Decrease In Yield Stress Research Articles

Simulation of mechanical response of carbon nanotube yarns under uniaxial tensile loading

Carbon nanotube (CNT) yarns (CNTYs) are microscopic assemblies of carbon nanotubes in the form of continuous fibers that have significant technological applications. Their applications as individual fibers or embedded in polymer composites demand tensile load bearing, but the mechanical response of CNTYs is yet not well understood. A sequential, three-step, multiscale finite element (FE) modeling approach is proposed to predict the stress-strain response of CNTYs under uniaxial tensile loading. The modeling approach is based on experimental observations, which motivates an idealized concept of the hierarchical structure of CNTYs discretized into three hierarchical levels: (i) nanoscale model of bundles comprising CNTs, (ii) mesoscale model of CNT fibrillars formed by bundles, and (iii) microscale model of the CNTYs comprising twisted CNT fibrillars. The results from each level feed the simulation of the upper level. The inherent randomness in the plexiform structure of CNTYs is addressed through the Monte Carlo method, and the effect of porosity and twist level are also included for the first time in modeling the CNTY. The simulations predict that the elastic modulus of the bundle is fairly independent of its diameter but the yield stress and strength decrease with increasing bundle diameter. The aspect ratio of the individual CNTs comprising the bundles is also shown to be a key factor determining the CNTY strength. The simulation results show that considering an orthotropic response at the microscale level provides stress-strain curves that match the experimental results. This model of the stress-strain response of CNTYs elucidates the factors affecting that response and provides critical information towards their use in a variety of applications.

Nanoscale Functional Additives Application in the Low Temperature Greases.

Due to the fact that the application of AW and EP additives in low-temperature greases may lead to worse high-temperature and anti-corrosion characteristics as well as additional burden on the environment due to the content of aggressive components, in this paper, the possibility of replacing these additives with NFA, which do not have these disadvantages, was investigated. The analysis of nanosized particles being used as functional additives in greases was carried out. The morphology of the following nanoparticles was studied: montmorillonite K 10, silica, calcium car-bonate and borate, halloysite, and molybdenum disulfide incorporated in halloysite tubes. The effect of nanostructured components on the physicochemical characteristics and anti-wear and anti-scuffing properties of complex lithium, polyurea, and polymer greases were studied. Maximal improvement of anti-wear and anti-scuffing characteristics of cLi-greases was reached when using silica and calcium borate. Maximal improvement of anti-scuffing properties of PU-lubricant was reached when using calcium carbonate and the two-component NFA based on halloysite, for anti-wear properties when adding silicon dioxide and halloysite. When the concentrations of silicon dioxide and calcium carbonate was increased from 1 to 3 wt.%, there was a decrease in yield stress of the structural frame of the PU-lubricant and its colloidal stability was worse. The increase of the concentration of calcium carbonate and borate nanoparticles in the studied range led to a significant improvement of the anti-wear and anti-scuffing characteristics of the PU grease, respectively. The greases properties’ dependence from the nanostructured functional additives’ introduction method and their concentration were investigated. Nanoparticles were added into the test lubricants before and after the thermo-mechanical dispersion stage. The addition of silicon dioxide and calcium carbonate NFA after the heat treatment stage led to worsening of the characteristics of the plastic material, and the increase of their concentration from 1 to 3 wt.% formed a harder structure of Li-grease. On the contrary, the addition of calcium borate NFA is recommended after the thermomechanical dispersion. The choice of nanoparticles and the method of their addition to the lubricants of various types was carried out according to the results of the previous stage of the research. Along with the analysis of the physicochemical characteristics and anti-wear and anti-scuffing properties of the lubricants, the structure of the dispersion phase of nanomodified lubricants were studied.

Influence of structure formation and properties of bimetal produced by ultrasound-assisted explosive welding

The aim of this paper was to study how ultrasonic vibrations during explosive welding influence the formation of the structure and properties of bimetal plate. The effect of changes in joint formation kinetics and in the structure and properties of the bimetal plate formed by explosive welding assisted by ultrasonic vibrations was determined. Ultrasound-assisted explosive welding resulted in improved strength and microhardness and decreased wave parameters and molten metal amount in the wave vortex areas compared to explosive welding without ultrasound. The influence of the propagation scheme, frequency and amplitude of the ultrasonic vibrations on the structure and property formation of the bimetal plate during explosive welding was demonstrated. The results of the influence of ultrasound on the weldable zone of dissimilar metals are discussed. Ultrasonic treatment of metal produces a decrease in yield stress, which results in modified metal surface layer properties and conditions for joint formation of collided plates during explosive welding.

