling is implemented. The outputs of the developed modeling are compared with available experimental observations in published data and remarkable agreement is observed.

Experimental and numerical studies on failure and energy absorption of composite thin-walled square tubes under quasi-static compression loading

Abstract To analysis the failure and energy absorption of carbon fiber reinforced polymer (CFRP) thin-walled square tube, the quasi-static axial compression loading tests are conducted for [±45]3s square tube, and the square tube after test is scanned to further investigate the failure mechanism. Three different finite element models, i.e. single-layer shell model, multi-layer shell model and stacked shell mode, are developed by using the Puck 2000 matrix failure criterion and Yamada Sun fiber failure criterion, and three models are verified and compared according to the experimental energy absorption metrics. The experimental and simulation results show that the failure mode of [±45]3s square tube is the local buckling failure mode, and the energy are absorbed mainly by intralaminar and interlaminar delamination, fiber elastic deformation, fiber debonding and fracture, matrix deformation cracking and longitudinal crack propagation. Three different finite element models can reproduce the collapse behaviours of [±45]3s square tube to some extent, but the stacked shell model can better reproduce the failure mode, and the difference of specific energy absorption (SEA) is minimum, which shows the numerical simulation results are in better agreement with the test results.

Multiaxial fatigue life prediction of composite laminates

A study of composite laminates under tension–torsion biaxial loading is presented. The focus is placed on fatigue lives of composite laminates under different tension–torsion biaxial fatigue loading paths. A macro-meso model used to predict multiaxial fatigue life of composite laminates is also presented in this paper. Firstly, a macro-scale 3D RVE corresponding to composite laminates is established to determine strain components in the material principal direction of each layer for each biaxial stress ratio. Secondly, a meso-scale 3D RVE corresponding to each layer with fibers distributed randomly is established, with progressive damage prediction method, biaxial strength of composite laminates can be predicted, and the final failure layer can be confirmed. Thirdly, select any one of fatigue loading path at which the final failure of composite laminates is fiber failure (matrix failure) to establish the reference curve for fiber (matrix). Finally, with reference curve, fatigue life of composite laminates under any biaxial loading path can be predicted. And numerical results show good agreements with experimental data.

FSI-based structural optimization of thin bladed composite propellers

Lamination of thin bladed composite marine propellers necessitates dropping layers following thickness variation to produce lighter propeller with good elastic damping. Composite blade is subjected to multiaxial loads resulted from nonuniformly distributed hydrodynamic pressure that cause the blade to undergo combined structural response of bent and twist therefore, strength evaluation of such tapered laminate is a highly nontrivial process that include significant fluid–structure interaction (FSI). This research aims to investigate the strength of composite propeller using unconstrained stacking-sequence optimization based on fully coupled CFD-FEA analysis. Different hub idealization techniques were studied to determine the most accurate treatment in predicting stress and deformation of the blade. Composite model configured for propeller VP1304 after modification on blade thickness and, initial analysis on balanced-stacking of [0, 90, 45,−45] were set as a benchmark for optimization process targeting to minimize failure index; calculated according to Puck failure theory considering fiber and matrix failure as well as delamination. Delamination is evidenced to be utmost critical mode of failure whereas, the optimization resulted in an optimum laminate with unbalanced nonsystematic stacking that succeeded to; reduce interlaminar stresses, avoid failure and, reduce maximum value of IRF (Inverse Reserve Factor) by 50% compared to the predefined balanced-stacking benchmark.

Failure Analysis of Composite Structures Using Multiscale Technique

Failure analyses of laminated fibrous composite structures were conducted using the failure criteria based on a multiscale approach. The failure criteria used the stresses and strains in the fiber and matrix materials, respectively, rather than those smeared values at the lamina level. The failure modes and their respective failure criteria consist of fiber failure, matrix failure and their interface failure explicitly. In order to determine the stresses and strains at the constituent material level (i.e. fiber and matrix materials), analytical expressions were derived using a unit-cell model. This model was used for the multiscale approach for both upscaling and downscaling processes. The failure criteria are applicable to both quasi-static loading as well as dynamic loading with strain rate effects.

