The aim of the present paper is to reveal the influence of different fiber orientations on the tool wear evolution and wear mechanism. Side-milling experiments with large-diameter milling tools are conducted. A finite...The aim of the present paper is to reveal the influence of different fiber orientations on the tool wear evolution and wear mechanism. Side-milling experiments with large-diameter milling tools are conducted. A finite element(FE) cutting model of carbon fiber reinforced plastics(CFRP)is established to get insight into the cutting stress status at different wear stages. The results show that different fiber orientations bring about distinct differences in the extent, profile and mechanism of tool wear. Severer wear occurs when cutting 45° and 90° plies, followed by 0°, correspondingly,the least wear is obtained when θ = 135°(θ represents the orientation of fibers). Moreover, the worn profiles of cutting tools when θ = 0° and 45° are waterfall edge, while round edge occurs whenθ = 135° and a combined shape of waterfall and round edge is obtained when θ = 90°. The wear mechanisms under different fiber orientations are strongly dependent on the cutting stress distributions. The evolution of tool wear profile is basically consistent with the stress distribution on the tool surface at different wear stages, and the extent of tool wear is determined by the magnitude of stress on the tool surface. Besides, the worn edges produce an actual negative clearance angle,which decreases the actual cutting thickness and leads to compressing and bending failure of fibers beneath the cutting region as well as low surface qualities.展开更多
In this study,the effect of fiber angle on the tensile load-bearing performance and damage failure characteristics of glass composite laminates was investigated experimentally,analytically,and numerically.The glass fa...In this study,the effect of fiber angle on the tensile load-bearing performance and damage failure characteristics of glass composite laminates was investigated experimentally,analytically,and numerically.The glass fabric in the laminate was perfectly aligned along the load direction(i.e.,at 0°),offset at angles of 30°and 45°,or mixed in different directions(i.e.,0°/30°or 0°/45°).The composite laminates were fabricated using vacuum-assisted resin molding.The influence of fiber orientation angle on the mechanical properties and stiffness degradation of the laminates was studied via cyclic tensile strength tests.Furthermore,simulations have been conducted using finite element analysis and analytical approaches to evaluate the influence of fiber orientation on the mechanical performance of glass laminates.Experimental testing revealed that,although the composite laminates laid along the 0°direction exhibited the highest stiffness and strength,their structural performance deteriorated rapidly.We also determined that increasing the fiber offset angle(i.e.,30°)could optimize the mechanical properties and damage failure characteristics of glass laminates.The results of the numerical and analytical approaches demonstrated their ability to capture the mechanical behavior and damage failure modes of composite laminates with different fiber orientations,which may be used to prevent the catastrophic failures that occur in composite laminates.展开更多
Increasing data indicate that cancer cell migration is regulated by extracellular matrixes and their surrounding biochemical microenvironment,playing a crucial role in pathological processes such as tumor invasion and...Increasing data indicate that cancer cell migration is regulated by extracellular matrixes and their surrounding biochemical microenvironment,playing a crucial role in pathological processes such as tumor invasion and metastasis.However,conventional two-dimensional cell culture and animal models have limitations in studying the influence of tumor microenvironment on cancer cell migration.Fortunately,the further development of microfluidic technology has provided solutions for the study of such questions.We utilize microfluidic chip to build a random collagen fiber microenvironment(RFM)model and an oriented collagen fiber microenvironment(OFM)model that resemble early stage and late stage breast cancer microenvironments,respectively.By combining cell culture,biochemical concentration gradient construction,and microscopic imaging techniques,we investigate the impact of different collagen fiber biochemical microenvironments on the migration of breast cancer MDA-MB-231-RFP cells.The results show that MDA-MB-231-RFP cells migrate further in the OFM model compared to the RFM model,with significant differences observed.Furthermore,we establish concentration gradients of the anticancer drug paclitaxel in both the RFM and OFM models and find that paclitaxel significantly inhibits the migration of MDA-MB-231-RFP cells in the RFM model,with stronger inhibition on the high concentration side compared to the low concentration side.However,the inhibitory effect of paclitaxel on the migration of MDA-MB-231-RFP cells in the OFM model is weak.These findings suggest that the oriented collagen fiber microenvironment resembling the late-stage tumor microenvironment is more favorable for cancer cell migration and that the effectiveness of anticancer drugs is diminished.The RFM and OFM models constructed in this study not only provide a platform for studying the mechanism of cancer development,but also serve as a tool for the initial measurement of drug screening.展开更多