Impact of Processing Conditions on Rheology, Tribology and Wet Lubrication Performance of a Novel Amino Lipid Hair Conditioner

The objective of this work was to carry out a comprehensive evaluation of the performance of a novel cationic amino lipid surfactant, Brassicyl Valinate Esylate (BVE), in contrast to conventional alkyl quaternary ammonium surfactants (quats), through a study of the effects of process mixing speed on its overall rheological, tribological and wet lubrication performance in comparison to BTAC and CTAC, two cationic surfactants widely used in cosmetics. The major cosmetic application of cationic surfactants is in the preparation of hair conditioners. Hence, this analysis was done firstly by conducting tensile combing tests to evaluate reduction in wet lubrication which translates to conditioning performance. The combing results serve as a testing metric that adequately corresponds to consumer perception of conditioned hair. To correlate this technically, yield stress measurements were conducted to establish rheologic profiles of the conditioner formulations, and in vitro tribological testing of the emulsion systems between two steel surfaces were done to technically simulate the spreading and rubbing of conditioner on the hair. The effect of processing conditions on the formulations was then evaluated. BVE was found to be an effective conditioning surfactant suitable as an eco-friendly replacement for BTAC and CTAC in hair conditioner formulations. The results showed that higher shear mixing rates during formulation lead to poorer performance effects evident through decreased yield stress values, lower percentage reduction in combing force and a higher coefficient of friction.

Mechanism of microstructure and texture evolution during shear loading of AA6063 alloys

The cyclic shear test of 6063 aluminum alloys under T4 and T6 conditions was carried out at room temperature. The microstructure and texture evolution were investigated using electron backscattered diffraction (EBSD) at several instances during cyclic shear deformation. Hardly any change in grain size was observed during the cyclic shear test of T4 and T6 samples. The local residual strain distribution measured in the form of average kernel misorientations (KAM) values increases continuously with an increase in shear strain for both samples. The increase in KAM value was higher for the T6 sample compared to the T4 sample during forward (F) shearing. On reversing the loading path, the increase in KAM value was higher for forward + reverse (FR) and forward + reverse + forward (FRF) straining of the T4 sample compared to the T6 sample. The cube texture was found to be unstable during shear deformation. A significant rotation of texture was observed in both T4 and T6 samples. However, the extent of rotation was slightly greater for the T6 sample as compared to the T4 sample. It was observed that the latent hardening of (1-11)<101>was more than (111)<1-01>in the T4 sample. Similarly, the latent hardening of (1-1-1)<011>was more than the (111)<1-01>in the T6 sample. The origin of latent hardening was attributed to the formation of sessile jogs during dislocation-dislocation interactions on different planes of T4 samples and the difference in volume fraction of precipitates on different planes of T6 samples. The mechanical properties show that the 0.2% YS increases with subsequent reverse and forward shearing for the T4 sample. However, the 0.2% YS during subsequent reverse shearing is lower than the initial forward shearing for the T6 sample. This decrease in yield stress upon loading reversal is attributed to the presence of deformation-induced intragranular back stresses within the T6 material. It is observed that the rate of cross slip of dislocations depends on the athermal dislocation content, presence of dislocation debris in the unfavorable grains, and the difference in the latent hardening values of different slip systems for the T4 and T6 materials.

Effect of filler wire and post weld heat treatment on the mechanical properties of laser beam-welded AA2198

The mechanical behavior of autogenously and non-autogenously laser beam-welded joints of Al-Cu-Li alloy AA2198 and the effect of post weld heat treatment are examined in this contribution. The deformation texture of the base material does not present any significant change in the macrotexture with applying different artificial ageing times. Autogenously and non-autogenously laser beam-welded joints present a decrease in yield stress and ultimate strength in the as-welded condition, approximately 45% and 36–38%, respectively, when compared with AA2198-Τ3 base material. The addition of the AA4047 filler wire increases the Si and Cu content in the grain interior and in the grain boundaries of the fusion zone of the welded joint. Micro-hardness measurements for autogenously laser-welded joints showed a decrease in hardness by 27% for the fusion zone and 42% for the heat-affected zone, when compared with the non-autogenously laser beam-welded joints. Α quality index was exploited to evaluate the tensile mechanical performance of the welded joints. It is observed that the non-autogenously welded joints always show a higher ‘quality’ than the respective autogenously welded joints and the highest quality index in terms of mechanical performance is achieved for the as-welded and the peak-aged conditions, respectively. Regardless of the post weld heat treatment condition, both autogenously and non-autogenously laser-welded specimens fractured in between the equiaxed and fusion zone during tensile loading.

