The effect of interfacial microstructure on the interfacial strength of glass fiber/polypropylene resin composites

In this study, a new method to form resin droplets on fibers has been developed, and samples for the single fiber pull-out test were prepared using this method. The effects of microstructure of polypropylene (PP) resin and the microstructure of interface between the glass fiber and PP resin on the interfacial strength have been investigated. In addition, the influence of the microstructure of the interface on the interfacial strength of glass fiberreinforced PP composites have been discussed. It has been found that in the pull-out test, the transcrystallinity formed at the interface between the glass fiber and PP resin improved the interfacial strength when no spherulites developed in the PP matrix. On the other hand, it has been found that when the spherulites were well developed in the PP matrix, the transcrystallinity formed at the interface reduced the interfacial strength. Finally, rapid cooling has been shown to improve the interfacial strength between the fiber and resin in the crystalline polymer matrix composites. © 1994 John Wiley & Sons, Inc.     

A theoretical study of the effect of an interfacial layer on the properties of composites

A theoretical analysis using finite element methods has been applied to oriented short-fiber composites and spherical particle composites in order to predict the influence of a finite layer at the interface on mechanical properties. In this study the interfacial layer has been modeled by assuming that a layer surrounds the interface and that this layer has a modulus of elasticity different than both the fiber and the matrix. The stress distribution near the interface has been determined as a function of the elastic constants of the interface layer and the interface layer volume fraction. This analysis has also been performed for two volume fractions of fibers and two fiber length to diameter ratios. From this stress distribution, the composite modulus and toughness have been determined as a function of interface modulus. It is theoretically shown that the toughness, measured by amount of strain energy absorbed, can be maximized by controlling the interface modulus. Furthermore, recent experimental results appear to verify the theory.     

The effects of surface treatments of fibers on the interfacial properties in single-fiber composites

The interfacial properties between fibers and the matrix contribute to the overall properties in high performance composites. Plasma treatments (Ar, O₂, CF₄/O₂, N₂/H₂) have been performed on carbon fibers to improve the fiber-matrix interaction. The treatment efficiency was checked by the single-fiber technique, while the surface chemistry and morphology were characterized by X-ray photoelectron spectroscopy (XPS), static secondary ion mass spectroscopy (SSIMS), and scanning electron microscopy (SEM). The O₂- and N₂/H₂-plasma treatments proved most effective both for introducing oxygen-containing functionalities at the fiber surface and for improving the interfacial shear strength of carbon fiber/epoxy composites. A relationship between the oxygen concentration at the fiber surface and the interfacial shear strength is demonstrated.     

Effects of interfacial adhesion on properties of polypropylene/Wollastonite composites

Wollastonite reinforced polypropylene (PP/CaSiO₃) composites were prepared by melt extrusion. A silane coupling agent and a maleic anhydride grafted PP (PP‐g‐MA) were used to increase the interfacial adhesion between the filler and the matrix. The increased adhesion observed by scanning electron microscopy (SEM) resulted in improved mechanical properties. A model was applied to describe the relationship between the interfacial adhesion and tensile properties of PP/CaSiO₃ composites. There is stronger interfacial adhesion between silane‐treated CaSiO₃ and polymer matrix containing PP‐g‐MA as a modifier. Results of dynamic mechanical thermal analysis (DMTA) showed that stronger interfacial adhesion led to higher storage modulus. The influence of CaSiO₃ particles on the crystallization of PP was studied by using differential scanning calorimetry (DSC). The introduction of CaSiO₃ particles does not affect the crystallization temperature and crystallinity of PP matrix significantly. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

界面粘接对填充复合材料力学性能的影响

利用原位聚合的方法将聚甲基丙烯酸甲酯（PMMA）包覆在滑石粉的表面,制得了含PMMA粘接层的滑石粉／PVC复合材料。聚合物粘接层类似于粘接材料的粘接剂的作用,它很好地改善了复合材料的界面粘附性,提高了复合材料的机械强度,由于聚合物粘和基体聚合物的相互扩散以及界面内应力的存在,和昨合材料中存在一个最佳的聚合物粘接层。     

基于界面相细观力学模型的耐火材料损伤本构多尺度模拟

耐火材料的本构关系模型是材料对外载荷所作变形响应的一种数学表达,是数值模拟准确性与否的基础。为此,在细观损伤力学模型多尺度特性的基础上,借助商业有限元软件的二次开发功能,通过编制用户子程序接口将其界面细观力学模型的损伤本构关系嵌入到软件中,首先在宏观尺度上对炉衬结构耐火材料进行了拉、压加载数值试验,数值模拟的结果可以与试验结果较好地吻合;之后借助代表体积RVE单元,采用不同灰度代表不同损伤状态,在微观尺度上对损伤进行了直观表征,成功实现了炉衬结构耐火材料的多尺度模拟。     

