Effect Of Interfacial Strength Research Articles

Multiscale analysis method and experiments for the transverse mechanical property of unidirectional fiber-reinforced composites

Carbon fiber-reinforced epoxy matrix composite laminates have been widely used in the case of advanced aero-engines, due to their high specific mechanical properties and mature production technology. In order to predict accurately the transverse mechanical properties of composites, this paper developed a multiscale analysis method which consists of three scales: At the microscale, an interfacial cohesive zone model is established based on atomic potential energy to describe the interface. At the mesoscale, a unit cell model is established to represent the fiber, matrix, and interface. At the macroscale, the homogenization method, failure criteria, and damage degradation models are utilized to predict transverse mechanical properties. The results of predictions are compared with experimental tests, and it is found that the maximum errors are less than 3%. Furthermore, the predicted damage evolution path aligns with the experimental results, thus validating the accuracy of the multiscale analysis method. By employing the multiscale analysis method, the effects of interfacial strength on the macroscopic transverse mechanical properties are analyzed. The simulation results indicate that: The interfacial strength has a more pronounced influence on the transverse strength and ultimate strain compared with the transverse modulus. Reducing the interfacial strength has a greater influence on the transverse modulus, strength, and ultimate strain than increasing the interfacial strength. The interfacial cohesive zone model can reflect the nonlinearity of epoxy matrix composite materials. Overall, the multiscale analysis method proves to be effective in accurately predicting the transverse mechanical properties of composites, and provides insights into the interfacial strength’s role in these properties.

The effect of interfacial strength on the mesoscopic damage characteristics of resin-mineral composite based on PFC3D

The effect of interfacial strength on the mesoscopic damage characteristics of resin-mineral composite based on PFC3D

Multi-axial elastic–viscoplastic curves of unidirectional carbon nanotube-polymer nanocomposites considering interphase and interface debonding using finite element modeling

This paper aims to predict the elastic-viscoplastic curves of unidirectional carbon nanotube (CNT)-reinforced polymer nanocomposites under the multi-axial tensions, including bi-axial transverse-transverse, bi-axial longitudinal-transverse and tri-axial longitudinal-transverse-transverse loadings by the use of finite element (FE) modeling. The role of the interphase between the CNT and polymer matrix as well as the debonding at the CNT/interphase interface in the stress-strain curves of nanocomposites is investigated. The polymer matrix and interphase region are characterized as elastic-viscoplastic materials, while the CNT behaves as the elastic material. The present results in uni-axial loading are compared to the available numerical outcomes for indicating the accuracy of the FE modeling. The simulation of multi-axial load conditions is based on the three-dimensional representative volume element (RVE) of the unidirectional CNT-polymer nanocomposite. The effect of interface strength on the elastic-viscoplastic stress-strain curves is examined under bi-axial and tri-axial loadings.

One developed finite element model used in nano-layered flaky Ti2AlC MAX ceramic particles reinforced magnesium composite

As one novel reinforcement used in magnesium composite, nano-layered flaky ternary MAX particle exhibits interesting anisotropic ceramic and metal properties. In order to accurately simulate the mechanical properties and damage behavior of MAX particle reinforced magnesium composite, we developed one finite element (FE) model based on 2D and 3D microstructural observations of 10 vol.% Ti2AlC-AZ91D composite. To improve the accuracy, matrix ductile damage, particle internal delamination deformation behaviors, and particle-matrix interfacial behaviors were respectively introduced into this model. The visual deformation processes of crack generation and propagation were carefully presented and discussed. The effects of interfacial strength and particle orientation on material properties were systematically investigated.

Effect of Interfacial Strength on Mechanical Behavior of Be/2024Al Composites by Pressure Infiltration.