Interplay of mechanics and chemistry governs wear of diamond-like carbon coatings interacting with ZDDP-additivated lubricants

Friction and wear reduction by diamond-like carbon (DLC) in automotive applications can be affected by zinc-dialkyldithiophosphate (ZDDP), which is widely used in engine oils. Our experiments show that DLC’s tribological behaviour in ZDDP-additivated oils can be optimised by tailoring its stiffness, surface nano-topography and hydrogen content. An optimal combination of ultralow friction and negligible wear is achieved using hydrogen-free tetrahedral amorphous carbon (ta-C) with moderate hardness. Softer coatings exhibit similarly low wear and thin ZDDP-derived patchy tribofilms but higher friction. Conversely, harder ta-Cs undergo severe wear and sub-surface sulphur contamination. Contact-mechanics and quantum-chemical simulations reveal that shear combined with the high local contact pressure caused by the contact stiffness and average surface slope of hard ta-Cs favour ZDDP fragmentation and sulphur release. In absence of hydrogen, this is followed by local surface cold welding and sub-surface mechanical mixing of sulphur resulting in a decrease of yield stress and wear.

Elastoplastic behavior of the γ-phase in Ni-based single crystal superalloys: A molecular dynamics study considering Re and temperature effect

Recent investigations suggest that the addition of trace Re element has a significant influence (the so-called Re-effect) on the mechanical properties of Ni-based single crystal superalloys. Nevertheless, the mechanisms for this Re-effect at different service temperatures are still unclear. The present work studied the elastoplastic deformation behavior of the γ phase in Ni-based single crystal superalloys by molecular dynamics, with the emphasis on Re-associated mechanisms at a wide range of Re contents (from 0 at.% to 9 at.%) and temperatures (from 300 K to 1100 K). The results indicate that the Re content and temperature have an obvious effect on the elastic modulus of the γ phase, the higher the Re content and temperature, the lower the elastic modulus. The yield stress and strain decrease with the increase of Re content and temperature. Both the temperature and Re content affect the formation and propagation of dislocations, which further leads to a correlation between the evolution of dislocations and stress-strain. In addition, the effects of size and strain rate on elastoplastic behavior are also studied.

Thermodynamic and shear effects of ultrasonic vibration on the flow‐induced crystallization of polypropylene

AbstractIn order to achieve optimal mechanical properties in injection‐molded parts, continuous ultrasonic vibration is applied to a mold cavity during the filling and solidification stages of injection molding. In this work, the effect of ultrasonic thermodynamics and ultrasonic shear on the condensed structure of the parts are studied. Thermocouple measurement results show that the increase in the temperature of the mold cavity surface caused by ultrasonic thermodynamics can reach up to 15°C; Molecular dynamics simulation results show that the molecular chain morphology under ultrasonic shear is more stretched during the melt flow process. Microscopic results show that with increasing ultrasonic power and ultrasonic time, the ultrasonic thermodynamic effect causes the thickness of the shear layer to increase. With increaseing ultrasonic power, the lamella thickness of the core layer increases, while the crystal size in the transition layer shows a trend of first decreasing and then increasing. The ultrasonic shear causes the overall crystallinity and β crystal content of the parts to increase with increaseing the ultrasonic power. The crystallinity starts to decrease when the ultrasonic vibration is still applied at a melt temperature below 67°C during cooling. When the ultrasonic power is increased to 1000 W and the ultrasonic vibration time is applied for 30 s, β spherulites transform to β‐transcrystalline. The yield stress results show that when the ultrasonic vibration time is 0–20 s, the yield stress of the parts increases with the ultrasonic power; while when the ultrasonic time is increased to 30 s, the yield stress decreases.