钎料合金对钎焊金刚石界面性能的影响

在钎焊金刚石工具制造过程中,金刚石/钎料/基体之间的界面反应产物和微观结构决定了钎料钎焊金刚石与基体之间的结合强度.因此,对界面反应产物及组织微观结构进行研究,进而探讨钎焊工艺的优化十分重要.文章对钎料与基体界面显微组织形貌,高频感应钎焊界面微观,钎焊层的微观组织,钎焊金刚石微结构,钎焊接头界面组织,激光钎焊界面微结构...     

Study on the interfacial properties of two‐dimensionally arranged glass fiber/epoxy resin model composites

The effect of interfiber distance on the interfacial properties in two dimensional multi‐E‐glass fiber/epoxy resin composites has been investigated using fragmentation test. In addition, the effect of the fiber surface treatment on the interfacial properties has been studied. We found that the interfacial shear strength decreased with the decreasing interfiber distance at the range of <50 μm and the extent of the decreasing was more serious as the increasing of the number of adjacent fiber. This is probably that the interface between the fiber and the resin was damaged by the breaking of adjacent fibers and the damage increased with minimizing the interfiber spacing and the number of adjacent fibers. We can guess that interfacial shear strength in real composites is much smaller than that of multifiber fragmentation sample with touched fiber. When the interfiber distance was >50 μm, the interfacial shear strengths were saturated regardless of fiber surface treatment and were in close agreement with those of the single fiber fragmentation test. Finally, the interfacial shear strength evaluated using two dimensional fragmentation tests are shown as real values in‐site regardless of fiber surface treatment, interfiber distance, and existing matrix cracks. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1541–1551, 2006     

Study on the interfacial properties of three‐dimensionally arranged glass fiber/epoxy resin model composites

The effect of interfiber distance on the interfacial properties in three‐dimensional multi‐E‐glass fiber/epoxy resin composites has been investigated using fragmentation test. In additions, the effect of the fiber surface treatment on the interfacial properties has been studied. The interfacial shear strength decreased with the decreasing the interfiber distance at the range of under 50 μm and the extent of the decreasing was more serious as the increasing of the number of adjacent fiber. This is probably due to the fact that the interface between the fiber and the resin was damaged by the adjacent fiber breaks and the damage increased with closing the interfiber spacing and the number of adjacent fiber. It was found that the interfacial shear strengths saturated when the interfiber distance was over 50 μm, the ones were saturated regardless of fiber surface treatment and the ones were in close agreement with those of the single fiber fragmentation test. Finally, the interfacial shear strength evaluated using three‐dimensional fragmentation tests are shown as real values in‐site regardless of fiber surface treatment, interfiber distance and existing of matrix cracks. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The effect of interfacial adhesion on the tensile behavior of polystyrene–glass-bead composites

The tensile behavior at 20°C of polystyrene-glass-bead composites has been studied at several glass concentrations. To gain insight into the role of interfacial adhesion, the bonding between glass and polystyrene was varied by using different silane coupling agents. In contrast to the elastic behavior, the crazing behavior of the composites was found to be considerably affected by the degree of interfacial adhesion. This is explained by means of the different mechanisms for craze formation at adhering and nonadhering glass beads, respectively. Furthermore, it was found that both elastic and crazing behavior of the composites are influenced by the glass bead concentration.     

不同聚合物基体对复合材料性能的影响

研究了以不同类型聚合物为基体的高分子夏合材料的导电性和力学强度的变化规律，并从聚合物的结晶性，对填料的粘结性及其表面张力等方面进行了分析。若基体的结晶性和极性较强，则在导电性提高的同时，冲击强度下降；若基体本身比较柔软且对填料有足够的亲和力，则在一定的填料含量范围内，导电性和冲击强度可同时提高。     

A study of the effect of oxygen plasma treatment on the interfacial properties of carbon fiber/epoxy composites

