无纺结构麻纤维复合材料疲劳性能及失效机理

近年来,以可持续性为特征的麻纤维因其在环境可接受性和商业可行性方面的优势而备受关注。以麻纤维代表之一的洋麻毡为增强材料,不饱和聚酯(UP)为基体,采用手工叠层和模压成型的方法制备了洋麻/UP复合材料。设计低周疲劳(低速低循环疲劳)和高周疲劳(高速多循环疲劳测试)来探讨其疲劳性能和疲劳极限,重点观察不同疲劳测试条件下麻纤维的断裂形态和失效机理。

An Effective Numerical Calculation Method for Multi-Time-Scale Mathematical Models in Systems Biology

The improvements of high-throughput experimental devices such as microarray and mass spectrometry have allowed an effective acquisition of biological comprehensive data which include genome, transcriptome, proteome, and metabolome (multi-layered omics data). In Systems Biology, we try to elucidate various dynamical characteristics of biological functions with applying the omics data to detailed mathematical model based on the central dogma. However, such mathematical models possess multi-time-scale properties which are often accompanied by time-scale differences seen among biological layers. The differences cause time stiff problem, and have a grave influence on numerical calculation stability. In the present conventional method, the time stiff problem remained because the calculation of all layers was implemented by adaptive time step sizes of the smallest time-scale layer to ensure stability and maintain calculation accuracy. In this paper, we designed and developed an effective numerical calculation method to improve the time stiff problem. This method consisted of ahead, backward, and cumulative algorithms. Both ahead and cumulative algorithms enhanced calculation efficiency of numerical calculations via adjustments of step sizes of each layer, and reduced the number of numerical calculations required for multi-time-scale models with the time stiff problem. Backward algorithm ensured calculation accuracy in the multi-time-scale models. In case studies which were focused on three layers system with 60 times difference in time-scale order in between layers, a proposed method had almost the same calculation accuracy compared with the conventional method in spite of a reduction of the total amount of the number of numerical calculations. Accordingly, the proposed method is useful in a numerical analysis of multi-time-scale models with time stiff problem.

玻璃纤维/大麻纤维增强聚丙烯混杂复合材料的力学性能和断裂特征(英文)

目前在土木工程,建筑,汽车等领域里使用的复合材料中,玻璃纤维是用量最大的增强材料。由于保护地球环境的呼声日趋高涨,天然纤维被期待着代替源于石油而且再利用困难的玻璃纤维,成为绿色复合材料的必要材料之一。本文通过注射成型工艺制作了玻璃短纤维,大麻短纤维以及混杂型纤维增强复合材料,并在拉伸实验中应用两种不同频率的声发射技术检测了拉伸断裂特性。实验发现,随着大麻纤维的加入和混杂复合材料绿色度的增加,复合材料的拉伸弹性模量随之线性增大,而拉伸强度基本保持不变。当大麻纤维的含量超过20wt%的时候,拉伸强度开始降低。在不同频率的声发射实验中,混杂型复合材料的声发射事件的产生都比单一纤维增强型复合材料要来的晚,也就是说,纤维的混杂有助于推迟微裂纹的产生。

Enhancement in Thermal Stability of Polyoxymethylene (POM)-Based Biopolymer Blend Materials

In this study, we demonstrate the enhancement in thermal stability of polyoxymethylene (POM)-based biopolymer blend materials. Polyoxymethylene (POM)/Polylactic acid (PLA) blends have been used as alternative biopolymer materials for supporting environmental problems with thermal stability feature. The effects on POM biopolymer blend materials with a controlled PLA amount in their compositions under various injection conditions, were investigated by thermogravimetric analysis, dynamic mechanical analysis, and differential scanning calorimetry. The POM/PLA biopolymer blend materials showed POM phase acted as a homogeneous nucleating site for increasing PLA crystallization, which improves storage modulus of the blend materials. The decomposition temperatures of POM/PLA biopolymer blends tend to shift around 30˚C - 50˚C lower compared to the decomposition temperatures of PLA. Thus, the decomposition temperature behavior of POM/PLA blends seems to be closer to POM. The suitable ratio in POM70/PLA30 resulted in the high strength of the blend materials. The POM/PLA biopolymer blend material was tested at various injection speeds and good miscibility was obtained at an injection speed of 100 mm/s. This enhancement of thermal stability in POM/PLA blend materials should be useful in the development of high-performance bio-based thermoplastic materials.

