Reduction In Tensile Strength Research Articles

A structured approach to the determination of residual stresses in an epoxy-amine coating and the influence of thermal ageing on the thermomechanical properties, residual stresses and the corresponding failure modes of coating

The purpose of this research was to develop a structured approach for the calculation of residual stresses in organic coatings through the experimental determination of thermomechanical properties of the epoxy-amine coating. The feasibility of this proposed method was validated by the presence of cracks on epoxy amine coating subjected to isothermal ageing at 180 °C for a period of 8 weeks, followed by thermal shock by water quenching at 0 °C, when the tensile strength of coating (8.00 MPa) was surpassed by the accumulated residual stress in the coating (9.66 MPa). The influence of thermal ageing on the thermomechanical properties, residual stresses and the corresponding failure modes were also evident. Significant variation of thermomechanical properties such as the increase in Tg from 77.60 °C to 120.50 °C, reduction of thermal expansion coefficient from 51.74×10−6°C−1 to 40.27×10−6°C−1, reduction of elastic modulus from 1600 MPa to 1400 MPa, and reduction of ultimate tensile strength from 27.00 MPa to 8.00 MPa after thermal ageing were observed. These variations have ultimately led to the increase of residual stresses in coatings that has resulted in the formation of cracks.

Moisture diffusion and tensile properties of epoxy-based and polyurethane-based flax-glass hybrid FRP under hygrothermal and weathering environments

This research presents tensile modulus and strength of flax-glass hybrid FRP (HFRP) flat coupons with different fibre volume fractions and fabric stacking sequences under constant hygrothermal (50 °C and 95% RH) and cyclic weathering (water spray-ultraviolet radiation) environments for six months. Two types of polymer (i.e., epoxy (EP) and polyurethane (PUR)) were employed in HFRP. Fourier transformed infrared spectroscopy (FTIR) was performed to identify the changes in functional groups of flax fibres and polymer matrix after exposures. The glass transition temperature (Tg) of polymer matrix was measured by differential scanning calorimetry (DSC), which was used to study the influence of environmental exposure on Tg. The 3D diffusion coefficients of EP-based flax FRP and glass FRP laminates were determined based on experimental moisture uptake and Fick's law. A coupled mass diffusion-stress analysis based on finite element (FE) model was conducted to simulate the moisture diffusion and swelling behaviour of HFRP. The results showed that hygrothermal and weathering exposures hardly affected tensile modulus of HFRP regardless of the matrix type. After the environmental exposure, EP-based HFRP experienced lower retention ratio of tensile strength (65.4–88.0%) compared to PUR-based HFRP (80.7–94.1%) because of higher moisture absorption in the EP-based HFRP. The influence of fabric stacking sequence on tensile strength reduction varied with different fibre volume fractions in EP-based HFRP, which was explained by the combined effects of the internal stress and damage propagation at flax-glass interface.

Fracture Toughness of Ti6Al4V/Cp-Ti Multi-Material Produced via Selective Laser Melting

Multi-materials can locally enhance the properties of products to improve their performance. In some cases, it might be necessary to improve the fracture toughness properties locally. This work is devoted to investigating the fracture toughness of multi-material Ti6Al4V/Cp-Ti specimens produced via laser powder bed fusion (L-PBF). The powder feeding and distributing system of the L-PBF machine was modified for programmable dual-powder feed capability. The multi-material Ti6Al4V/Cp-Ti samples analyzed in this work are layered materials, where the Ti6Al4V alloy serves as the base material and Cp-Ti is present as separate layers. Samples of this type rely on the principle of crack inhibition, where fracture energy is dissipated in the more ductile Cp-Ti layers. Two variants of alternating ductile layers were studied. The microstructure of the materials and interfacial zone were analyzed using an optical microscope. Chemical composition was examined with a scanning electron microscope. The size of the interfacial zone in the multi-material averaged between 250 and 300 μm. A comparison of the tensile tests results with the literature data (of relatively pure Ti6Al4V alloy) reveals that there is a minor reduction in ultimate tensile strength and elongation. The obtained results confirm the possibility of locally increasing fracture toughness through the creation of a multi-material structure using L-PBF.