A microscopic elasto-plastic damage model for characterizing transverse responses of unidirectional fiber-reinforced polymer composites

Abstract A phenomenological-based micromechanical method, comprising the coupling of the matrix constitutive model and the cohesive zone (CZM) model at fiber-matrix interfaces, is presented to investigate the mechanical behaviors of unidirectional (UD) fiber-reinforced polymer (FRP) composites subjected to transverse tension and compression. The key point of this method is the establishment of a novel elasto-plastic damage constitutive model using a fracture plane based yield criterion. Both plastic deformation and progressive failure procedure is incorporated in the implicit simulation. Special focus is given to the determination of the input values of constituent material properties, suggesting that directly using the macroscopic matrix properties to characterize the mechanical responses at the microscale level may bring large discrepancies in homogenized stress-strain responses of UD composites. A parametrical study is also carried out to calibrate cohesive parameters. The numerical results, in good agreement with experimental measurements, clearly reveal the damage scenarios and the dominant failure mechanisms. It can be concluded that the debonding of the fiber-matrix interfaces is responsible for the ultimate transverse tensile strength, while compression failure is governed by two possible modes, i.e. matrix compressive failure if matrix failure firstly occurs, and matrix tensile and interface debonding failure when debonding initiates first. Besides, the distribution of fracture plane angles in matrix is examined to further validate the predictive capacity of the proposed model.

Progressive Failure Analysis of Laminates with Embedded Wrinkle Defects Based on an Elastoplastic Damage Model.

Out-of-plane wrinkling has a significant influence on the mechanical performance of composite laminates. Numerical simulations were conducted to investigate the progressive failure behavior of fiber-reinforced composite laminates with out-of-plane wrinkle defects subjected to axial compression. To describe the material degradation, a three-dimensional elastoplastic damage model with four damage modes (i.e., fiber tensile failure, matrix failure, fiber kinking/splitting, and delamination) was developed based on the LaRC05 criterion. To improve the computational efficiency in searching for the fracture angle in the matrix failure analysis, a high-efficiency and robust modified algorithm that combines the golden section search method with an inverse interpolation based on an existing study is proposed. The elastoplastic damage model was implemented in the finite-element code Abaqus using a user-defined material subroutine in Abaqus/Explicit. The model was applied to the progressive failure analysis of IM7/8552 composite laminates with out-of-plane wrinkles subjected to axial compressive loading. The numerical results showed that the compressive strength prediction obtained by the elastoplastic damage model is more accurate than that derived with an elastic damage model. The present model can describe the nonlinearity of the laminate during the damage evolution and determine the correct damage locations, which are in good agreement with experimental observations. Furthermore, it was discovered that the plasticity effects should not be neglected in laminates with low wrinkle levels.

Study of machining induced surface defects and its effect on fatigue performance of AZ91/15%SiCp metal matrix composite

The quality of surface generated in a peripheral milling of AZ91/SiCp/15% for varying machining conditions and its effect on the fatigue performance are investigated in this study. The machined surface quality was evaluated through roughness measurements and SEM micrographs of the machined surface. Tensile tests were performed to measure the mechanical properties of the composite. Subsequently, fatigue life of milled specimens was measured through axial fatigue tests at four loading conditions. Optical and SEM/EDS micrographs of the fractured surface were studied to identify the crack initiation site and propagation mechanism. Specimens machined at a lower feed rate of 0.1 mm/rev was found to have excellent surface finish and consequently higher fatigue life. At 0.3 mm/rev, the presence of feed marks and other surface defects resulted in a drastic decrease in fatigue life. Five distinct regions were identified on the fractured surface, particle fracture along and perpendicular to the surface, voids in the matrix due to particle debonding and pull out and typical ductile failure of matrix with embedded SiC particles.

Failure Analysis of Unidirectional Ceramic Matrix Composite Lamina and Cross-Ply Laminate under Fiber Direction Uniaxial Tensile Load: Cohesive Zone Modeling and Brittle Fracture Mechanics Approach

The current research work presents the computational micromechanical analysis of the room temperature tensile failure behavior of unidirectional (UD) and cross-ply (0/90) ceramic matrix composites (CMCs). For computational micromechanical analysis, three-dimensional (3D) representative volume element (RVE) and multi-fiber multilayer RVE (M2 RVE) models are generated that are representative of the lamina and the laminate under investigation. The RVE and M2 RVE models are generated by replicating the fiber distribution, and the placement of the fibers observed in a microscopic image of an actual CMC laminate. The generated RVE models consist of the discrete representation of individual constituent phases of the CMC such as fibers, interphase, matrix, and the fiber–interphase interface region. Under the applied external tensile load, the fiber–interphase interface interactions are modeled using the cohesive elements that follow the bilinear traction separation law. The matrix, fiber, and interphase materials failure behavior is captured using a brittle cracking model. In order to validate the proposed numerical methodology, the predicted average stress–strain curve at the UD laminate level is compared to the experimental stress–strain curve reported in the literature. In addition, the observed different phases in the predicted stress–strain curve are validated with the literature data. Using the proposed numerical methodology, a detailed local stress–strain and damage analysis leads to an observation that the so-called ductile stress–strain behavior (kink in the stress–strain curve) of a CMC UD laminate under uniaxial fiber direction tensile loads is mainly caused by the matrix damage initiation. Apart from the SiC material properties such as strength and fracture energy, it is also observed that the RVE size influences the average strength and failure strain predictions using computational micromechanics.

