Interfacial Debonding Research Articles

Effects of interfacial debonding on the stability of finitely strained periodic microstructured elastic composites.

Predicting failure initiation in nonlinear composite materials, often referred to as metamaterials, is a fundamental challenge in nonlinear solid mechanics. Microstructural failure mechanisms encompass fracture, decohesion, cavitation, compression-induced contact and instabilities, affecting their unconventional static and dynamic performances. To fully take advantage of these materials, especially in extreme applications, it is imperative to predict their nonlinear behaviour using reliable, accurate and computationally efficient numerical methodologies. This study presents an innovative nonlinear homogenization-based theoretical framework for characterizing the failure behaviour of periodic reinforced hyperelastic composites induced by reinforcement/matrix decohesion and interaction between contact mechanisms and microscopic instabilities. Debonding and unilateral contact between different phases are incorporated by employing an enhanced cohesive/contact model, which features a special nonlinear interface constitutive law and an accurate contact formulation within the context of finite strain continuum mechanics. The theoretical formulation is demonstrated using periodically layered composites subjected to macroscopic compressive loading conditions along the lamination direction. Numerical results illustrate the ways in which debonding phenomena, in conjunction with fibre microbuckling, may influence the critical loads of the examined composite solid. The sensitivity of the results obtained through the proposed contact-cohesive model at finite strain with respect to its implementation is also explored. This article is part of the theme issue 'Current developments in elastic and acoustic metamaterials science (Part 1)'.

Finite element simulation of the effect of particle shape and thermal residual stress on the tensile properties of NbCp/Fe composites

To optimize the microstructure and properties of NbCp/Fe composites, this study considered factors such as load transfer, plastic strain, matrix damage, and interface debonding. A two-dimensional finite element model was constructed using ABAQUS software. Random adsorption algorithm was used to realize the random distribution of particles within the representative volume element, and interface damage was described using a cohesive zone model. The effects of particle shape and thermal residual stress on the tensile properties of NbCp/Fe composites were investigated. The results show that circular particles uniformly distribute the stress during the tensile process, effectively enhancing the tensile properties of the composites. Conversely, triangular particles, with obvious sharp corners, reduce their tensile properties, particularly in the presence of thermal residual stresses, which further aggravates the stress concentration between the particles and the matrix. This leads to a decrease in the strength and toughness of the material.

Study on ultrasonic elliptical vibration-assisted grinding mechanism and surface quality of C/SiC composite material

2.5D C/SiC composites have excellent mechanical properties and broad application prospects in the aerospace field. This study investigates the ultrasonic elliptical vibration-assisted grinding mechanism of 2.5D C/SiC composites in different structural directions. A surface roughness prediction model considering abrasive grain protrusion height, brittle-plastic transition of materials and the influence of ultrasonic vibration is established. Experimental results show that material removal involves matrix and fiber fracture, fiber pullout and interface debonding. Ultrasonic vibration causes intermittent cutting, producing finer chip particles and numerous cross microgrooves, reducing subsurface damage. The roughness prediction model is in good agreement with the experimental trend. When the grinding speed is increased from 1 m/s to 8.9 m/s, the surface roughness Ra is reduced by 30.1 %. When the feed speed is increased from 50 mm/min to 650 mm/min, the surface roughness Ra is increased by 47.6 %. When the grinding depth is increased from 0.01 mm to 0.04 mm, the surface roughness Ra is increased by 53.2 %. This study provides a reference for efficient and low-damage processing of fiber-reinforced ceramic matrix composites.

Constructing Mechanochromic Fluorescent Interphase via Core-Shell Microcapsules: A Route for Interface Reinforcing and Damage Self-Reporting of CFRP Composites.