Colorless, transparent, and shape memory polyurethane networks with high strength and recyclability

AbstractThe traditional thermoset polyurethanes (PUs) can be recycled through the dynamic carbamate bonds under specific conditions. However, there is limited research on the structural evolution and property changes of these PUs before and after recycling. Herein, we designed and fabricated a thermoset polyurethane network (PCU) using polyhexamethylene carbonate diol (PHMC‐diol) as soft segments, and isophorone diisocyanate (IPDI) and glycerol (GLY) as hard segments. Through careful formulation design, the PCU demonstrated colorless transparency (with up to 86% transmission), shape memory properties, and reprocessing capabilities, all achieved without introducing other dynamic covalent bonds. Furthermore, the PCU exhibited excellent mechanical properties, boasting a tensile strength of 59.2 ± 3.7 MPa and the elongation at break of 674.8 ± 37.3%. Of particular interest, the PCU samples displayed solid‐state plasticity and impressive shape memory performance, with shape fixity and recovery ratios exceeding 90%. Leveraging the combination of solid‐state plasticity and shape memory, the PCU samples demonstrated the ability to achieve arbitrary shape manipulations. Upon recycling, it was observed that the cross‐linking density of the PCU samples decreased, resulting in the formation of byproducts and subsequently leading to a reduction in tensile strength. Nonetheless, the PCU samples prepared in this study exhibit potential as thermadapt shape memory and recyclable materials.

Investigation of Dispersion Kinetics of Particulate Lubricants and their Effect on the Mechanical Strength of MCC Tablets

IntroductionTablets are commonly produced by internally adding particulate lubricants, which are known to possibly lower the mechanical strength of tablets. This reduction is caused by the coverage of matrix forming components by lubricant particles, resulting in decreased interparticulate interactions. The known incompatibilities with some active compounds of the predominantly used lubricant, magnesium stearate, call for the in-depth characterization of alternative lubricants.PurposeInvestigation of the dispersion behavior of five commonly applied pharmaceutical lubricants by mathematically modeling the dispersion kinetics for short and extended mixing times.MethodsThe dispersion behavior of five different pharmaceutical lubricants were examined by systematically varying lubricant concentration and mixing time of binary formulations and evaluating the kinetic of tensile strength reduction by theoretically estimating the surface coverage based on particle sizes.ResultsFor short mixing times, a unifying relationship between compactibility reduction and theoretical surface coverage was identified. Subsequently, for extended mixing times, distinct differences in the shear strength and dispersion kinetics of the investigated lubricants were found.ConclusionsThe lubricant particle size controls the tensile strength reduction if short mixing times are applied. For extended mixing times, the investigated lubricants can be divided into two groups in terms of dispersion kinetics. Possible underlying reasons are discussed in detail in order to enhance the general understanding of lubricant dispersions in tablet formulations.

Experimental evaluation of the durability of glass Textile-Reinforced concrete

Textile reinforced concrete (TRC) is a promising alternative to conventional steel-reinforced systems, especially for slender, lightweight structural and nonstructural applications. One of the critical parameters to be accounted for in the design of these composites is their long-term mechanical performance, especially the reduction in tensile capacity with time. This paper looks at the influence of aging on the response of textiles and composites with AR- and E-glass fibers. Six coated glass textiles were exposed to three alkaline solutions with different pH ranges. Accelerated aging of the composites with these textiles was carried out with the hot water immersion method at 50 °C, and the reductions in tensile strength are compared with the results from the natural aging of composites over 4 years. Two matrices were used in the studies to identify the improvements due to lower water/binder ratio and matrix porosity. The change in the morphology of fibers and coating after exposure is discussed with observations from scanning electron microscopy (SEM). The type and extent of textile coating have a profound influence on the residual strength of the composite. The composites with higher strength matrix showed better retention of strength. The trend of degradation in alkaline exposure, accelerated and natural aging is discussed with the comparison of the deterioration mechanism observed from microstructural studies in each case.