Wellbore stability and failure regions analysis of shale formation accounting for weak bedding planes in ordos basin

Borehole instability problem is one of the key problems in drilling engineering, especially the shale formation with bedding planes and natural fractures, the failure of shale rock could be divided into two parts, shear failure across intact rock matrix and slippage failure in shale bedding, resulting in more serious borehole instability problem during drilling process. In this study, combining with rock strength anisotropy, a method of failure region around wellbore is developed for layered rocks on the basis of isotropic borehole stability model. The effect of shale bedding occurrence on failure region around wellbore, what was hardly conducted by former researchers, is examined systematically. The results show that, polar plot of critical lower mud weight with rock strength anisotropy considered reflects the actual situation of a shale formation; the shale bedding strength, pore pressure and intrinsic cohesion are the three most impact parameters on wellbore stability. Moreover, the maximum failure depth is no longer in the minimum principal stress, but locates in four corners at top and bottom of wellbore, which is induced by slippage failure in laminated formations; the collapse of wellbore will be aggravated due to the overlapping of failure in rock matrix and bedding. This proposed model not only can provide guiding suggestions for well constructions and cementations, but also can be used as an effective complement to provide richer ground stress inversion data.

Fracture initiation pressure and failure modes of tree-type hydraulic fracturing in gas-bearing coal seams

Tree-type hydraulic fracturing is a new technology that can uniformly increase the permeability of coal seams. The existing initiation pressure prediction models do not fully consider the characteristics of coal seams and are not suitable for tree-type hydraulic fracturing. In this paper, an initiation pressure prediction model considering coal seam joints and gas pressure is established. In this model, the fracture failure modes of coal seam fracturing are calculated separately to accurately predict the failure mode and initiation pressure. Statistics and reasons are obtained for the fracture initiation position and the failure mode of tree-type hydraulic fracturing under different conditions. The fracture failure modes of a gas-bearing coal seam are mainly tensile failure and coal matrix failure, and tensile failure along bedding planes is the most common. The effects of 7 factors, including coal seam geological parameters, fracturing hole arrangement parameters and tree-type branch borehole arrangement parameters, on the fracture initiation pressure of tree-type hydraulic fracturing are analyzed. Among them, the angle between the tree-type branch borehole and the maximum principal ground stress direction is the only major influential factor that can be artificially controlled. The fracture initiation pressure is lowest when the tree-type branch borehole lies along the direction of the minimum principal ground stress. The results of a field experiment show that the theoretical initiation pressure and the actual initiation pressure are within 6.3%. In addition, compared with traditional fracturing technology, tree-type hydraulic fracturing technology can reduce the initiation pressure. The proposed model can provide a reference for field applications of tree-type hydraulic fracturing technology.

A fast algorithm for fracture simulations representing fibre breakage and matrix failure in three-dimensional fibre composites

A linear, periodic, three-dimensional shear-lag model of unidirectionally-reinforced composites that allows for fibre breakage, and matrix failure is proposed. Matrix failure can take the form of matrix splitting or interfacial debonding. A computationally efficient scheme for its solution is developed. This scheme exploits the translation invariance of the elastostatic fields due to failed elements in the periodic cell, and is asymptotically faster than the classical eigensolution-based approach. The new computational scheme is used to illustrate the influence of matrix failure on the elastostatic fields induced by small clusters of fibre breaks in several test problems. Monte Carlo simulations of fracture in model three-dimensional composite specimen with Weibull-distributed fibre segment strengths are also performed. Matrix failure is found to considerably alter fracture development, to weaken the median specimen, and to reduce the variability in composite strength.

Optimal orientation of fibre composites for strength based on Hashin\u2019s criteria optimality conditions

The Hashin’s strength criteria are usually employed in first ply failure and damage-onset analysis of fibre-reinforced composites. This work presents optimality conditions of local material orientations for these criteria, in terms of principal stresses and material strength parameters. Each criterion (matrix tensile/compressive, fibre tensile/compressive modes) has its conditions separately derived, analytically, based on a fixed stress field assumption. The conditions found show that orientations which coincide and do not coincide with principal stress directions may minimise local failure indices. These solutions are employed in a proposed algorithm, named HA-OCM (Hashin Optimality Criteria Method), which selectively satisfies the matrix failure modes (either tensile or compressive), iteratively and finite element-wise in composites. It is demonstrated that the HA-OCM is able to design single-layer plane structures with improved failure loads in comparison with designs following only maximum (in absolute) principal stress orientations. Results show that the material orientations have a trend to end up either aligned or at 90° with maximum in absolute principal stress directions. Global optima for compliance are, however, not guaranteed. To give an idea of gains in terms of failure loads, some HA-OCM designs show improvements of 71% and 140%, for example, in comparison with principal stress design.