Effects of Film Thickness on The Work of Fracture Between Adhesives and Glass

In this investigation, the fracture energy of joints consisting of soda lime glass sandwiched around either an acrylate or poly(vinyl butyral) (PVB) was studied. This was accomplished for various adhesive thicknesses with the use of a tapered double cantilever beam specimen loaded in mode I. For adhesive thicknesses varying between 0.03 mm and 0.80 mm, the fracture energies ranged from 15 to 95 Pam for the glassy acrylate joints and from 375 to 1060 Pam for the more rubbery PVB joints. While the fracture energy was relatively independent of thickness for the acrylate joints, there was an increasing trend in toughness for the PVB joints. The fracture energy of the acrylate joints was modeled with a process zone model with reasonable results while the fracture energy of the PVB joints was modeled with constraints on the plastic zone. Scanning electron microscopy and measured bulk adhesive properties provided necessary input into the models.     

Effects of Substrate Orientation and Metal Film Thickness on the Intrinsic Strength, Intrinsic Fracture Energy, and Total Fracture Energy of Tantalum–Sapphire Interfaces

Parameters that characterize interface fracture are defined, and procedures to measure them are discussed. The interface strength σ_o is measured by using a novel laser spallation experiment, which uses a laser-induced stress wave to separate the interface. The intrinsic ( G _o) and total ( G _c) fracture energies are measured using a double cantilever beam experiment performed at ambient and cryogenic temperatures, respectively. These experiments are used to obtain relationships between G _c and G _o, and between σ_o and G _o, for interfaces between sputter-deposited polycrystalline Ta coatings and sapphire substrates. The intrinsic toughness and strength were modified by changing the orientation of the sapphire surface (basal and prismatic), while G _c was varied by changing the test temperature (ambient and cryogenic) and the thickness (1–3 μm) of the ductile Ta layer. Besides providing values that have interest in their own right, the work presented here provides a general framework for designing interfaces in bonded structures and serves as a basis to develop atomistic and continuum interface fracture models.     

Thickness Dependence of Fracture Stress in Glass Films Coated on Silicon

The stress required for spontaneous fracture of glass films on a silicon substrate was found to be proportional to the reciprocal square root of the film thickness. A simple fracture theory, with an assumption of a wedgelike crack shape, explained this relationship well.     

韧性聚合物材料的基本断裂功和变形行为研究

用双边缺口拉伸试样研究了几种聚烯烃塑料薄片在平面应力条件下的破坏行为。从断裂功 -韧带长度关系得到反映断裂韧性的材料常数比基本断裂功和反映材料塑性变形行为的比非基本断裂功 ,藉此分析和解释了这些材料的韧性和塑性特征 ;同时验算处理表明这些材料的试样断裂伸长与韧带长度均呈直线关系 ,线性回归相关系数达到 0 97～ 0 99,由此求得了反映临界裂纹张开位移的材料参数等。这些参数可用于研究材料的变形能力和断裂行为 ,解释材料的破坏机理     

Plastic Deformation and the Fracture Surface Energy of Sodium Chloride

A correlation between plastic deformation at crack tips in sodium chloride and the measured value of the fracture surface energy is presented. Plastic deformation can either aid or hinder crack growth, depending on the mode of deformation at the crack tip. If plane-stress deformation occurs, crack motion is hindered by step formation, dislocation generation, and plastic blunting of the crack tip. If plane-strain deformation occurs, crack motion is aided by stress fields that arise from the deformation. The specific surface free energy of sodium chloride, {100} plane, is estimated to be less than 0.37 J/m².     