In this paper, two kinds of Be/2024Al composites were prepared by the pressure infiltration method using two different beryllium powders as reinforcements and 2024Al as a matrix. The effect of interfacial strength on the mechanical behavior of Be/2024Al composites was studied. Firstly, the microstructure and mechanical properties of the two composites were characterized, and then the finite element analysis (FEA) simulation was used to further illustrate the influence of interfacial strength on the mechanical properties of the two Be/2024Al composites. The mechanical tensile test results show that the tensile strength and elongation of the beryllium/2024Al composite prepared by the blocky impact grinding beryllium powder (blocky-Be/2024Al composite) are 405 MPa and 1.58%, respectively, which is superior to that of the beryllium/2024Al composite prepared by the spherical atomization beryllium powder (spherical-Be/2024Al composite), as its strength and elongation are 331 MPa and 0.38%, respectively. Meanwhile, the fracture of the former shows brittle fracture of beryllium particles and ductile fracture of aluminum, while the latter shows interface debonding. Further FEA simulation illustrates that the interfacial strength of the blocky-Be/2024Al composite is 600 MPa, which is higher than that of the spherical-Be/2024Al composite (330 MPa). Therefore, it can be concluded that the better mechanical properties of the blocky-Be/2024Al composite contribute to its stronger beryllium/aluminum interfacial strength, and the better interfacial strength might be due to the rough surface and microcrack morphology of blocky beryllium particles. These research results provide effective experimental and simulation support for the selection of beryllium powder and the design and preparation of high-performance beryllium/aluminum composites.

Decipher the ultra-high strengthening and toughening efficiency of GNS-MgO/Mg layered composite with in-situ enhanced interface

Constructing graphene/metal layered structure serves as a promising way to solve the strength-toughness trade-off of metallic materials, while the weak interlayer interfaces usually lead to premature failure of the composites. This work focuses on the interfaces of the GNS-MgO/Mg layered composite with ultra-high strengthening and toughening efficiency. The yield strength and elongation were increased by 137% and 16.5%, with impressively 0.13 wt% GNS-MgO nano layers. Interface analysis based on atomistic simulations, interface observation, fractography, and AFM observation clarify the crucial role of MgO films and thinner GNSs in delaying crack initiation. Statistics based on EBSD and in-house codes, TEM observation, and atomistic simulations demonstrate the effect of GNS-MgO layers on higher density of geometry necessary dislocations (GNDs) and statistical storage dislocations (SSDs). Additional back stress hardening induced by GNDs and SSDs provides the GNS-MgO/Mg composite with ultra-high strengthening efficiency. This study provides comprehensive insights into the interfacial design and the effects of interface strength on mechanical properties of layered composites. The proposed preparation method could be extended to other graphene/metal systems.

Effect of interface strength on electromigration-induced inlaid copper interconnect degradation: Experiment and simulation

AbstractBoth in situ microscopy experiments at embedded inlaid copper interconnect structures and numerical simulations based on a physical model provide information about electromigration-induced degradation mechanisms in on-chip interconnects. It is shown that the modification of the bonding strength of the weakest interface results in completely changed degradation and failure mechanisms. Transmission electron microscopy (TEM) images of standard Cu/SiNxinterfaces are compared with strengthened interfaces, e. g., after applying an additional metal coating or a self-assembled monolayer (SAM) on top of the polished copper lines. The changed degradation mechanisms as observed with the in situ scanning electron microscopy (SEM) experiment and as predicted based on the numerical simulations are explained based on TEM images.

Interlaminar Crack Propagation Analysis of ENF Specimens Based on the Cohesive Zone Model

Based on classical laminated plate theory and cohesive zone model, a theoretical model of general delamination cracked laminates is established for crack propagation of pure mode Ⅱ ENF specimen. Compared with the conventional beam theory, the proposed model fully consideres the softening process of the cohesive zone and introduced the nonlinear behavior of ENF specimens before failure. The predicted failure load is smaller than the beam theory and closer to the experimental data in literature. Compared with the beam theory with only fracture toughness considered, the proposed model can simultaneously analyze the influence of interface strength, fracture toughness and initial interface stiffness on the load-displacement curves in ENF tests. The results show that the interface strength mainly affects the mechanical behavior of specimens before failure, but has no influence on crack propagation. The fracture toughness is the main parameter affecting crack propagation, and the initial interface stiffness only affects the linear elastic loading section. The length of cohesive zone increases with the increase of fracture toughness and decreases with the increase of interface strength. The effect of interface strength on the length of cohesive zone is more obvious than fracture toughness. When the tip of the adhesive zone reaches the half-strength of the specimen, the length of the adhesive zone decreases to a certain extent.

