樹脂基納米復合材料力學行為及增強機理研究
發(fā)布時間：2018-07-14 16:19
【摘要】：納米復合材料由于其優(yōu)良的綜合性能,特別是其性能的可設計性被廣泛應用于航空航天、國防、交通和體育等領域。納米顆粒具有顆粒尺寸小、比表面積大、表面能高、表面原子所占比例大等特點,以及其特有的宏觀量子隧道效應,使得納米復合材料在力熱光電等領域的研究方興未艾,比如在力學方面,由于納米顆粒表面效應帶來的增強效應使得納米顆粒增韌復合材料得到了深入而廣泛的研究。但是國內外關于納米復合材料在動態(tài)力學性能方面的研究工作開展較少,對納米顆粒的增強機理認識還不夠全面。因此對不同物理性質的納米顆粒開展相關研究,以期對顆粒增強機理有更深入的認識,這對顆粒增強復合材料的設計與應用具有重要的意義。本文基于分離式Hopkinson桿實驗技術,系統(tǒng)地研究了基體環(huán)氧樹脂以及分別由納米SiO2和納米橡膠顆粒增強的環(huán)氧樹脂基復合材料壓縮力學性能測試。對影響Hopkinson壓桿實驗精度的各因素進行了系統(tǒng)分析,得到了材料的力學行為與應變率、顆粒性能和顆粒含量的相關性;通過有限元分析軟件建立復合材料的unit cell模型,對復合材料中顆粒作用機理進行了分析研究;根據環(huán)氧樹脂類材料的力學響應,建立了含有8個參數的本構關系。論文所取得的主要結論為:(1)通過對Hopkinson壓桿加載試樣過程的解析分析表明:對于本文研究的環(huán)氧樹脂類材料,即使施加于試樣中的應力沒有完全達到平衡,只要加載時間超過兩個特征時間,根據三波法計算出的試樣應力應變曲線也是足夠精確。若以彈性模量的精確度為標準,計算的誤差在5%之內。通過優(yōu)化設計加載波,提出了一組優(yōu)化應力波構型的解析解。對于線彈性材料試樣在小應變加載下,滿足該方程的應力波可以在兩個特征時間之后,實現試樣內應力平衡和恒定應變率加載,相應的有限元模擬和基于脆性砂石材料的試驗也證實了該方程的準確性和可行性。(2)在復合材料動態(tài)彈性模量測試精度研究中,發(fā)現壓痕效應、試樣和桿不完全接觸是材料動態(tài)彈性模量測不準的兩大因素。對于金屬類高彈性模量材料,通過有限元分析得知常規(guī)尺寸的試樣和壓桿端面間嚴重的壓痕效應導致彈性模量測量誤差遠大于5%。當采用轉接頭和長試樣時可以將測試誤差降低,相應有限元分析證實了該方案的可行性。而對于聚合物類低彈性模量材料,可以通過增大試樣直徑以避免較大的壓痕效應,通過采用本文開發(fā)的豎直Hopkinson桿加載技術,改善試樣和桿端面的接觸狀態(tài),實現了聚合物材料動態(tài)彈性模量的精確測量。(3)通過對環(huán)氧樹脂材料進行一系列壓縮試驗發(fā)現:環(huán)氧樹脂材料力學變形能否完全恢復的臨界載荷大于材料的彈性極限,其數值非常接近峰值應力。對環(huán)氧樹脂材料在峰值應力處變形機理進行研究,推斷出可能的變形機理:當施加于材料中的載荷達到峰值應力時,材料內部分子鏈三維網狀結構中交聯點開始斷裂破壞,隨之啟動了應變軟化的變形過程,由這些分子鏈鏈段運動造成的形變是不能自主恢復的。(4)通過對剛性顆粒SiO2增強復合材料的峰值應力和相應的應變率敏感性分析研究發(fā)現:該顆粒增強效應不明顯�；趗nit cell模型數值模擬結果表明:剛性顆粒增強效果依賴于基體材料的本構特征,即受制于基體環(huán)氧樹脂材料峰值應力后的應變軟化率。進一步的模擬研究發(fā)現:當軟化率低到一定程度時,即使添加剛性顆粒,其增強效果也可以為負,即減弱了復合材料的力學性能。通過對柔性橡膠顆粒增強復合材料的峰值應力和相應的應變率敏感性研究發(fā)現:雖然橡膠顆粒減弱了材料的峰值應力,但是顆粒在大變形下的應變硬化階段的增強效果顯著。Unit cell模型模擬發(fā)現:在大變形下,由于橡膠顆粒的不可壓縮性,顆粒表現為具有剛性顆粒的增強效果。(5)基于環(huán)氧樹脂材料的力學響應特征,提出了一種本構方程,該方程由Maxwell模型、Weibull模型和指數函數組成。模型采用8個參數,可以較好地反映環(huán)氧樹脂類材料的峰值應力以及應變軟化、平臺應力和應變硬化等三大特征,并且容易拓展表征以此為基體的顆粒增強復合材料的力學響應。
[Abstract]:Nanocomposites have been widely used in aerospace, national defense, transportation and sports, due to their excellent comprehensive properties, especially their performance. Nano particles have small particle size, large surface area, high surface energy, large proportion of surface atoms, and its unique macroscopic quantum tunneling effect. The research of rice composite materials in the field of force and photoelectricity is in the ascendant. For example, in the mechanical aspect, the enhancement effect caused by the surface effect of nano particles makes the Nano Particles Toughened composites have been extensively studied. However, the research work on the dynamic mechanical properties of nanocomposites at home and abroad is less. The understanding of the enhancement mechanism of nano particles is not fully understood. Therefore, it is of great significance for the design and application of particle reinforced composites to carry out the related research on the nanoparticles with different physical properties, which is of great significance for the design and application of particle reinforced composites. Based on the separation type Hopkinson rod experiment technology, this paper systematically studies the base. The compressive mechanical properties of epoxy resin and epoxy resin matrix composites reinforced by nano SiO2 and nano rubber particles were tested. The factors affecting the experimental precision of Hopkinson pressure bar were systematically analyzed. The mechanical behavior and strain rate, the correlation of particle properties and particle content were obtained, and the finite element analysis was used. The unit cell model of composite material is established and the mechanism of particle action in the composite is analyzed and studied. According to the mechanical response of the epoxy resin material, the constitutive relation with 8 parameters is established. The main conclusions obtained in this paper are as follows: (1) the analytical analysis of the loading sample process of the Hopkinson pressure bar shows that: The stress and strain curves calculated by the three wave method are accurate enough that the stress and strain curves calculated according to the