Simulation of the Interphase of Insert Injection Moldings

In this work, the generalizing of the finite element method (FEM) of thermoplastic prepreg insert injection molding composites was investigated. The specimens were prepared using glass fiber/polyamidc 6 (GF/PA6) inserted prepreg, and their characteristics were investigated and compared under ANSYS workbench program. The prediction of the bending initial fracture point under analytical tensile testing with interlayer on prepreg insert moldings was focused. It was found that the bending initial fracture point was applied to predict by matching the shear stress. There was obtained from analytical tensile testing and bending analysis. Therefore, it can be obtained the optimum of the clastic modulus ratio on the injection part/interlayer/insert part by using FEM via ANSYS workbench.

Inference of General Mass Action-Based State Equations for Oscillatory Biochemical Reaction Systems Using <i>k</i>-Step Genetic Programming

Systems biology requires the development of algorithms that use omics data to infer interaction networks among biomolecules working within an organism. One major type of evolutionary algorithm, genetic programming (GP), is useful for its high heuristic ability as a search method for obtaining suitable solutions expressed as tree structures. However, because GP determines the values of parameters such as coefficients by random values, it is difficult to apply in the inference of state equations that describe oscillatory biochemical reaction systems with high nonlinearity. Accordingly, in this study, we propose a new GP procedure called “k-step GP” intended for inferring the state equations of oscillatory biochemical reaction systems. The k-step GP procedure consists of two algorithms: 1) Parameter optimization using the modified Powell method—after genetic operations such as crossover and mutation, the values of parameters such as coefficients are optimized by applying the modified Powell method with secondary convergence. 2) GP using divided learning data—to improve the inference efficiency, imposes perturbations through the addition of learning data at various intervals and adaptations to these changes result in state equations with higher fitness. We are confident that k-step GP is an algorithm that is particularly well suited to inferring state equations for oscillatory biochemical reaction systems and contributes to solving inverse problems in systems biology.

Withdraw: Improvement on Adhesion Properties of Insert Injection Molding Composites: Effect of Inserted Parts, Adhesive Lengths and Injection Conditions

Short Retraction Notice The paper does not meet the standards of "Open Journal of Composite Materials". This article has been retracted to straighten the academic record. In making this decision the Editorial Board follows COPE's Retraction Guidelines. The aim is to promote the circulation of scientific research by offering an ideal research publication platform with due consideration of internationally accepted standards on publication ethics. The Editorial Board would like to extend its sincere apologies for any inconvenience this retraction may have caused. Editor guiding this retraction: Prof. Chengye Fan (EiC of OJCM) The full retraction notice in PDF is preceding the original paper, which is marked "Withdraw".

Reactive Compatibilization of Short-Fiber Reinforced Poly(lactic acid)Biocomposites

Poor interfacial adhesion between biobased thermoplastics and natural fibers is recognized as a major drawback for biocomposites.To be applicable for the large-scale production,a simple method to handle is of importance.This work presented poly(lactic acid)(PLA)reinforced with short-fiber and three reactive agents including anhydride and epoxide groups were selected as compatibilizers.Biocomposites were prepared by one-step meltmixing methods.The influence of reactive agents on mechanical,dynamic mechanical properties and morphology of PLA biocomposites were investigated.Tensile strength and storage modulus of PLA biocomposites incorporated with epoxide-based reactive agent was increased 13.9%and 37.4%compared to non-compatibilized PLA biocomposite,which was higher than adding anhydride-based reactive agent.SEM micrographs and Molau test exhibited an improvement of interfacial fiber-matrix adhesion in the PLA biocomposites incorporated with epoxide-based reactive agent.FTIR revealed the chemical reaction between the fiber and PLA with the presence of epoxide-based reactive agents.

Effects of Ultrasonic Waves during Resin Impregnation on the Mechanical Properties of Unidirectional Composite Materials

Effects of ultrasonic vibrations on mechanical properties of fiber reinforced plastics were investigated during molding resin impregnation process in vacuum assisted resin transfer molding.?The vacuum bag including the preformed each?non-crimp fabrics (carbon and glass fibers)?was placed in a water bath of an ultrasonic wave generator during resin impregnation. The mechanical properties of the laminates were evaluated?through the mechanical strength tests and scanning electron microscope?(SEM) observation. The results revealed that ultrasonic waves improved transverse tensile, flexural, interlaminar shear, and compressive strengths of the carbon fiber (CF) laminates and interlaminar shear and compressive strengths of the glass fiber (GF) laminates. It was found from SEM observation that the fracture modes of the CF and GF laminates processed using ultrasonic waves were resin fracture. Accordingly, the adhesion of the fiber/resin interface was improved by oscillating ultrasonic vibration during resin impregnation, leading to an increase of the interface strength.

