Interfacial Debonding Research Articles

Tensile mechanical behavior and failure mechanism of 2.5D woven fabric reinforced aluminum matrix composites involving residual stress

The tensile behavior of two and a half-dimensional (2.5D) woven fabric reinforced Al matrix composites involving residual stress was investigated experimentally and numerically. The residual stress and subsequent tensile behavior of the composites were predicted by multiscale finite element modeling. And the correctness of numerical simulation is verified by residual stress, tensile curve, surface strain diagram and fracture morphology. The results show that the inhomogeneous residual stress leads to the damage of the matrix and interface in the interweaving area of yarns. During the tensile process, the surface strain exhibits an obvious periodic distribution characteristic, which is related to the arrangement of yarns. With the increase of tensile strain, local matrix and interface damage accumulate and expand leading to the weft yarn cracking, matrix failure and interface debonding successively. The abrupt fracture of the composite can be attributed to the axial fracture of warp yarn, which exhibits obvious fiber fracture and pull-out characteristic.

Micromechanics-based modeling of temperature-dependent effective moduli of fiber reinforced polymer composites with interfacial debonding

In this paper, the dimensionless debonding length of fiber at various temperatures was obtained based on the maximum shear stress criterion. Then Hill's stress–strain relations were employed to determine the equivalent elastic moduli of the fiber in the debonding zone. Finally, a micromechanics model of temperature-dependent effective moduli of fiber reinforced polymer composites was developed, which is capable of including the effects of interfacial debonding and its evolution with temperature. To validate this model, temperature-dependent effective moduli of several polymer composites were calculated and benchmarked with experimental results extracted from the published literature, demonstrating the validity of the present model. This study offers an efficient method to forecast the temperature-dependent effective moduli, thereby helping to save considerable time and resources by reducing high-temperature testing. Furthermore, parametric studies were conducted to obtain constructive insights into the sensitivity of the debonding length and effective moduli to the material parameters at different temperatures.

Fatigue performance of carbon fiber‐reinforced polymer strengthened single‐edge cracked steel plates: Effects of adhesive property and CFRP arrangement

AbstractCarbon fiber‐reinforced polymer (CFRP) is increasingly used to improve the fatigue behavior of damaged steel structures due to its advantages, including high strength and convenient processing. However, several issues, such as the effects of the adhesive property and CFRP arrangement, still need to be studied. In this study, a total of 20 single‐cracked steel specimens were tested under fatigue load, including two unstrengthened specimens, six single‐sided strengthened specimens, and 12 double‐sided strengthened specimens. The failure mode, fatigue life, crack propagation pattern, and interface damage development were obtained from experiments. The results show that epoxy resin structural adhesives (adhesives Araldite 420 and J133C) have the best bonding properties with CFRP. For the conventional epoxy adhesives, Araldite 420 and J133C can considerably improve fatigue life, which increased by more than 44.84 times to unstrengthened specimens. CFRP plate strengthening can significantly improve the fatigue life of single‐edge cracked steel plates. For the double‐sided strengthened specimens, the fatigue life can be improved by 6.93–44.84 times that of unstrengthened specimens. For the single‐sided, the fatigue life can be improved by 2.24–2.77 times. Properties of epoxy adhesive have a more significant effect on fatigue life compared to the thickness of the CFRP plate due to debonding.Highlights Ductile epoxy adhesives are most conducive to improving the fatigue behavior of CFRP strengthened steel plates. The fatigue life of steel plates can be improved by increasing the thickness of CFRP plates and using double‐sided CFRP strengthening. Interface debonding is the main failure mode of CFRP plates strengthening single‐edge cracked steel plates under fatigue.

Mechanical behavior of cavity and dislocation evolution induced by interfacial debonding of Cu/SiC composites

Mechanical behavior of cavity and dislocation evolution induced by interfacial debonding of Cu/SiC composites

Electrospun nanofiber interleaving through double infusion method to induce pseudo‐ductile damage resistance response in carbon/epoxy composites