In this work, effects of the interface modification on the carbon fiber‐reinforced epoxy composites were studied. For this purpose, the surface of carbon fibers were modified by oxygen plasma treatment. The surface characteristics of carbon fibers were studied by X‐ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), dynamic contact angle analysis (DCAA), and dynamic mechanical thermal analysis (DMTA), respectively. The interlaminar shear strength (ILSS) was also measured. XPS and AFM analyses indicated that the oxygen plasma treatment successfully increased some oxygen‐containing functional groups concentration on the carbon fiber surfaces, the surface roughness of carbon fibers was enhanced by plasma etching and oxidative reactions. DCAA and DMTA analyses show that the surface energy of carbon fibers increased 44.9% after plasma treatment for 3 min and the interfacial bonding intensities A and α also reached minimum and maximum value respectively. The composites exhibited the highest value of ILSS after oxgen plasma treated for 3 min. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Influence of interfacial interactions on the properties of PVC/cellulosic fiber composites

The surface properties at the interface between thermoplastic and cellulosic fibers strongly influence the mechanical properties of plastic/cellulosic fiber composites. This paper examines the role of surface acid-base properties of plasticized PVC and cellulosic fibers on the mechanical properties of the composites. The acid-base surface characteristics of cellulosic fibers were modified by treating the fibers with γ-aminopropyltriethoxysilane (A-1100), dichlorodiethylsilane, phthalic anhydride, and maleated polypropylene. The empirical acid (K_A) and base (K_D) characteristics (i.e., electron donor/acceptor abilities) of untreated and treated fibers, as well as plasticized PVC, were determined using inverse gas chromatography (IGC) technique. These parameters were used to yield information on the acid-base pair interactions that were correlated with the tensile and notched Izod impact properties of the composites. Acid-base pair interactions have been found to be a valuable parameter in the design of surface modification strategies intended to optimize the tensile strength of the composites. By tailoring the acid-base characteristics of cellulosic fibers and plasticized PVC, a composite with equal tensile strength and greater modulus than unfilled PVC was developed. However, the acid-base factors did not correlate with tensile modulus, the elongation at break, and the notched Izod impact property of PVC/newsprint fiber composites. Aminosilane has been observed to be a suitable adhesion promoter for PVC/wood composites improving significantly the tensile strength of the composites. Other treatments (dichlorodiethylsilane, phtalic anhydride, and maleated polypropylene) were found to be ineffective, giving similar strength compared to the composites with untreated cellulosic fibers. FTIR spectroscopy results suggested that aminosilane was effective because treated cellulosic fibers can react with PVC to form chemical bonds. The resulting bond between PVC and cellulosic fibers accounts for the effectiveness of aminosilane, when compared with other coupling agents.     

Dependence of interfacial strength on the anisotropic fiber properties of jute reinforced composites

The upsurge in research on natural fiber composites over the past decade has not yet delivered any major progress in large scale replacement of glass fiber in volume engineering applications. This article presents data on injection‐molded jute reinforced polypropylene and gives a balanced comparison with equivalent glass reinforced materials. The poor performance of natural fibers as reinforcements is discussed and both chemical modification of the matrix and mercerization and silane treatment of the fibers are shown to have little significant effect on their level of reinforcement of polypropylene in comparison to glass fibers. A hypothesis is proposed to explain the poor performance of natural fibers relating their low level of interfacial strength to the anisotropic internal fiber structure. POLYM. COMPOS., 31:1525–1534, 2010. © 2009 Society of Plastics Engineers     

The effect of the refining process on the interfacial properties of palm oil

The interfacial tension of palm oil against water at 60°C was determined in the presence of monoglycerides with (i) different acyl chain lengths, (ii) the same acyl chain length but with different unsaturation, and (iii) different phospholipids. The interfacial tensions of the oil/water interface were depressed, albeit to different extents, by the presence of these substances, depending on the acyl chain length, unsaturation, and the chemical structure of the species adsorbed. The adsorption of the saturated monoglycerides C12∶0, C14∶0, C16∶0, C18∶0 and the unsaturated monoglycerides of C18∶1 and C18∶3 is consistent with a Langmuir isotherm at the palm oil/water interface. However, fitting of the data for C18∶2, l-α-phosphatidylcholine, and lysophosphatidylcholine to the Langmuir isotherm is less satisfactory. The surface areas of the materials adsorbed at the palm oil/water interface are much larger than those of liquid condensed films and closer to those for liquid expanded films. The influence of the nature of the oil (triglycerides), the minor components in the oil, and thier interactions with the added lipids at the oil/water interface are briefly discussed. The effect of the refining process on the interfacial properties of palm oil against water was also studied. The efficiency of the refining process in minor oil contaminants’ removal and the quality of the oil obtained as reflected by the interfacial properties of the oil is discussed.     