Automatic production and precise positioning of carbon fiber reinforced plastics (FRP) require precise detection of the fiber orientations. This paper presents an automatic method for detecting fiber orientations of...Automatic production and precise positioning of carbon fiber reinforced plastics (FRP) require precise detection of the fiber orientations. This paper presents an automatic method for detecting fiber orientations of sewed carbon fibers in the production of FRP. Detection was achieved by appropriate use of regional filling, edge detection operators, autocorrelation methods, and the Hough transformation. Regional filling was used to reduce the influence of the sewed regions, autocorrelation was used to clarify the fiber directions, edge detection operators were used to extract the edge features for the fiber orientations, and the Hough transformation was used to calculate the angles. Results for two kinds of carbon fiber materials show that the method is relatively quick and precise for detecting carbon fiber orientations.展开更多
Three different kinds of closure model of fiber orientation tensors were applied to simulate numerically the hydrodynamic stability of fiber suspensions in a channel flow. The effects of closure models and three_dimen...Three different kinds of closure model of fiber orientation tensors were applied to simulate numerically the hydrodynamic stability of fiber suspensions in a channel flow. The effects of closure models and three_dimensional (3_D) orientation distribution of fibers on the results of stability analysis were examined. It is found that the relationship of the behavior in hydrodynamic stability and the parameter of the fiber given by all the three models are the same. However, the attenuation of flow instability is most distinct using 3_D hybrid model because the orientation of the fiber departures from the flow direction, and least apparent using its 2_D counterpart for that the fibers show a tendency towards alignment with the flow direction in this case.展开更多
A model relating the translational and rotational transport of orientation distribution function (ODF) of fibers to the gradient of mean ODF and the dispersion coefficients is proposed to derive the mean equation fo...A model relating the translational and rotational transport of orientation distribution function (ODF) of fibers to the gradient of mean ODF and the dispersion coefficients is proposed to derive the mean equation for the ODE Then the ODF of fibers is predicted by numerically solving the mean equation for the ODF together with the equations of turbulent boundary layer flow. Finally the shear stress and first normal stress difference of fiber suspensions are obtained. The results, some of which agree with the available relevant experimental data, show that the most fibers tend to orient to the flow direction. The fiber aspect ratio and Reynolds number have significant and negligible effects on the orientation dis- tribution of fibers, respectively. The additional normal stress due to the presence of fibers is anisotropic. The shear stress of fiber suspension is larger than that of Newtonian solvent, and the first normal stress difference is much less than the shear stress. Both the additional shear stress and the first normal stress difference increase with increasing the fiber concentration and decreasing fiber aspect ratio.展开更多
Engineered cementitious composites(ECC),also known as bendable concrete,were developed based on engineering the interactions between fibers and cementitious matrix.The orientation of fibers,in this regard,is one of th...Engineered cementitious composites(ECC),also known as bendable concrete,were developed based on engineering the interactions between fibers and cementitious matrix.The orientation of fibers,in this regard,is one of the major factors influencing the ductile behavior of this material.In this study,fiber orientation distributions in ECC beams influenced by different casting techniques are evaluated via numerical modeling of the casting process.Two casting directions and two casting positions of the funnel outlet with beam specimens are modeled using a particle-based smoothed particle hydrodynamics(SPH)method.In this SPH approach,fresh mortar and fiber are discretized by separated mortar and fiber particles,which smoothly interact in the computational domain of SPH.The movement of fiber particles is monitored during the casting simulation.Then,the fiber orientations at different sections of specimens are determined after the fresh ECC stops flowing in the formwork.The simulation results show a significant impact of the casting direction on fiber orientation distributions along the longitudinal wall of beams,which eventually influence the flexural strength of beams.In addition,casting positions show negligible influences on the orientation distribution of fibers in the short ECC beam,except under the pouring position.展开更多
The process of in situ tumors developing into malignant tumors and exhibiting invasive behavior is extremely complicated.From a biophysical point of view,it is a phase change process affected by many factors,including...The process of in situ tumors developing into malignant tumors and exhibiting invasive behavior is extremely complicated.From a biophysical point of view,it is a phase change process affected by many factors,including cell-to-cell,cell-to-chemical material,cell-to-environment interaction,etc.In this study,we constructed spheroids based on green fluorescence metastatic breast cancer cells MDA-MB-231 to simulate malignant tumors in vitro,while constructed a three-dimensional(3D)biochip to simulate a micro-environment for the growth and invasion of spheroids.In the experiment,the 3D spheroid was implanted into the chip,and the oriented collagen fibers controlled by collagen concentration and injection rate could guide the MDA-MB-231 cells in the spheroid to undergo directional invasion.The experiment showed that the oriented fibers greatly accelerated the invasion speed of MDA-MB-231 cells compared with the traditional uniform tumor micro-environment,namely obvious invasive branches appeared on the spheroids within 24 hours.In order to analyze this interesting phenomenon,we have developed a quantitative analyzing approach to explore strong angle correlation between the orientation of collagen fibers and invasive direction of cancer cell.The results showed that the oriented collagen fibers produced by the chip can greatly stimulate the invasion potential of cancer cells.This biochip is not only conducive to modeling cancer cell metastasis and studying cell invasion mechanisms,but also has the potential to build a quantitative evaluation platform that can be used in future chemical drug treatments.展开更多
