Surface-based Cohesive Behavior Research Articles

Experimental and numerical investigation on the compression after high-velocity impact behavior of composite laminates

Considering the differences in damage mechanism between high-velocity impact (HVI) and low-velocity impact (LVI), this study conducted HVI tests and compression-after-impact (CAI) tests to reveal the post-impact compression behavior of laminates manufactured by unidirectional prepreg tape and exposed a completely different mechanical response in residual strength compared to that of LVI. By controlling the impact velocity within the range of 200 m/s ̃ 380 m/s, three kinds of impact results were obtained, including un-penetrated and penetrated conditions. Different CAI damage morphologies can be observed in these laminates. In order to fully understand the CAI damage mechanism induced by different HVI events, a surface-based cohesive behavior and a CDM intralaminar damage model were implemented. In addition, a more complete picture of the compression behavior after HVI was observed through the simulation results, which is of great help in estimating the residual strength of post-impact laminates. However, the HVI damage was introduced through the spherical steel projectiles, and the sample size was determined based on ASTM D7137, which might be different factors from the application conditions.

A simulative study on the effect of friction coefficient and angle on failure behaviors of GLARE subjected to low-velocity impact

Abstract The aim of this paper is to study the effect of friction coefficient and impact angle on the failure behaviors of glass fiber reinforced aluminum laminates (GLARE) under the low-velocity impact (LVI) loading. A methodology is developed in commercial software ABAQUS/Explicit, and its accuracy is verified based on the results of comparison between simulation and experiment. In the simulation, Johnson–Cook flow stress model and surface-based cohesive behavior are carried out to simulate the damage evolution of aluminum alloy layers and delamination at the interface. Further, both the dynamic response history and damage mechanism characterization of these hybrid laminates are presented and compared carefully. Additionally, due to the advantage of simulation, it is accurate and easy to discuss on the evolution of the damage contour consisting of the damage degree of composite and metal layers as well as the interface between them. Finally, the influence rules of friction coefficient and angle on the failure behaviors of GLARE under LVI are drawn clearly.

Lateral behaviour of masonry walls with different types of brick bonds, aspect ratio and strengthening measures by polypropylene bands and wire mesh

The paper presents a comparative study of the performances of unreinforced masonry (URM) wall units with each of the four types of brick bonds: Header bond, Stretcher bond, English bond and Flemish bond under lateral or representative seismic loading. The load-carrying capacity, stress distribution, and failure mechanisms for each case have been obtained and interpreted. A plasticity-based simplified micro-model approach and the extended finite element method (XFEM) were used, including surface-based cohesive behaviour. The model is validated against the experimental and computational results available in the literature by a well-known software named ABAQUS. The hysteretic curves obtained in each case under cyclic loading are presented to compare the energy dissipation capacity for each case. The aspect ratio of the wall significantly influences the failure mechanism and peak load-carrying capacity. After that, the effect of strengthening using polypropylene band and wire mesh is also studied, showing a considerable increase in strength for a marginal cost increase.

Simulation of thermal barrier coating spallation induced by the initiation/growth/coalescence of internal crack and interfacial crack based on a real image model

In the furnace cycle test, the growth of oxide film leads to the propagation and coalescence of multiple cracks near the interface, which should be responsible for the spallation of thermal barrier coatings (TBCs). A TBC model with real interface morphology is created, and the near-interface large pore is retained. The purpose of this work is to clarify the mechanism of TBC spallation caused by successive initiation, propagation, and linkage of cracks near the interface during thermal cycle. The dynamic growth of thermally grown oxide (TGO) is carried out by applying a stress-free strain. The crack nucleation and arbitrary path propagation in YSZ and TGO are simulated by the extended finite element method (XFEM). The debonding along the YSZ/TGO/BC interface is evaluated using a surface-based cohesive behavior. The large-scale pore in YSZ near the interface can initiate a new crack. The ceramic crack can propagate to the YSZ/TGO interface, which will accelerate the interfacial damage and debonding. For the TGO/BC interface, the normal compressive stress and small shear stress at the valley hinder the further crack propagation. The growth of YSZ crack and the formation of through-TGO crack are the main causes of TBC delamination. The accelerated BC oxidation increases the lateral growth strain of TGO, which will promote crack propagation and coalescence. The optimization design proposed in this work can provide another option for developing TBC with high durability.

