This article investigates the interest of using in-situ piezoelectric(PZT and PVDF)disks to perform real-time Structural Health Monitoring(SHM)of glass fiber-reinforced polymer composites submitted to var-ious tensile...This article investigates the interest of using in-situ piezoelectric(PZT and PVDF)disks to perform real-time Structural Health Monitoring(SHM)of glass fiber-reinforced polymer composites submitted to var-ious tensile loadings.The goal is to evaluate the working range and SHM potential of such embedded transducers for relatively simple mechanical loadings,with the long-term aim of using them to monitor complete 3D structures submitted to more complex loadings.SHM is performed acquiring the electrical capacitance variation of the embedded transducers.To study the potential links between the insitu capacitance signal and the global response of the loaded host specimens,a multi-instrumentation composed of external Nondestructive Testing techniques was implemented on the surfaces of the specimens to search for multi-physical couplings between these external measurements and the capacitance curves.Results confirmed the non-intrusiveness of the embedded transducers,and allowed estimating their working domain.PZT capacitance signal follows well the mechanical loadings,but the piezoceramic transducer gets damaged after a determined relatively low strain level due to its brittleness.The limits of this working domain are extended by using a stretchable PolyVinylidene Fluoride(PVDF)polymer transducer,allowing this one to perform in-situ and real-time SHM of its host tensile specimens until failure.展开更多
The fluorescent complex Eu（TTA）2（Phen）（MA） （HTTA=2-Thenoyltrifluoroacetone, Phen=1,10-phenanthroline, MA=Maleic an- hydrider） was synthesized and characterized with elemental analysis, infrared spectrum （IR）...The fluorescent complex Eu（TTA）2（Phen）（MA） （HTTA=2-Thenoyltrifluoroacetone, Phen=1,10-phenanthroline, MA=Maleic an- hydrider） was synthesized and characterized with elemental analysis, infrared spectrum （IR）, scanning electron microscope （SEM）, X-ray Diffraction（XRD）, differential scanning calorimetry（DSC）, and fluorescent measurement. To explore the effect of different physical dispersion state of Eu-complex on the fluorescent property of the Eu-complex/silicon rubber composites, various quantifies of Eu（TTA）2（phen） （MA） were mixed with silicon rubber （SIR） and peroxide to form uncured composites. These composites were vulcanized to obtain cured Eu-complex/SiR composites at 250 ℃, which was higher than the melting-point of Eu-complex. The SEM, XRD, DSC, and the fluorescent measurement of these composites showed that both the complex molecules dispersed in the silicon rubber during the melting process and the parent Eu-complex particles had positive effects on fluorescent property, whereas the re-crystallized Eu-complex particles and the aggregating complexes formed during the melting-process had negative effects on fluorescent property. For the uncured composites, their fluorescent intensities almost did not change with the increasing amount of Eu-complex. Furthermore, for the composites with small content of Eu-complex, their fluorescent intensities decreased significantly after curing, and this difference in fluorescent intensity became smaller as the content of Eu-complex increases.展开更多
In order to enhance the interfacial adhesion of carbon fiber(CF)and polymer matrix,a multiscale gradient modulus intermediate layer with rigid-flexible(GO-PA)hierarchical structure was designed and fabricated between ...In order to enhance the interfacial adhesion of carbon fiber(CF)and polymer matrix,a multiscale gradient modulus intermediate layer with rigid-flexible(GO-PA)hierarchical structure was designed and fabricated between CFs and matrix by a facile and businesslike strategy.The polarity,roughness and wettability of CFs surface as well as the thickness of intermediate layer in composite have been significantly increased after rigid-flexible hierarchical structure was constructed.The IFSS,ILSS,compression and impact toughness manifested that the hierarchical structure could bring about a fantastic improvement(76.8%,46.4%,40.7%and 37.8%)for the interfacial and mechanical properties than other previous reports.Consequently,the establishment of CF surface with gradient modulus rigid-flexible hierarchical structure via regulation of nanoparticles and polymer array would open a new,viable and promising route to obtaining high-performance composites.展开更多