Finite Element Modelling of Prestressed Concrete Piles in Soft Soils, Case Study: Northern Jakarta, Indonesia

Jakarta is faced with limited land resources due to its position as the capital city of Indonesia. Therefore, numerous high-rise buildings are being constructed to solve this problem and provide accommodations for a large number of Jakarta residents. Studies have shown that prestressed concrete piles (spun piles) are commonly used as the foundations of high-rise buildings in metropolitan cities across Indonesia, especially in the Northern Jakarta Coastal area, which is predominant with deep soft soils deposit. To further assess and verify the ultimate capacity of the pile, a static loading test was conducted. However, not all results from the field test produced ideal, accurate, precise, and reliable load-settlement curve (until failure) results. Therefore, this study aims to determine the soil properties for the analysis of prestressed concrete spun piles with a diameter of 600 mm in the Northern Jakarta coastal area based on the standard penetration test values (SPT-N). It is a case study of a well-documented static pile load test using the kentledge system. Back analyses were performed by the finite element method to obtain the extrapolated load-settlement curve. Furthermore, the effect of interface strength between pile and soil on the load-settlement curve was also investigated. The results showed that a reduction of interface strength leads to a smaller load–settlement curve. In addition, several geotechnical engineering parameters of soil, such as the undrained shear strength and effective young's modulus, were established using data from an in-situ soil site investigation and empirical correlations with SPT-N.

Structural performance of damaged rigid pipe rehabilitated by centrifugal spray on mortar liner

There has been growing interest in using trenchless technology, especially centrifugal spraying techniques, to renovate the sewer pipe network in China. In this study, a damaged reinforced concrete pipe (RCP) (i.e., 14.7% vertical deformation) with one-meter diameter is rehabilitated by centrifugally spraying on a 50 mm thickness mortar lining. The ultimate (Du) D-load only increased by 2% compared to host pipe’s residual strength; however, other pipe properties exhibited improvement. Based on the behavior of two experimental results, finite element models were established, and an innovative pipeline damage quantization model was proposed. Through parameter sensitivity analysis, the effects of interface strength and fracture energy on pipe bearing capacity were studied. It was discovered that interface bonding performance affected the service load of the rehabilitated pipe. From the analysis of pipeline initial state deformation influence on the repaired structure bearing capacity, it was discovered that selecting a reasonable repair time point can effectively improve the functionality of the pipe network and reduce repair costs. An analysis of RCPs structural repair with a vertical deformation larger than 14% revealed that it is difficult to repair damaged pipes only employing mortar spraying. A structural design method based on the service load and ultimate load is presented in this paper.

Micro-CT based trans-scale damage analysis of 3D braided composites with pore defects

Pore defects that inevitably produce during the manufacturing process, have distinct effects on the mechanical properties of 3D braided composites. A trans-scale method coupled with Micro-CT is developed to investigate the strength and damage behavior of 3D braided composites with pore defects. Pore defects and yarns are measured by Micro-CT and reconstructed. Then, the trans-scale finite element models are established on the Micro-CT data. The progressive damage model and cohesive-zone model are applied to simulate the damage behavior of braided composites, and effects of interface strength are also investigated. Effective properties of yarns are predicted by the micro-scale analysis and then transferred to conduct the meso-scale analysis. The meso-scale finite element model can predict the stress-strain response well, which has been validated by experiments. The failure modes of yarn damage, matrix cracking and interface debonding are recognized and correspond well with the final failure morphology of the sample. The damage appears around the pore defects and then develops to the weak region in the matrix. The interface properties show diverse influences on yarns and braided composites under different loading conditions. As experimentally demonstrated, the present research scheme can well capture the void features, and therefore efficiently predict the tensile behavior of 3D braided composites considering pore defects.

Ballistic performance of UHMWPE laminated plates and UHMWPE encapsulated aluminum structures: Numerical simulation

The ballistic performance of ultra-high molecular weight polyethylene (UHMWPE) laminated plates and UHMWPE encapsulated aluminum structures were numerically characterized. Full three-dimensional continuum model for each type of target was built, and the UHMWPE was simulated using a sub-laminate approach with a composite material model. Simulation results were compared with existing experimental measurements, with good agreement achieved both on final deformation morphology and ballistic data. Underlying penetration mechanisms of laminated plate were then explored, and the effect of interface strength was quantified. The ballistic improvement of UHMWPE encapsulated aluminum structures was mainly attributed to the stretching of lateral swathing laminates. However, the benefit of encapsulation decreased as the initial impact velocity or lateral dimensions of encapsulated structure were increased. These findings are helpful for designing lightweight UHMWPE composite structures with superior ballistic resistance.

