Статті в журналах: "Multidirectional damage"

1

Qi, Wenxuan, Weixing Yao, and Haojie Shen. "A multidirectional damage model for fiber-reinforced plastic laminates under static load." Journal of Composite Materials 54, no. 2 (July 2, 2019): 153–66. http://dx.doi.org/10.1177/0021998319854148.

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A multidirectional damage model based on continuum damage mechanics for fiber-reinforced composite laminates is proposed in this paper. The influence of three main damage mechanisms, including transverse matrix cracking, local delamination, and fiber breakage, on the multidirectional stiffness properties of composite laminates is analyzed by introducing macro phenomenological damage variables. Then the mechanical behavior of elementary ply in laminates is modeled based on these damage variables. Besides, relations between micro-level damage variables and macro-level damage variables are established. Damage evolution laws of the three damage mechanisms are proposed to predict the degradation of multidirectional stiffness and failure strength of composite laminates under quasi-static loading. The experiment of cross-ply glass fiber-reinforced plastic laminates is carried out, and the prediction results show good agreement with the experimental results.

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2

Liu, Dunwen, Jianjun Zhang, Yu Tang, Yinghua Jian, and Caiwu Cai. "Damage Analysis of Concrete Structure under Multidirectional Shaped Charge Blasting Using Model Experiment and Ultrasonic Testing." Advances in Civil Engineering 2021 (March 22, 2021): 1–11. http://dx.doi.org/10.1155/2021/6677041.

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Quantitatively analyzing multidirectional shaped charge blasting energy distribution and improving the rock-fracturing efficiency have been a challenging problem in blasting and civil engineering. In this work, we carry out four groups of concrete model experiments using ultrasonic testing, comparing conventional blasting, and multidirectional shaped charge blasting. Then, the probability and statistics method is used to quantitatively analyze the blasting damage and the energy distribution. The test results show that ultrasonic testing and statistics model can quantitatively evaluate the damage law and energy distribution of blasting. By comparing with conventional blasting method, the multidirectional shaped charge blasting with V-shaped multidirectional shaped energy groove has achieved the effect of energy accumulation. It increases the distribution of energy in the rock crack district, increases the blasting damage range, and improves the rock-fracturing efficiency of blasting. The V-shaped multidirectional shaped energy groove can be used as a new approach for rock fracturing in similar projects.

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3

Comola, F., T. Lykke Andersen, L. Martinelli, H. F. Burcharth, and P. Ruol. "Damage pattern and damage progression on breakwater roundheads under multidirectional waves." Coastal Engineering 83 (January 2014): 24–35. http://dx.doi.org/10.1016/j.coastaleng.2013.09.004.

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4

Li, Wei, Yinghonglin Liu, Peng Jiang, Fuping Guo, and Jiahao Cheng. "Study on Delamination Damage of CFRP Laminates Based on Acoustic Emission and Micro Visualization." Materials 15, no. 4 (February 16, 2022): 1483. http://dx.doi.org/10.3390/ma15041483.

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This study investigated the mechanism of delamination damage in the double cantilever beam (DCB) standard test by the use of the strain energy release rate. The curve of the strain energy release rate was verified by the Rise Angle (RA) method. For this purpose, 24-layer carbon fiber/epoxy multidirectional laminates with interface orientations of 0°, 30°, 45°, and 60° were fabricated according to the standard ASTM D5528(13). In the course of this test, acoustic emission (AE) was used for real-time monitoring, and combined with micro visualization, the damage mechanism of composite multidirectional laminates was studied at multiple scales. Combining the AE detection results with micro visualization, it is found that the AE parameters and the damage to multidirectional laminates could realize a one-to-one correspondence. Through the study of the variation of the RA value, load, and strain energy release rate with the crack length, it is proved that the AE parameters can effectively characterize the initiation of delamination damage.

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5

Birur, A., A. Gupta, and J. Raghavan. "Creep Rupture of Multidirectional Polymer Composite Laminates — Influence of Time-Dependent Damage." Journal of Engineering Materials and Technology 128, no. 4 (June 23, 2006): 611–17. http://dx.doi.org/10.1115/1.2345454.

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Evolution of various damage modes with time, in multidirectional laminates of a polymer composite (Hexcel F263-7/T300) subjected to a constant load, was experimentally studied and correlated to experimental creep rupture results to understand the influence of the former on the latter. Influence of various parameters, such as stress, temperature, thickness of inner plies, and outer-ply constraint, on damage evolution was evaluated. Observed damages include transverse (also referred in the literature as matrix cracks) cracking due to in-plane stresses, vertical cracking due to out-of-plane normal stress, delamination due to interlaminar stresses, splitting, and fiber fracture. The sequence of evolution of these damages varied with laminate stacking sequence, stress, and temperature. These damages significantly influenced one another and the creep rupture time.

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6

Hu, Ping, Ran Tao, Xiaole Li, and Gilles Lubineau. "Decomposing the coupling damage in mode I multidirectional delamination." Composites Science and Technology 229 (October 2022): 109684. http://dx.doi.org/10.1016/j.compscitech.2022.109684.

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7

Sivashanker, S. "Damage propagation in multidirectional composites subjected to compressive loading." Metallurgical and Materials Transactions A 32, no. 1 (January 2001): 171–82. http://dx.doi.org/10.1007/s11661-001-0113-y.

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8

Liu, Yinghonglin, Jiang Peng, Wei Li, Chang Yang, Ping Sun, and Xiaowei Yan. "Predicting the Delamination Mechanisms of Multidirectional Laminates Using the Energy Release Rate Obtained from AE Monitoring." Materials Evaluation 80, no. 1 (January 1, 2022): 34–47. http://dx.doi.org/10.32548/10.32548/2022.me-04254.

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This study investigates delamination damage mechanisms during the double cantilever beam standard test using the strain energy release rate. The acoustic emission parameter is used to replace the original calculation method of measuring crack length to predict delamination. For this purpose, 24-layer glass/epoxy multidirectional specimens with different layups, and interface orientations of 0°, 30°, 45°, and 60°, were fabricated based on ASTM D5528 (2013). Acoustic emission testing (AE) is used to detect the damage mechanism of composite multidirectional laminates (combined with microscopic real-time observation), and it is verified that the strain energy release rate can be used as a criterion for predicting delamination damage in composite materials. By comparing the AE results with the delamination expansion images observed by microvisualization in real time, it is found that the acoustic emission parameters can predict the damage of laminates earlier. Based on the data inversion of the acoustic emission parameters of the strain energy release rate, it is found that the strain energy release rate of the specimens with different fiber interface orientations is consistent with the original calculated results.