The use of terahertz time-domain spectroscopy(THz-TDS)for the nondestructive testing and evaluation(NDT&E)of materials and structural systems has attracted significant attention over the past two decades due to it...The use of terahertz time-domain spectroscopy(THz-TDS)for the nondestructive testing and evaluation(NDT&E)of materials and structural systems has attracted significant attention over the past two decades due to its superior spatial resolution and capabilities of detecting and characterizing defects and structural damage in non-conducting materials.In this study,the THz-TDS system is used to detect,localize and evaluate hidden multi-delamination defects(i.e.,a three-level multi-delamination system)in multilayered GFRP composite laminates.To obtain accurate results,a wavelet shrinkage de-noising algorithm is used to remove the noise from the measured time-of-flight(TOF)signals.The thickness and location of each delamination defect in the z-direction(i.e.,through-the-thickness direction)are calculated from the de-noised TOF signals considering the interaction between the pulsed THz waves and the different interfaces in the GFRP composite laminates.A comparison between the actual and the measured thickness values of the delamination defects before and after the wavelet shrinkage denoising process indicates that the latter provides better results with less than 3.712%relative error,while the relative error of the non-de-noised signals reaches 16.388%.Also,the power and absorbance levels of the THz waves at every interface with different refractive indices in the GFRP composite laminates are evaluated based on analytical and experimental approaches.The present study provides an adequate theoretical analysis that could help NDT&E specialists to estimate the maximum thickness of GFRP composite materials and/or structures with different interfaces that can be evaluated by the THz-TDS.Also,the accuracy of the obtained results highlights the capabilities of the THz-TDS for the NDT&E of multilayered GFRP composite laminates.展开更多
PLLA-magnesium composites have been widely investigated as potential biodegradable materials for bone implants.Lower/higher corrosion resistance of the crystalized/amorphous magnesium alloys allows tailoring of biodeg...PLLA-magnesium composites have been widely investigated as potential biodegradable materials for bone implants.Lower/higher corrosion resistance of the crystalized/amorphous magnesium alloys allows tailoring of biodegradability rate.In this work,the amorphous Mg_(65)Zn_(30)Ca_(5)was investigated versus traditional crystalized Mg_(65)Zn_(30)Ca_(5),and a PLLA-Mg_(65)Zn_(30)Ca_(5)composite has been successfully fabricated using hot injection process.Furthermore,the high corrosion resistance of the amorphous Mg_(65)Zn_(30)Ca_(5)prevented the high alkalization and deterioration of mechanical strength.In addition,the high Zn content intended to improve the glass forming ability,also enhances the anti-bacterial property of the PLLA-Mg_(65)Zn_(30)Ca_(5)composite.The remarkable performance of the PLLA-Mg_(65)Zn_(30)Ca_(5)composite shows its promising application in bone repair and tissue regeneration.展开更多
The natural rubber/zinc disorbate composite was prepared by the in situ formation of zinc disorbate from zinc oxide and sorbic acid in natural rubber. The structure variations of fillers during mixing and vulcanizatio...The natural rubber/zinc disorbate composite was prepared by the in situ formation of zinc disorbate from zinc oxide and sorbic acid in natural rubber. The structure variations of fillers during mixing and vulcanization processes were studied by X-ray diffraction(XRD) and Fourier-transform infrared spectroscopy(FTIR). The effects of zinc disorbate amount on processing performance and glass transition temperature(Tg) of compounds and the mechanical properties of vulcanizates were also determined. The XRD and FTIR analyses results indicate that the zinc disorbate is formed from the reaction of zinc oxide and sorbic acid during the mixing procedure followed by graft copolymerizing with NR molecules to form composite networks during vulcanization, which is initiated by dicumyl peroxide. Thus the mechanical properties of NR-based composite are increased significantly and Tg shifted towards to higher temperature.展开更多