The role of interfacial H-bonding on the electrical properties of UV-cured resin filled with hydroxylated Al2O3 nanoparticles

Surface hydroxylation of crude Al2O3 (c-Al2O3) nanoparticles by H2O2 was conducted to tailor the electrical properties of UV-cured resin. The hydroxyl groups on Al2O3 particles were designed to establish hydrogen bonding between the hydroxyl and carboxyl groups, which favors the enhancement of interfacial strength between fillers and UV-cured resin matrix. The effect of interfacial strength on the electrical properties was investigated. Owing to the improved interfacial strength, it can be conjectured that a larger volume of the interaction zone exists in UV-cured resin/hydroxylated Al2O3 (UV/h-Al2O3) composites. As a consequence, the number of deeper traps is increased, restraining the charge migration and raising the charge injection barrier. Thus, UV/h-Al2O3 composites exhibit remarkably enhanced breakdown strength, improved volume resistivity and suppressed space charge accumulation in comparison with that of UV/c-Al2O3 composites at the same filler content. It was found that the addition of 0.5 wt% h-Al2O3 increases the AC breakdown strength and volume resistivity by 15.5% and 367.9%, respectively. Our results suggest that hydroxylation is an efficient way to improve the electrical properties of UV-cured resin nanocomposites, thus promoting stereolithography 3D printing in the application of electrical and electronic fields.

Effects of interface strength on damage to railway slab–track joints under temperature rise

To study the effect of interface strength on the damage of railway slab–track joints, a finite-element model of slab joint damage was established based on the cohesive zone model. The damage behaviour of slab joints with two interfaces was analysed, and the effect of the interface strength between slab joint and slab and between asphalt cement mortar and slab on slab joint damage was studied. The specimens were designed to determine the interface properties. It was found that breakage of the narrow joint and fracture at the junction between the broad joint and narrow joint were the main damage patterns of the slab joint. The effect of the interface strength between the slab joint and slab was obvious. The interface strength should be elevated by better preparation of the contacting faces before pouring. Improving the interface strength between the mortar layer and slab cannot effectively reduce the damage.

Effect of interface strength on the mechanical behaviour of bio-inspired composites: A molecular dynamics study

Nanoscale composites inspired from biological materials such as nacre and bone are excellent candidates for improving the mechanical properties of ceramic matrix composites (CMC) or in general any brittle-matrix composites. These composites are based on the regularly staggered model (RSM) and on the stair-wise staggered model (SSM), and consist of stiffer platelets embedded in a compliant matrix. The interface between the platelets and the matrix plays a key role as an enormous amount of interfacial area exists in the nanocomposite materials. We investigate the influence of interface strength on the overall mechanical properties and deformation mechanisms of bio-inspired brittle-matrix nanocomposites. Atomistic simulations are used for this purpose and the interface strength is controlled by varying the binding energy between the platelet atoms and the matrix atoms. We found that the mechanical properties of both models initially increase with the interface strength. However, above a critical value, the trend changes drastically between the two models. The RSM model continues to maintain the flow stress and toughness at higher interface strengths, due to the persistence of deformation mechanisms such as bulk matrix plasticity and platelet pullout. In contrast, in the SSM model the flow stress and toughness are deteriorated as softening of stress and fracturing of platelets occur at higher interface strengths. The knowledge gained from this study paves new way for the development of bio-inspired ceramic-matrix composites with improved mechanical properties.