This paper proposes an individual fitness method genetic algorithm(IFM-GA)for carbon fiber-reinforced plastic(CFRP).The strength of CFRP depends on the carbon fiber allocation and orientation.Waste carbon fiber is gen...This paper proposes an individual fitness method genetic algorithm(IFM-GA)for carbon fiber-reinforced plastic(CFRP).The strength of CFRP depends on the carbon fiber allocation and orientation.Waste carbon fiber is generated if this design is inappropriate.Consequently,CFRPs are less cost-effective.It is necessary to optimize the allocation and orientation as design variables to solve this problem.The problem involves combinatorial optimization.The genetic algorithm(GA)is suitable for combinatorial optimization.However,it is difficult to obtain an optimal solution using the GA owing to the large number of combinations.Hence,the IFM-GA is developed in this study.It is a GA-based method with a different fitness calculation.The GA calculates the fitness of each design,whereas the IFM-GA calculates the fitness of each design element.As a result,the IFM-GA yields a higher-stiffness design than the GA.To conclude,the IFM-GA can enable optimum fiber allocation and orientation,whereas the GA cannot.展开更多
The influence of fiber orientation,flow yaw angle and length-to-thickness ratio on flutter characteristics of angle-ply laminated plates in supersonic flow is studied by finite element approach.The structural model is...The influence of fiber orientation,flow yaw angle and length-to-thickness ratio on flutter characteristics of angle-ply laminated plates in supersonic flow is studied by finite element approach.The structural model is established using the Reissner-Mindlin theory in which the transverse shear deformation is considered.The aerodynamic pressure is evaluated by the quasi-steady first-order piston theory.The equations of motion are formulated based on the principle of virtual work.With the harmonic motion assumption,the flutter boundary is determined by solving a series of complex eigenvalue problems.Numerical study shows that (1) The flutter dynamic pressure and the coalescence of flutter modes depend on fiber orientation,flow yaw angle and length-to-thickness ratio;(2) The laminated plate with all fibers aligned with the flow direction gives the highest flutter dynamic pressure,but a slight yawing of the flow from the fiber orientation results in a sharp decrease of the flutter dynamic pressure;(3) The angle-ply laminated plate with fiber orientation angle equal to flow yaw angle gives high flutter dynamic pressure,but not the maximum flutter dynamic pressure;(4) With the decrease of length-to-thickness ratio,an adverse effect due to mode transition on the flutter dynamic pressure is found.展开更多
We report on the optical trapping and orientation of Escherichia coli(E.coli) cells using two tapered fiber probes.With a laser beam at 980 nm wavelength launched into probe I, an E. coli chain consisting of three cel...We report on the optical trapping and orientation of Escherichia coli(E.coli) cells using two tapered fiber probes.With a laser beam at 980 nm wavelength launched into probe I, an E. coli chain consisting of three cells was formed at the tip of probe I. After launching a beam at 980 nm into probe II, the E.coli at the end of the chain was trapped and oriented via the optical torques yielded by two probes. The orientation of the E. coli was controlled by adjusting the laser power of probe II. Experimental results were interpreted by theoretical analysis and numericalsimulations.展开更多
The orientation of suspended fibers in the turbulent contraction is strongly related to the contraction ratio,which in some cases may be detrimental to the actual production.Here for a certain contraction ratio,the co...The orientation of suspended fibers in the turbulent contraction is strongly related to the contraction ratio,which in some cases may be detrimental to the actual production.Here for a certain contraction ratio,the contraction geometry shape is optimized to obtain the desired fiber orientation.In view of the nonlinearity and the complexity of the turbulent flow equations,the parameterized shape curve,the dynamic mesh and a quasi-static assumption are used to model the contraction with the variable boundary and to search the optimal solution.Furthermore the Reynolds stress model and the fiber orientation distribution function are solved for various wall shapes.The fiber orientation alignment at the outlet is taken as the optimization objective.Finally the effect of the wall shape on the flow mechanism is discussed in detail.展开更多