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9

Liu, Yinghonglin, Peng Jiang, Wei Li, Chang Yang, Ping Sun, and Xiaowei Yan. "Predicting the Delamination Mechanisms of Multidirectional Laminates Using the Energy Release Rate Obtained from AE Monitoring." Materials Evaluation 80, no. 1 (January 1, 2022): 34–47. http://dx.doi.org/10.32548/2022.me-04254.

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This study investigates delamination damage mechanisms during the double cantilever beam standard test using the strain energy release rate. The acoustic emission parameter is used to replace the original calculation method of measuring crack length to predict delamination. For this purpose, 24-layer glass/epoxy multidirectional specimens with different layups, and interface orientations of 0°, 30°, 45°, and 60°, were fabricated based on ASTM D5528 (2013). Acoustic emission testing (AE) is used to detect the damage mechanism of composite multidirectional laminates (combined with microscopic real-time observation), and it is verified that the strain energy release rate can be used as a criterion for predicting delamination damage in composite materials. By comparing the AE results with the delamination expansion images observed by microvisualization in real time, it is found that the acoustic emission parameters can predict the damage of laminates earlier. Based on the data inversion of the acoustic emission parameters of the strain energy release rate, it is found that the strain energy release rate of the specimens with different fiber interface orientations is consistent with the original calculated results.

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10

Athanasopoulos, N., and V. Kostopoulos. "Damage detection via Joule effect for multidirectional carbon fiber reinforced composites." Applied Physics Letters 101, no. 11 (September 10, 2012): 114109. http://dx.doi.org/10.1063/1.4751992.

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11

Gara, Souhir, Samir M'hamed, and Oleg Tsoumarev. "Temperature measurement and machining damage in slotting of multidirectional CFRP laminate." Machining Science and Technology 22, no. 2 (October 5, 2017): 320–37. http://dx.doi.org/10.1080/10910344.2017.1365892.

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12

Aghajani, Sepideh, Mohammadreza Hemati, and Shams Torabnia. "Life prediction of wind turbine blades using multi-scale damage model." Journal of Reinforced Plastics and Composites 40, no. 17-18 (April 5, 2021): 644–53. http://dx.doi.org/10.1177/0731684421995886.

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Wind turbine blade life prediction is the most important parameter to estimate the power generation cost. Due to the price and importance of wind blade, many experimental and theoretical methods were developed to estimate damages and blade life. A novel multiaxial fatigue damage model is suggested for the life prediction of a wind turbine blade. Fatigue reduction of fiber and interfiber characteristics are separately treated and simulated in this research. Damage behavior is considered in lamina level and then extended to laminate; hence, this model can be used for multidirectional laminated composites. The procedure of fatigue-induced degradation is implemented in an ABAQUS user material subroutine. By applying the fatigue damage model, life is estimated by the satisfaction of lamina fracture criteria. This model provides a comprehensive idea about how damage happens in wind blades regarding a multi-axis fatigue loading condition.

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13

Sun, Weiwei, Dina D’Ayala, Jinxing Fu, Wentao Gu, and Jun Feng. "Seismic vulnerability assessment of a high-rise molten-salt solar tower based on incremental dynamic analysis." E3S Web of Conferences 194 (2020): 01005. http://dx.doi.org/10.1051/e3sconf/202019401005.

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This paper investigates the seismic performance of a high-rise molten-salt solar tower by finite element modelling. The integrated and separated models for solar tower based on the concrete damage plastic model are validated by matching the behaviour of similar reinforced concrete chimney specimens. The modal analysis demonstrates the first four modes of the solar tower are translational vibration. Seismic simulations are developed through the incremental dynamic analysis. The most disadvantageous position of the tower is all concentrated in the opening section under multidirectional seismic excitations. The top displacement of the tower under bidirectional and three-directional earthquake actions is larger than that under unidirectional earthquake actions. The results of the seismic vulnerability assessment show that when the PGA equals to 0.035g, the tower will be intact; when the PGA equals to 0.1g (design peak ground acceleration), the probability of the moderate damage state is within 1.5%; when the PGA equals to 0.22g (maximum considered earthquake), the probability of the destruction state is below 0.7%. The seismic partitioned fragility analysis of the tower under multidirectional earthquake excitations illustrates that there are two peaks in the vulnerability surfaces. The anti-collapse analysis indicates the tower has a good seismic performance under multidirectional seismic excitations.

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14

Suk, Recep, and Gökhan Altintaș. "Behavior of multidirectional friction dampers." Journal of Vibration and Control 26, no. 21-22 (February 20, 2020): 1969–79. http://dx.doi.org/10.1177/1077546320909978.

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Earthquakes are catastrophic events causing loss of lives, injuries, and extensive losses in properties. Majority of the life and property losses of earthquakes are dependent on the incapabilities of the building stock to resist earthquakes. Although unsuitable design, analyses, and production techniques play a major role as the main reasons for the poor performance of buildings against earthquakes, buildings constructed in accordance with building codes also suffer from the devastating impact of earthquakes. In this context, the lack of proper management and adequate damping of the energy caused by earthquakes is a major cause of structural damage in earthquakes. The efficiency of conventional basic elements in structures with energy damping is very limited and may not be sufficient for the damping of a large amount of earthquake-induced energy. Thanks to the rapid advances in technology and associated engineering techniques, numerous new products, and production and calculation techniques are underway to mitigate the devastating effects of earthquakes on buildings. In this study, it was aimed to theoretically and experimentally investigate the performance of a versatile friction-type seismic damper that eliminates earthquake energy. The damper is designed using a spherical surface friction joint to respond to all loads regardless of the loading direction. The damper can be easily adjusted to the desired capacity by means of bolt tensioning elements. Experiments have been carried out for various shear loads and damping parameters. Furthermore, numerical analysis of the model was carried out by use of the finite element method. The results of this study revealed that the shear load capacity of the device did not change at different frequencies. Analyzing the effect of the equipment on a structure, it was understood that it reduces roof displacement and periods of the structure. The analysis revealed that the damper significantly improved the earthquake performance of the structure.

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15

Rahimian Koloor, Seyed, Atefeh Karimzadeh, Noorfaizal Yidris, Michal Petrů, Majid Ayatollahi, and Mohd Tamin. "An Energy-Based Concept for Yielding of Multidirectional FRP Composite Structures Using a Mesoscale Lamina Damage Model." Polymers 12, no. 1 (January 7, 2020): 157. http://dx.doi.org/10.3390/polym12010157.