AbstractCarbon composites are susceptible to invisible damage development such as matrix cracking, fiber kinking, and interfacial debonding upon external transverse loading. These incipient damages may interact to evolve into life‐limiting delamination propagating both in in‐plane and transverse directions. This study addressed that by interleaving carbon/epoxy composites with electrospun nylon 6 nanofibers adopting a double infusion method. Damage resistance results showed that the optimum nanofiber areal weight (17.35 g/m2) offered a 27% improvement in specific total toughness. The emergence of pseudo‐ductility substantially enhanced the plastic toughness (46.15%) of interleaved composites. The load required for initial matrix cracking was 65.49% higher, and number of matrix cracking events was suppressed by 84.11% at the optimum areal weight of interleave. Fractography revealed frequent interlaminar crossings and delamination crack bridging as two major toughness mechanisms. Both the external damage area and delaminated area increased with increment in nanofiber areal weight.Highlights Electrospun nanofibre interleaved carbon/epoxy composites were fabricated through a double infusion method to characterize damage resistance. Acoustic data of matrix cracking was rationalized to show the effectiveness of nanofiber interleaves in suppressing this damage type. Microstructural factors and mechanisms contributing to the improved toughness of optimally interleaved composites were identified. External damage/delaminated areas of interleaved composites were correlated with nanofiber areal weights.

Tensile impact behaviors and damage mechanism of woven carbon fiber-reinforced-polymer laminates considering adiabatic shear band

In this study, the tensile impact behavior and damage mechanism of a two-dimensional woven carbon-fiber-reinforced-polymer (CFRP) laminates under different high strain rates are investigated. The damage morphologies are illustrated and studied using meso-macroscale finite element analysis (FEA) and Split Hopkinson bar (SHB) test, FEA results are compared and validated with the SHB test results, and proved to be correct with enough accuracy. The matrix crack first appeared, the tensile stress wave propagated along the interface, which causes shear failure at the interface, which dominated the failure of the specimen and formed adiabatic shear bands inside each ply, the adiabatic shear bands begin to develop in areas with interfacial damage, they are formed after structural damage and propagate in the direction of the interface, accompanied by damage evolution. High strain rate 1400, 1600, and 2400 s−1 impacts tend to lead to direct failure of composite laminates compared to low strain rate 600, and 800 s−1 impacts, the Young’s modulus with high strain rate 1400, 1600, and 2400 s−1 are more than twice as much compared to low strain rate 600, and 800 s−1. The plain-woven CFRP laminates is characterized with strain-rate-hardeningeffect and strain rate sensitivity, with increase of high strain rate from 600 to 2400 s−1, the Young’s modulus increases from 8.91 to 35.7 GPa, whereas the yield strength increases from 397 to 1298 MPa. The delamination occurs between the plies after crack generation inside the epoxy resin matrix, and begins at a certain strain value after the elastic phase, the micro-cracks propagated along the fiber bundle-matrix interface, thus causing interfacial debonding due to shear stress, these factors result in a strain-rate hardening effect.

Behavior of FRP-engineered cementitious composite layer and concrete interface with FRP anchors

The problem of low material utilization caused by premature interface debonding is prevalent in carbon fiber-reinforced polymer (CFRP)-reinforced concrete structures. In this study, the influence of anchors on the bonding and behavior of the FRP-engineered cementitious composite (ECC) layer and concrete interface was analyzed. A total of 42 single shear tests were performed to investigate the interface–bond behavior between the FRP-ECC layer and concrete under static load in case of anchor reinforcement. The variables mainly include the matrix type, anchor location, anchor spacing, and number of anchors. The results show that the anchor can increase the interfacial load-carrying capacity up to 85%; the maximum slip value of the interface can also be enhanced. Furthermore, the influence of the location, spacing, and number of anchors on the interface bonding performance is closely related to the effective bonding length and post-anchor bond length. The effective bonding length is 400 mm based on the strain distribution calculation and analysis. The test results provide valuable information for FRP anchor reinforcement in FRP-ECC composite layer-reinforced concrete structures.

Analytical modeling of fiber–matrix interface failure in unidirectional laminae subjected to in-plane shear loads

Unidirectional laminae subjected to in-plane shear loads present complex behavior with strong nonlinear response. A novel analytical model is proposed considering a unit cell with square symmetry and circular fiber cross-section taking into account the failure on the interface between fiber and matrix. The interface failure is a shear-driven phenomenon described by a constant value during the failure process. The model validation is performed using two different approaches: the analytical estimations are compared with experimental data, and finite-element simulations are employed to evaluate the influence of fiber volume fraction. The proposed analytical model captures the main features of experimental data showing its capability and reliability to represent the complex interface debonding propagation phenomenon. Numerical simulations show in-plane shear stress–strain curves for four distinct unidirectional laminae with different fiber volume fractions. Results attest the model capability to describe composite materials with composite failure, essentially characterized by the interface behavior.