Fiber-reinforced composite materials have excellent specific stiffness,specific strength,and other properties,and have been increasingly widely used in the field of advanced structures.However,the design space dimensi...Fiber-reinforced composite materials have excellent specific stiffness,specific strength,and other properties,and have been increasingly widely used in the field of advanced structures.However,the design space dimensions of fiber-reinforced composite materials will expand explosively,bringing challenges to the efficient analysis and optimal design of structures.In this paper,the authors propose an explicit topology optimization method based on the moving morphable components for designing the fiber-reinforced material.We constrain the intersection area between components to guarantee the independence of each component and avoid the situation that one component is cut by other components.Adding the fiber orientation angle as a design variable,the method can optimize the structural layout and the fiber orientation angle concurrently under the given number of fiber layers and layer thickness.We use two classical examples to verify the feasibility and accuracy of the proposed method.The optimized results are in good agreement with the designs obtained by the 99-line code.The authors also popularize the proposed method to engineering structure.The results manifest that the proposed method has great value in engineering application.展开更多
Spinal cord injury(SCI)is an overwhelming and incurable disabling condition,for which increasing forms of multifunctional biomaterials are being tested,but with limited progression.The promising material should be abl...Spinal cord injury(SCI)is an overwhelming and incurable disabling condition,for which increasing forms of multifunctional biomaterials are being tested,but with limited progression.The promising material should be able to fill SCI-induced cavities and direct the growth of new neurons,with effective drug loading to improve the local micro-organism environment and promote neural tissue regeneration.In this study,a double crosslinked biomimetic composite hydrogel comprised of acellularized spinal cord matrix(ASCM)and gelatin-acrylated-β-cyclodextrin-polyethene glycol diacrylate(designated G-CD-PEGDA)hydrogel,loaded with WAY-316606 to activate canonical Wnt/β-catenin signaling,and reinforced by a bundle of three-dimensionally printed aligned polycaprolactone(PCL)microfibers,was constructed.The G-CD-PEGDA component endowed the composite hydrogel with a dynamic structure with a self-healing capability which enabled cell migration,while the ASCM component promoted neural cell affinity and proliferation.The diffusion of WAY-316606 could recruit endogenous neural stem cells and improve neuronal differentiation.The aligned PCL microfibers guided neurite elongation in the longitudinal direction.Animal behavior studies further showed that the composite hydrogel could significantly recover the motor function of rats after SCI.This study provides a proficient approach to produce a multifunctional system with desirable physiological,chemical,and topographical cues for treating patients with SCI.展开更多
Uni-directional carbon/carbon composites with high thermal conductivity are suitable to supply continuous thermal protection for future reentry vehicles since they could reduce surface temperature and ablation rates s...Uni-directional carbon/carbon composites with high thermal conductivity are suitable to supply continuous thermal protection for future reentry vehicles since they could reduce surface temperature and ablation rates simultaneously in harsh environments.In this work,the high thermal conductivity carbon/carbon composites were prepared by chemical vapor infiltration.After heat-treatment,both their open porosity and internal friction increase due to the fiber/matrix thermal expansion mismatch;while their thermal conductive performance become better due to more complete carbon structure.With raising heat-treatment temperature from 1800℃to 2450℃,the mass and linear ablation rates of C/C composites with fibers vertical to the oxyacetylene torch for 60 s decrease from 0.66 mg/s and 2.95μm/s to 0.51 mg/s and 2.05μm/s respectively.The improved ablation resistance is resulted from the increased thermal conductivity from 282 to 508 W/(m·K)and more carbon fibers exposed to the flame during ablation,which have better oxidation resistance than those of carbon matrix.While such ablation rates become larger for composites with fibers parallel to the flame,from 1.02 mg/s and 3.73μm/s to 1.28 mg/s and 5.0μm/s respectively since the ablation occurred more easily through gaps at the fiber/matrix interfaces,which become larger and are always exposed to the flame for this case.展开更多
Experiments carried out using a lung model with a single horizontal bifurcation under different steady inhalation conditions explored the orientation of depositing carbon fibers, and particle deposition frac- tions. T...Experiments carried out using a lung model with a single horizontal bifurcation under different steady inhalation conditions explored the orientation of depositing carbon fibers, and particle deposition frac- tions. The orientations of deposited fibers were obtained from micrographs. Specifically, the effects of the sedimentation parameter (γ), fiber length, and flow rate on orientations were analyzed. Our results indicate that gravitational effect on deposition cannot be neglected for 0.0228 〈 γ 〈 0.247. The absolute orientation angle of depositing fibers decreased linearly with increasing y for values 0.0228 〈 γ 〈 0.15. Correspondence between Stokes numbers and y suggests these characteristics can be used to estimate fiber deposition in the lower airways. Computer simulations with sphere-equivalent diameter models for the fibers explored deposition efficiency vs. Stokes number. Using the volume-equivalent diameter model, our experimental data for the horizontal bifurcation were replicated. Results for particle deposition using a lung model with a vertical bifurcation indicate that body position also affects deposition.展开更多
基金supported by the National Natural Science Foundation of China(No.52075380)the Natural Science Foundation of Tianjin(Nos.21JCYBJC00610 and 19JCYBJC19000).