The Effect of Curative Concentration on Thermal and Mechanical Properties of Flexible Epoxy Coated Jute Fabric Reinforced Polyamide 6 Composites

Many researchers have shown interest in the reinforcement of commodity thermoplastic with natural fibers. However, the drawback of natural fibers is their low thermal processing temperatures, that border around 200℃. In this investigation, we tried to improve the thermal stability of natural fibers with the use of flexible epoxy surface coating that could facilitate processing with engineering thermoplastics. Jute fabric and Polyamide 6 (PA6) composites were prepared by compression molding. The thermal decomposition characteristics of the jute fabric were evaluated by using thermo gravimetric analysis (TGA). Mechanical analysis was conducted to evaluate tensile test and three point bending test of composite. It was found that thermal degradation resistance of jute fabric was improved by coating with flexible epoxy resin. Moreover, the flexural modulus improved with increasing curative concentration. The interfacial interaction between the epoxy and PA6 was clearly indicated by the photo micrographs of the polished cross sections of the coated and uncoated jute fabric/PA6 composites.

Effect of Needle Punching Process on a Chopped Strand Mat Composite with an Open Hole

The easiest and most reliable joining method is the mechanical joint with a bolt and nut or rivet. However, in the case of composite laminates, mechanical joint properties decrease because of lower interlaminar properties compared to in-plane properties around hole.?This study investigated needle punching process with the aim of improving the mechanical properties in the thickness direction of fiber-reinforced plastic composite laminates with an open hole. Needle punching process was applied to glass fiber chopped strand matused as the reinforcement for the composite laminates. Open-hole tensile tests and observations of end cross-sections after the tests were performed. The tensile properties and fracture mechanism of the specimens subjected to needle punching process were investigated. In addition, characteristic distance (a parameter for evaluating resistance to fracture in open-hole tensile test specimens) was also calculated to examine the effects of needle punching process conditions on fracture toughness. Tensile strength was improved by more than 15% by needle punching process. However, when a certain needle punching density was exceeded, the mechanical properties worsened. In addition, characteristic distance increased with increasing needle punching density. Thus, these results suggest that there is an optimal needle punching density with respect to strength and characteristic distance.

Quasi-Static Flexural Properties of a Pultruded Glass Fiber/Unsaturated Polyester Square Pipe

This paper explores quasi-static flexural properties and fracture behavior of a pultruded glass fiber/unsaturated polyester square pipe for automotive structural applications. Three-point flexural testing is performed in an Instron Universal Testing Machine with steel jigs supporting the top and bottom surfaces of the pipe. Acoustic emission (AE) measurements are recorded during flexural testing to evaluate initial fracture in the pipe structure. After final fracture, five cross-sections of the pipe are cut at 50-mm intervals along the longitudinal axis, with the first cut located at the mid-span of the pipe. Cross-sections of a pipe from an interrupted test where initial fracture is detected from the AE method are also prepared. Damage locations and behavior on each cross-section are observed. The flexural testing results show that the cumulative AE counts increase rapidly from 2.5 kN, that final failure occurs at a maximum load of approximately 13 kN, and that corresponding initial and final failure occurs in the two corner regions on the compressive side of flexural loading. Failure initiates by stress concentrations due to the upper jig on the top surface during bending. The cross-sectional observations also reveal clear deformation behavior of the pipe where failure is present, marked by inward bending of the top surface and upper corners located on the compressive side, near the jig. The locations of maximum stresses and deformations obtained from finite element analysis of this pipe structure are in very good agreement with the experimental observations.

The Determination of Interfacial Shear Strength in Short Fiber Reinforced Poly Ethylene Terephthalate by Kelly-Tyson Theory

The interfacial shear strength value measuring by the modified Kelly-Tyson equation method was studied the measurement accuracy. The measuring accuracy by using the modified Kelly-Tyson equation method is compared to the nano-indentation testing method. The results and an influential factor are described. An error in the modified Kelly-Tyson equation is verified to avoid the incorrect measurement when the interfacial shear strength was measured by the modified Kelly-Tyson equation. To study the different interfacial shear strength behavior, short fiber reinforced PET composites were fabricated. In this study, an advance fabricating technique for short fiber reinforced composite as direct fiber feeding process is conducted to fabricate GF/recycled PET for studying the interfacial shear strength. The result indicates that the modified Kelly-Tyson equation method accurately provides the accurate interfacial shear strength value, if it is conducted with the sample without a horizontally aligned fiber. So the high fiber loading content sample should be avoided to get the more accuracy result. The large horizontally aligned fiber area into specimens extremely resulted in the incorrect measurement of the interfacial shear strength value by the modified Kelly-Tyson equation method. The fiber agglomeration factor and the sensitively horizontally aligned fiber area must be considered its influence on the measuring for improving the equation effectiveness.