Distributed fiber optic sensing for micro- and macro-crack quantification: an interfacial-fracture-energy-based model

Clarifying the strain transfer between the host material with a crack opening displacement (COD) and the optical fiber after interfacial debonding remains a critical challenge for crack quantification. The interfacial debonding induced a triangular form strain profile around the crack due to the residual shear stresses at the interface. This study investigated the interfacial shear stress-slip relationship between the bare fiber and its coating layer through a plate splitting test. Based on that, we proposed an interfacial-fracture-energy-based analytical model to convert distributed fiber optic strains before and after interfacial debonding to CODs of micro- and macro-cracks. The accuracy of the model under a single crack was validated through plate splitting tests and the experimental data reported in the literature. Furthermore, experimental results from a four-point beam test were utilized to investigate the feasibility of the model under multiple cracks. The model, assisted by the strain superposition strategy, accurately quantified the CODs of multiple cracks before interfacial debonding but failed when interfacial debonding occurred. In addition, we proposed a simplified method based on the linear relationship between the debonded lengths and the corresponding CODs, which facilitates evaluation of the CODs after debonding.

Thermo-oxidative aging induced multi-scale shrinkage and damage in 3D angle-interlock woven composites

The deterioration of resin and interface in composites deteriorate during high-temperature service, would impact both the thermal stability and overall performance significantly. This paper focused on the experimental characterization of multi-scale damage and resin shrinkage within composites induced by thermo-oxidative aging using Micro-CT, SEM and Confocal Interferometric Microscopy (CIM), and exploring the coupling mechanism between them. The results show that damage distribution and propagation are affected by the hierarchical structure of 3-D angle-interlock fabric. Macro-CIM shows that maximum resin shrinkage depth depends on the resin width and aging time. Resin shrinkage profile evolution demonstrated the accelerating effect of resin crack on shrinkage. Micro-CIM shows that macro yarn cracks form through the accumulation of micro resin cracks in resin-rich areas and fiber/resin interface debonding. The formation of fiber/resin interface crack is tied to the resin shrinkage state, only occurring when the surrounding resin shrinkage slope exceeds a specific threshold value.

A multi-purpose adhesive with high strength and bond sensitive stress sensing

Despite the important roles of pressure-sensitive adhesives (PSA) and hot-melt adhesives (HMA) in wood furniture, aerospace, and other fields, the inherent contradiction between them owing to their different molecular mechanisms remains a great challenge in developing high-performance, multi-purpose adhesives. In this study, butylphenyl crosslinked polymers were constructed to overcome the intrinsic contradiction between PSA and HMA and to develop a multi-purpose adhesive. The formation of electrostatic interactions and hydrogen bonding networks between inter/intramolecular functional groups gave PSA excellent adhesive strength (3.0 MPa) and peel strength (4.7 N/cm) at light pressures of 0.3 MPa. Interestingly, PSA has the ability to achieve repeatable bonding performance at the gluing interface and excellent underwater bonding performance owing to its special crosslinked network structure consisting of long alkane chains and the synergistic effect of fillers (rosin and nano-silica). Multifunctionalities, such as heterointerfacial adhesion, rapid bonding, reuse, interfacial debonding, and container leakage repair, have been achieved.

Free vibration analysis of hygrothermally stable stiffened composite plates with plate-stiffener interfacial debonding