Computational model for predicting the low-velocity impact resistance and tolerance of composite laminates

We present a numerical model for predicting the low velocity impact resistance and tolerance of multidirectional carbon fiber-reinforced composite laminates made of non-crimp fabric. A finite element model is developed wherein the heterogeneous plies are replaced by equivalent homogeneous orthotropic plies. The low-velocity impact of a carbon–epoxy laminate is investigated using an explicit finite element model. Intralaminar failure and damage is evaluated using the 3D Hashin failure criteria and a surface-based cohesive behavior is implemented to capture the delamination between the plies. Following the low velocity impact, the finite element model is subjected to axial compression to investigate the compressive residual strength after impact, which is a measure of damage tolerance. The computational model is used to investigate the impact resistance and tolerance of a 24-ply multidirectional symmetric laminate reinforced with carbon fiber non-crimp fabric. The low velocity impact response and the compressive residual strength after impact are validated with experimental data for different levels of impact energy. It is found that the computational model can predict the impact resistance and damage tolerance for impact energies up to 50 J.

Numerical modeling of a masonry arch structure

To investigate the structural behavior and estimate the strength capacity of masonry arch structures, experimental testing can be challenging at large scales. In such a case, numerical modeling is considered as an interesting alternative. In this work, two ready-to-use modeling techniques are proposed. The first one is based on the detailed micro-modeling in which the brick and mortar were modeled using concrete damaged plasticity model and the brick-mortar interface was modeled by the surface-based cohesive behavior model. These constitutive laws are already implemented in the ABAQUS environment without the need for specific subroutines. The second technique is based on the homogenization approach to derive the equivalent characteristics of masonry, which is then modeled as one continuous element. Both techniques were used to simulate the experimental behavior of a masonry arch subjected to in-plane bending. Finally, comparison between experimental and numerical results of the two methods shows the capability of the proposed homogenization approach to simulate the behavior of masonry arch structures with a sufficient degree of accuracy and a reduced computational cost.

The effects of TGO growth stress and creep rate on TC/TGO interface cracking in APS thermal barrier coatings

To design reliable thermal barrier coatings (TBCs), it is essential to elucidate the interface failure mechanism and establish a better life-prediction model. Up to now, how the variations of thermally grown oxide (TGO) growth stresses and creep rates affect the interfacial cracking behavior between top coat (TC) and TGO has not been clearly studied. In this work, the thermos-mechanical model with simplified cosine curve interface morphology in TBCs is developed utilizing numerical simulation software (ABAQUS). According to the calculated stress states of TC/TGO interface, the possible damage scenarios are inferred. On this basis, the interface crack nucleation and propagation is simulated by the surface-based cohesive behavior. General features of the interface crack are in good coincidence with previous conjectures. Furthermore, large TGO growth stresses will trigger off premature cracking, conversely, the formation of TC/TGO interface crack can be postponed due to large TGO creep rates. In addition, the dominant fracture mode of TC/TGO interface is impacted by the variations of TGO growth stresses as well as its creep rate. The position of interface fracture mode transition has been shifted to a certain extent.

Detailed Micromodeling and Multiscale Modeling of Masonry under Confined Shear and Compressive Loading

Detailed micromodeling (DMM), macromodeling, and multiscale modeling (MM) as a transitional solution between the two have been extensively used in the last years to model masonry. However, most previous works are based on an advanced theoretical background and/or require a user-defined subroutine, which may restrict their application in engineering practice. This paper proposes a practical and ready-to-use alternative to model and analyze small- and large-scale masonry using DMM and MM. To this end, brick–mortar interfaces were modeled using surface-based cohesive behavior; concrete damaged plasticity was used to model the nonlinear behavior of brick, mortar, and homogenized masonry. These constitutive models have already been implemented in ABAQUS software version 6.14. Mechanical characteristics of the homogenized masonry were derived from simple numerical tests conducted on a representative volume element. Numerical analyses were validated by comparison with experimental results of a confined shear test. It was shown that the DMM provides high accuracy in the simulation of the failure mechanism. The proposed homogenization technique for the MM, on the other hand, provides a satisfactory degree of accuracy with a significant computational cost savings. Both techniques can be used to predict the behavior of masonry at different scales.