Gas Bubble Evolution in Polycrystalline UMo Fuels Under Elastic-Plastic Deformation: A Phase-Field Model With Crystal-Plasticity

In monolithic UMo fuels, the interaction between the Al cladding and large gas bubble volumetric swelling causes both elastic-plastic and creep deformation. In this work, a phase-field model of gas bubble evolution in polycrystalline UMo under elastic-plastic deformation was developed for studying the dynamic interaction between evolving gas bubble/voids and deformation. A crystal plasticity model, which assumes that the plastic strain rate is proportional to resolved shear stresses of dislocation slip systems on their slip planes, was used to describe plastic deformation in polycrystalline UMo. Xe diffusion and gas bubble evolution are driven by the minimization of chemical and deformation energies in the phase-field model, while evolving gas bubble structure was used to update the mechanical properties in the crystal plasticity model. With the developed model, we simulated the effect of gas bubble structures (different volume fractions and internal gas pressures) on stress-strain curves and the effect of local stresses on gas bubble evolution. The results show that 1) the effective Young’s modulus and yield stress decrease with the increase of gas bubble volume fraction; 2) the hardening coefficient increases with the increase of gas bubble volume fraction, especially for gas bubbles with higher internal pressure; and 3) the pressure dependence of Xe thermodynamic and kinetic properties in addition to the local stress state determine gas bubble growth or shrinkage. The simulated results can serve as a guide to improve material property models for macroscale fuel performance modeling.

Limitations of small-scale yielding for fatigue crack growth

The work described here has led to a simple criterion that defines the boundary of the small-scale yielding, SSY, regime to avoid invalid use of the LEFM parameter, ΔK, as the characterising parameter for fatigue crack growth rate. The approach proposed is based on the analysis of crack tip opening displacement, CTOD, and its separation into elastic and plastic components. SSY conditions are shown to dominate when the elastic component of CTOD is >75% of the total CTOD measured at a distance of 8 μm (the finite element mesh size) behind the crack tip, i.e., Δδe/Δδt > 75%. Large-scale yielding, LSY, conditions become dominant for relatively large values of plastic CTOD, Δδe/Δδt < 60%. An increase in crack length (and therefore of ΔK), a decrease in yield stress of the material and the existence of plane stress conditions all promote LSY. The results obtained from various loading and geometric conditions simulated in this work demonstrate that caution should be used in assuming that the use of ΔK is valid even for high strength alloys like Ti6Al4V. In this material, the boundary of the elastic regime was crossed and SSY conditions lost, for the longest crack lengths studied and in the case of overloads.

Physicochemical and Rheological Properties of Cross‐Linked Litchi Kernel Starch and Its Application in Development of Bio‐Films

AbstractIn this study, starch from a non‐conventional source, that is, litchi is extracted and cross‐linked (CL) with varying concentrations (1%, 3%, and 5%) of sodium trimetaphosphate (STMP). The starches are characterized for their physicochemical, pasting, rheological, and thermal properties. Bio‐films are also prepared from these starches and analyzed for selected barrier and mechanical properties. The results indicate that an increase in cross linking agent concentration resulted in a significant decrease in amylose content, swelling power (SP), and solubility of starches. Peak viscosity (PV) and breakdown viscosity (BV) of CL starches are lower in comparison to native starch. Steady shear properties reveal that magnitudes of yield stress (σo) and consistency index (K) decrease upon increase in the concentration of cross linking reagent. CL starches exhibit significantly (p &lt; 0.05) higher transition temperatures than native starch. Native starch film shows water solubility of 43.66% while for films from CL starches, the values ranged between 35.12 and 41.53%. Significant (p &lt; 0.05) reduction in water vapor permeability (WVP) values of CL starch films (1.24–1.52 g m Pa−1 s−1 m−2) is observed in comparison to native (2.32 g m Pa−1 s−1 m−2) starch films. Cross linking significantly improves tensile strength (TS) of films, however, films elongation is lower (14.71–17.97%) than native starch film (19.88%).

Effects of polycarboxylate superplasticizer on rheological properties and early hydration of natural hydraulic lime

As one of the main materials for grouting repair, the workability of natural hydraulic lime (NHL) has been concerned widely. In this paper, effects of polycarboxylate superplasticizer (PCE) on rheological properties and early hydration of natural hydraulic lime (NHL2) and their correlations were systematically investigated. Results show that the fluidity of NHL2 paste improves significantly and tends to a stable state at a certain dosage in the presence of PCE. It is found that PCE makes the flocculated structures in paste disassemble and produces more small particles. The results can lead to a decrease in yield stress and plastic viscosity, further improving rheological properties. The retardation effect of PCE on NHL2 hydration can depress the crystallization and early formation of calcium hydroxide Ca(OH)2 and calcium silicate hydrate (C–S–H). The effect can reduce water consumption during mixing, which has a positive influence on rheological properties.