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Composite structures are made of multidirectional (MD) fiber-reinforced polymer (FRP) composite laminates, which fail due to multiple damages in matrix, interface, and fiber constituents at different scales. The yield point of a unidirectional FRP composite is assumed as the lamina strength limit representing the damage initiation phenomena, while yielding of MD composites in structural applications are not quantified due to the complexity of the sequence of damage evolutions in different laminas dependent on their angle and specification. This paper proposes a new method to identify the yield point of MD composite structures based on the evolution of the damage dissipation energy (DDE). Such a characteristic evolution curve is computed using a validated finite element model with a mesoscale damage-based constitutive model that accounts for different matrix and fiber failure modes in angle lamina. The yield point of composite structures is identified to correspond to a 5% increase in the initial slope of the DDE evolution curve. The yield points of three antisymmetric MD FRP composite structures under flexural loading conditions are established based on Hashin unidirectional (UD) criteria and the energy-based criterion. It is shown that the new energy concept provides a significantly larger safe limit of yield for MD composite structures compared to UD criteria, in which the accumulation of energy dissipated due to all damage modes is less than 5% of the fracture energy required for the structural rupture.

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16

Michel, Laurent, Sebastian Garcia, Chen Yao, Christine Espinosa, and Frédéric Lachaud. "Experimental and Numerical Investigation of Delamination in Curved-Beam Multidirectional Laminated Composite Specimen." Key Engineering Materials 577-578 (September 2013): 389–92. http://dx.doi.org/10.4028/www.scientific.net/kem.577-578.389.

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Composite corners are generally tested under four point-bending to identify Inter-Laminar Tensile Strength design values. Hereafter several lay-ups have been defined in order to characterize very different damage evolution processes. Damage monitoring has been performed with the help of Digital Image Correlation, Acoustic Emission and Fast Video Recorder. The different processes leading to final failures have been identified. A deterministic continuous composite material model is used to investigate these phenomena. Initiation and evolution up to saturation and fracture are implemented for various damage mechanisms and for delamination. A first comparison between experiments and numerical simulations is presented.

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17

Montesano, John, and Chandra Veer Singh. "Critical stiffness damage envelopes for multidirectional laminated structures under multiaxial loading conditions." Materials & Design 91 (February 2016): 218–29. http://dx.doi.org/10.1016/j.matdes.2015.11.110.

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18

Caglar, Muge, Gungor Karaguzel, Guzide Gokhan-Ocak, Duygu Yasar, Sibel Berker-Karauzum, Tekinalp Gelen, Fatma Nur Celik, Necdet Demir, and Mustafa Melikoglu. "Multidirectional and simultaneous evaluation of gastroschisis-related intestinal damage in chick embryos." Journal of Pediatric Surgery 49, no. 11 (November 2014): 1577–84. http://dx.doi.org/10.1016/j.jpedsurg.2014.06.019.

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19

Asadi, Amir, and J. Raghavan. "Influence of time-dependent damage on creep of multidirectional polymer composite laminates." Composites Part B: Engineering 42, no. 3 (April 2011): 489–98. http://dx.doi.org/10.1016/j.compositesb.2010.12.003.

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20

Vellios, L., V. Kostopoulos, and S. A. Paipetis. "Fatigue Effect on the Dynamic Properties of Cfrp Composites." Advanced Composites Letters 3, no. 4 (July 1994): 096369359400300. http://dx.doi.org/10.1177/096369359400300405.

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Damage developing during fatigue of composite laminates affects both dynamic modulus of elasticity and damping coefficient of the material. It has been shown that the effect of fatigue on the damping coefficient is of particular importance. The damping variation could be used to characterise the damage state of the material, produced by fatigue. A model relating damage with damping was developed to correlate damage development to mechanical response. The damping coefficients of the composite of the fatigue test were measured at various stages, using the flexural free vibration of the test coupon hi cantilever configuration. The method was applied both in multidirectional and unidirectional laminates.

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21

Naghipour, Paria, Evan J. Pineda, Brett A. Bednarcyk, Steven M. Arnold, and Anthony M. Waas. "Fatigue analysis of notched laminates: A time-efficient macro-mechanical approach." Journal of Composite Materials 51, no. 15 (September 15, 2016): 2163–80. http://dx.doi.org/10.1177/0021998316668569.

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A coupled, transversely isotropic, deformation and damage fatigue model has been implemented within the finite element method and utilized, along with a static progressive damage model, to predict the fatigue life, stiffness degradation as a function of number of cycles, and post-fatigue tension and compression response of notched, multidirectional laminates. The material parameters for the fatigue model were obtained utilizing ply-level classical lamination theory simulations and the provided [0], [90] and [±45] experimental composite laminate S–N data. Within the fatigue damage model, the transverse and shear stiffness properties of the plies were degraded with an isotropic scalar damage variable. The stiffness damage in the longitudinal (fiber) ply direction was suppressed, and instead the strength of the fiber was degraded as a function of fatigue cycles. A maximum strain criterion was used to capture the failure in each element, and once this criterion was satisfied, the longitudinal stiffness of the element was eliminated. The resulting, degraded properties were then used to calculate the new stress state. This procedure was repeated until final failure of the composite laminate was achieved or a specified number of cycles was reached. For post-fatigue tension and compression behavior, four internal state variables were used to control the damage and failure. The predictive capability of the above-mentioned approach was assessed by performing blind predictions of notched multidirectional IM7/977-3 composite laminate response under fatigue and post-fatigue tensile and compressive loading, followed by a recalibration phase. Tabulated data along with detailed results (i.e. stress–strain curves as well as damage evolution states at given number of cycles compared to experimental data) for all laminates are presented.

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22

Duboust, N., H. Ghadbeigi, C. Pinna, S. Ayvar-Soberanis, A. Collis, R. Scaife, and K. Kerrigan. "An optical method for measuring surface roughness of machined carbon fibre-reinforced plastic composites." Journal of Composite Materials 51, no. 3 (July 28, 2016): 289–302. http://dx.doi.org/10.1177/0021998316644849.

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Characterization of the damage induced by machining of fibre-reinforced composites is usually performed by measuring surface roughness. Contact-based surface profilometers are the most used equipment in industry; however, it has been found that there are performance limitations which may result when used to measure machined heterogeneous composite surfaces. In this research, surface roughness is characterised using a commercial non-contact optical method, and compared with a conventional stylus profilometer. Unidirectional and multidirectional carbon fibre laminates were edge trimmed and slot milled. The variation in surface roughness was compared using different tool types, fibre orientations and cutting parameters. Surface damage and cutting mechanisms were assessed by using scanning electron microscope images, and the suitability of roughness parameters were also analysed including: Sa, Skewness and Kurtosis. Using the optical system allowed accurate roughness calculation of individual plies on a multidirectional laminate with different fibre orientations. The research has also shown that the optical system, including the use of areal roughness parameters, can increase the accuracy of roughness measurement for machined fibrous composite surfaces and is less sensitive to measurement position than the stylus.