Composite made of short-cut carbon fiber mat and vinyl ester resin was observed to be an effective sensor for tensile strain up to 6 000με. Based on its strain sensitivity, a skin-like sensitive layer which can cont...Composite made of short-cut carbon fiber mat and vinyl ester resin was observed to be an effective sensor for tensile strain up to 6 000με. Based on its strain sensitivity, a skin-like sensitive layer which can continuously cover the structural surface to sense strain in large area was developed. The sensitive layer was applied to continuously monitor the deformation of a simply supported beam. The result indicates that the fractional change in electrical resistance of the sensitive layer reversibly reflects the beam deformation in each section and describes the distribution of the average strain of the beam. The effect of temperature change on the monitoring was studied by monitoring tests conducted at different temperatures ranging from 20 to 80 ℃, which reveals temperature sensitivity in the sensitive layer and the temperature dependence of the piezoresistive behavior when the temperature exceeds 50 ℃. By the application of differential conaection principle, a method for temperature compensation was established and the gauge factor for the monitoring was dramatically increased. This method was verified experimentally.展开更多
It is well known that voids have detrimental effects on the performance of composites. This study aims to provide a practical method for predicting the effects of process induced voids on the properties of composites....It is well known that voids have detrimental effects on the performance of composites. This study aims to provide a practical method for predicting the effects of process induced voids on the properties of composites. Representative volume elements （RVE） for carbon fibre/epoxy composites of various fibre volume fractions and void contents are created, and the moduli and strengths are derived by finite element anal- ysis （FEA）. Regression models are fitted to the FEA data for predicting composite properties including tensile, compressive and shear. The strengths of composite laminates including tensile strngth and interlaminar shear strength （ILSS） are calculated with the aid of the developed models. The model predictions are compared with various experimental data and good agreement is found. The outcome from this study provides a useful optimisation and robust design tool for realising affordable composite prod- ucts when process induced voids are taken into account.展开更多
文摘This article investigates the interest of using in-situ piezoelectric(PZT and PVDF)disks to perform real-time Structural Health Monitoring(SHM)of glass fiber-reinforced polymer composites submitted to var-ious tensile loadings.The goal is to evaluate the working range and SHM potential of such embedded transducers for relatively simple mechanical loadings,with the long-term aim of using them to monitor complete 3D structures submitted to more complex loadings.SHM is performed acquiring the electrical capacitance variation of the embedded transducers.To study the potential links between the insitu capacitance signal and the global response of the loaded host specimens,a multi-instrumentation composed of external Nondestructive Testing techniques was implemented on the surfaces of the specimens to search for multi-physical couplings between these external measurements and the capacitance curves.Results confirmed the non-intrusiveness of the embedded transducers,and allowed estimating their working domain.PZT capacitance signal follows well the mechanical loadings,but the piezoceramic transducer gets damaged after a determined relatively low strain level due to its brittleness.The limits of this working domain are extended by using a stretchable PolyVinylidene Fluoride(PVDF)polymer transducer,allowing this one to perform in-situ and real-time SHM of its host tensile specimens until failure.