Perylenediimide-chitosan/γ-poly (glutamic acid) microcapsules sizing (PDI-CS/γ-PGA) core-shell microcapsule is designed and used to establish a novel interphase in carbon fiber/epoxy (CF/EP) composite, and the interfacial property, as well as the damage self-reporting of the composite, is compared with desized carbon fiber (CF-desized)/EP and commercial carbon fiber (CF-COM)/EP composite. The ruptured PDI-CS/γ-PGA microcapsule exhibits strong "turn-on" green fluorescence from the released PDI upon mechanical stimuli. The anchoring of PDI-CS/γ-PGA microcapsule on carbon fiber with PDI-CS/γ-PGA microcapsules sizing (CF@PDI-CS/γ-PGA) surface results in increased chemical activity and roughness, exhibiting a weak green fluorescence signal instead of non-fluorescence on CF-desized and CF-COM surface. The transverse fiber bundle tensile (TFBT) strength of CF@PDI-CS/γ-PGA composite is 80.97% and 31.09% higher than those of CF-desized/EP and CF-COM/EP composite, which is attributed to the mechanical interlocking and chemical bonding interaction between carbon fiber and epoxy matrix by introducing PDI-CS/γ-PGA microcapsule with spherular structure and active groups. After microdroplet testing, the strong "turn-on" green fluorescence signal of the released PDI from the microcapsules is detected in the interfacial debonding regions, realizing the microscopic damage self-reporting of CF@PDI-CS/γ-PGA composite.

Experimental and numerical estimation of complex stress intensity factor for the completely debonded anti-crack embedded into a weak matrix using domain integral method

The problem of interface debonding is of fundamental importance in understanding the stress transfer mechanism and behavior of weak interfaces present due to rigid stiffeners. A domain integral method based on Betti’s reciprocal theorem was adopted to compute the complex stress intensity factor (SIF) for the completely debonded anti-crack (discontinuity) with mixed boundary conditions. The domain integral approach is based on two admissible mechanical states, which comprise of actual and auxiliary elastic fields. The singular auxiliary fields in terms of angular variations for the completely debonded anticrack were obtained using the full-field solution. The obtained angular variations were compared with the Williams eigenvalue problem for completeness. The displacement and strains were obtained using digital image correlation (DIC) experiments and numerical simulation for parallel and perpendicular orientations of the discontinuity. The obtained DIC strain contours revealed the presence of anti-symmetric and symmetric variation on the bonded side of the anti-crack. The complex SIF is estimated experimentally and numerically based on the domain integral method to seek a better comparison with the analytical estimate. The SIF estimated for the perpendicular orientation is higher than the parallel orientation.

Detection of Debonding Defects in Carbon Fiber-Reinforced Polymer (CFRP)-Rubber Bonded Structures Based on Active Lamb Wave Energy Analysis.

Carbon fiber-reinforced polymers (CFRPs) are widely used in the fabrication of solid rocket motor casings due to their exceptional performance. However, the bonding interface between CFRP and viscoelastic materials (rubber) is prone to debonding damage during service and storage under complex environmental conditions, which poses a significant threat to the structural integrity and reliability of the engine. Existing nondestructive testing (NDT) methods, such as X-ray imaging, infrared thermography, and ultrasonic testing, although somewhat effective, exhibit significant limitations in detecting interfacial defects in deep or multilayered composite materials, particularly under the challenging conditions of service and storage. This study proposes an innovative method based on active Lamb wave energy analysis and introduces the Damage Evolution Factor (DEF), specifically designed to detect and evaluate interfacial debonding defects in CFRP-rubber bonded structures within solid rocket motors during service and storage. Through numerical simulations and experimental validation, we selected the A0 mode Lamb wave, which is more sensitive to interfacial damage, as the incident wave and excited it on the surface of the structure. Displacement time-history response signals at observation points under different damage models were extracted and analyzed, and DEF values were calculated. The results show that DEF values increase with the size of the interfacial debonding damage. Similar trends were observed in experimental studies, further validating the effectiveness of this method and demonstrating that DEF can be used for the quantitative evaluation of interfacial debonding defects in CFRP-rubber bilayer bonded structures.

Dynamic mechanical behavior of titanium matrix composites reinforced with graphene nanoplatelets

In this investigation, graphene nanoplatelets reinforced pure titanium matrix (GNPs/TA1) composites were synthesized via short-term ball milling followed by spark plasma sintering. The mechanical properties and microstructure evolution of these composites were examined under both quasi-static and dynamic compression conditions. The results indicate that as the strain rate increases from 10−3 to 3000 s−1, the yield strength rises from 436.9 MPa to 1209.6 MPa, consistent with the positive strain rate effect. The superior yield strength of GNPs/TA1 composites arises from the dynamic Hall-Petch effect, dislocation strengthening and load transfer strengthening, with the contribution from load transfer strengthening being the most significant due to the reinforcement's (TiC-GNPs-TiC) facilitation of load transfer. As the strain rate increases, interfacial debonding gradually extends along the reinforcement and grain boundaries, but no macroscopic fracture occurred in this study. At a strain rate of 3000 s−1 during compression, {112‾2}, {101‾2}, and {11 2‾ 1} twins were generated. However, at a strain rate of 10 s−1, only {112‾2} and {101‾2} twins were produced, while {11 2‾ 1} twin was inhibited. Under high strain rate loading, the plastic flow behavior of GNPs/TA1 composites was predicted using the Johnson-Cook constitutive model, modified to account for adiabatic temperature rise, and the predictions showed good agreement with experimental results.

