Decrease In Interfacial Strength Research Articles

Axial Impact Response of Carbon Fiber-Reinforced Polymer Structures in High-Speed Trains Based on Filament Winding Process.

The continuous increase in the operating speed of rail vehicles demands higher requirements for passive safety protection and lightweight design. This paper focuses on an energy-absorbing component (circular tubes) at the end of a train. Thin-walled carbon fiber-reinforced polymer (CFRP) tubes were prepared using the filament winding process. Through a combination of sled impact tests and finite element simulations, the effects of a chamfered trigger (Tube I) and embedded trigger (Tube II) on the impact response and crashworthiness of the structure were investigated. The results showed that both triggering methods led to the progressive end failure of the tubes. Tube I exhibited a mean crush force (MCF) of 891.89 kN and specific energy absorption (SEA) of 38.69 kJ/kg. In comparison, the MCF and SEA of Tube II decreased by 21.2% and 21.9%, respectively. The reason for this reduction is that the presence of the embedded trigger in Tube II restricts the expansion of the inner plies (plies 4 to 6), thereby affecting the overall energy absorption mechanism. Based on the validated finite element model, a modeling strategy study was conducted, including the failure parameters (DFAILT/DFAILC), the friction coefficient, and the interfacial strength. It was found that the prediction results are significantly influenced by modeling methods. Specifically, as the interfacial strength decreases, the tube wall is more prone to circumferential cracking or overall buckling under axial impact.

Interfacial characteristics of fiber asphalt mastic and aggregates: Impact on mixture crack resistance performance

The interfacial characteristics between fiber-modified asphalt mastics and aggregates play a crucial role in the performance of asphalt mixtures. To explore these interfacial interaction characteristics, three types of fibers (basalt, glass, and polyester), five levels of fiber content (ranging from 0.1% to 0.5% by mixture mass), and two types of aggregates (limestone and basalt) were selected, and an optimal mixture design was established. Contact angle tests, binder bond strength tests, and disk-shaped compact tension tests were conducted to investigate the impact of fiber type, fiber content, and aggregate type on interface characteristics. The results indicate that the addition of fibers can enhance the interfacial strength, with basalt fibers exhibiting superior reinforcement effects. As fiber content increases, the influence of aggregate type on interfacial strength decreases. Under ambient conditions, a composite failure mode was observed, while at low temperatures, cohesive failures dominated. The incorporation of fibers led to an increase in interfacial cohesion strength. The interfacial interaction strength between fiber asphalt mastic and aggregates exhibits a favorable linear correlation with the fracture energy and peak crack mouth opening displacement of the asphalt mixture. Overall, this study elucidates the microscopic mechanisms involved in fiber asphalt mixtures, laying the foundation for further in-depth research.

Microstructure-based simulation on the mechanical behavior of particle reinforced metal matrix composites with varying particle characteristics

The mechanical performance of metal matrix composites strengthened with particles is predominantly contingent upon the attributes of the incorporated particles. Attaining the optimal particle size, morphology, and interfacial bonding within the composites is paramount for improving the comprehensive properties. In this study, an experimentally congruent model was devised to validate the feasibility of the model predicated on the actual microstructure of the composite. The modeling procedure encapsulated matrix and particle failure, as well as surface-based cohesive damage at the interface, to precisely portray the mechanism of action for the particle characteristics. Additionally, the mechanical behavior and failure evolution mechanism of the composites were simulated by manipulating the pertinent particle factors, including size distribution, interfacial strength, and morphology. The findings demonstrated that an appropriate size distribution between particles and more rounded particles can mitigate stress and strain concentration within the matrix interstitial to particles, resulting in a considerable enhancement in the mechanical performance of the composites. As the interfacial strength decreases, the initial failure progression of the composite shifts from initial cracking within the matrix induced by stress-strain concentration to interfacial failure caused by interfacial debonding, ultimately accelerating the failure of composite. This research will bolster the comprehension of the correlations between microstructural features and mechanical performance in metal matrix composites strengthened with particles, providing an innovative simulation-assisted experimental approach for the rapid development and preparation of novel metal matrix composites.