基金the National Natural Science Foundation of China,the China Energy Conservation Investment Corporation (50173004 and 50503002)the Beijing New Star Project (2003A11)+2 种基金the National High-Tech. Research Developing Foundation (863,2003AA324030)Beijing Municipal Commission of Education (JD100100403)National Key Project of Scientific and Technical Supporting Programs Funded by Ministry of Science & Technology of China (2006BAE03B)
文摘The fluorescent complex Eu（TTA）2（Phen）（MA） （HTTA=2-Thenoyltrifluoroacetone, Phen=1,10-phenanthroline, MA=Maleic an- hydrider） was synthesized and characterized with elemental analysis, infrared spectrum （IR）, scanning electron microscope （SEM）, X-ray Diffraction（XRD）, differential scanning calorimetry（DSC）, and fluorescent measurement. To explore the effect of different physical dispersion state of Eu-complex on the fluorescent property of the Eu-complex/silicon rubber composites, various quantifies of Eu（TTA）2（phen） （MA） were mixed with silicon rubber （SIR） and peroxide to form uncured composites. These composites were vulcanized to obtain cured Eu-complex/SiR composites at 250 ℃, which was higher than the melting-point of Eu-complex. The SEM, XRD, DSC, and the fluorescent measurement of these composites showed that both the complex molecules dispersed in the silicon rubber during the melting process and the parent Eu-complex particles had positive effects on fluorescent property, whereas the re-crystallized Eu-complex particles and the aggregating complexes formed during the melting-process had negative effects on fluorescent property. For the uncured composites, their fluorescent intensities almost did not change with the increasing amount of Eu-complex. Furthermore, for the composites with small content of Eu-complex, their fluorescent intensities decreased significantly after curing, and this difference in fluorescent intensity became smaller as the content of Eu-complex increases.
基金the National Natural Science Foundation of China(Nos.51803102 and 51903129)Natural Science Foundation of Shandong Province(Nos.201807070028 and 201808220020)+2 种基金the Source Innovation Project of Qingdao(No.19-6-2-75-cg)Industry and Education Cooperation Program of The Ministry of Education(Nos.201802201002,201901078008 and 201802230009)Opening Project of Shanxi Province Key Laboratory of Functional Nanocomposites,North University of China(No.NFCM202001).
文摘In order to enhance the interfacial adhesion of carbon fiber(CF)and polymer matrix,a multiscale gradient modulus intermediate layer with rigid-flexible(GO-PA)hierarchical structure was designed and fabricated between CFs and matrix by a facile and businesslike strategy.The polarity,roughness and wettability of CFs surface as well as the thickness of intermediate layer in composite have been significantly increased after rigid-flexible hierarchical structure was constructed.The IFSS,ILSS,compression and impact toughness manifested that the hierarchical structure could bring about a fantastic improvement(76.8%,46.4%,40.7%and 37.8%)for the interfacial and mechanical properties than other previous reports.Consequently,the establishment of CF surface with gradient modulus rigid-flexible hierarchical structure via regulation of nanoparticles and polymer array would open a new,viable and promising route to obtaining high-performance composites.
基金National Natural Science Foundation of China(Grant Nos.52275096,52005108,52275523)Fuzhou-Xiamen-Quanzhou National Independent Innovation Demonstration Zone High-end Equipment Vibration and Noise Detection and Fault Diagnosis Collaborative Innovation Platform ProjectFujian Provincial Major Research Project(Grant No.2022HZ024005)。
文摘The use of terahertz time-domain spectroscopy(THz-TDS)for the nondestructive testing and evaluation(NDT&E)of materials and structural systems has attracted significant attention over the past two decades due to its superior spatial resolution and capabilities of detecting and characterizing defects and structural damage in non-conducting materials.In this study,the THz-TDS system is used to detect,localize and evaluate hidden multi-delamination defects(i.e.,a three-level multi-delamination system)in multilayered GFRP composite laminates.To obtain accurate results,a wavelet shrinkage de-noising algorithm is used to remove the noise from the measured time-of-flight(TOF)signals.The thickness and location of each delamination defect in the z-direction(i.e.,through-the-thickness direction)are calculated from the de-noised TOF signals considering the interaction between the pulsed THz waves and the different interfaces in the GFRP composite laminates.A comparison between the actual and the measured thickness values of the delamination defects before and after the wavelet shrinkage denoising process indicates that the latter provides better results with less than 3.712%relative error,while the relative error of the non-de-noised signals reaches 16.388%.Also,the power and absorbance levels of the THz waves at every interface with different refractive indices in the GFRP composite laminates are evaluated based on analytical and experimental approaches.The present study provides an adequate theoretical analysis that could help NDT&E specialists to estimate the maximum thickness of GFRP composite materials and/or structures with different interfaces that can be evaluated by the THz-TDS.Also,the accuracy of the obtained results highlights the capabilities of the THz-TDS for the NDT&E of multilayered GFRP composite laminates.