Development of Cockleshell-Derived CaCO₃for Flame Retardancy of Recycled PET/Recycled PP Blend

Recycled polyethylene terephthalate (RPET) and recycle polypropylene (RPP) blends filled with a renewable filler, i.e. cockleshell-derived CaCO3 (CS) were prepared as an environmental friendly thermoplastic composite. The effects of CS particle size and content on thermal stability, mechanical performance and flame retardant properties of the blends were investigated. Thermogravimetric analysis was performed to elucidate the thermal decomposition kinetics of the filled composites. The iso-conversion of the Flynn-Wall-Ozawa was developed by the second order polynomial function for thermal oxidative degradation of the blends while peak derivative temperature from the Kissinger method was able to verify the mechanism of degradation in these blends. The results indicated that both CS and commercial grade CaCO3 improved thermal stability and enhanced the stiffness as well as impact performance of the blends. However, this could only be achieved when high filler content was present in the RPET/RPP blends.

Application of Nanofiber Fabricated by Cotton Candy Method to Electric Double-Layer Capacitor

In recent years, application of carbon-based nano material to electrode material has been paid attention, however, due to its higher cost, it would be difficult to put it into practical use. Then, we have proposed to make nano carbon fiber with lower production cost. The purpose of our research was, to apply our nano carbon fiber to electrical double-layer capacitor electrode. We used cotton candy method to make nano fiber, and applied microwave heating for carbonization. By applying nano carbon fiber to electrical double-layer capacitor electrode, we got results that thicker electrode containing nano carbon fiber leads to lower resistance value, compared with electrode without containing nano carbon fiber. From this result, it was indicated that by containing nano carbon fiber, the electric bypass was formed in the electrode.

Investigation of the Flexural Properties and Failure Behavior of Unidirectional CF/Nylon 6 and CF/Epoxy Composites

In this work, flexural properties and failure behavior of unidirectional (UD) carbon fiber reinforced polyamide 6 (CF/Nylon 6) and epoxy resin (CF/ Epoxy) laminates were investigated through three-point bending test. The mechanical properties and failure behavior of 0 and 90 degree CF/Nylon 6 and CF/Epoxy laminates were discussed based on the fiber volume fraction, fiber distribution, void content, interfacial properties, transversal tensile strength and fracture toughness. The effects of fiber volume fraction, fiber distribution, void content and their hybrid effect on the flexural properties were investigated. Step-by-step observation and scanning electron microscope observation of laminates after flexural tests were employed to analyze the fracture process.

Barrier, Adsorptive, and Mechanical Properties of Containers Molded from PET/PP Blends for Use in Pharmaceutical Solutions

In this study, the adsorptive properties of L-menthol, moisture vapor transmission rate, and mechanical properties of poly (ethylene terephthalate) (PET), polypropylene (PP), and their blends were evaluated in containers fabricated by injection molding without a compatibilizing agent. These containers intended to hold pharmaceutical solutions containing lipophilic chemicals such as L-menthol. By the addition of a small amount of PP, the moisture barrier properties of PET were effectively improved, but its anti-adsorptive property was reduced. The strength of the PET/PP blends was reduced, but some PET/PP blends were still able to bear the experimental load required for application in eye-drop containers. PET/PP = 9/1 and PET/PP = 8/2 were found to be most applicable for using in the fabrication of containers for medicinal solutions.

Erratum to “Improvement on Adhesion Properties of Insert Injection Molding Composites: Effect of Inserted Parts, Adhesive Lengths and Injection Conditions” [Open Journal of Composite Materials (2017) 197-206]

The original online version of this article (Pinpathomrat, B. and Hamada, H. (2017) Improvement on Adhesion Properties of Insert Injection Molding Composites: Effect of Inserted Parts, Adhesive Lengths and Injection Conditions. Open Journal of Composite Materials, 7, 197-206. https://doi.org/10.4236/ojcm.2017.74013) unfortunately contains several mistakes in Figures 1-4, and Figure 6.