The Scaffold-Articular Cartilage Interface: A Combined In Vitro and In Silico Analysis Under Controlled Loading Conditions.

The optimal method to integrate scaffolds with articular cartilage has not yet been identified, in part because of our lack of understanding about the mechanobiological conditions at the interface. Our objective was to quantify the effect of mechanical loading on integration between a scaffold and articular cartilage. We hypothesized that increased number of loading cycles would have a detrimental effect on interface integrity. The following models were developed: (i) an in vitro scaffold-cartilage explant system in which compressive sinusoidal loading cycles were applied for 14 days at 1 Hz, 5 days per week, for either 900, 1800, 3600, or 7200 cycles per day and (ii) an in silico inhomogeneous, biphasic finite element model (bFEM) of the scaffold-cartilage construct that was used to characterize interface micromotion, stress, and fluid flow under the prescribed loading conditions. In accordance with our hypothesis, mechanical loading significantly decreased scaffold-cartilage interface strength compared to unloaded controls regardless of the number of loading cycles. The decrease in interfacial strength can be attributed to abrupt changes in vertical displacement, fluid pressure, and compressive stresses along the interface, which reach steady-state after only 150 cycles of loading. The interfacial mechanical conditions are further complicated by the mismatch between the homogeneous properties of the scaffold and the depth-dependent properties of the articular cartilage. Finally, we suggest that mechanical conditions at the interface can be more readily modulated by increasing pre-incubation time before the load is applied, as opposed to varying the number of loading cycles.

205 CFRPの超臨界流体によるリサイクルが回収炭素繊維の界面強度特性に及ぼす影響(0S6-1自動車構造への応用を目指した複合材料技術I,OS6目勣軍構造への応用を目指した複合材料技術)

Carbon-fiber reinforced epoxy was decomposed using supercritical methanol to reclaim carbon fibers. The tensile and interfacial strength of the reclaimed carbon fibers was measured. The tensile strength decreased by 2-10% after decomposition treatment. The interfacial strength decreased by 23-25% after decomposition treatment XPS analysis revealed that functional groups on carbon fibers reduced due to treatment. In addition, the interlaminar shear strength of composite plates was measured. The interlaminar shear strength was not affected by the decrease of interfacial strength.

Numerical Investigation of Interface Debonding of Particle Reinforced Composites by Unit Cell Model

Abstract Due to its high specific stiffness and strength, good damage tolerance capabilities, and good fatigue resistance with respect to the traditional materials, metal matrix composite materials (MMCs) have attracted much research interests in recent years. It is known that interface debonding plays an important role in the thermo-mechanical behavior of the MMCs. In the present study, the effect of interface debonding on the mechanical properties of MMCs has been studied by a new periodic unit cell model, the multi-particle cubic (MPC) model, which is proposed with the consideration of the inhomogeneous structures within the MMCs. The representative cell is constructed by several randomly distributed elastic spheres, matrix material and interfacial region with the perfect bonding initially. And the onset of damage was assumed to follow a maximum normal stress criterion. The simulated results agree well with the experimental results. It is found that with the decrease of interfacial strength, the degradation of the composite resulted from the initiation and propagation of interfacial damage becomes severe. Damage evolution of the interface is further investigated with the increase of plastic strain. In additions, the predictions from the MPC model have also been compared with those from the single particle cubic (SPC) model.

The determination of the delamination resistance in thermal barrier coating system by four-point bending tests

The delamination resistance in a plasma-sprayed thermal barrier coating (TBC) system was evaluated by means of a modified four-point bending test. In this work, in order to study the effect of the interface roughness between the bond coating (BC) and the top coating (TC), two kinds of the powder with the different particle size were used for spraying the BC material. In addition, the influence of the isothermal aging on the delamination resistance was also investigated. The experimental results indicate that the effect of the TC/BC interface roughness wasn't significant. The energy release rate G c, which was estimated by the modified four-point bending tests, increased with increasing aging time at 1000 °C, on the other hand, the scatter of it decreased with increasing aging time. The crack mainly propagated in the top coating for as-sprayed condition and at the top-coating/bond-coating interface after thermal aging for 2000 h. The energy release rate G c was correlated with the fracture strength of the weakest parts of the TBC specimen. The energy release rate G c increased with thermal aging until a critical time due to the sintering of the top-coating expired. It can be expected that G c will decrease with the thermal aging after the critical aging time because the top-coating/bond-coating interfacial strength decreases by the TGO growth. The critical aging time in this work is approximately 2000 h.