Parametric study on bond of GFRP bars in alkali-activated cement concrete

Bond behaviour plays an important role in the design and performance of reinforced-concrete structures. In this study, finite-element modelling is used to perform a parametric study. The bond between the glass fibre-reinforced polymer (GFRP) bar and alkali-activated cement concrete is modelled by surface-based cohesive behaviour. The accuracy of the model is validated by comparing model predictions with experimental results. The effect of concrete cover, bar diameter, compressive strength, lead length, embedment length and GFRP elastic modulus on bond behaviour is investigated. Each of these parameters are varied based on a range of applicable values to study their influence on bond behaviour. The parametric study showed that bond behaviour is mainly affected by concrete cover, bar diameter, embedment length and the compressive strength of the concrete. The effect of the elastic modulus of the GFRP bar is not as pronounced as that of the other parameters, while the influence of lead length can be avoided by providing enough unbonded length at the loaded end. The parametric study is further used to calibrate a well-known bond equation and develop a new regression equation for predicting the maximum bond stress. The predicted results from these equations showed a good agreement with the experimental results as well as those of the finite-element model.

Failure analysis of 2D C/SiC composite z-pinned/bonded hybrid single-lap joints

Z-pinned/bonded hybrid joints are widely used in the 2D C/SiC composite structures, whose mechanical behavior and failure mechanisms are directly related with the structure integrity. The hybrid joints for 2D C/SiC composite structures are formed by depositing SiC into the gap of z-pinned joints. To evaluate the SiC bonding effect, the tensile experiments for two kinds of z-pinned joints with and without bonded layer were conducted. It was proved that the failure modes of the pin were the tensile and shear failure, and the bonded layer was the interlaminar shear failure of the substrate plate instead of the shear failure of SiC bonded layer due to the smaller interlaminar shear strength. The bonded zone states of specimens were also examined, which were reproduced in the shell-fastener numerical model with surface-based cohesive behavior. Combining with shear strength theory, a numerical model is developed to study the failure processes of the hybrid joints. The SiC bonded zone areas can also greatly influence the failure response of the hybrid joints. The large SiC bonded layer zone can improve the shear strength of the joints. The failure of the joints is determined by the SiC bonded layer when the SiC bonded zone is large enough. This study can be helpful to evaluate and design the SiC bonded zone states of the hybrid joints in the engineering application.

Out-of-plane behavior of rammed earth walls under seismic loading: Finite element simulation

Rammed earth (RE) is a sustainable material which is made by compacting the soil in a formwork. The earthquake performance of RE structures is an important topic, however the out-of-plane seismic behavior of RE structures has not been thoroughly investigated in the literature. The objective of the present paper is to study the out-of-plane seismic behavior of RE walls by using finite element method. The model used involved the concrete damage plasticity (CDP) model to simulate the nonlinear behavior of the earthen layers, a surface-based cohesive behavior to simulate the linear and nonlinear behavior of the interlayers (between the layers). The parameters of the model were first validated through the simulations of available experimental tests in the literature for both in-plane and out-of-plane loading. Then, a U-shaped RE wall was modelled which was composed of one longitudinal wall (4.6-m-length × 2.4-m-height × 0.5-m-thickness) and two transversal flanges (2-m-length). Effects of the bond beam (on the top of the walls), the interlayers and different earthquake amplitudes were studied. The results showed that the implementation of the interlayers in the model had clear influences on the ultimate load and the failure modes but the inter-storey-drift was few affected; the bond beam played an important role for the out-of-plane seismic behavior of the RE wall. The performance of the studied RE structure was satisfying until a seismic amplitude of 0.223 g.

A computational approach to investigate optimal cutting speed configurations in rotational needle biopsy cutting soft tissue

The rotational cutting method has been used in needle biopsy technologies to sample tough tissues, such as calcifications in the breast. The rotational motion of the needle introduces shear forces to the cutting surface such that the cutting force in the axial direction is reduced. As a result, tissue samples with large volume and better quality can be obtained. In order to comprehensively understand the effect of the needle rotation to the axial cutting force under a wide range of the needle insertion speed, this paper demonstrates a computational approach that incorporates the surface-based cohesive behavior to simulate a rotating needle cutting soft tissue. The computational model is validated by comparing with a cutting test dataset reported in the literature. The validated model is then used to generate response surfaces of the axial cutting force and torque in a large parameter space of needle rotation and insertion speeds. The results provide guidelines for selecting optimal speed configurations under different design situations.