The effect of loading rate on the interfacial behavior of overmolded hybrid fiber reinforced polypropylene composites

In the present work, the interfacial behavior of overmolded hybrid fiber reinforced polypropylene composites (hybrid composites) under the loading rate of 1, 10, and 100 mm/min are studied by experimental methods. The interfacial mechanical properties of hybrid composites are determined by monotonic and cycle loading-unloading single-lap-shear tests. The experimental results reveal that interfacial shear strength increases with loading rate, while the shear stiffness shows insensitive to loading rate. A regression function is built to describe the variation of interfacial shear strength with loading rate. The cyclic loading-unloading curves of hybrid composites samples indicate that loading rate effects on the interfacial nonlinear behavior of hybrid composites are considered by affecting plastic deformation. In addition, scanning electron microscopy and digital image correlation observations reveal the failure mechanisms of overmolded hybrid composites. The failure behavior of overmolded hybrid composites is mainly CFRT laminate failure for all cases. The evolution of non-uniform strain fields indicates that the fracture of overmolded thermoplastic composites may initiate at the edges and spread out to the far fields.     

The effect of chemical-vapor-deposition conditions on the properties of carbon-carbon composites

Properties are given for as-deposited and heat-treated carbon-felt, carbon-matrix composites infiltrated at deposition temperatures of 1100 and 1400°C, and pressures of 20 and 630 Torr. A thermal stress figure of merit was calculated for each material, with the heat-treated composite infiltrated at 1400°C and 630 Torr yielding the highest value. As with most graphitizing carbon materials, heat-treatment resulted in a decrease of the flexural strengths and moduli. The strength-to-modulus ratios, however, increased, being highest for deposition conditions of 1400°C and 630 Torr. Heat-treatment also resulted in an increase in thermal conductivity and a decrease in thermal expansion. These changes were related to the degree of crystallinity and to the formation of cracks within the matrix.     

The effect of metal coatings on the interfacial bonding strength of ceramics to copper in sintered Cu-SiC composites

Cu-SiC composites are very promising materials which have high thermal and electrical conductivity and may find many applications. Unfortunately, the main disadvantage of these materials is the dissolution of silicon in copper at elevated temperature, which significantly reduces their properties. In order to overcome this problem particles can be coated with a protective material before sintering. In this paper– the influence of three different metallic coatings on bonding strength were investigated. SiC particles were coated with tungsten, chromium or titanium. As reference a material with uncoated particles was prepared. The experiments were carried out with the use of microtensile tester. The highest increase in strength was observed in the case of chromium coating. On the other hand, the titanium coating, which was of very poor quality, decrease the bonding strength in comparison with uncoated particles. Furthermore, scanning electron and optical microscopes were used to determine the mechanism of debonding.     

Study on interfacial debonding stress and damage mechanisms of C/SiC composites using acoustic emission

Among ceramic matrix composites (CMCs), carbon fiber-reinforced silicon carbide matrix (C/SiC) composites are widely used in numerous high-temperature structural applications because of their superior properties. The fiber–matrix (FM) interface is a decisive constituent to ensure material integrity and efficient crack deflection. Therefore, there is a critical need to study the mechanical properties of the FM interface in applications of C/SiC composites. In this study, tensile tests were conducted to evaluate the interfacial debonding stress on unidirectional C/SiC composites with fibers oriented perpendicularly to the loading direction in order to perfectly open the interfaces. The characteristics of the material damage behaviors in the tensile tests were successfully detected and distinguished using the acoustic emission (AE) technique. The relationships between the damage behaviors and features of AE signals were investigated. The results showed that there were obviously three damage stages, including the initiation and growth of cracks, FM interfacial debonding, and large-scale development and bridging of cracks, which finally resulted in material failure in the transverse tensile tests of unidirectional C/SiC composites. The frequency components distributed around 92.5 kHz were dominated by matrix damage and failure, and the high-frequency components distributed around 175.5 kHz were dominated by FM interfacial debonding. Based on the stress and strain versus time curves, the average interfacial debonding stress of the unidirectional C/SiC composites was approximately 1.91 MPa. Furthermore, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDXS) were used to observe the morphologies and analyze the chemical compositions of the fractured surfaces. The results confirmed that the fiber was completely debonded from a matrix on the fractured surface. The damage behaviors of the C/SiC composites were mainly the syntheses of matrix cracking, fiber breakage, and FM interfacial debonding.