three wave method are accurate, if the loading time is more than two characteristic times. An analytical solution for the optimization of the stress wave configuration is presented. For the linear elastic material specimen under small strain loading, the stress wave satisfies the stress balance and the constant strain rate loading after two characteristic time. The corresponding finite element simulation and the experiment based on the brittle sand material also confirm the accuracy of the equation. (2) in the study of the testing precision of dynamic modulus of elasticity of composite materials, it is found that the indentation effect and the incomplete contact between the specimen and the rod are the two factors of the uncertainty of the dynamic modulus of elasticity of the material. For the high elastic modulus material of the metal class, the serious indentation effect between the specimen and the end face of the pressure rod is found by the finite element analysis. The measurement error of the modulus of elasticity is much greater than that of 5%. when the test error can be reduced when the connecting head and the long sample are used. The corresponding finite element analysis confirms the feasibility of the scheme. For the polymer with low modulus of elasticity, the diameter of the sample can be increased to avoid the larger indentation effect, and the vertical Hopkinson developed in this paper is adopted. The rod loading technique improves the contact state of the specimen and rod end face and realizes the accurate measurement of the dynamic elastic modulus of the polymer material. (3) through a series of compression tests on the epoxy resin material, it is found that the critical load of the complete recovery of the mechanical deformation of the epoxy resin material is larger than the elastic limit of the material, and its value is very close to the peak value. Force. The deformation mechanism of epoxy resin material at peak stress is studied, and the possible deformation mechanism is deduced. When the load in the material is reached to peak stress, the crosslinking point in the three-dimensional network structure of the internal molecular chain of the material begins to break and destroy, and then the deformation process of the strain softening is started, which is made by the movement of these chain segments. The deformation can not be recovered independently. (4) through the analysis of the peak stress and the corresponding strain rate sensitivity of the rigid particle reinforced SiO2 reinforced composite, it is found that the enhancement effect of the particle is not obvious. The results of the unit cell model numerical simulation show that the reinforcement effect of rigid particles depends on the constitutive characteristics of the matrix material, that is, it is restrained. The strain softening rate after the peak stress of the matrix epoxy resin is further studied. It is found that when the softening rate is low to a certain extent, even adding rigid particles, the reinforcement effect can be negative, that is, the mechanical properties of the composites are weakened. The peak stress and corresponding strain of the composites are strengthened by the flexible rubber particles. The rate sensitivity study found that although the rubber particles weakened the peak stress of the material, the enhancement effect of the particle in the strain hardening stage under large deformation was significant.Unit cell model simulation found that, under the large deformation, the particles showed an enhanced effect with rigid particles due to the incompressibility of the rubber particles. (5) based on epoxy resin material A constitutive equation is proposed, which consists of Maxwell model, Weibull model and exponential function. The model can well reflect the peak stress and strain softening of epoxy resin, the stress and strain hardening of the epoxy resin materials, and it is easy to expand the characterization by 8 parameters. The mechanical response of the particle reinforced composite.