Mode-l Fracture Behaviour of Adhesive Joints. Part I. Relationship Between Fracture Energy and Bond Thickness

The fracture properties of adhesive joints of aluminium were investigated using a rubber-modified tough epoxy resin system (G_IC = 2.76 kJ/m²) as adhesive material. Compact tension (CT) adhesive joints were manufactured for a wide range of bond thickness t (from 0.05mm to 10mm) and fracture tests conducted under static load. Scanning electron microscopy (SEM) was used to examine the fracture surface morphology. A large deformation elastic- plastic finite element model was developed to evaluate the J-integral value for different bond thickness. The fracture energy, J_c , was found to be highly dependent on the bond thickness and was lower than that of the bulk adhesive. As the bond thickness was increased J_c also increased, though not monotonically, towards the fracture energy of the bulk adhesive. This result was caused by the complicated interactions between the stress and strain fields, plastic deformation of the adhesive around the crack tip, constraint from the adherends and the failure path. It was shown that values of J_c as a function of bond thickness correlated well with the variation of plastic zone height. Scanning electron micrographs from the fracture surfaces of the CT adhesive joints illustrated that the failure path was mainly cohesive through the centre-plane of the adhesive layer. Brittle fracture mechanisms were observed for thin bonds (0.04mm < t< 0.5 mm) but tough fracture mechanisms were identified for thick bonds (t > 1 mm).     

Evaluation of Mode-II Fracture Energy of Adhesive Joints with Different Bond Thickness

A study on the mode-II edge-sliding fracture behaviour of aluminium-adhesive joints was carried out. Compact pure shear (CPS) adhesive joints of different bond thickness were produced using a rubber-modified epoxy resin as the adhesive. An analytical model was developed to calculate the stress distribution along the bond line of the joint. A crack-closure technique was used to evaluate the mode-II strain energy release rate. G _II, as a function of the adhesive bond thickness. The results indicated that for a given applied load, G _II increased gradually with the bond thickness. A finite element model (FEM) was also developed to evaluate the stress state along the bond line and the strain energy release rate of the CPS specimens. Consistent results were obtained between the theoretical model and finite element analysis. Scanning electron micrographs of the fracture surface illustrated a mainly interfacial fracture path between the adherends and the adhesive for all adhesive joint specimens. The critical fracture load increased very rapidly with bond thickness in the range 0.02 mm to 0.1 mm but remained constant thereafter. However, the mode-II critical fracture energy rose more gradually as the bond thickness was increased.     

Evaluation of Mode-II Fracture Energy of Adhesive Joints with Different Bond Thickness

A study on the mode-II edge-sliding fracture behaviour of aluminium-adhesive joints was carried out. Compact pure shear (CPS) adhesive joints of different bond thickness were produced using a rubber-modified epoxy resin as the adhesive. An analytical model was developed to calculate the stress distribution along the bond line of the joint. A crack-closure technique was used to evaluate the mode-II strain energy release rate. G_II, as a function of the adhesive bond thickness. The results indicated that for a given applied load, G_II increased gradually with the bond thickness. A finite element model (FEM) was also developed to evaluate the stress state along the bond line and the strain energy release rate of the CPS specimens. Consistent results were obtained between the theoretical model and finite element analysis. Scanning electron micrographs of the fracture surface illustrated a mainly interfacial fracture path between the adherends and the adhesive for all adhesive joint specimens. The critical fracture load increased very rapidly with bond thickness in the range 0.02 mm to 0.1 mm but remained constant thereafter. However, the mode-II critical fracture energy rose more gradually as the bond thickness was increased.     

工艺因素对磁控溅射法制备钛酸锶钡薄膜性能的影响

磁控溅射技术在薄膜制备领域有着广泛的应用.本文在介绍磁控溅射法制备薄膜材料的基本原理和流程基础之上,详细分析了溅射工艺参数(溅射功率、温度、溅射气压、氧分压)对BST薄膜性能的影响,并提出了研究中需要解决的一些问题.     