Damage identification of plain-woven composites at T > Tg using AE: Damage clustering and initiation detection

In this work, the damage modes and their initiation detections of plain-woven composites under tensile and compressive loads at T > Tg are investigated by conducting a comprehensive analysis of AE signals, including the feature selection, algorithm comparison and clustering validity. According to a newly proposed Pearson correlation coefficient cumulative criterion, the PF and PA are the most representative features of AE signals. A systematic comparison of K-Means, GMM and Hierarchical model, reveals that the Hierarchical model is the most suitable clustering algorithm for plain-woven composites at T > Tg. The cluster validity indexes combined with microscopic observations identify matrix cracking, interface debonding and fiber breakage as the three dominant damage modes, with PF ranges of [0–200 kHz], [200–350 kHz] and [350–600 kHz], respectively, and independent of different loading conditions. Three damage initiation criteria, sentry function, b-value and cumulative AE counts, are compared and the sentry function is determined to be optimal. The damage initiations of matrix cracking, interface debonding and fiber breakage within plain-woven composites at T > Tg can be effectively detected by AE.

Two-stage work-hardening of a transformable B2-enhanced metallic glass composite by molecular dynamics simulation

The crystalline-amorphous interfaces play vital roles in affecting martensitic transformation, shear band nucleation and interface stability. Though both quasi-static and dynamic mechanical behaviors of shape memory enhanced bulk metallic glass composites have been studied via experiments, the atomic-level interactions among martensitic transformation, localized shear softening and interfacial strain concentration imposed by strain rate remain elusive. We employ molecular dynamics simulations to study strain rate effect on uniaxial compression behavior of transformable B2–CuZr enhanced bulk metallic glass composite. As strain rate increases, the proportion of martensitic transformation accelerates. During the competition among martensitic transformation induced-hardening, shear induced-softening and interface debonding, a two-stage work-hardening is observed, which is in agreement with experimental findings.

An Experimental Study on the Thermomechanical Coupling Effects of Carbon-Fiber-Reinforced Polyetheretherketone under Dynamic Impact.

Carbon-fiber-reinforced polyetheretherketone (CF/PEEK) composites are widely utilized in aerospace, medical devices, and automotive industries, renowned for their superior mechanical properties and high-temperature resistance. Despite these advantages, the thermomechanical coupling behavior of CF/PEEK under dynamic loading conditions is not well understood. This study aims to explore the thermomechanical coupling effects of CF/PEEK at elevated strain rates, employing Hopkinson bar impact tests and scanning electron microscopy (SEM) for detailed characterization. Our findings indicate that an increase in temperature led to significant reductions in the yield strength, peak stress, and specific energy absorption of CF/PEEK, while fracture strain had no significant effect. For instance, at 200 °C, the yield strength, peak stress, and specific energy absorption decreased by 39%, 37%, and 38%, respectively, compared to their values at 20 °C. Furthermore, as the strain rate increased, the yield strength, peak stress, specific energy absorption, and fracture strain all exhibited strain-hardening effects. However, as the strain rate further increased, above 4000 s-1, the enhancing effect of the strain rate on the yield strength and peak stress gradually diminished. The interaction of the temperature and strain rate significantly affected the mechanical performance of CF/PEEK under high-speed impact conditions. While the strain rate generally enhanced these properties, the strain-hardening effect on the yield strength weakened as the temperature increased, and both the temperature and strain rate contributed to the increase in specific energy absorption. Microdamage mechanism analysis revealed that interface debonding and sliding between the fibers and the matrix were more pronounced under static compression than under dynamic compression, thereby diminishing the efficiency of stress transfer. Additionally, higher temperatures caused the PEEK matrix to soften and exhibit increased viscoelastic behavior, which in turn affected the material's toughness and the mechanisms of stress transfer. These insights hold substantial engineering significance, particularly for the optimization of CF/PEEK composite design and applications in extreme environments.