Stiffeners are frequently utilized in many engineering projects because they boost strength while adding only a small amount of weight to the overall structure. The environments that the stiffened composite constructions are typically exposed to are harsh, which can result in damage like interlayer delamination and debond at the plate-stiffener interface, which can cause catastrophic failure. As a result, it is necessary to examine these structures’ dynamic behavior in addition to their stability performance. The current study attempts to investigate the free vibration response of stiffened composite plates with plate-stiffener interfacial debonding under hygrothermal circumstances using a robust finite element (FE) model. The skin and stiffener flange are simulated in the current work using a 9-noded heterosis element to prevent the shear-locking issue. Additionally, to considerably enhance computational performance, the stiffener web is formulated as a 3-noded isoparametric beam element with the torsion correction factor. Additionally, a dummy node is created to represent the debond, and a fictitious spring is added to stop the nodes from interpenetrating one another. Three schemes of hygrothermally stable laminates (θ/(90- θ))s, (22.5/−67.5)s and (77.5/−12.5)s are considered to identify the stiffened plate configuration with improved free vibration characteristics. Further, extensive parametric analyses are conducted on the obtained stiffened plate with improved performance in a hygrothermal environment by considering debond at the skin-stiffener interface. The vibrational behavior of the debonded plate is shown to be significantly more affected by moisture than by temperature. Additionally, the debond has a more obvious impact on the vibration characteristics in the plate with a centrally attached stiffener than in the plate with an eccentricity attached stiffener. As a result, the established FE formulation is anticipated to be trustworthy and computationally effective while effectively analyzing the debonded stiffened panel’s free vibration behavior in a hygrothermal environment.

Numerical mapping relationship between process parameters and mechanical properties of unidirectional carbon/carbon composites

This paper proposes an innovative algorithm derived from the isothermal chemical infiltration process to generate quasi-real microstructures of unidirectional carbon/carbon composites. This algorithm, which can predict the relationship between the composite density and infiltration time, is termed the isothermal chemical infiltration algorithm. To further evaluate the relationship between the process parameters and the mechanical properties, a mesoscale finite element model of the unidirectional carbon/carbon composite is established based on the isothermal chemical infiltration algorithm. After validation, the developed numerical model is employed to study the effects of the infiltration time, pressure, and temperature on the effective mechanical properties. The results show that the transverse modulus and tensile strength increase with an increase in the infiltration time, pressure, and temperature, with the effect of temperature being the most significant. In parallel, it is revealed that the complete failure of unidirectional carbon/carbon composites results from interfacial debonding and propagation of multiple cracks during transverse tension. The proposed model has potential applications in the process design and optimization of high-performance carbon/carbon composites.

Assessment of Structural Integrity and Interfacial Debonding in Carbon Fiber/Epoxy Composites Undergoing Hygrothermal Aging

Assessment of Structural Integrity and Interfacial Debonding in Carbon Fiber/Epoxy Composites Undergoing Hygrothermal Aging

Conch-shell-inspired porcelain ceramic tile/Kevlar fabric composites with excellent combination of strength, toughness and shock resistance

For various engineering applications in public, ceramics with exceptional strength, toughness and shock resistance are imminently required, but traditional ceramics struggle to meet these demands due to their fragility. Inspired by the shape of natural conch shells, this work offers a simple hot press approach to fabricate layered porcelain ceramic tile/Kevlar fabric composites, yielding excellent mechanical properties and the capacity for non-catastrophic failure. It was concluded that composites? excellent mechanical performance is attributed to the resin/fabric content. The composite with the resin/fabric content of 45.5 vol.% had an outstanding combination of high strength (310.5 ? 6.2MPa) and excellent fracture toughness (6.83 ? 0.09MPa?m1/2), whereas the sample with 36.4 vol.% resin/fabric content had the maximal impact energy of 2.04 ? 0.09 J, which is much better than those of traditional ceramics. The strong resistance to fracture is a result of the proper interfacial bonding and the presence of elastic component, which enables toughening mechanisms such as crack deflection, fibre pull-out and interfacial debonding. This finding provides useful guidance for replacing lowperformance ceramics in engineering applications with cost-effective ceramic composites.

Mechanical behaviors of steel-CFRP plate bonded joints after freezing-thawing cycles

The effective bonding between the steel element and carbon fiber reinforced polymer (CFRP) is critical for applying the CFRP to strengthen steel elements. The severe service environment always affects the interfacial bond strength, resulting in a reduction in strengthening efficiency. To research the interfacial bond performance between the steel element and CFRP plate after freezing-thawing environment, this paper conducted studies on the mechanical behaviors of steel-CFRP plate joints. Experiments indicated that the freezing-thawing environment did not influence the failure mode, but decreased the interfacial ultimate capacity of double-shear specimens. The ultimate load is reduced by 14.5% after exposure to 300 freezing-thawing cycles. An approximate bilinear bond-slip relationship is employed for expressing the interfacial bond-slip behavior of all specimens, and the freezing-thawing environment has a negative influence on the bond-slip behavior. By determining the degeneration laws of bond-slip parameters after experiencing freezing-thawing cycles, the bilinear bond-slip model considering freezing-thawing effect was developed. Moreover, the three-dimensional FE modelling was implemented based on the mixed-mode cohesive zone model. The comparisons of the test and FE results show that the FE results are consistent with the test results, and the interfacial damage and debonding process can also be precisely predicted. The numerical modelling also reveals that the asymmetric debonding of the two interfaces can affect the ultimate load, which leads to a higher scatter of test results for the double-shear joint.