Failure characterization of solid structures based on an equivalence of cohesive zone model

Cohesive zone models have been widely used to model interface crack initiation and propagation both in single-material media and bi-material systems. For single-material media with cohesive elements inserted into interface among segments, in order to ensure that the introduction of interface cohesive zone models does not affect the mechanical properties of single-material media before the softening stage of cohesive zone models, a selection criterion of stiffness of cohesive elements is proposed theoretically firstly based on the properties’ equivalence. Taking the softening stage into account, the mechanical responses of the overall stress-strain relationship of single-material media, for the cases of stable increase of strain and snap-back instability of strain, are both obtained, and the related energy mechanism are investigated. For bi-material systems with cohesive elements at interface between two materials, the thickness-dependent failure characteristics of systems in uniaxial tension are found, which is attributed to the difference of the releasing rate of elastic strain energy in the materials with different thicknesses. Furthermore, as a more complex application of cohesive elements, based on the selection criterion proposed, failure behaviors of the ceramic coating/substrate systems under three-point bending are modeled by finite element method and inserting cohesive elements into the coating segments and the coating/substrate interface simultaneously. The simulation results indicate the transition of dominated failure mode from coating cracking to interface delamination with increasing coating thickness, and show faster damage of thick coating systems, agreeing with experimental results. The effects of interface strength and toughness of cohesive elements on failure are also revealed. These results can provide guidance for the application of cohesive elements, and help us better understand the overall failure behaviors of interface systems.

Micromechanical Investigation of Debonding Processes in Composite Solid Propellants

AbstractThe micromechanical damage of a composite solid propellant was observed by in situ scanning electron microscopy. Based on the damage characteristics, a cohesive interfacial element was adopted to model the debonding processes along the particles and the binder interface. The effects of interfacial strength and microcracks in the binder on the debonding process of propellant were also examined. The results show that interfacial debonding is the propellant's main failure mode under tension. Finite element method analyses with a cohesive interfacial element could predict the heterogeneous strain and stress fields as well as the processes of the particles separated from the binder. Interfacial strength plays a significant role in macroscopic behaviors of the propellant. Microcracks in the binder significantly influence the debonding process. The numerical simulation results reasonably reflect the corresponding experimental results. These results provide the basis for the prediction of mechanical properties and the optimal design of the composite solid propellant.

Assessment of failure and cohesive zone length in co-consolidated hybrid C/PEKK butt joint

The failure mechanisms and the cohesive zone length (CZL) during fracture of a recently developed butt jointed thermoplastic composite are evaluated in this paper. The laminated skin and the web were made of AS4/PEKK. The butt joint (filler) was injection molded from 20% short AS4 filled PEKK. The skin and web were co-consolidated together with the filler to form a hybrid butt joint structure. The crack initiation and propagation in the filler and the delamination at the skin-filler interface were captured using a high-speed camera. It was found from the experimental observations that the crack initiated in the filler and then propagated towards the skin-filler interface in less than 33 μs under three-point bending. A numerical model was developed using the finite element method in ABAQUS to predict the failure and CZL. The crack initiation and progression in the filler was predicted using the Virtual Crack Closure Techniques (VCCT) and the delamination at the skin-filler interface was modelled using the cohesive surfaces. The predicted stiffness of the specimen, the location of crack initiation and propagation as well as the force drop during delamination were in good agreement with experiments. The development of CZL was critically assessed and it was found that the CZL increases during mix mode delamination. The effect of interface strength and critical energy release rate on the CZL was investigated in the parameter analysis.

The effects of interfacial strength on fractured microcapsule

The effects of interfacial strength on fractured microcapsule are investigated numerically. The interaction between crack and microcapsule embedded in mortar matrix is modeled based on cohesive approach. The microcapsules are modelled with variation of core-shell thickness ratio and potential cracks are represented by pre-inserted cohesive elements along the element boundaries of the mortar matrix, microcapsules core, microcapsule shell, and at the interfaces between these phases. Special attention is given to the effects of cohesive fracture on the microcapsule interface, namely fracture strength, on the load carrying capacity and fracture probability of the microcapsule. The effect of fracture properties on microcapsule is found to be significant factor on the load carrying capacity and crack propagation characteristics. Regardless of core-shell thickness ratio of microcapsule, the load carrying capacity of self-healing material under tension increases as interfacial strength of microcapsule shell increases. In addition, given the fixed fracture strength of the interface of microcapsule shell, the higher the ratio core-shell thickness, the higher the probability of microcapsules being fractured.

Effects of Interfacial Strength on Damage Behavior in Bolted Joint of CFRP/Titanium Foils Laminates

Effects of Interfacial Strength on Damage Behavior in Bolted Joint of CFRP/Titanium Foils Laminates