An elastic-constant stress cohesive zone model for an orthotropic piezoelectric actuator adhesively bonded to a substrate

One of the common failure mechanisms observed in electromechanical systems utilizing actuators, sensors, or flexible electronics is the occurrence of interfacial debonding. In this paper, an elastic-constant stress cohesive zone model is constructed to analyze the interface behavior of piezoelectric actuators used in electromechanical systems when imperfectly bonded to a host medium. The analytical formulation treats the piezoelectric actuator as an orthotropic thin film, employing the membrane assumption. It is assumed that the cohesive zone extends from a point, initially unknown, to the edge of the film. The governing integro-differential equation is solved for various bonding scenarios, including perfect bonding with cohesive zones at the edges, an elastic case with a delaminated zone at the center, and an elastic case with both a delaminated zone at the center and cohesive zones at the edges of the film. Detailed examinations are conducted to explore the effects of stiffness ratio parameters and critical actuating voltage on the stresses within the film and substrate as well as the cohesive zone length. The results indicate that the cohesive zone length covers 45% of the film length when the actuating voltage has a fivefold increase over the critical threshold. For the imperfect bonding, the surface in-plane stress of the substrate exhibits a tensile peak near the boundary of the cohesive zone in addition to compressive singularities at the edges of the film. The shear stress singularity factor has an asymptotic behavior as the actuating voltage goes beyond the critical threshold. The critical actuating voltage reduces by a factor of 5% only if the delamination length does not exceed 70% of the film length.

The impact of glycol water exposure on PA6/GF30 properties

The current paper aims to study the behavior of Polyamide 6 (PA6) and Polyamide 6 reinforced with 30% of short glass fibers (PA6GF30) under glycol water (GW) mixture used for cars as coolant fluid. Samples were fully immersed in the mixture of GW (20:80) at 50°C, 70°C and 90°C for up to 80 days and periodically weighted. Results gathered revealed the occurrence of substantial changes especially for PA6 samples aged at 90°C. The long term ageing leads to the formation of ester species due to thermo-oxidation as pointed out by Infrared spectroscopy analysis. Moreover, dynamic mechanical analysis measurements showed that glycol water acted as an effective plasticizer in lowering the Tg of the polyamide 6. This plasticizer effect was confirmed by the gain of ductility at early stage of ageing for both materials (PA6 and PA6GF30). Nevertheless, after 80 days of ageing the effect of glycol water ageing is no longer physical in nature and an overall loss of mechanical properties was noticed. Indeed, an embrittlement of PA6 was measured that can be attributed to a decrease of the level of entanglements within the polymer. Nevertheless, for PA6GF30 material, the loss of strength and stiffness was the result of the interfacial debonding between the fibers and the matrix.

Investigation of interfacial debonding identification for concrete filled steel tube columns based on acoustic signals

A method was proposed to address challenges in detecting debonding in concrete-filled steel tube (CFST) columns by analyzing acoustic signals. In this approach, wavelet time-frequency diagrams are initially derived through the application of continuous wavelet transform to acoustic signals acquired from tapping on columns. The wavelet time-frequency diagrams serve as data samples for training the MobileNetv2 convolutional neural network model in order to identify concrete debonding. The laboratory test results show that the MobileNetv2 model achieved 100 % accuracy for both the training and verification sets, and 99 % accuracy for the test set. Four CFST columns in a high-rise building under construction were also measured. The findings indicate a recognition accuracy ranging from 86.7 % to 90 % and an error rate that falls within an acceptable range. These results confirm the viability of the method outlined in this paper for detecting debonding in CFST columns using acoustic signals.

Monitoring of interface separation damage in buckling-restrained steel plate shear walls using piezoelectric based smart aggregates under cyclic loading

Interface debonding damage is a critical issue for many prefabricated concrete components. Various studies have employed different methods to detect debonding behaviors and provided quantitative damage indexes. In this paper, we propose a novel monitoring approach for detecting interface debonding damage in Engineered Cementitious Composite (ECC) panel-restrained composite steel plate shear walls (SPSWs) using piezoelectric ceramics (PZT). Four SPSWs were designed with different types of concrete, steel plate thicknesses, and bolt arrangements for the cyclic loading experiment. Energy data was collected for time-domain and wavelet packet analysis. The root mean square deviation (RMSD) was then calculated to provide a quantitative damage index for the specimens. The highest damage indices for each specimen were 0.770, 0.963, 0.988, and 1, respectively, which corresponded well with the actual damage scenarios. The experiments verified that using PZT can accurately monitor debonding damage in SPSWs.