文摘The aim of the present paper is to reveal the influence of different fiber orientations on the tool wear evolution and wear mechanism. Side-milling experiments with large-diameter milling tools are conducted. A finite element(FE) cutting model of carbon fiber reinforced plastics(CFRP)is established to get insight into the cutting stress status at different wear stages. The results show that different fiber orientations bring about distinct differences in the extent, profile and mechanism of tool wear. Severer wear occurs when cutting 45° and 90° plies, followed by 0°, correspondingly,the least wear is obtained when θ = 135°(θ represents the orientation of fibers). Moreover, the worn profiles of cutting tools when θ = 0° and 45° are waterfall edge, while round edge occurs whenθ = 135° and a combined shape of waterfall and round edge is obtained when θ = 90°. The wear mechanisms under different fiber orientations are strongly dependent on the cutting stress distributions. The evolution of tool wear profile is basically consistent with the stress distribution on the tool surface at different wear stages, and the extent of tool wear is determined by the magnitude of stress on the tool surface. Besides, the worn edges produce an actual negative clearance angle,which decreases the actual cutting thickness and leads to compressing and bending failure of fibers beneath the cutting region as well as low surface qualities.
文摘In this study,the effect of fiber angle on the tensile load-bearing performance and damage failure characteristics of glass composite laminates was investigated experimentally,analytically,and numerically.The glass fabric in the laminate was perfectly aligned along the load direction(i.e.,at 0°),offset at angles of 30°and 45°,or mixed in different directions(i.e.,0°/30°or 0°/45°).The composite laminates were fabricated using vacuum-assisted resin molding.The influence of fiber orientation angle on the mechanical properties and stiffness degradation of the laminates was studied via cyclic tensile strength tests.Furthermore,simulations have been conducted using finite element analysis and analytical approaches to evaluate the influence of fiber orientation on the mechanical performance of glass laminates.Experimental testing revealed that,although the composite laminates laid along the 0°direction exhibited the highest stiffness and strength,their structural performance deteriorated rapidly.We also determined that increasing the fiber offset angle(i.e.,30°)could optimize the mechanical properties and damage failure characteristics of glass laminates.The results of the numerical and analytical approaches demonstrated their ability to capture the mechanical behavior and damage failure modes of composite laminates with different fiber orientations,which may be used to prevent the catastrophic failures that occur in composite laminates.
基金support from the National Natural Science Foundation of China(Grant Nos.11974066,12174041,12104134,T2350007,and 12347178)the Fundamental and Advanced Research Program of Chongqing(Grant No.cstc2019jcyj-msxm X0477)+3 种基金the Natural Science Foundation of Chongqing(Grant No.CSTB2022NSCQMSX1260)the Science and Technology Research Program of Chongqing Municipal Education Commission(Grant No.KJQN202301333)the Scientific Research Fund of Chongqing University of Arts and Sciences(Grant Nos.R2023HH03 and P2022HH05)College Students’Innovation and Entrepreneurship Training Program of Chongqing Municipal(Grant No.S202310642002)。
文摘Increasing data indicate that cancer cell migration is regulated by extracellular matrixes and their surrounding biochemical microenvironment,playing a crucial role in pathological processes such as tumor invasion and metastasis.However,conventional two-dimensional cell culture and animal models have limitations in studying the influence of tumor microenvironment on cancer cell migration.Fortunately,the further development of microfluidic technology has provided solutions for the study of such questions.We utilize microfluidic chip to build a random collagen fiber microenvironment(RFM)model and an oriented collagen fiber microenvironment(OFM)model that resemble early stage and late stage breast cancer microenvironments,respectively.By combining cell culture,biochemical concentration gradient construction,and microscopic imaging techniques,we investigate the impact of different collagen fiber biochemical microenvironments on the migration of breast cancer MDA-MB-231-RFP cells.The results show that MDA-MB-231-RFP cells migrate further in the OFM model compared to the RFM model,with significant differences observed.Furthermore,we establish concentration gradients of the anticancer drug paclitaxel in both the RFM and OFM models and find that paclitaxel significantly inhibits the migration of MDA-MB-231-RFP cells in the RFM model,with stronger inhibition on the high concentration side compared to the low concentration side.However,the inhibitory effect of paclitaxel on the migration of MDA-MB-231-RFP cells in the OFM model is weak.These findings suggest that the oriented collagen fiber microenvironment resembling the late-stage tumor microenvironment is more favorable for cancer cell migration and that the effectiveness of anticancer drugs is diminished.The RFM and OFM models constructed in this study not only provide a platform for studying the mechanism of cancer development,but also serve as a tool for the initial measurement of drug screening.
基金Supported by the DAAD (German Academic Exchange Service) on Its Exchange Student Program
文摘Automatic production and precise positioning of carbon fiber reinforced plastics (FRP) require precise detection of the fiber orientations. This paper presents an automatic method for detecting fiber orientations of sewed carbon fibers in the production of FRP. Detection was achieved by appropriate use of regional filling, edge detection operators, autocorrelation methods, and the Hough transformation. Regional filling was used to reduce the influence of the sewed regions, autocorrelation was used to clarify the fiber directions, edge detection operators were used to extract the edge features for the fiber orientations, and the Hough transformation was used to calculate the angles. Results for two kinds of carbon fiber materials show that the method is relatively quick and precise for detecting carbon fiber orientations.