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23

D’haen, Jonas J. A., Michael May, Christian Boegle, and Stefan Hiermaier. "Damage Evolution Analysis on Compression-Loaded Multidirectional Carbon Fiber Laminates Using Ex-Situ CT Scans." Journal of Composites Science 6, no. 2 (February 19, 2022): 63. http://dx.doi.org/10.3390/jcs6020063.

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Damage evolution inside compression-loaded laminates is a crucial aspect when designing crash structures. In this study, ex situ CT scanning is used to identify damage evolution in multidirectional composite laminates. Multiple CT scans throughout the stress–strain envelope are used to quantify the internal damage and failure propagation of a [45, −45, 90]s carbon fiber laminate. Initially, observed damage occurs in form of delamination between the −45° and 90° layers. Afterward, shear failure propagates from the central layers throughout the entire laminate. Shear failure in the middle two layers expands after continued loading up to double shear failure. The same distinct failure sequence is observed in multiple specimens, and the small deviation supports consistency. Furthermore, the stress–strain envelope of the successive load cycles matches closely with reference measurements.

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24

Iliescu, Daniel, Daniel Gehin, Mohammed Nouari, and Franck Girot. "Damage modes of the aeronautic multidirectional carbon/epoxy composite T300/914 in machining." International Journal of Materials and Product Technology 32, no. 2/3 (2008): 118. http://dx.doi.org/10.1504/ijmpt.2008.018976.

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25

Edalat-Behbahani, A., J. A. O. Barros, and A. Ventura-Gouveia. "Three dimensional plastic-damage multidirectional fixed smeared crack approach for modelling concrete structures." International Journal of Solids and Structures 115-116 (June 2017): 104–25. http://dx.doi.org/10.1016/j.ijsolstr.2017.03.006.

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26

McLaughlin, P. V., M. G. Mirchandani, and P. V. Ciekurs. "Infrared Thermographic Flaw Detection in Composite Laminates." Journal of Engineering Materials and Technology 109, no. 2 (April 1, 1987): 146–50. http://dx.doi.org/10.1115/1.3225954.

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Research performed to develop thermography as a routine rapid flaw detection tool for large composite structures is presented. The externally applied thermal field (EATF) technique is described whereby surface cracks or sub-surface impact damage creates detectable surface temperature perturbations when heated. EATF thermographic procedures and flaw detection capabilities in multidirectional and unidirectional graphite and glass fiber composites are described. The method’s advantages and limitations are outlined.

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27

Trybus, Ewa, Teodora Król, and Wojciech Trybus. "The Multidirectional Effect of Azelastine Hydrochloride on Cervical Cancer Cells." International Journal of Molecular Sciences 23, no. 11 (May 24, 2022): 5890. http://dx.doi.org/10.3390/ijms23115890.

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A major cause of cancer cell resistance to chemotherapeutics is the blocking of apoptosis and induction of autophagy in the context of cell adaptation and survival. Therefore, new compounds are being sought, also among drugs that are commonly used in other therapies. Due to the involvement of histamine in the regulation of processes occurring during the development of many types of cancer, antihistamines are now receiving special attention. Our study concerned the identification of new mechanisms of action of azelastine hydrochloride, used in antiallergic treatment. The study was performed on HeLa cells treated with different concentrations of azelastine (15–90 µM). Cell cycle, level of autophagy (LC3 protein activity) and apoptosis (annexin V assay), activity of caspase 3/7, anti-apoptotic protein of Bcl-2 family, ROS concentration, measurement of mitochondrial membrane potential (Δψm), and level of phosphorylated H2A.X in response to DSB were evaluated by cytometric method. Cellular changes were also demonstrated at the level of transmission electron microscopy and optical and fluorescence microscopy. Lysosomal enzyme activities-cathepsin D and L and cell viability (MTT assay) were assessed spectrophotometrically. Results: Azelastine in concentrations of 15–25 µM induced degradation processes, vacuolization, increase in cathepsin D and L activity, and LC3 protein activation. By increasing ROS, it also caused DNA damage and blocked cells in the S phase of the cell cycle. At the concentrations of 45–90 µM, azelastine clearly promoted apoptosis by activation of caspase 3/7 and inactivation of Bcl-2 protein. Fragmentation of cell nucleus was confirmed by DAPI staining. Changes were also found in the endoplasmic reticulum and mitochondria, whose damage was confirmed by staining with rhodamine 123 and in the MTT test. Azelastine decreased the mitotic index and induced mitotic catastrophe. Studies demonstrated the multidirectional effects of azelastine on HeLa cells, including anti-proliferative, cytotoxic, autophagic, and apoptotic properties, which were the predominant mechanism of death. The revealed novel properties of azelastine may be practically used in anti-cancer therapy in the future.

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28

Edalat-Behbahani, A., J. A. O. Barros, and A. Ventura-Gouveia. "Application of plastic-damage multidirectional fixed smeared crack model in analysis of RC structures." Engineering Structures 125 (October 2016): 374–91. http://dx.doi.org/10.1016/j.engstruct.2016.07.013.

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29

Jiao, Shaoni, Jian Li, Fei Du, Lei Sun, and Zhiwei Zeng. "Characteristics of Eddy Current Distribution in Carbon Fiber Reinforced Polymer." Journal of Sensors 2016 (2016): 1–8. http://dx.doi.org/10.1155/2016/4292134.

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The paper studies the characteristics of eddy current (EC) distribution in carbon fiber reinforced polymer (CFRP) laminates so as to guide the research and operation of eddy current testing of CFRP. To this end, an electromagnetic field computation model of EC response to CFRP based on the finite element method is developed. Quantitative analysis of EC distribution in plies of unidirectional CFRP reveals that EC changes slowly along the fiber direction due to the strong electrical anisotropy of the material. Variation of EC in plies of multidirectional CFRP is fast in both directions. The attenuation of EC in the normal direction in unidirectional CFRP is faster than that in isotropic material due to faster diffusion of EC. In multidirectional CFRP, EC increases near the interfaces of plies having different fiber orientations. The simulation results are beneficial to optimizing sensor design and testing parameters, as well as damage detection and evaluation.