Rheological characterization of ball-milled corn stover with different fragmentation scales at high-solids loading

A fundamental understanding of the rheology of high-solids lignocellulose slurry is essential for the design of efficient cellulosic ethanol production processes and bioreactors. Here we analyzed the rheological properties of high-solids corn stover slurries with particles size ranged from tissue scale to cellular scale. Results showed that the apparent viscosity/yield stress decreased with the increase of free water amount and the decrease of particle size, and the quantitative relationships among them were obtained. A 300-fold and 130-fold decrease in apparent viscosity and yield stress (30 % solids loading) were observed when the corn stover was reduced to cellular scale (≤ 50 μm). Further analysis revealed that size reduction to tissue scale reduces the viscosity and yield stress by alleviating the interactions between particles, while size reduction to cellular scale not only weakens the particle interactions, but also increases free water amount due to destruction of cell lumen, thus greatly enhances the rheological behaviors. And this improvement is undoubtedly of great significance for inter-unit operation and mixing energy saving.

Utilization of waste glass powder as partial replacement of cement for the cementitious grouts with superplasticizer and viscosity modifying agent binary mixtures: Rheological and mechanical performances

The utilization of waste glass in cement-based grouting materials has attracted a lot of interests due to its ability of improving rheological properties and stability. The purport of this research was to investigate the feasibility of the grouts containing waste glass powder (WGP), superplasticizer (SP), and viscosity modifying agent (VMA). For all testing mixtures, the water to binder ratio was maintained at 0.5. The selected mixtures were used to evaluate properties of mini-slump, marsh cone flow time, thixotropy, bleeding capability, autogenous shrinkage, compressive strength, and flexural strength. The statistical analysis method was adopted to further assess the synergistic effect of WGP, SP, and VMA. The testing results indicated that the use of 15% WGP as cement replacement improved the mini-slump diameter, and marsh cone flow time, in the meantime, decreased yield stress and plastic viscosity. Moreover bleeding capacity and mechanical properties were enhanced simultaneously. The method of Decision Matrix Analysis (DMA) was carried out to comprehensively evaluate and analyze the effect of each component in the grouts, and the results shown that WGP had notably positive effects on the properties of grouts.

Optimization of physicochemical, textural, and rheological properties of sour cherry jam containing stevioside by using response surface methodology.

The response surface method (RSM) was used to produce sour cherry jam containing stevia sweetener with favorable physicochemical, textural, and rheological properties. The experiments were designed based on RSM using a central composite design (CCD) with three independent variables: sugar, pectin, and stevia. Sample processing was performed at five levels of sucrose (10%–50%), pectin (0.1%–0.5%), and stevia (0.2%–0.6%) at a constant fruit weight of 300 g. To evaluate the jam, the physicochemical, textural, and rheological properties of the jam were determined and optimized. The concentrations of sucrose, pectin, and stevia had a significant effect on the textural and rheological properties of the jam. The results showed that increasing the concentration of sucrose is the main factor in increasing the soluble solids and the total sugar content of the jam. Pectin had a positive effect on textural characteristics such as hardness and adhesiveness of the jam, while the cohesiveness of the jam decreased with increasing pectin. Herschel–Bulkley model was appropriate for describing the rheological behavior of the stable state of sour cherry jam containing stevia. Decreasing sucrose concentration is accompanied by a decrease in yield stress and consistency index of jam samples due to the TSS reduction. Pectin also had a positive effect on the amount of yield stress and consistency index. Dynamic rheological tests indicated that the sour cherry jam is a weak gel. The predominant viscose behavior and the formation of a dilute solution were evident in the samples with 10% and 20% sucrose concentrations. The most favorable condition for the production of the jam was obtained at a 36.5% sugar, 0.277% pectin, and stevia 0.30%.