A multiscale interfacial cyclic debonding model for fibre-reinforced composites using micromechanics and molecular dynamics

In this study, a novel multiscale model based on the finite-volume direct averaging micromechanics (FVDAM) theory and molecular dynamics (MD) was developed to predict the interfacial cyclic debonding behaviour of composites. At the microscale, a solid interface with accumulated damage was incorporated using FVDAM, which enabled the simulation of both localised and homogenised interfacial damage responses under cyclic loading; a significant reduction in strength was observed after 10 loading cycles, implying the interfacial damage accumulation. At the atomic-scale, an interface model was built and subjected to cyclic loadings using MD simulation; the stress peak after 5 cycles was approximately half of the initial value, which provides damage parameters for upper-scale calculations and reveals the fundamental mechanism of interfacial cyclic debonding. The experimental data of unidirectional SCS-6/Ti-15-3 composites under cyclic loading were adopted to verify the proposed model. Furthermore, the influence of thermal residual stress and fibre orientation was investigated, which offers valuable insights for composite design and manufacturing.

An analysis of interfacial debonding in beaded fiber composites

An analysis of interfacial debonding in beaded fiber composites

In-situ manipulation of TiB whisker orientation and investigation of its high-temperature mechanical properties in titanium matrix composites

“SPS pre-sintering + SPS reactive hot extrusion” (SPSHE) is a promising technique for manipulating the orientation of TiB whiskers (TiBw) in discontinuously reinforced titanium matrix composites (DRTMCs). In the current study, (12.4 vol % TiBw +2.9 vol % TiC)/Ti6Al4V composites were prepared using SPSHE technology, successfully achieving both the normalization of TiBw orientation and a high aspect ratio. Specifically, the [010] axis of TiBw was aligned with the extrusion direction, and the average aspect ratio was 24.86. Tensile tests were conducted on the DRTMC samples at temperatures of 873 K, 923 K, and 973 K. The results demonstrate that SPSHE significantly enhances the high-temperature strength of the composite. At 873 K, the DRTMC exhibited an exceptionally high tensile strength of 732.2 ± 20 MPa. The main strengthening mechanisms of the DRTMC include load transfer strengthening from TiBw and TiC particles, solution strengthening, fine grain strengthening and dislocation strengthening. Moreover, at 873 K and 923 K, the dominant failure mode of the reinforcement was a load-bearing fracture. However, as the test temperature increased to 973 K, a mixed failure mode of load-bearing fracture and interface debonding was observed in the reinforcement.

Experimental study on the mechanical behavior of segmental joints of shield tunnels strengthened by a steel plate-UHPC composite

This research proposed a new technology to strengthen segment joints in shield tunnels based on steel plate-UHPC composite. In order to understand the strengthen mechanism of the steel plate-UHPC composite on the segmental joints, full-scale experiments were conducted to study the characteristics of the strengthened joints, including deformation, crack development, interface behavior, stress distribution, and the failure process. The results demonstrate that the deformation process under sagging moments involves four stages: elastic deformation, elastic–plastic deformation, debonding, and failure, whereas under hogging moments, the deformation can be summarized into three stages: elastic–plastic deformation, debonding, and failure. The use of UHPC strengthening facilitates more extensive crack development, and promotes uniform stress distribution within the concrete, with efficient utilization of material properties. The presence of anchor screws maintains a certain level of ductility after interface debonding. A significant improvement in the ultimate bearing capacity and flexural stiffness of specimens was observed with the use of steel plate-UHPC composite. The ultimate bearing capacity of initially strengthened specimens under sagging and hogging moments is increased by 503.3% and 72.2%, respectively, and the flexural stiffness is increased by 177.9% and 3803.2%, respectively. Moreover, the pre-damaged state of the strengthened specimen exhibits a significant increase in ultimate bearing capacity and flexural stiffness under a sagging moment, while remaining basically unchanged under a hogging moment.