Mechanical Failure of Core-Shell Cathode Particles: The Effects of Concentration-Dependent Material Properties and Phase Field Fracture Modelling

The use of core-shell cathode particles in lithium-ion batteries is an attractive approach to enhancing energy density whilst retaining lifetime, through reducing undesired reactions at the electrode-electrolyte interface and limiting the volume change of the electrode particles. However, mechanical failure through the fracture and debonding of the core-shell interface is a major challenge. In this work, we employ a coupled finite-element model to predict and mitigate the mechanical failure of core-shell cathode structures, taking as example a particle of NMC811 (core) coated with NMC111 (shell). In particular, we focus on two aspects:The first one involves the assumptions of material properties as inputs of the model. The material properties are often considered constant by battery modelling researchers, yet these parameters can vary significantly during charge/discharge. For example, experiments have unveiled a three-orders-of-magnitude drop in the diffusion coefficient of NMC materials during discharge [1]. Here, we incorporate material properties obtained from experimental data, including concentration-dependent diffusion coefficient obtained from GITT measurement and partial molar volume derived from in situ X-ray diffraction data. Our results indicate that when assuming a concentration-dependent partial molar volume, the maximum values of tensile hoop stress in the shell are nearly three times lower than those predicted with constant average properties, diminishing the likelihood of fracture.When accounting for concentration-dependent diffusion coefficient, large concentration gradient is observed near the outer surface of the core due to reduced lithium mobility at high states of lithiation, hindering full electrode capacity utilisation. The significant concentration gradient and capacity underutilisation align with direct observations from experiments [2]. Notably, these phenomena cannot be captured in modelling if assuming constant diffusion coefficient. These findings offer new perspectives on the performance and design of core-shell electrode particles. Safe design maps in terms of core size and shell thickness to mitigate fracture and debonding are obtained.The second focus of this work is the utilisation of phase field fracture model in predicting cracking behaviours within the core-shell particle. Phase field modelling provides a continuous representation of cracks, enabling the tracking of complex cracking patterns [3]. We predict cracking behaviors caused by volume changes during charge/discharge, as well as inaccessible capacity and newly created active surface area caused by cracking. Our multiphyics model can hopefully act as a catalyst, accelerating the development process of the core-shell structured cathode particles and shortening the time to market of advanced batteries with extended lifetime.

Experimental Investigations on Tensile and Shear Behavior of the Interface Between UHP-ECC and Concrete

Ultra-high performance engineered cementitious composite (UHP-ECC), which is known for its exceptional compressive strength, tensile strength, and ductility, has been emerged as a promising option for repairing and strengthening reinforced concrete (RC) structures. The bond between UHP-ECC and normal concrete is the key issue for the material to be successfully implemented. This paper presents an experimental investigation focused on understanding the tensile and shear behavior of the bonding interface between UHP-ECC and concrete. A total of 78 specimens were prepared and tensile splitting tests and push-out tests were carried out. The study examined key parameters including the strength of the concrete substrate, the roughness of the interface, and the moisture condition at the interface. Various failure modes are observed in the specimens under tensile splitting force and direct shear force, and it is found that the influence of the key parameters varied depending on the type of failure mode. In specimens experiencing full interface debonding or interface failure combined with substrate cracks, the roughness of the interface and the moisture degree have a significant impact on the tensile and shear strength. Conversely, in specimens with full substrate disruption, the strength of the substrates plays a more significant role. Additionally, the study reveals that the grooving treatment is highly effective in improving the shear strength of the interface, but its impact on enhancing the tensile strength is comparatively less pronounced. Prediction models for the tensile and shear strength of the interface are established and verified against the test results. The proposed models provide valuable insights into the behavior of the UHP-ECC to concrete interface and can aid in predicting its performance in practical applications.

Al2O3-MnS Inclusions and Pitting Corrosion in the Weld Heat-Affected Zone

Manganese sulfide inclusions have been identified as a key factor contributing to the degradation of pitting corrosion resistance in both carbon and stainless steels. However, the precise reasons behind the differential reactivity of various sulfides, with some serving as active sites for pitting while others remain inactive, are not yet fully understood. The effect of debonding occurring at the interface between these inclusions and the steel matrix in relation to pitting corrosion has not been extensively investigated. In this study, an examination of a service-exposed pipeline girth weld was conducted. Immersion testing in blowdown water and multiscale characterization techniques investigated the inclusion-matrix interface debonding within the heat-affected zone. Our findings suggest that interfacial debonding is more likely at the Al2O3- MnS cluster interface. This observation offers a rationale for the selective reactivity of sulfides that form clusters with oxides, highlighting the likelihood that only sulfides clustering with oxides act as active pitting initiation sites.