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30

Sapate, Mr Vishal M., and Mr Nikhil S. Jadhav. "Comparative Study on Damage Index of RCC Frame Considering Fiber Discretization Technique." International Journal for Research in Applied Science and Engineering Technology 10, no. 7 (July 31, 2022): 1420–27. http://dx.doi.org/10.22214/ijraset.2022.45492.

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Abstract: Damage indices which take into account both maximum deformation and cyclic effects were developed by Park and Ang. In the field of structural engineering, it’s observed that the Park and Ang damage index is mostly used for RCC structure. The damage index parameter assessed based on plastic hinge approach which is not effective to consider the coupled response between axial force and flexural moment especially in nonlinear domain. The accurate damage evaluations of structure are depending on other parameter such as, accurate modelling of frame, selection ground motion records. Masonry infill walls are widely used as partitions all over the world. Commonly masonry walls are not considered in the damage evaluation process because they are supposed to act as non-structural members or elements. Fiber discretization technique is used to consider inelastic behaviors of member. Single strut is model as infill wall in multidirectional. Results obtained from this study show that the accuracy of damage index totally depends on damage parameter consideration and modeling of building. The coupled effects give more realistic damage of structure as compared with other damage parameters.

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31

Kashtalyan, M., and C. Soutis. "Modelling of stiffness degradation due to cracking in laminates subjected to multi-axial loading." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 374, no. 2071 (July 13, 2016): 20160017. http://dx.doi.org/10.1098/rsta.2016.0017.

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The paper presents an analytical approach to predicting the effect of intra- and interlaminar cracking on residual stiffness properties of the laminate, which can be used in the post-initial failure analysis, taking full account of damage mode interaction. The approach is based on a two-dimensional shear lag stress analysis and the equivalent constraint model of the laminate with multiple damaged plies. The application of the approach to predicting degraded stiffness properties of multidirectional laminates under multi-axial loading is demonstrated on cross-ply glass/epoxy and carbon/epoxy laminates with transverse and longitudinal matrix cracks and crack-induced transverse and longitudinal delaminations. This article is part of the themed issue ‘Multiscale modelling of the structural integrity of composite materials’.

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Flis, Marian. "Ecological, legal and economic aspects of evaluating the damages caused by wild animals / Ekologiczne, prawne i ekonomiczne aspekty oceny szkód wyrządzanych przez dzikie zwierzęta." Ochrona Srodowiska i Zasobów Naturalnych 24, no. 3 (September 1, 2013): 53–58. http://dx.doi.org/10.2478/oszn-2013-0029.

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Abstract This paper presents the ecological grounds of interaction between animals and their living habitats, which in economic terms is referred to as damages. In addition, an analysis of the legal and economic aspects of the liability for damages caused by wild animals in different types of natural habitats was carried out. Liability for damages is a special law in relation to the general principles of civil law in this area. At the same time, it is also limited, both objectively and subjectively. The increase in the interaction of animals with environments, which results directly in the size of compensation amounts paid, is closely associated with the dynamics in the number of damaging species, whereas the specificity of the damage results from the behavior of perpetrator animals. Multidirectional preventive measures using different methods generally produce short-term effects and their use is not always economically justified.

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Laux, Tobias, Khong Wui Gan, Rodrigo P. Tavares, Carolina Furtado, Albertino Arteiro, Pedro P. Camanho, Ole T. Thomsen, and Janice M. Dulieu-Barton. "Modelling damage in multidirectional laminates subjected to multi-axial loading: Ply thickness effects and model assessment." Composite Structures 266 (June 2021): 113766. http://dx.doi.org/10.1016/j.compstruct.2021.113766.

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Pinyaev, S. I., T. P. Kuzmenko, N. V. Revina, M. V. Parchaykina, A. S. Pronin, I. V. Syusin, O. S. Novozhilova, V. V. Revin, E. V. Chudaikina, and E. S. Revina. "Influence of Resveratrol on Oxidation Processes and Lipid Phase Characteristics in Damaged Somatic Nerves." BioMed Research International 2019 (December 11, 2019): 1–9. http://dx.doi.org/10.1155/2019/2381907.

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It has been shown that the intensification of oxidative processes is observed when somatic nerves of rats are damaged. Accumulation of malondialdehyde occurs, and the phase properties of the lipid bilayer change, especially in the distal part of the nerve. Under the same conditions, there are multidirectional changes in the activity of antioxidant enzymes, superoxide dismutase (SOD) activity decreases, and catalase (CAT) activity increases. Under the action of resveratrol, there is a decrease in the number of TBA-active products in both areas of the damaged nerve. Alongside resveratrol action, SOD and CAT activity tends to return towards the control values. Similar patterns are observed in the action of resveratrol on the phase states of lipids with the damage to somatic nerves. By summarizing the data obtained, it can be claimed that when the nerve is damaged, profound changes occur both in the lipid component and in the antioxidant system. Resveratrol has a stabilizing effect on the studied parameters, and a longer period of time is required for their complete recovery.

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Reid, John D. "Dual-Support Breakaway Sign with Modified Fuse Plate and Multidirectional Slip Base." Transportation Research Record: Journal of the Transportation Research Board 1528, no. 1 (January 1996): 61–68. http://dx.doi.org/10.1177/0361198196152800106.

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Dual-support breakaway signs have been used across the country for more than 25 years and have been credited with saving many lives. A very important feature of this system is the ability of its support to swing up and out of the way when it is struck by an errant vehicle. Another critical feature of the sign system is its ability to withstand wind loads without causing structural damage to the system. A modified dual-support breakaway sign system that improves on both criteria is proposed. A dual-support breakaway sign with a multidirectional slip base performed acceptably during full-scale crash testing. The sign tested consisted of 4.8-m-tall, W6 × 9-wide flange posts with a sign 3.05 m wide by 2.44 m tall. The research indicated that the modified system does not pose any significant hazard for vehicles striking one of the supports at angles of up to 25 degrees. Changing the material of the fuse plate to an A572 Grade 50 steel creates a stronger connection that significantly improves the wind load capacity of the sign system. The proposed material for the fuse plate did not hinder the safety performance of the sign: the fuse plate performed as designed under full-scale testing.

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Criado, Víctor, Norberto Feito, José Luis Cantero Guisández, and José Díaz-Álvarez. "A New Cutting Device Design to Study the Orthogonal Cutting of CFRP Laminates at Different Cutting Speeds." Materials 12, no. 24 (December 6, 2019): 4074. http://dx.doi.org/10.3390/ma12244074.