On the fatigue properties of material extrusion 3D-printed biodegradable composites reinforced with continuous flax fibers

Nowadays, additive manufacturing is increasingly used for prototypes and low-volume products. Firstly, it offers great design freedom; however, the components must inevitably have certain design artifacts that cause stress concentrations. To this end, composites of biodegradable PLA (polylactic acid) matrix and continuous flax fibers were fabricated in this study using material extrusion 3D printing. Static characterization and mechanical fatigue tests between 103 and 2·106 load cycles were performed for plain specimens, three types of notches for the matrix, and two composite configurations. The notches only slightly affected the static performance of the tested materials. Accordingly, compared to the unnotched versions, the PLA matrix and composites exhibited a reduction in tensile strength of up to 8% and 19%, respectively. It was found that compared to the PLA matrix, the fatigue strength at high cycles increased by 1.8 and 2.3 times for the plain composite with a fiber volume fraction of 7.8% and 14% fibers, respectively. In the fatigue of notched composites, the notch effect is reduced by fibers in the tip. The fatigue strength is up to 1.9 and 2.9 times higher compared to the notched matrix for the composite with a smaller and larger volume fraction, respectively.

Exploring particle-current collector contact damage in Li-ion battery using DEM-FEM scheme

Calendering is an essential step in the manufacturing process of lithium-ion batteries. However, the intrusion of active particles into metal foil can damage the current collector during calendering. Here, we investigate the changes in surface morphology and the tensile properties of current collector after calendering. The damage mechanisms of tensile strength reduction for current collector due to compressive pressure are revealed by combining the calendering tests, tensile experiments, and simulations. Specifically, the DEM-FEM scheme is proposed, which combines the discrete element method (DEM) with the finite element method (FEM) to characterize the mechanical behavior of current collectors after the intrusion of active particles. The results show that the current collectors become more brittle and vulnerable with the increase of compressive pressure. Finally, the failure phase diagrams are presented during the winding and electrochemical processes. This study can reveal the failure behavior of current collectors and guides the electrode manufacturing optimization.

Analysis of the quality of aluminum overhead conductors after 30 years of operation

Overhead power conductors (OHL), which are installed in transmission and distribution lines, are designed for a service life of min. 30–50 years. During this time, the OHL conductors should work in a safe and fault-free state with the highest current capacity. This article refers to the testing of aluminum conductors after 30 years of operation. The mechanical properties and structural characteristics of the conductor were tested. The analysis of the quality of the supplied wire samples carried out with a scanning microscope allowed us to distinguish three types of wire damage, namely: corrosion on the surface of the outer layer, wires, local melting, and loss of cross section and wire breakage. On the basis of a detailed analysis of the areas of damage to wires from the tested OHL conductors, it can be stated that the main cause of their breakage is local smelting areas caused by an electric arc.High temperatures affect local material melting, leading to a large reduction and the consequence of strength decreasing. This situation leads to the loss of the conductor's carrying capacity and ultimately to its destruction. During 30 years, conductors had to be subjected to frequent short circuits caused by changing weather conditions, i.e., high wind or storms. The paper dealt with the results of the mechanical properties test, which showed that the aluminium wires are lower than those required by the standard. The greatest degradation of the strength properties occurs on the wires of the outer layer of conductor. The center wires show a negligible reduction in tensile strength.

Optimization of Thermal Conductivity and Tensile Properties of High-Density Polyethylene by Addition of Expanded Graphite and Boron Nitride.

Due to its mechanical, rheological, and chemical properties, high-density polyethylene (HDPE) is commonly used as a material for producing the pipes for transport of various media. Low thermal conductivity (0.4 W/mK) narrows down the usage of HDPE in the heat exchanger systems. The main goal of the work is to reduce the vertical depth of the HDPE pipe buried in the borehole by increasing the thermal conductivity of the material. This property can be improved by adding certain additives to the pure HDPE matrix. Composites made of HDPE with metallic and non-metallic additives show increased thermal conductivity several times compared to the thermal conductivity of pure HDPE. Those additives affect the mechanical properties too, by enhancing or degrading them. In this research, the thermal conductivity and tensile properties of composite made of HDPE matrix and two types of additives, expanded graphite (EG) and boron nitride (BN), were tested. Micro-sized particles of EG and two different sizes of BN particles, micro and nano, were used to produce composite. The objective behind utilizing composite materials featuring dual additives is twofold: firstly, to enhance thermal properties, and secondly, to improve mechanical properties when compared with the pure HDPE. As anticipated, the thermal conductivity of the composites exhibited an eightfold rise in comparison to the pure HDPE. The tensile modulus experienced augmentation across all variations of additive ratios within the composites, albeit with a marginal reduction in tensile strength. This implies that the composite retains a value similar to pure HDPE in terms of tensile strength. Apart from the enhancement observed in all the aforementioned properties, the most significant downside of these composites pertains to their strain at yield, which experienced a reduction, declining from the initial 8.5% found in pure HDPE to a range spanning from 6.6% to 1.8%, dependent upon the specific additive ratios and the size of the BN particles.