基金ProjectsupportedbytheNationalNaturalScienceFoundationofChina (No .1 0 3 72 0 90 )
文摘Three different kinds of closure model of fiber orientation tensors were applied to simulate numerically the hydrodynamic stability of fiber suspensions in a channel flow. The effects of closure models and three_dimensional (3_D) orientation distribution of fibers on the results of stability analysis were examined. It is found that the relationship of the behavior in hydrodynamic stability and the parameter of the fiber given by all the three models are the same. However, the attenuation of flow instability is most distinct using 3_D hybrid model because the orientation of the fiber departures from the flow direction, and least apparent using its 2_D counterpart for that the fibers show a tendency towards alignment with the flow direction in this case.
基金The project supported by the Major Program of National Natural Science Foundation of China(10632070)
文摘A model relating the translational and rotational transport of orientation distribution function (ODF) of fibers to the gradient of mean ODF and the dispersion coefficients is proposed to derive the mean equation for the ODE Then the ODF of fibers is predicted by numerically solving the mean equation for the ODF together with the equations of turbulent boundary layer flow. Finally the shear stress and first normal stress difference of fiber suspensions are obtained. The results, some of which agree with the available relevant experimental data, show that the most fibers tend to orient to the flow direction. The fiber aspect ratio and Reynolds number have significant and negligible effects on the orientation dis- tribution of fibers, respectively. The additional normal stress due to the presence of fibers is anisotropic. The shear stress of fiber suspension is larger than that of Newtonian solvent, and the first normal stress difference is much less than the shear stress. Both the additional shear stress and the first normal stress difference increase with increasing the fiber concentration and decreasing fiber aspect ratio.
基金This work belongs to the project No.T2021-97TD in 2021 funded by Ho Chi Minh City University of Technology and Education,Vietnam.
文摘Engineered cementitious composites(ECC),also known as bendable concrete,were developed based on engineering the interactions between fibers and cementitious matrix.The orientation of fibers,in this regard,is one of the major factors influencing the ductile behavior of this material.In this study,fiber orientation distributions in ECC beams influenced by different casting techniques are evaluated via numerical modeling of the casting process.Two casting directions and two casting positions of the funnel outlet with beam specimens are modeled using a particle-based smoothed particle hydrodynamics(SPH)method.In this SPH approach,fresh mortar and fiber are discretized by separated mortar and fiber particles,which smoothly interact in the computational domain of SPH.The movement of fiber particles is monitored during the casting simulation.Then,the fiber orientations at different sections of specimens are determined after the fresh ECC stops flowing in the formwork.The simulation results show a significant impact of the casting direction on fiber orientation distributions along the longitudinal wall of beams,which eventually influence the flexural strength of beams.In addition,casting positions show negligible influences on the orientation distribution of fibers in the short ECC beam,except under the pouring position.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11974066 and 11674043)the Fundamental Research Funds for the Central Universities,China(Grant No.2019CDYGYB007)the Natural Science Foundation of Chongqing,China(Grant No.cstc2019jcyj-msxmX0477).
文摘The process of in situ tumors developing into malignant tumors and exhibiting invasive behavior is extremely complicated.From a biophysical point of view,it is a phase change process affected by many factors,including cell-to-cell,cell-to-chemical material,cell-to-environment interaction,etc.In this study,we constructed spheroids based on green fluorescence metastatic breast cancer cells MDA-MB-231 to simulate malignant tumors in vitro,while constructed a three-dimensional(3D)biochip to simulate a micro-environment for the growth and invasion of spheroids.In the experiment,the 3D spheroid was implanted into the chip,and the oriented collagen fibers controlled by collagen concentration and injection rate could guide the MDA-MB-231 cells in the spheroid to undergo directional invasion.The experiment showed that the oriented fibers greatly accelerated the invasion speed of MDA-MB-231 cells compared with the traditional uniform tumor micro-environment,namely obvious invasive branches appeared on the spheroids within 24 hours.In order to analyze this interesting phenomenon,we have developed a quantitative analyzing approach to explore strong angle correlation between the orientation of collagen fibers and invasive direction of cancer cell.The results showed that the oriented collagen fibers produced by the chip can greatly stimulate the invasion potential of cancer cells.This biochip is not only conducive to modeling cancer cell metastasis and studying cell invasion mechanisms,but also has the potential to build a quantitative evaluation platform that can be used in future chemical drug treatments.