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Carbon Fiber-reinforced plastics (CFRPs) are widely used in the aerospace industry due to their highly mechanical properties and low density. Most of these materials are used in high-risk structures, where the damage caused by machining must be controlled and minimized. The optimization of these processes is still a challenge in the industry. In this work, a special cutting device, which allows for orthogonal cutting tests, with a linear displacement at a wide range of constant cutting speeds, has been developed by the authors. This paper describes the developed cutting device and its application to analyze the influence of tool geometry and cutting parameters on the material damage caused by the orthogonal cutting of a thick multidirectional CFRP laminate. The results show that a more robust geometry (higher cutting edge radius and lower rake angle) and higher feed cause an increase in the thrust force of a cutting tool, causing burrs and delamination damage. By reducing the cutting speed, the components with a higher machining force were also observed to have less surface integrity control.

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Masud, Manzar, Moosa S. M. Al Kharusi, Muhammad Umair Ali, Aamir Mubashar, Shaik Javeed Hussain, Adnan Tariq, Gulfam Ul Rehman, Mahmood Hassan Akhtar, and Shama Javeed. "Prediction of the Ultimate Strength of Notched and Unnotched IM7/977-3 Laminated Composites Using a Micromechanics Approach." Polymers 13, no. 20 (October 11, 2021): 3491. http://dx.doi.org/10.3390/polym13203491.

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This paper proposes a multi-scale analysis technique based on the micromechanics of failure (MMF) to predict and investigate the damage progression and ultimate strength at failure of laminated composites. A lamina’s representative volume element (RVE) is developed to predict and calculate constituent stresses. Damages that occurred in the constituents are calculated using separate failure criteria for both fiber and matrix. Subsequently, the volume-based damage homogenization technique is utilized to prevent the localization of damage throughout the total matrix zone. The proposed multiscale analysis procedure is then used to investigate the notched and unnotched behavior of three multi-directional composite layups, [30, 60, 90, −60, 30]2S, [0, 45, 90, −45]2S, and [60, 0, −60]3S, subjected to static tension and compression loading. The specimen is fabricated from unidirectionally reinforced composite (IM7/977-3). The prediction of ultimate strength at failure and equivalent stiffness are then benchmarked against the experimental test data. The comparative analysis with various failure models is also carried out to validate the proposed model. MMF demonstrated the capability to correctly predict the ultimate strength at failure for a range of multidirectional composites laminates under tensile and compressive load. The numerically predicted findings revealed a good agreement with the experimental test data. Out of the three investigated composite layups, the simulated results for the quasi-isotropic [0, 45, 90, −45]2S layup agreed extremely well with the experimental results with all the percentage errors within 10% of the measured failure loads.

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Athanasopoulos, N., and V. Kostopoulos. "Erratum: “Damage detection via Joule effect for multidirectional carbon fiber reinforced composites” [Appl. Phys. Lett. 101, 114109 (2012)]." Applied Physics Letters 102, no. 25 (June 24, 2013): 259901. http://dx.doi.org/10.1063/1.4812403.

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Li, Qiang, Hongtao Jia, Qing Qiu, Yongzhu Lu, Jun Zhang, Jianghong Mao, Weijie Fan, and Mingfeng Huang. "Typhoon-Induced Fragility Analysis of Transmission Tower in Ningbo Area Considering the Effect of Long-Term Corrosion." Applied Sciences 12, no. 9 (May 9, 2022): 4774. http://dx.doi.org/10.3390/app12094774.

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The purpose of this paper was to investigate the influence of long-term corrosion on the deterioration of wind resistance of a steel transmission tower during its service life. An analytical model for predicting the long-term corrosion depth of carbon steel was established, and the corrosion depth of carbon steel in the Ningbo area was predicted based on the local atmospheric environment data. With the help of typhoon full-track simulation and wind field simulation technology, a joint probability distribution model of multidirectional extreme wind speeds was constructed using the t-Copula function to determine the typhoon climate of the transmission tower site. Finite element models of the ZM4 cathead transmission tower under 30/60/90 corrosion years were then established, respectively, according to the predicted corrosion depth of carbon steel in Ningbo. Three damage modes, i.e., minor damage, moderate damage and severe damage, corresponding to the transmission tower under wind loads, were defined, and pushover analyses were used to determine the limit values of each damage mode so as to obtain the typhoon-induced fragility curves of the transmission tower within 30/60/90 corrosion years. The results show that the increase in corrosion age leads to a deterioration in the nominal mechanical properties of the transmission tower components, making the damage probability to the transmission tower increase. Under the typhoon wind loads of a 50-year return period in the most unfavorable wind direction in Ningbo, the probability of moderate damage of the tower is within 10% and the probability of minor damage is controlled between 10% and 40%.

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Radchenko, V. G., and P. V. Seliverstov. "AGE-RELATED CHANGES IN THE LIVER." HERALD of North-Western State Medical University named after I.I. Mechnikov 9, no. 1 (March 15, 2017): 110–16. http://dx.doi.org/10.17816/mechnikov201791110-116.

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In the process of life the human body undergoes a number of changes which, in lead to its aging. Physiological aging is accompanied by irreversible functional and organic restructuring of all systems and organs, including the liver. The most common cause of diffuse changes of a parenchyma of the liver in elderly patients is steatosis, which is an important role of mitochondrial dysfunction. For the treatment and prevention of liver diseases, against skin aging is inevitable, it is expedient to apply preparations with a multidirectional effect on the various links in the pathogenesis of liver damage. Systematic implementation of preventive measures will allow older people to maintain good health and performance for years to come.

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R. Koloor, S. S., A. Karimzadeh, M. R. Abdullah, M. Petrů, N. Yidris, S. M. Sapuan, and M. N. Tamin. "Linear-Nonlinear Stiffness Responses of Carbon Fiber-Reinforced Polymer Composite Materials and Structures: A Numerical Study." Polymers 13, no. 3 (January 22, 2021): 344. http://dx.doi.org/10.3390/polym13030344.