Energy saving potential of interstage screen fractionation for production of board grade BCTMP

Over the last few decades, the continuing decline in mechanical pulp-based grades has led pulp producers to modify operations and implement measures to reduce production costs in order to stay competitive. In spite of a considerable effort to reduce energy consumption, the latter is still a major portion of production costs in the process of making bleached chemithermomechanical pulp (BCTMP). In this study, we evaluated the impact of interstage screening fractionation (ISSF) and secondary refining strategy for producing BCTMP with the objective of reducing refining energy consumption while maintaining or improving bulk and strength properties. In the first step and to establish a baseline for a mill’s existing configuration, the collected primary refined pulp and reject streams from the ISSF were refined in a high consistency (HC) refiner to target freeness levels. The accepts and refined rejects streams were recombined, and their properties were compared to those of the refined primary pulp. The results showed that, at a given freeness of 400 mL and compared to the control case (without fractionation), the ISSF using an 0.070 in. basket followed by rejects refining could lead to about 25% energy saving in the second stage HC refining. Handsheet properties showed that utilization of ISSF could produce BCTMP with higher bulk and similar average fiber length and tear index. However, a slight reduction in tensile strength was observed. In the second set of trials, the primary refined pulp and the rejects from the ISSF using the 0.070 in. basket were refined by a low-consistency (LC) refiner. The results showed that, at the same freeness of 400 mL and compared to refined primary pulp, the ISSF saved about 26% in net LC refining energy. At a specific edge load (SEL) of 0.4 J/m, the produced pulp had similar bulk and strength properties compared to those of the control sample. A higher SEL of 0.6 J/m in LC refining could further decrease net refining energy consumption; however, it also led to reduction in fiber length, bulk, and strength properties.

Tensile properties of PVA and PE fiber reinforced engineered cementitious composites containing coarse silica sand

To mitigate the shrinkage of engineered cementitious composites, coarse silica sand has been employed to substitute ultrafine silica sand in recent years. However, for the different matrix strengths and fiber types, the mechanism of coarse silica sand on ECC tensile performance is different. In this paper, coarse silica sand was introduced into PVA fiber (PVA-ECCs) and PE fiber reinforced ECCs (PE-ECCs), and the impact of silica sand with different particle sizes on the tensile properties of PVA-ECCs and PE-ECCs was investigated. Results indicate that a larger size of silica sand leads to more and larger pores and a looser matrix, which is not conducive to fiber dispersion and fiber/matrix interfacial bonding, resulting in a reduction in tensile strength. Additionally, increasing the silica sand particle size can availably decrease the matrix fracture toughness of PE-ECCs, making the matrix more prone to cracking, promoting saturation cracking behavior and increasing tensile strain capacity, whereas PVA-ECCs have the opposite trend. Moreover, microstructural analyses using SEM were conducted to analyze the impact of coarse silica sand and ultrafine silica sand on the tensile behaviors.

Recycled Tire Fibers Used as Reinforcement for Recycled Polyethylene Composites

This study proposes a simple approach to separate most rubber particles from recycled tire fibers (RTFs) and to determine their rubber content using thermogravimetric analysis (TGA)/calcination. Furthermore, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDAX), and Fourier transform infrared spectroscopy (FTIR) analyses are used to investigate the separation process and materials compositions. Afterwards, a series of composites based on recycled post-consumer low-density polyethylene (rLDPE) with clean fiber (CF) and residual ground rubber particles (GR) is prepared at different filler concentrations (0–30%) via extrusion compounding before using compression molding and injection molding for comparison. In all cases, injection molding leads to higher strength and modulus but lower elongation at break. The results show that incorporating 30 wt.% of CF into rLDPE yields a remarkable improvement in tensile strength (15%), tensile modulus (192%) and flexural modulus (142%). On the other hand, the incorporation of up to 30 wt.% of GR results in a reduction in both tensile strength and flexural modulus by 15%, confirming the critical role of the cleaning process for RTF in achieving the best results.