施镀工艺参数对化学镀沉积速率的影响

各种工艺参数对化学镀沉积速度影响的研究是化学镀中的关键问题之一,文献尚无系统的研究,本文全面总结研究了金属盐浓度,还原剂浓度,络合剂浓度,ＰＨ值,施镀温度与时间对化学镀沉积速度的影响和原因。     

工艺参数对水辅注塑弯管壁厚的影响

利用华南理工大学自主研发的注水系统和水辅注塑弯管模具,研究了熔体温度、模具温度、注水延迟时间、熔体注射量、注水压力、注水温度、熔体注射速率和熔体注射压力等8个水辅成型主要工艺参数对聚丙烯制品壁厚偏差率的影响,并分析了影响机理。结果表明,部分工艺参数对于制品弯曲段的壁厚偏差率有影响;增加注水延迟时间,降低注水压力和模具温度,短射填充区的制品壁厚的偏差率有所减小;提高熔体温度,壁厚偏差率的波动幅度增大。     

Effects of Thickness on Piezoelectric Properties of Highly Oriented Lead Zirconate Titanate Films

Lead zirconate titanate (PZT) films were deposited on platinized silicon substrates by spin coating using PZT sols containing polyvinylpyrrolidone (PVP) as an additive. PZT films with a 60/40 composition and a thickness of up to 8 μm were fabricated by repeating the deposition process 15 times on highly oriented (100) and (111) seed layers with the same composition. The films grew well in the direction of the seed layers and had a uniform and smooth surface without any cracks. As the thickness of the films increased, the grain size remained almost the same, but the effective d ₃₃ value increased steadily. The thickness dependence of the piezoelectric properties was attributed to the residual stress of the films.     

Effects of Temperature and Strain Rate on the Dynamic Fracture Properties of HTPB Propellant

In order to study the influence of temperature and strain‐rate on HTPB propellant fracture capability under impact loading conditions, a dynamic fracture experiment at different temperatures was carried out by using the cracked straight‐through Brazilian disc (CSTBD) specimen on the split Hopkinson pressure bar (SHPB), and the dynamic initiation fracture toughness of the HTPB propellant was obtained. Experimental results indicate that the proposed dynamic fracture testing for the HTPB propellant is effective. The dynamic initiation fracture toughness is obviously sensitive to temperature and strain‐rate, and its value increases with decreasing temperature and increasing strain rate, and a linearity relationship exists between the fracture toughness and the logarithm of the strain rate, and the linearity also increases with increasing loading rate. A master curve of quadratic function for the fracture toughness was obtained.     

荷能粒子在类金刚石膜形成中的作用

类金刚石膜由于其优异性能和广泛应用已引起越来越多的研究兴趣。尽管各种化学和等离子体辅助ＣＶＤ和ＰＶＤ技术已用来沉积类金刚石膜（ＤＬＣ膜）,但其形成机理仍不清楚。本文通过分析荷能离子的作用,应用热峰效应和离子刻蚀效应来解释ＤＬＣ膜的形成     

乙烯掺杂对硅薄膜沉积速率和形貌的影响

采用APCVD工艺用硅烷和乙烯为原料在620℃沉积硅薄膜.用AFM观察薄膜表面形貌,用SEM扫描截面测量薄膜厚度.FTIR光谱表明薄膜中存在Si-C.研究了C2H4/SiH4摩尔比对膜厚的影响,随着C2H4/SiH4的增大,薄膜的沉积速率降低,表明乙烯掺杂会抑制薄膜生长,同时乙烯的加入减弱了颗粒的异常长大.     

镀膜参数对浮法玻璃热反射合金膜性能的影响

通过改变气体流量、镀膜温度、锡槽保护气用量,研究浮法玻璃在线镀膜参数对热反射合金膜的影响.采用扫描电子显微镜和能谱仪分析膜层的表面形貌、厚度和化学组成,采用分光光度计分析镀膜玻璃的光学性能和颜色指标,并配制5 mol/L的H2SO4溶液测试薄膜的耐酸性能.结果表明,随着气体流量增大,镀膜层厚度增大,膜层颗粒度基本不变,...     