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The stiffness response or load-deformation/displacement behavior is the most important mechanical behavior that frequently being utilized for validation of the mathematical-physical models representing the mechanical behavior of solid objects in numerical method, compared to actual experimental data. This numerical study aims to investigate the linear-nonlinear stiffness behavior of carbon fiber-reinforced polymer (CFRP) composites at material and structural levels, and its dependency to the sets of individual/group elastic and damage model parameters. In this regard, a validated constitutive damage model, elastic-damage properties as reference data, and simulation process, that account for elastic, yielding, and damage evolution, are considered in the finite element model development process. The linear-nonlinear stiffness responses of four cases are examined, including a unidirectional CFRP composite laminate (material level) under tensile load, and also three multidirectional composite structures under flexural loads. The result indicated a direct dependency of the stiffness response at the material level to the elastic properties. However, the stiffness behavior of the composite structures depends both on the structural configuration, geometry, lay-ups as well as the mechanical properties of the CFRP composite. The value of maximum reaction force and displacement of the composite structures, as well as the nonlinear response of the structures are highly dependent not only to the mechanical properties, but also to the geometry and the configuration of the structures.

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Brodziak-Dopierała, Barbara. "Lead – factors affecting its content in bone tissue." Pomeranian Journal of Life Sciences 66, no. 4 (February 1, 2020): 23–29. http://dx.doi.org/10.21164/pomjlifesci.745.

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Abstract Lead is an element whose presence in the environment results mainly from man’s activities. It infiltrates the bodies of living organisms in many ways; in the human body, it has a multidirectional activity, causing anemia, kidney damage, mental retardation in children, genotoxicity, impaired immune function, damage to the nervous system and an inhibition of heme synthesis. Lead also affects bones; its concentrations there, in contrast to soft tissues, are dependent on exposure and increase throughout ones lifespan. This element is the most often studied and described metal in the bone tissue. The aim of this study was to determine the factors that influence the content of lead in the bone tissue and trace its content in this tissue based on literature data. The analysis of the collected literature showed an incredibly wide range of lead content in human bones was observed. This could be due to the different methods of determination (AAS, ICP-AES, K x-ray fluorescence) and the weight of the sample (dry or wet).

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43

Chuang, Tze-jer, Zheng-Dong Wang, and Dongdi Wu. "Analysis of Creep in a Si-SiC C-Ring by Finite Element Method." Journal of Engineering Materials and Technology 114, no. 3 (July 1, 1992): 311–16. http://dx.doi.org/10.1115/1.2904178.

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The long-term creep deformation of a siliconized silicon carbide ceramic C-ring subjected to a compression load at 1300°C in air is studied by the finite element method. Based on asymmetric creep responses observed under uniaxial creep tests, multidirectional constitutive equations in power-law form are derived using the parameters of effective stress/strain. The elastic solutions are first solved and used as a guide to reach the final mesh design and as initial conditions. Solving the initial value problem in which equilibrium and constitutive equations are satisfied at all times, this model gives time-history of stresses and displacements. Fair agreements were obtained in load-point displacement rate, damage zone, neutral axis locations, stress relaxation and redistribution when compared with simple curved beam theory and experimental data. As common with other nonlinear problems, the convergence of the finite element solutions strongly depends on the time step as well as the finess of the element size, particularly at the regions where principal stresses are close to the threshold stress for creep damage.

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Revishvili, A. Sh, G. G. Kаrmаzаnovsky, G. P. Plotnikov, K. A. Zamyatina, A. V. Geise, A. V. Galstyan, and M. S. Rubtsov. "Dynamics of pulmonary injury and extracorporeal methods of hemocorrection in patients with Sars-CoV-2." Medical Visualization 24, no. 3 (October 10, 2020): 12–25. http://dx.doi.org/10.24835/1607-0763-2020-3-12-25.

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Purpose. To assess changes in the degree of pulmonary injury in patients with Sars-CoV-2 after extracorporeal hemocorrection methods (ECHCM).Material and methods. 27 patients with Sars-CoV-2 underwent 48 ECHCM procedures - plasma separation, nonselective cytosorption hemoperfusion, dialysis-filtration techniques. After arriving in the hospital all patients underwent MSCT of the chest organs. The examination was conducted according to the standard protocol of MSCT of the chest organs and reconstruction of soft and high-resolution on a Philips Ingenuity CT 64 multi- detector computed tomograph. The following scanning parameters were used for the standard protocol: 64 × 0.625 collimation, 1 mm reconstruction, 0.5 mm increment. The patient was lying on his back with his arms thrown back behind his head during the procedure. A scan area including the chest was planned by the plan scan. Assessment of the scans was carried out in the Diсom-images viewing module of medical hardware- software complex “ArchiMed” (Med-Ray. Russia, 2004). The percentage of lung parenchyma lesions as well as the severity (CT-1–4) were evaluated according to the recommendations “Radiation diagnosis of coronavirus disease (COVID-19): organization, methodology, interpretation of the results”. CT examinations were compared not earlier than 4 days before ECHCM and not later than 5 days after.Result. With isolated plasmaseparation, the “ground glass” zones passed into the consolidation zones, the total volume of the lesion decreased and the pneumatization increased. In isolated hemoperfusion the dynamics is multidirectional: there are more consolidation zones, less ground glass zones in general, the process is stabilized and the zones of lung tissue damage are reduced. With isolated hemodiafiltration, the consolidation zones decreased, the pneumatization of the lung tissue increased, and subsequently the volume of the lesion and the consolidation zones increased significantly. By combined procedures there are multidirectional dynamics.Conclusion. The effect of ECMGC use on the degree and volume of lung tissue damage in patients with Sars- CoV-2 was not revealed.

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WU, W. C., T. C. WONG, and T. H. YIP. "Chronic Finger Joint Instability Reconstructed With Bone–Ligament–Bone Graft from the Iliac Crest." Journal of Hand Surgery 29, no. 5 (October 2004): 494–501. http://dx.doi.org/10.1016/j.jhsb.2004.03.014.

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Five patients with chronic instability of digital joints presented with instability and functional disability. Two patients had ulnar collateral ligament damage of the thumb metacarpophalangeal joint and another had chronic multidirectional instability due to radial collateral ligament, dorsal capsule and palmar plate laxity of the metacarpophalangeal joint of the thumb. The fourth patient had a lax radial collateral ligament and palmar plate of the proximal interphalangeal joint of the little finger and the fifth had chronic laxity of the ulnar collateral ligament of the interphalangeal joint of the thumb. All were reconstructed with bone–ligament–bone graft harvested from the iliac crest. The graft was fixed with screws and joint stability was achieved intra-operatively in all patients. All patients achieved a stable joint with improved functional performance at final followup.

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Yang, Yicheng, Sai Yemmaleni, Ikkyun Song, and In Ho Cho. "Cell Network-Based Formulas for Fast Determination of Flexural Stiffness Reduction of U-Shaped Core Shear Walls." Earthquake Spectra 34, no. 2 (May 2018): 867–91. http://dx.doi.org/10.1193/010317eqs003m.