Experimental study on mechanical properties and bond behavior of wire and arc additive manufacturing steel bar

Wire and arc additive manufacturing (WAAM) technology is a feasible method for manufacturing steel bars to achieve the digital and automatic construction of reinforced concrete structures. However, the bond behavior between the WAAM steel bar and concrete does not meet the requirements of engineering applications. To enhance the bond behavior of the WAAM steel bar, the profiled corrugated steel bar is proposed. In this paper, one group of the natural roughness steel bar and three groups of the profiled corrugated steel bar with varying rib depths were fabricated using WAAM. A comprehensive description of the manufacturing principle and macrostructure of the WAAM steel bar was provided. Additionally, the mechanical properties and bond behavior of the WAAM steel bar were systematically investigated. The results show that the manufacturing precision of the WAAM steel bar can be improved by dynamically controlling the molten pool. The structure of the corrugated rib significantly enhances the bond strength and initial stiffness, with a slight reduction in the equivalent tensile strength and elongation compared to the WAAM natural roughness steel bar. Moreover, the normalized bond strength and initial stiffness of the WAAM profiled corrugated steel bar increase with the increase in rib depth. The experimental curve shows that the five-branch bond stress-slip model developed in this study can evaluate the bond behavior between the WAAM steel bar and concrete satisfactorily.

Investigation of alkali-silica reaction on mortars with alternative binder systems: Alkali activated Slags and Celitement

This study investigates the resistance against alkali-silica reaction (ASR) of two alternative binder systems, alkali-activated slag (AAS) and Celitement (Celite). Experimental studies on expansion and mechanical strength are carried out. Coupled kinetic and equilibrium thermodynamic modeling is used to clarify the role of binder chemistry on ASR. It was observed that under accelerated conditions OPC based mortars were more susceptible to ASR compared to AAS and Celite-based mortars. Based on experimental and modeling results, a correlation is shown between the dissolution of silica and the degree of expansion, but no correlation was found between the predicted amount of ASR products and the measured degree of expansion. Finally, the expansion degree could only be correlated with the reduction in compressive and flexural tensile strength for ASR-exposed samples.

Experimental testing of stainless steel bolt assemblies at elevated temperatures

This paper presents the results from a programme of elevated temperature tests focussing on the tensile behaviour of austenitic stainless steel bolts of grade A2–80 and A4–70. The tensile tests were carried out on bolt assemblies in the temperature range of 20 °C and 900 °C under a steady-state approach. Following the tests, a suite of tensile strength reduction factors were derived and these were compared with the existing bolt reduction factors proposed in the literature along with the codified values for equivalent stainless steel plate materials. The comparisons reveal that the manufacturing process of the stainless steel bolt, particularly the nature of thread rolling, can significantly affect their fire performance. For example, the present study reported a reduction factor of 0.098 for A4–70 at 800 °C as opposed to 0.176 (80% higher) and 0.34 (250% higher) for a bolt formed through a different manufacturing process and equivalent stainless steel plate materials, respectively. It was also concluded that while both the tensile strength and the ductility of stainless steel bolts gradually decrease with increasing temperature, stainless steel bolts retain a higher portion of their room temperature tensile strength compared with equivalent high strength carbon steel bolts beyond high temperatures of 450 °C for A2–80 bolts and 400 °C for A4–70 bolts.

Short-term durability of GFRP stirrups under wet-dry and freeze–thaw cycles

GFRP stirrups are a promising alternative to conventional steel stirrups due to their non-corrosive nature. However, their performance under cyclic exposure to wet-dry and freeze–thaw conditions in seawater needs to be evaluated to ensure their long-term durability and sustainability. This study investigates the tensile strength of glass fibre reinforced polymer (GFRP) stirrups under seawater wet-dry cycles and seawater and tap water freeze–thaw cycles. In total, 220stirrups in two different shapes, i.e. U and L shapes, and two different diameters, i.e. 6 mm and 8 mm were manufactured, conditioned, and tested under stirrup tensile test. Conditioned stirrups were subjected to 9 months and 18 months wet-dry cycles in seawater at 25 ℃, 40 ℃, and 60 ℃, and 9 months and 18 months freeze–thaw cycles in seawater and tap water. At first, the samples underwent a fast deterioration rate, which then decreased as the conditioning period progressed from 9 months to 18 months. The strength retention values of L-shaped stirrups were found to be higher than those of U-shaped stirrups, regardless of the environmental conditions or diameter. The maximum tensile strength reductions of 31%, 28% and 16% were observed, respectively after exposure to 18 months conditioning in seawater wet-dry cycles at 60 ℃, freeze–thaw in seawater, and freeze–thaw in tap water.