Evaluation of cement sheath integrity subject to enhanced pressure

Well-cementing (cementation) is an influential stage of a wellbore completion, as the cement sheath is responsible for providing a complete zonal isolation. Therefore, it is of utmost importance to understand the cement mechanical failure mechanisms since well cement failure and interfacial debonding between the cement and casing and cement and rock formations can lead to a barrier failure. During the wellbore lifetime, a cement sheath is subjected to pressure loading variations. This paper demonstrates the results of an experimental-numerical study to investigate the cement sheath integrity after being subjected an enhanced pressure. A constitutive model specifically formulated for the modelling of quasi-brittle materials is applied to the investigation of cement sheath integrity, incorporating both compression and tensile damage mechanisms. Laboratory experiments are carried out to obtain strength properties of cement class G followed by calibration of the model parameters based on the obtained experimental results. A three-dimensional finite element framework employing the constitutive model for cement sheath and a surface-based cohesive behaviour for the interfaces is developed for integrity investigations. The effects of different orientations of in-situ stresses, different stiffness's of surrounding rock, and the eccentricity of the casing within the wellbore on the integrity of the cement and interfaces are investigated. The significance of cement sheath centralisation and elevated risk of cement mechanical failure caused by wellbore operations in anisotropic fields with soft rocks formation were highlighted. Furthermore, the relatively high magnitude of tensile damage (cracking index) within the cement sheath confirms the importance of tensile properties to be incorporated into the constitutive modelling.

Axial splitting of conical frusta: Experimental and numerical study and crashworthiness optimization

This paper investigates the axial splitting process of thin-walled conical aluminum frusta, experimentally and numerically. The specimens were prepared using the spinning method and some edge slits were created at the specified locations. The specimens were axially compressed between a rigid plate on top and a rigid conical die at the bottom using Zwick universal testing machine. Some key parameters of energy absorbers such as specific absorbed energy (SAE), non-dimensional load-carrying capacity (NLC) and undulation of load-carrying capacity (ULC) were extracted from the load-displacement diagrams. Effects of different parameters such as specimen wall semi-apical angle, die semi-apical angle, number, and length of initial slits were studied on the energy absorption capability of specimens. The numerical analyses were performed by finite element method using Abaqus/Implicit software package. The surface-based cohesive behavior technique which works only with implicit solver was employed for cracks propagation. The numerical simulations were compared with experiments and good agreements were found between numerical and experimental results. To find the optimum energy absorber parameters, the design of experiments (DOE) method was employed. Using the existing data and applying the Taguchi technique, the optimal specimens with best SAE, ULC, and NLC were found. To check the efficiency of the DOE approach, these specimens were fabricated and tested and it was observed that the tested specimens had the best SAE, ULC, and NLC among all specimens. So, the excellent performance of DOE technique in present application was proved.

Interfacial bonding between CFRP and mechanically-treated aluminum liner surfaces for risers

The bonding between metal and carbon fiber-reinforced polymer (CFRP) composites is important in structures such as composite risers. Surface treatment of the metal is required to improve the metal-composite bonding. In this study, the effects of two mechanical surface treatment methods on the bonding between carbon/epoxy composites and aluminum are studied. The treatment methods investigated are grit blasting and grooving. Mechanical tests are performed and the test results are used with finite element simulations to study the failure and damage mechanisms at the composite-metal interface. The mechanical response and damage propagation at the metal-composite interface are modeled successfully using surface-based cohesive behavior. The finite element simulations gave insight into the way that the grooving treatment method improved the composite-metal bonding.

Pullout simulation of post installed chemically bonded anchors in UHPFRC

An experimental and numerical study was completed in order to examine the mechanical behaviour of post-installed bonded anchors in ultra-high performance fibre reinforced concrete with a compressive strength higher than 130 MPa. The aim was to analyse the failure mechanisms in static pullout tests and to suggest a simple numerical model, which can be employed in a design stage, to reproduce the global behaviour of the anchor. The experimental observations show that a combined pullout and concrete cone failure occurred for an embedment depth of 40 mm and a steel rod failure for an embedment depth of 100 mm. The numerical model was set up using Abaqus software, by adopting the concrete damage plastic model and a surface-based cohesive behaviour for the interface concrete-anchor. The obtained failure modes and ultimate loads are in good agreement with experimental results. A minimum embedment depth of 50 mm was assessed to prevent a pullout failure of the anchor.