文摘This paper proposes an individual fitness method genetic algorithm(IFM-GA)for carbon fiber-reinforced plastic(CFRP).The strength of CFRP depends on the carbon fiber allocation and orientation.Waste carbon fiber is generated if this design is inappropriate.Consequently,CFRPs are less cost-effective.It is necessary to optimize the allocation and orientation as design variables to solve this problem.The problem involves combinatorial optimization.The genetic algorithm(GA)is suitable for combinatorial optimization.However,it is difficult to obtain an optimal solution using the GA owing to the large number of combinations.Hence,the IFM-GA is developed in this study.It is a GA-based method with a different fitness calculation.The GA calculates the fitness of each design,whereas the IFM-GA calculates the fitness of each design element.As a result,the IFM-GA yields a higher-stiffness design than the GA.To conclude,the IFM-GA can enable optimum fiber allocation and orientation,whereas the GA cannot.
基金supported by China Postdoctoral Science Founda-tion (20090451045)
文摘The influence of fiber orientation,flow yaw angle and length-to-thickness ratio on flutter characteristics of angle-ply laminated plates in supersonic flow is studied by finite element approach.The structural model is established using the Reissner-Mindlin theory in which the transverse shear deformation is considered.The aerodynamic pressure is evaluated by the quasi-steady first-order piston theory.The equations of motion are formulated based on the principle of virtual work.With the harmonic motion assumption,the flutter boundary is determined by solving a series of complex eigenvalue problems.Numerical study shows that (1) The flutter dynamic pressure and the coalescence of flutter modes depend on fiber orientation,flow yaw angle and length-to-thickness ratio;(2) The laminated plate with all fibers aligned with the flow direction gives the highest flutter dynamic pressure,but a slight yawing of the flow from the fiber orientation results in a sharp decrease of the flutter dynamic pressure;(3) The angle-ply laminated plate with fiber orientation angle equal to flow yaw angle gives high flutter dynamic pressure,but not the maximum flutter dynamic pressure;(4) With the decrease of length-to-thickness ratio,an adverse effect due to mode transition on the flutter dynamic pressure is found.
基金supported by the Program for Changjiang Scholars and Innovative Research Team in University (IRT13042)the National Natural Science Foundation of China (No. 61205165)
文摘We report on the optical trapping and orientation of Escherichia coli(E.coli) cells using two tapered fiber probes.With a laser beam at 980 nm wavelength launched into probe I, an E. coli chain consisting of three cells was formed at the tip of probe I. After launching a beam at 980 nm into probe II, the E.coli at the end of the chain was trapped and oriented via the optical torques yielded by two probes. The orientation of the E. coli was controlled by adjusting the laser power of probe II. Experimental results were interpreted by theoretical analysis and numericalsimulations.
基金supported by the National Natural Science Foundation of China(Grant No.11302110)the Public Project of Science and Technology Department of Zhejiang Province(Grant No.2015C31152)+1 种基金the Natural Science Foundation of Ningbo(Grant No.2014A610086)“Wang Weiming”Entrepreneurship Supporting Fund
文摘The orientation of suspended fibers in the turbulent contraction is strongly related to the contraction ratio,which in some cases may be detrimental to the actual production.Here for a certain contraction ratio,the contraction geometry shape is optimized to obtain the desired fiber orientation.In view of the nonlinearity and the complexity of the turbulent flow equations,the parameterized shape curve,the dynamic mesh and a quasi-static assumption are used to model the contraction with the variable boundary and to search the optimal solution.Furthermore the Reynolds stress model and the fiber orientation distribution function are solved for various wall shapes.The fiber orientation alignment at the outlet is taken as the optimization objective.Finally the effect of the wall shape on the flow mechanism is discussed in detail.
基金supports from the National Key Research and Development Plan(2020YFB1709401)the National Natural Science Foundation of China(11872138,11702048),Dalian Young TechStar Project(2019RQ045,2019RQ069)and the Scientific Research Fund Project of Education Department of Liaoning Province(JDL2020021).
文摘Fiber-reinforced composite materials have excellent specific stiffness,specific strength,and other properties,and have been increasingly widely used in the field of advanced structures.However,the design space dimensions of fiber-reinforced composite materials will expand explosively,bringing challenges to the efficient analysis and optimal design of structures.In this paper,the authors propose an explicit topology optimization method based on the moving morphable components for designing the fiber-reinforced material.We constrain the intersection area between components to guarantee the independence of each component and avoid the situation that one component is cut by other components.Adding the fiber orientation angle as a design variable,the method can optimize the structural layout and the fiber orientation angle concurrently under the given number of fiber layers and layer thickness.We use two classical examples to verify the feasibility and accuracy of the proposed method.The optimized results are in good agreement with the designs obtained by the 99-line code.The authors also popularize the proposed method to engineering structure.The results manifest that the proposed method has great value in engineering application.