Mechanical property and damage mechanism of ultrasonic vibration assisted tensile Cf/SiC composites

Ceramic matrix composites (CMCs) have a wide range of applications in key areas, such as aerospace and defense, and to study the mechanical properties and damage mechanisms of fiber-reinforced CMCs under different tensile conditions. Firstly, an ultrasonic vibration tensile device was designed, based on stress superposition and softening effect, the ontological relationship of materials under ultrasonic vibration-assisted stretching was established to study the damage mechanism of materials under different vibration conditions. The results show that tensile damage has multiple damage mechanisms occurring, i.e., matrix multiple cracking, interfacial debonding, and fiber fracture, and is also the main cause of nonlinear characteristics. Under high-frequency alternating load, the tensile strength decreased by up to 32 MPa, and the strain at break increased by up to 0.24 %; the tensile damage mechanism changed, the interfacial strength of the fiber and matrix decreased, the fiber toughness increased significantly, and the fracture morphology became flatter.

Mechanical property analysis and optimization of nano-hydroxyapatite coated carbon fiber reinforced hydroxyapatite composites

Carbon fiber (CF) is one of ideal reinforcements to hydroxyapatite (HA) owing to its unique structure, excellent biocompatibility and high mechanical properties. However, the mechanical property of CF reinforced HA (CF/HA) composites cannot be effectively improved due to the mismatch in surface properties and thermal expansion coefficients between CF and HA. In order to solve the problems, nano-hydroxyapatite (nHA) coating with different thickness was fabricated on the CF surface. The effect of the coating thickness on mechanical property of nHA-coated CF/HA composites was studied by finite element analysis. The CF with proper nHA coating thickness was subsequently used to reinforce HA. The compressive strength of nHA-coated CF/HA composites was approximately 97.3 % and 164.6 % higher than those of the uncoated CF/HA composites and pure HA ceramics, respectively. The interface properties and crack propagation were analyzed by cohesive element in the finite element analysis. The toughening mechanism of the composites included interfacial debonding, crack deflection, crack branching, and crack bridging. The mechanical properties of nHA-coated CF/HA composites were enhanced due to the strong interfacial bonding strength and reducing cracking in HA matrix. The prepared nHA-coated CF/HA composites satisfy the requirement of the mechanical properties of human load-bearing bone. It can be used to prepare cages, plates, screws, pins and other compact bone substitute parts in bone grafting. The study provided a method for construction of nHA-coated CF/HA composites with the designed properties by adjusting the nHA coating on the fiber and can be used to design other fibers reinforced ceramic matrix composites.

Phase-field modelings of fracture investigate the influence of interfacial effects on damage and optimal material distribution in brittle inclusion-matrix structures

This present work uses the phase-field modelings to investigate the influence of interfacial effects on damage and mechanical behavior, as well as the optimal distribution of the inclusion shape within brittle inclusion-matrix structures in various typical cases. These two constituent phases in the structures are assumed to be either isotropic or anisotropic. To achieve these goals, this work will: (i) use the phase-field modelings either considering or neglecting interfacial debonding, and the anisotropic phase-field modeling; (ii) determine and incorporate the strain tensor orthogonal decompositions into each specific phase-field modeling to enhance the accuracy and effectiveness of the simulation methods; (iii) combine the phase-field modelings with the BESO topology optimization algorithm to analyze the influence of interfacial effects on relationship curves and the optimal distribution of the inclusion shape. Through proposed numerical examples, it is demonstrated that the interfacial effects strongly influence crack paths, behavior curves, and optimal material distribution in structures. When considering interfacial effects, cracks are almost unable to penetrate into the inclusion phase. However, when neglecting interfacial effects, cracks propagate into the inclusion phase. This reason makes the structure more difficult to damage than when considering the interfacial effects, as evidenced by greater peak load values in behavior curves and greater total fracture resistance of the material. Especially in the example of inclusion phase optimization, the total fracture resistance value of the case neglecting interfacial effects is more than 107.9% greater than that considering interfacial effects.