Effect of casing eccentricity on cement sheath integrity

Cement sheaths play an important role in providing zonal isolation and preventing the migration of formation fluids to aquifers and the surrounding environment. The condition of a cement sheath may change because of the imposed pressure and temperature alterations during a wellbore lifetime. Cement sheath mechanical failure may happen because of poor cement placement, development of cracks within the cement sheath and debonding at the cement sheath, casing and rock interfaces. A three-dimensional finite element framework, employing an appropriate constitutive model (Concrete Damage Plasticity, CDP) for cement sheath and a surface-based cohesive behaviour for the interfaces, is developed for integrity investigations. The incorporation of the CDP is very advantageous to model quasi-brittle materials due to its capabilities to simulate both compression and tensile damage. The effect of casing eccentricity on stress distribution within the cement sheath and the integrity of the cement sheath is investigated while enhancing the wellbore pressure. Three different degrees of casing eccentricity (30%, 50% and 70%) were considered. The huge stress concertation within the narrower part of the cement sheath makes this section susceptible to compression and tensile damage. The high magnitude of compression and tensile damage in the scenario with 70% casing eccentricity highlights the importance cement sheath centralisation.

Experimental and numerical studies on the impact response of damage-tolerant hybrid unidirectional/woven carbon-fibre reinforced composite laminates

Abstract A woven five-harness satin (5HS) weave with AS4 carbon fibres, and unidirectional high strength IMS60 carbon fibres were used to manufacture hybrid laminates, using resin infusion, to assess their performance in low velocity impact tests. Load/energy-time curves and load-displacement curves were extracted from the experimental data, and non-destructive C-scanning was performed on all pre- and post-impacted specimens to quantify the extent of damage incurred. A finite element-based computational damage model was developed to predict the material response of these hybrid unidirectional/woven laminates. The intralaminar damage model formulation, by necessity, consists of two sub-models, a unidirectional constitutive model and a woven constitutive model. The built-in surface-based cohesive behaviour in Abaqus/Explicit was used to define the interlaminar damage model for capturing delamination. The reliability of this model was validated using in-house experimental data obtained from standard drop-weight impact tests. The simulated reaction-force and absorbed energy showed excellent agreement with experiment results. The post-impact delamination and permanent indentation deformation were also accurately captured. The accuracy of the damage model facilitated a quantitative comparison between the performance of a hybrid unidirectional/woven (U/W) laminates and a pure unidirectional (PU) carbon-fibre reinforced composite laminates of equivalent lay-up. The hybrid laminates were shown to yield better impact resistance.

Simulating masonry wall behaviour using a simplified micro-model approach

In this paper, a simplified micro-model approach utilising a combination of plasticity-based constitutive models and the extended finite element method (XFEM) is proposed. The approach is shown to be an efficient means of simulating the three-dimensional non-linear behaviour of masonry under monotonic in-plane, out of plane and cyclic loads. The constitutive models include surface-based cohesive behaviour to capture the elastic and plastic behaviour of masonry joints and a Drucker Prager (DP) plasticity model to simulate crushing of masonry under compression. The novel use of XFEM in simulating crack propagation within masonry units without initial definition of crack location is detailed. Analysis is conducted using standard finite element software (Abaqus 6.13) following a Newton Raphson algorithm solution without employing user-defined subroutines. The capability of the model in terms of capturing non-linear behaviour and failure modes of masonry under vertical and horizontal loads is demonstrated via comparison with a number of published experimental studies.

Improvement of Progressive Damage Model to Predicting Crashworthy Composite Corrugated Plate

To predict the crashworthy composite corrugated plate, different single and stacked shell models are evaluated and compared, and a stacked shell progressive damage model combined with continuum damage mechanics is proposed and investigated. To simulate and predict the failure behavior, both of the intra- and inter- laminar failure behavior are considered. The tiebreak contact method, 1D spot weld element and cohesive element are adopted in stacked shell model, and a surface-based cohesive behavior is used to capture delamination in the proposed model. The impact load and failure behavior of purposed and conventional progressive damage models are demonstrated. Results show that the single shell could simulate the impact load curve without the delamination simulation ability. The general stacked shell model could simulate the interlaminar failure behavior. The improved stacked shell model with continuum damage mechanics and cohesive element not only agree well with the impact load, but also capture the fiber, matrix debonding, and interlaminar failure of composite structure.