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Reinforced concrete (RC) core shear wall is one of the most widely used earthquake-resisting systems. Degradation of a core wall's flexural stiffness is vital for understanding the natural frequency shift of the damaged building. But it is hard to capture, often necessitating complex finite element analyses (FEAs). This study seeks to provide an efficient tool to quickly determine the remaining flexural stiffness of U-shaped core walls. Importantly, the tool is designed to require only the easy-to-collect observational damage information. Of primary novelty is a network of microscopic unit cells, each consisting of nonlinear concrete and steel springs along with a compression-only gap. Validations with three U-shaped walls tested under complex and multidirectional loading paths show that the proposed formulas appear promising in quickly determining the trend of degrading flexural stiffness compared with a high-precision multiscale FEA program. All the formulas written in Matlab codes are made publicly available. Using the portable formulas running on a laptop, practicing engineers and researchers will be able to swiftly diagnose core U-shaped walls after quick on-site or laboratory observations.

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Zou, Luohuan, Yu Gong, Dingli Tian, Libin Zhao, Jianyu Zhang, and Ning Hu. "Effect of interface angle on mode I delamination damage behavior of multidirectional fully isotropic laminates with the same global stiffness." Thin-Walled Structures 182 (January 2023): 110211. http://dx.doi.org/10.1016/j.tws.2022.110211.

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Khatri, Bilal, Jan Rehra, Sebastian Schmeer, Ulf Breuer, and Frank Balle. "Metal/Carbon-Fiber Hybrid Composites—Damage Evolution and Monitoring of Isothermal Fatigue at Low and Elevated Temperatures." Journal of Composites Science 6, no. 3 (February 23, 2022): 67. http://dx.doi.org/10.3390/jcs6030067.

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Carbon-fiber-reinforced polymers (CFRPs) are the standard lightweight composite material for structural applications in aviation. The addition of metallic fibers to CFRPs to form metal/carbon-fiber hybrid composites (MCFRPs) has been shown to improve the elastic and plastic properties and to enable a non-destructive method for structural health monitoring over the material’s service life. In this paper, the results from the fatigue experiments on these hybrid composites at −55, 25 and 120 °C are discussed. Multidirectional CFRP and MCFRP laminates, fabricated using the autoclave method, were tested and compared under different fatigue loading conditions, while being simultaneously monitored for temperature and electrical resistance. Magnetic phase measurements were additionally carried out for the chosen metastable austenitic steel fibers in the MCFRPs. The results show that the improved ductility of the hybrid composite due to the presence of the steel fibers leads to better performance under fatigue loads and a less-brittle failure behavior. Based on the chemical composition of the metastable austenitic steel fibers, a temperature and plastic deformation-dependent phase transformation was observed, which could potentially lead to a method for non-destructive structural health monitoring of the hybrid composite over its service life.

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Koczurkiewicz-Adamczyk, Paulina, Katarzyna Klaś, Agnieszka Gunia-Krzyżak, Kamil Piska, Kalina Andrysiak, Jacek Stępniewski, Sławomir Lasota, et al. "Cinnamic Acid Derivatives as Cardioprotective Agents against Oxidative and Structural Damage Induced by Doxorubicin." International Journal of Molecular Sciences 22, no. 12 (June 9, 2021): 6217. http://dx.doi.org/10.3390/ijms22126217.

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Doxorubicin (DOX) is a widely used anticancer drug. However, its clinical use is severely limited due to drug-induced cumulative cardiotoxicity, which leads to progressive cardiomyocyte dysfunction and heart failure. Enormous efforts have been made to identify potential strategies to alleviate DOX-induced cardiotoxicity; however, to date, no universal and highly effective therapy has been introduced. Here we reported that cinnamic acid (CA) derivatives exert a multitarget protective effect against DOX-induced cardiotoxicity. The experiments were performed on rat cardiomyocytes (H9c2) and human induced-pluripotent-stem-cell-derived cardiomyocytes (hiPSC-CMs) as a well-established model for cardiac toxicity assessment. CA derivatives protected cardiomyocytes by ameliorating DOX-induced oxidative stress and viability reduction. Our data indicated that they attenuated the chemotherapeutic’s toxicity by downregulating levels of caspase-3 and -7. Pre-incubation of cardiomyocytes with CA derivatives prevented DOX-induced motility inhibition in a wound-healing assay and limited cytoskeleton rearrangement. Detailed safety analyses—including hepatotoxicity, mutagenic potential, and interaction with the hERG channel—were performed for the most promising compounds. We concluded that CA derivatives show a multidirectional protective effect against DOX-induced cardiotoxicity. The results should encourage further research to elucidate the exact molecular mechanism of the compounds’ activity. The lead structure of the analyzed CA derivatives may serve as a starting point for the development of novel therapeutics to support patients undergoing DOX therapy.

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Zhao, Guifang, Yiwen Ge, Chenyingnan Zhang, Leyi Zhang, Junjie Xu, Ling Qi, and Wenliang Li. "Progress of Mesenchymal Stem Cell-Derived Exosomes in Tissue Repair." Current Pharmaceutical Design 26, no. 17 (June 7, 2020): 2022–37. http://dx.doi.org/10.2174/1381612826666200420144805.

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Mesenchymal stem cells (MSCs) are a kind of adult stem cells with self-replication and multidirectional differentiation, which can differentiate into tissue-specific cells under physiological conditions, maintaining tissue self-renewal and physiological functions. They play a role in the pathological condition by lateral differentiation into tissue-specific cells, replacing damaged tissue cells by playing the role of a regenerative medicine , or repairing damaged tissues through angiogenesis, thereby, regulating immune responses, inflammatory responses, and inhibiting apoptosis. It has become an important seed cell for tissue repair and organ reconstruction, and cell therapy based on MSCs has been widely used clinically. The study found that the probability of stem cells migrating to the damaged area after transplantation or differentiating into damaged cells is very low, so the researchers believe the leading role of stem cell transplantation for tissue repair is paracrine secretion, secreting growth factors, cytokines or other components. Exosomes are biologically active small vesicles secreted by MSCs. Recent studies have shown that they can transfer functional proteins, RNA, microRNAs, and lncRNAs between cells, and greatly reduce the immune response. Under the premise of promoting proliferation and inhibition of apoptosis, they play a repair role in tissue damage, which is caused by a variety of diseases. In this paper, the biological characteristics of exosomes (MSCs-exosomes) derived from mesenchymal stem cells, intercellular transport mechanisms, and their research progress in the field of stem cell therapy are reviewed.

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