Temperature and Loading Rate Effects on the Fracture Behaviour of Adhesively Bonded GFRP Nylon-6,6

The combined effect of varying test temperature and loading rate on the Mode II fracture toughness of plasma-treated GFRP Nylon-6,6 composites bonded using a silica-reinforced epoxy adhesive has been studied. End notch flexure tests have shown that the adhesive system used in this study offers a wide range of fracture energies that are extremely sensitive to changes in temperature and loading rate. Increasing the test temperature resulted in a substantial reduction in the Mode II fracture toughness of the adhesive, with the value of G_IIc at 60°C being approximately one-half of the room temperature value. In contrast, increasing the crosshead displacement rate at a given temperature has been shown to increase the value of G_IIc by up to 250%. Compression tests performed on bulk adhesive specimens revealed similar trends in the value of [sgrave]_y with temperature and loading rate. In addition, it was found that the plasma treatment employed in this study resulted in stable crack propagation through the adhesive layer under all testing conditions.

A more detailed understanding of the effect of varying temperature and loading rate on the failure mechanisms occurring at the crack tip was achieved using the double end notch flexure (DENF) geometry, which was considered in tandem with the fracture surface morphologies. Here, changes in the degree of matrix shear yielding and particle-matrix debonding were used to explain the trends in [sgrave]_y and G_IIc.     

Effects of Heating Rate on Stress Evolution in Alkoxide-Derived Silica Gel-Coating Films

Silica gel films were deposited by spin coating on single-crystal Si wafers using an acid-catalyzed Si(OC₂H₅)₄ solution as a coating solution. The gel films were heated at various rates, where in situ stress measurement was conducted. In-plane tensile stress developed during the course of heating, and was found to be larger at lower heating rates at temperatures up to 350°C. The larger stress was thought to cause cracking at lower temperatures, which was previously observed at lower heating rates in in situ observation. The larger stress at lower heating rates was basically ascribed to the larger degrees of densification, which was revealed in the larger extent of reduction in thickness as well as in Si–OH/Si–O–Si and O–H/Si–O–Si infrared absorption band area ratios at lower heating rates. The difference in stress at different heating rates appeared to originate mainly in the difference observed at low temperatures below 130°C, suggesting that the heating rate particularly affects the densification that occurs via solvent evaporation. The increment in stress was reduced over 400°C when the heating rate was low, which was thought to result from the higher degree of densification already achieved below 400°C as well as the structural relaxation occurring at such high temperatures.     

Effects in Surface Free Energy of Sputter-Deposited VNx Films

Vanadium nitride (VN _x ) thin films have attracted much attention for semiconductor integrated circuit (IC) packaging molding dies, and forming tools due to their excellent hardness and, thermal stability. VN _x thin films with VN_0.45, VN_0.83, VN_1.22, VN_1.73, VN_2.06 were prepared using a radio frequency (RF) sputter technique. The experimental results showed that the contact angle at 20°C increases with increasing nitrogen content of the VN _x films, to 101.4° corresponding to VN_1.73 and then decreased. In addition, the contact angles decreased with increasing surface temperature, because an increase of the surface temperature disrupts the hydrogen bonds between water and the films and the water gradually vaporizes. The total surface fee energy (SFE) at 20°C decreased with nitrogen content of the VN _x films to 29.8 mN/m (VN_1.73) and then increased. This is because a larger contact angle means weaker hydrogen bonding which results in a lower SFE. The polar SFE component had the same trend as the total SFE, but the dispersive SFE component had the opposite trend. The polar SFE component is also lower than the dispersive SFE component. This is because hydrogen bonds are polar. The total SFE, dispersive SFE and polar SFE of the VN _x films all decrease with increasing surface temperature. This is because with increasing temperature, water evaporates from the surface, disrupting hydrogen bonds and hence increasing surface entropy. The film roughness has an obvious effect on the SFE and there is tendency for the SFE to increase with increasing film surface roughness. As a result the SFE and surface roughness can be expressed in terms of a simple ratio function.