Long-term moisture diffusion in vinylester resin and CFRP rebars: A 20-year case study

Moisture absorption in polymer composites is a slow process that can take several decades, so it is often modelled without experimental verification. This unique study reports the moisture diffusion in epoxy vinylester (VE) resin and carbon fibre reinforced pultruded (CFRP) rebars over a period of 20 years at ambient temperature. Non-Fickian diffusion in VE is modelled by the unified two-phase model, which combines the bound water or hindered diffusion and the polymer relaxation concepts. Calculations based on the short-term projection with an unknown true saturation moisture content result in highly underestimated predictions. The true secondary equilibrium is 30–60% higher than the Fickian "pseudo-equilibrium". Moisture absorption of CFRP rebars at 98% RH was studied on short and long samples to identify the axial and radial diffusivities. The concept of apparent diffusivity, combining edge and anisotropy effects, is extended to the case of cylindrical rebars. Rebars absorb up to 0.55% of moisture following the Fickian behaviour, and the predictions are consistent with the calculations using the microstructural considerations. Calculations based on short-term projections result in highly overestimated axial diffusivity and the ratio of diffusion anisotropy. Long-term ageing of VE resulted in up to a 40% reduction in tensile strength and a 10 °C reduction in glass transition temperature. The interlaminar shear strength of CFRP rebars decreased by 30%, and its partial retention after moisture desorption indicated interphase degradation. The results will contribute to an understanding of water diffusion and environmental ageing of VE-based composites, bridging the gap between real-life degradation performance and accelerated durability predictions.

Effect of ECAP on Microstructure, Mechanical Properties, Corrosion Behavior, and Biocompatibility of Mg-Ca Alloy Composite

This study investigates the effects of incorporating MgO into magnesium–calcium (Mg-Ca) alloy composites and subjecting them to the equal channel angular pressing (ECAP) process on the resulting mechanical and corrosive properties, as well as biocompatibility. Initially, the incorporation of MgO into the Mg-Ca alloy composites did not yield significant improvements in grain refinement, tensile strength, or corrosion rate reduction, despite exhibiting improved biocompatibility. However, upon subjecting the Mg-Ca-MgO alloy composites to the ECAP process, noteworthy outcomes were observed. The ECAP process resulted in substantial grain refinement, leading to significant improvements in tensile strength. Furthermore, a marked decrease in corrosion rate was observed, indicating enhanced corrosion resistance. Additionally, the biocompatibility of the Mg-Ca-MgO alloy composites improved after undergoing the ECAP process. These findings highlight the synergistic effect of incorporating MgO and employing the ECAP process, providing valuable insights into the development of advanced magnesium-based materials with superior mechanical properties, reduced corrosion rates, and improved biocompatibility.

Effect of thermal ageing on electrical, mechanical properties of glass fiber reinforced polymer and its impact on service life

The mechanical and electrical properties of polymer composites often degrade due to environmental factors and shorten their service life. This article presents the effect of high temperatures on the mechanical and electrical characteristics of glass fiber reinforced composites and from the measurements, an attempt is made to predict the service life. Electrical conductivity, impedance and resistance are studied with a short-term temperature effect at 30, 60, 120, and 180 °C. The effect of temperature exposure at 120 and 160 °C for 1000, 2000, and 3000 h has been investigated to assess the changes in flexural, compressive, and tensile properties and for prediction of service life. Morphological studies are carried out to support some of the experimental results. The mechanical properties of composites are observed to deteriorate with the duration of aging. Flexural, tensile, and compressive strengths reveal a reduction of 8, 10, and 9%, after aging at 3000 h at 160 °C. The tensile strength and tensile modulus at 120 °C aged for 3000 h exhibit minimal changes as compared to unaged composites. However, with an increase in temperature to 160 °C, there is a reduction in tensile strength and modulus of composites by less than 10%, and 6% compared to composites with nanofillers. The variations in compression strength at 120 and 160 °C is not significant. Based on the reduction of tensile strength with temperature, the service life of composites has been estimated. For a predicted service life of 20 years, composites with nanofillers would be able to retain tensile strength of 90% of tensile strength.