基金supported by National Natural Science Foundation of China(Grant No.82071361,32160209,82160357 and 31900840)Guangxi Key Laboratory of basic and translational research of Bone and Joint Degenerative Diseases,China(Grant No.21-220-06)Guangxi Biomedical Materials Engineering Research Center for Bone and Joint Degenerative Diseases,China.
文摘Spinal cord injury(SCI)is an overwhelming and incurable disabling condition,for which increasing forms of multifunctional biomaterials are being tested,but with limited progression.The promising material should be able to fill SCI-induced cavities and direct the growth of new neurons,with effective drug loading to improve the local micro-organism environment and promote neural tissue regeneration.In this study,a double crosslinked biomimetic composite hydrogel comprised of acellularized spinal cord matrix(ASCM)and gelatin-acrylated-β-cyclodextrin-polyethene glycol diacrylate(designated G-CD-PEGDA)hydrogel,loaded with WAY-316606 to activate canonical Wnt/β-catenin signaling,and reinforced by a bundle of three-dimensionally printed aligned polycaprolactone(PCL)microfibers,was constructed.The G-CD-PEGDA component endowed the composite hydrogel with a dynamic structure with a self-healing capability which enabled cell migration,while the ASCM component promoted neural cell affinity and proliferation.The diffusion of WAY-316606 could recruit endogenous neural stem cells and improve neuronal differentiation.The aligned PCL microfibers guided neurite elongation in the longitudinal direction.Animal behavior studies further showed that the composite hydrogel could significantly recover the motor function of rats after SCI.This study provides a proficient approach to produce a multifunctional system with desirable physiological,chemical,and topographical cues for treating patients with SCI.
基金supported by the National Natural Science Foundation of China [grant numbers 51572223,51727804]
文摘Uni-directional carbon/carbon composites with high thermal conductivity are suitable to supply continuous thermal protection for future reentry vehicles since they could reduce surface temperature and ablation rates simultaneously in harsh environments.In this work,the high thermal conductivity carbon/carbon composites were prepared by chemical vapor infiltration.After heat-treatment,both their open porosity and internal friction increase due to the fiber/matrix thermal expansion mismatch;while their thermal conductive performance become better due to more complete carbon structure.With raising heat-treatment temperature from 1800℃to 2450℃,the mass and linear ablation rates of C/C composites with fibers vertical to the oxyacetylene torch for 60 s decrease from 0.66 mg/s and 2.95μm/s to 0.51 mg/s and 2.05μm/s respectively.The improved ablation resistance is resulted from the increased thermal conductivity from 282 to 508 W/(m·K)and more carbon fibers exposed to the flame during ablation,which have better oxidation resistance than those of carbon matrix.While such ablation rates become larger for composites with fibers parallel to the flame,from 1.02 mg/s and 3.73μm/s to 1.28 mg/s and 5.0μm/s respectively since the ablation occurred more easily through gaps at the fiber/matrix interfaces,which become larger and are always exposed to the flame for this case.
基金We acknowledge the financial support of the Foundation for the National Natural Science Foundation of China (No. 51176035), and Author of National Excellent Doctoral Dissertation of China (No. 201040). In addition, financial support was provided to Xiaole Chen under the Research and Innovation Project for College Gradua- tes of Jiangsu Province (CXZZ12_0099), the Fundamental Research Funds for the Central Universities, China Scholarship Council (No. 201306090085), and Scientific Research Foundation of Graduate School of Southeast University (No. YBJJ1209). The experience gained by Xiaole Chen as a CSC-supported Visiting Student in the Computational Multi-Physics Lab (MAE Dept., NC State University, Raleigh, USA) is also acknowledged. Table 3, Figs. 5 and 7 were provided by Josin Tom, based on his spring 2015 course-project report for MAE558. Professor Goodarz Ahmadi at Clarkson Univer- sity (Clarkson, USA) provided advice for our experimental set-up, and Professor Yong Lu at Southeast University provided guidance in programming the image-processing method.
文摘Experiments carried out using a lung model with a single horizontal bifurcation under different steady inhalation conditions explored the orientation of depositing carbon fibers, and particle deposition frac- tions. The orientations of deposited fibers were obtained from micrographs. Specifically, the effects of the sedimentation parameter (γ), fiber length, and flow rate on orientations were analyzed. Our results indicate that gravitational effect on deposition cannot be neglected for 0.0228 〈 γ 〈 0.247. The absolute orientation angle of depositing fibers decreased linearly with increasing y for values 0.0228 〈 γ 〈 0.15. Correspondence between Stokes numbers and y suggests these characteristics can be used to estimate fiber deposition in the lower airways. Computer simulations with sphere-equivalent diameter models for the fibers explored deposition efficiency vs. Stokes number. Using the volume-equivalent diameter model, our experimental data for the horizontal bifurcation were replicated. Results for particle deposition using a lung model with a vertical bifurcation indicate that body position also affects deposition.