【學位授予單位】：西北工業(yè)大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TB33
本文編號：2122220
[Abstract]:Nanocomposites have been widely used in aerospace, national defense, transportation and sports, due to their excellent comprehensive properties, especially their performance. Nano particles have small particle size, large surface area, high surface energy, large proportion of surface atoms, and its unique macroscopic quantum tunneling effect. The research of rice composite materials in the field of force and photoelectricity is in the ascendant. For example, in the mechanical aspect, the enhancement effect caused by the surface effect of nano particles makes the Nano Particles Toughened composites have been extensively studied. However, the research work on the dynamic mechanical properties of nanocomposites at home and abroad is less. The understanding of the enhancement mechanism of nano particles is not fully understood. Therefore, it is of great significance for the design and application of particle reinforced composites to carry out the related research on the nanoparticles with different physical properties, which is of great significance for the design and application of particle reinforced composites. Based on the separation type Hopkinson rod experiment technology, this paper systematically studies the base. The compressive mechanical properties of epoxy resin and epoxy resin matrix composites reinforced by nano SiO2 and nano rubber particles were tested. The factors affecting the experimental precision of Hopkinson pressure bar were systematically analyzed. The mechanical behavior and strain rate, the correlation of particle properties and particle content were obtained, and the finite element analysis was used. The unit cell model of composite material is established and the mechanism of particle action in the composite is analyzed and studied. According to the mechanical response of the epoxy resin material, the constitutive relation with 8 parameters is established. The main conclusions obtained in this paper are as follows: (1) the analytical analysis of the loading sample process of the Hopkinson pressure bar shows that: The stress and strain curves calculated by the three wave method are accurate enough that the stress and strain curves calculated according to the three wave method are accurate, if the loading time is more than two characteristic times. An analytical solution for the optimization of the stress wave configuration is presented. For the linear elastic material specimen under small strain loading, the stress wave satisfies the stress balance and the constant strain rate loading after two characteristic time. The corresponding finite element simulation and the experiment based on the brittle sand material also confirm the accuracy of the equation. (2) in the study of the testing precision of dynamic modulus of elasticity of composite materials, it is found that the indentation effect and the incomplete contact between the specimen and the rod are the two factors of the uncertainty of the dynamic modulus of elasticity of the material. For the high elastic modulus material of the metal class, the serious indentation effect between the specimen and the end face of the pressure rod is found by the finite element analysis. The measurement error of the modulus of elasticity is much greater than that of 5%. when the test error can be reduced when the connecting head and the long sample are used. The corresponding finite element analysis confirms the feasibility of the scheme. For the polymer with low modulus of elasticity, the diameter of the sample can be increased to avoid the larger indentation effect, and the vertical Hopkinson developed in this paper is adopted. The rod loading technique improves the contact state of the specimen and rod end face and realizes the accurate measurement of the dynamic elastic modulus of the polymer material. (3) through a series of compression tests on the epoxy resin material, it is found that the critical load of the complete recovery of the mechanical deformation of the epoxy resin material is larger than the elastic limit of the material, and its value is very close to the peak value. Force. The deformation mechanism of epoxy resin material at peak stress is studied, and the possible deformation mechanism is deduced. When the load in the material is reached to peak stress, the crosslinking point in the three-dimensional network structure of the internal molecular chain of the material begins to break and destroy, and then the deformation process of the strain softening is started, which is made by the movement of these chain segments. The deformation can not be recovered independently. (4) through the analysis of the peak stress and the corresponding strain rate sensitivity of the rigid particle reinforced SiO2 reinforced composite, it is found that the enhancement effect of the particle is not obvious. The results of the unit cell model numerical simulation show that the reinforcement effect of rigid particles depends on the constitutive characteristics of the matrix material, that is, it is restrained. The strain softening rate after the peak stress of the matrix epoxy resin is further studied. It is found that when the softening rate is low to a certain extent, even adding rigid particles, the reinforcement effect can be negative, that is, the mechanical properties of the composites are weakened. The peak stress and corresponding strain of the composites are strengthened by the flexible rubber particles. The rate sensitivity study found that although the rubber particles weakened the peak stress of the material, the enhancement effect of the particle in the strain hardening stage under large deformation was significant.Unit cell model simulation found that, under the large deformation, the particles showed an enhanced effect with rigid particles due to the incompressibility of the rubber particles. (5) based on epoxy resin material A constitutive equation is proposed, which consists of Maxwell model, Weibull model and exponential function. The model can well reflect the peak stress and strain softening of epoxy resin, the stress and strain hardening of the epoxy resin materials, and it is easy to expand the characterization by 8 parameters. The mechanical response of the particle reinforced composite.
【學位授予單位】：西北工業(yè)大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TB33
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