Enhancing the mechanical integrity of the implant–bone interface with BoneWelding® technology: Determination of quasi‐static interfacial strength and fatigue resistance

The BoneWelding technology is an innovative bonding method, which offers new alternatives in the treatment of fractures and other degenerative disorders of the musculoskeletal system. The BoneWelding process employs ultrasonic energy to liquefy a polymeric interface between orthopaedic implants and the host bone. Polymer penetrates the pores of the surrounding bone and, following a rapid solidification, forms a strong and uniform bond between implant and bone. Biomechanical testing was performed to determine the quasi-static push-out strength and fatigue performance of 3.5-mm-diameter polymeric dowels bonded to a bone surrogate material (Sawbones solid and cellular polyurethane foam) using the BoneWelding process. Fatigue tests were conducted over 100,000 cycles of 20-100 N loading. Mechanical test results were compared with those obtained with a comparably-sized, commercial metallic fracture fixation screw. Tests in surrogate bone material of varying density demonstrated significantly superior mechanical performance of the bonded dowels in comparison to conventional bone screws (p < 0.01), with holding strengths approaching 700 N. Even in extremely porous host material, the performance of the bonded dowels was equivalent to that of the bone screws. For both cellular and solid bone analog materials, failure always occurred within the bone analog material surrounding and distant to the implant; the infiltrated interface was stronger than the surrounding bone analog material. No significant decrease in interfacial strength was observed following conditioning in a physiological saline solution for a period of 1 month prior to testing. Ultrasonically inserted implants migrated, on average, less than 20 microm over, and interfacial stiffness remained constant the full duration of fatigue testing. With further refinement, the BoneWelding technology may offer a quicker, simpler, and more effective method for achieving strong fixation and primary stability for fracture fixation or other orthopaedic and dental implant applications.

The effect of structure and chemistry on the strength of FeCrAl(Y)/sapphire interfaces: II. Strength of interfaces

The interfacial strengths of the FeCrAl/Al2O3 and FeCrAlY/Al2O3 interfaces in both as-deposited and annealed state were measured quantitatively by the laser spallation technique. The results show that in the as-deposited state, the presence of Y significantly improved the interfacial strength from 330±31 to 686±36 MPa. However, after annealing the films at 850°C for 16 h, the interfacial strength of the Y-free samples increased to 545±68 MPa, while the interfacial strength of Y-containing sample decreased to 599±22 MPa. The increase in the interfacial strength of the Y-free films was attributed to an improvement in the crystalline quality of the interface. The decrease in interfacial strength of the annealed Y-containing film in spite of the improvement in the crystalline quality of the interface was attributed to the depletion of Y at the interface due to formation of yttrium oxide precipitates. This is further proved that the presence of Y improves the strength of FeCrAl/Al2O3 interfaces significantly.

The Effect of Y on the Strength of FeCrAl Alloy/Sapphire Interfaces

ABSTRACTThe effect of Y on the interfacial strength of the FeCrAl/sapphire system has been quantitatively measured by the laser-spallation technique in order to understand the ‘reactive element effect’. The presence of Y improved the interfacial strength of the FeCrAl/sapphire interface in the as-deposited state from 330±31 MPa to 686±36 MPa. However, after a high temperature anneal of 16 hours at 850°C, the interfacial strength of the Y-free samples increased to 545±68 MPa, while the interfacial strength of Y-containing sample decreased to 599±22 MPa. The increase in the interfacial strength of the Y-free films was attributed to an improvement in the crystalline quality of the interface. The decrease in interfacial strength of the annealed Y-containing film in spite of the improvement in the crystalline quality of the interface was attributed to the depletion of Y at the interface due to formation of Y2O3 precipitates, again consistent with the view that Y improves the strength of FeCrAl/sapphire interfaces significantly.