基金supported by National Natural Science Foundation of China(Grant No.51471120)
文摘PLLA-magnesium composites have been widely investigated as potential biodegradable materials for bone implants.Lower/higher corrosion resistance of the crystalized/amorphous magnesium alloys allows tailoring of biodegradability rate.In this work,the amorphous Mg_(65)Zn_(30)Ca_(5)was investigated versus traditional crystalized Mg_(65)Zn_(30)Ca_(5),and a PLLA-Mg_(65)Zn_(30)Ca_(5)composite has been successfully fabricated using hot injection process.Furthermore,the high corrosion resistance of the amorphous Mg_(65)Zn_(30)Ca_(5)prevented the high alkalization and deterioration of mechanical strength.In addition,the high Zn content intended to improve the glass forming ability,also enhances the anti-bacterial property of the PLLA-Mg_(65)Zn_(30)Ca_(5)composite.The remarkable performance of the PLLA-Mg_(65)Zn_(30)Ca_(5)composite shows its promising application in bone repair and tissue regeneration.
基金Founded by the Central Public-interest Scientific Institution Basal Research Fund for Chinese Academy of Tropical Agricultural Sciences(No.1630122018005)
文摘The natural rubber/zinc disorbate composite was prepared by the in situ formation of zinc disorbate from zinc oxide and sorbic acid in natural rubber. The structure variations of fillers during mixing and vulcanization processes were studied by X-ray diffraction(XRD) and Fourier-transform infrared spectroscopy(FTIR). The effects of zinc disorbate amount on processing performance and glass transition temperature(Tg) of compounds and the mechanical properties of vulcanizates were also determined. The XRD and FTIR analyses results indicate that the zinc disorbate is formed from the reaction of zinc oxide and sorbic acid during the mixing procedure followed by graft copolymerizing with NR molecules to form composite networks during vulcanization, which is initiated by dicumyl peroxide. Thus the mechanical properties of NR-based composite are increased significantly and Tg shifted towards to higher temperature.
基金Funded by the National Natural Science Foundation of China(No.50878169)the Project of State Key Laboratory of Refractories and Metallurgy(Wuhan University of Science and Technology)(No.G201407)
文摘Composite made of short-cut carbon fiber mat and vinyl ester resin was observed to be an effective sensor for tensile strain up to 6 000με. Based on its strain sensitivity, a skin-like sensitive layer which can continuously cover the structural surface to sense strain in large area was developed. The sensitive layer was applied to continuously monitor the deformation of a simply supported beam. The result indicates that the fractional change in electrical resistance of the sensitive layer reversibly reflects the beam deformation in each section and describes the distribution of the average strain of the beam. The effect of temperature change on the monitoring was studied by monitoring tests conducted at different temperatures ranging from 20 to 80 ℃, which reveals temperature sensitivity in the sensitive layer and the temperature dependence of the piezoresistive behavior when the temperature exceeds 50 ℃. By the application of differential conaection principle, a method for temperature compensation was established and the gauge factor for the monitoring was dramatically increased. This method was verified experimentally.
文摘It is well known that voids have detrimental effects on the performance of composites. This study aims to provide a practical method for predicting the effects of process induced voids on the properties of composites. Representative volume elements （RVE） for carbon fibre/epoxy composites of various fibre volume fractions and void contents are created, and the moduli and strengths are derived by finite element anal- ysis （FEA）. Regression models are fitted to the FEA data for predicting composite properties including tensile, compressive and shear. The strengths of composite laminates including tensile strngth and interlaminar shear strength （ILSS） are calculated with the aid of the developed models. The model predictions are compared with various experimental data and good agreement is found. The outcome from this study provides a useful optimisation and robust design tool for realising affordable composite prod- ucts when process induced voids are taken into account.