Deformation behavior of HfNbTaTiZr high entropy alloy singe crystals and polycrystals

Abstract Deformation behavior of equiatomic HfNbTaTiZr high entropy alloy single crystals and polycrystals were investigated. The single crystalline specimens could be obtained from the coarse-grained polycrystals annealed just below the melting point. 1/2 screw dislocations played an important role in the deformation behavior, similar to body centered cubic (bcc) metals. Moreover, a yield stress anomaly was found to appear in the alloys solutionized at 1473 K. The yield stress decreased rapidly with increasing temperature up to 673 K, while the stress increased at 873 K. Further increase in temperature resulted in a decrease in yield stress. It is also noted that the microstructure of the alloys depended strongly on annealing temperature. At 773–1073 K, phase separation into two bcc phase took place, while the hexagonal close-packed (hcp) phase was precipitated at 773–973 K. The ω phase which is typical in β-titanium alloys was also observed at 673 K. The strain-rate sensitivity of the deformation behavior and micro-Vickers hardness after the heat treatment suggest that the dynamic precipitation of the hcp phase is responsible for the yield stress anomaly.

Yield stress behavior of colloidal gels with embedded active particles

The yield stress behavior of colloidal gels with embedded active particles is studied with three experiments: start-up of steady shear, oscillatory strain amplitude sweep, and creep testing. Activity is generated by Janus particles with a platinum hemisphere; these particles undergo self-diffusiophoretic and self-electrophoretic motion in hydrogen peroxide solutions. The free particle active motion of the Janus colloids is consistent with an active energy of 25 times thermal energy at the highest hydrogen peroxide concentration studied. Consistent with prior work, the gels with embedded active particles display enhanced microdynamics and a reduction in linear viscoelastic moduli. Furthermore, at the activity levels studied, the yield stress decreases by as much as threefold for gels with an active-to-passive particle ratio of only 1:1200. We additionally find the yield strain is independent of activity. The significant reduction in yield stress at a very low active-to-passive particle ratio is modeled by combining the theory of how activity changes the spring constant of interparticle bonds in the gel with an argument that the number of active fractal clusters in the gel—rather than the number of active particles—drives the activity-induced softening of rheological properties. We estimate that 1 in 40 fractal clusters in the gel is active due to the presence of an active particle. This approach explains how an extremely small fraction of active particles causes a substantial change in both linear and nonlinear rheological properties. The results and modeling are potentially useful for the creation of gels with multistate mechanical properties.

Rheological properties of magnesium phosphate cement with different M/P ratios

Magnesium phosphate cement (MPC) with unique advantages of quick setting and high early-strength has been used as grouting materials. The rheological properties of MPC, being vitally important for site operation, need to be studied further. Dead burnt magnesia (MgO) and phosphate (ADP) are the main raw materials for preparing MPC. This study measured the rheological properties with different M/P ratios, and the mechanisms of M/P ratio were studied by characterizing the zeta potential, 1H NMR relaxation signal, water film thickness, mineral changes and electrical impedance. Experimental results indicate that both the yield stress (τ0) and plastic viscosity (η) decrease firstly and then increase gradually with increasing the M/P ratio from 2.5:1 to 4.5:1. Higher M/P ratio decreases the interparticle water film thickness and accelerates the initial hydration rate remarkably, which is responsible for the change in rheological parameters. Low field NMR, TG-DTG analysis and Nyquist plots confirm the quicker initial hydration in MPC with higher M/P ratio. The change in hydration products is very slight during the rheological property measurements. Nyquist plots show that the MPC paste with lower M/P ratios has more compact microstructure and lower porosity at several hours. In a word, initial hydration rate is the most important factor influencing the rheological properties of MPC, and the separation distance among solid particles is the secondary factor.

A numerical, theoretical and experimental study of the effect of thermocycling on the matrix-filler interface of dental restorative materials

ObjectiveThermocycling is widely used to age dental composites but with very different results from one study to another, even with apparent similar conditions. This study aims at understanding better the relative damaging speed of matrix and fillers, based on theoretical models. MethodsEight formulations of an experimental dental material were produced. The same organic matrix was used and silanated barium glass particles were added as fillers with different filler ratios. Samples were thermocycled up to 10 000 cycles. Three-point bending tests were carried out at different steps. The yield stress was measured among other mechanical properties. ResultsComposite properties were degraded by thermocycling. The decrease was slight during the first 5 000 cycles whereas it decreased significantly after 10 000 cycles. The Turcsányi model asserts that the interface yield stress is slightly affected in the first 5 000 cycles and then falls down, while the decrease of matrix yield stress is linear. SignificanceEach component of a composite does not age at the same rate. First, the matrix acts as a protector until the water finds its way to the interphase. The filler silanization treatment is highly sensitive to hydrolysis and is damaged rapidly from that moment. Numerical simulations and surface observations confirmed that cracks appear to propagate in the neighbourhood of the interface but not directly within it.