Thermal-shock behavior of a Nicalon-fiber-reinforced hybrid glass-ceramic composite

A Nicalon-fiber-reinforced hybrid composite with a matrix of barium magnesium aluminosilicate (BMAS) glass with silicon carbide whiskers was subjected to thermal shock from elevated to ambient temperatures. The combination of SiC whisker and BMAS glass resulted in a hybrid matrix with a lower thermal expansion than that of the fibers, inducing tensile stresses in the fiber upon thermal shock. This stress state resulted in microstructural damage in the form of fiber cracking and cracking along the fiber/matrix interface, as opposed to the conventional matrix cracking which is typically observed in ceramic-matrix composites. Significant damage in the composite was only observed after three thermal shock cycles. Flexural resonance measurements, used to evaluate thermal shock-induced changes in Young's modulus, showed a reduction in modulus that correlated well with the onset of microstructural damage. Finally, fiber push-out tests, performed to evaluate changes in fiber/matrix interface strength after thermal cycling, indicated a slight decrease in interfacial strength, which was attributed to recession of the carbon-rich fiber surface during thermal shock.

A computational model of ceramic microstructures subjected to multi-axial dynamic loading

A model is presented for the dynamic finite element analysis of ceramic microstructures subjected to multi-axial dynamic loading. This model solves an initial-boundary value problem using a multi-body contact model integrated with interface elements to simulate microcracking at grain boundaries and subsequent large sliding, opening and closing of microcracks. An explicit time integration scheme is adopted to integrate the system of spatially discretized ordinary differential equations. A systematic and parametric study of the effect of interface element parameters, grain anisotropy, stochastic distribution of interface properties, grain size and grain morphology is carried out. Numerical results are shown in terms of microcrack patterns and evolution of crack density, i.e., damage kinetics. The brittle behavior of the microstructure as the interfacial strength decreases is investigated. Crack patterns on the representative volume element vary from grains totally detached from each other to a few short cracks, nucleated at voids, except, for the case of microstructures with initial flaws. Grain elastic anisotropy seems to play an important role in microfracture presenting higher values of crack density than the isotropic case. The computational results also show that decreasing the grain size results in a decrease in crack density per unit area at equal multiaxial dynamic loading. Histograms of crack density distribution are presented for the study of the stochasticity of interface parameters. Finally, a strong dependency with grain shape is observed for different microstructures generated using Voronoi Tessellation. The micromechanical model here discussed allows the study of material pulverization upon unloading. The qualitative and quantitative results presented in this article are useful in developing more refined continuum theories on fracture properties of ceramics.

The effect of the moisture absorption on the interfacial strength of polymeric matrix composites

Seven composite material systems have been studied to determine their potential suitability for structural applications for continuous immersion in sea water. The matrices of these composites have been found to absorb moisture with saturation occurring at 0.6%–2% of the matrix weight of additional moisture over approximately 1% present after fabrication, when soaked at ambient temperature in simulated sea water, with 20.7 MPa (3000 p.s.i.) hydrostatic pressure giving a very minor increase in moisture absorption. Pure water absorption gave a slightly higher saturation level than did simulated sea water. With the exception of the graphite/vinylester composites, the degradation in transverse tensile strength and interfacial shear strength due to moisture absorption has been found to vary from 0%–22%, with the thermoset/graphite systems and the vinylester/glass systems both showing sufficient promise to justify further study. The observed correlation in the decrease in interfacial shear strength due to moisture absorption with decreases in transverse tensile strength supports the hypothesis that the moisture-induced degradation is associated with a decrease in the interfacial strength rather than the degradation of matrix mechanical properties. In situ fracture observations in the scanning electron microscope further support this hypothesis.