Fatigue life prediction of matrix dominated polymer composite materials

Fatigue life prediction is investigated analytically for matrix dominated polymer composite laminates having nonlinear stress/strain response, based on the fatigue modulus concept. Fatigue modulus degardation rate at any fatigue cycle was assumed as a power function of number of fatigue cycles. A new stress function describing the relation of initial fatigue modulus and elastic modulus was used to account for material non‐linearity at the first cycle. It was assumed that fatigue modulus at failure is proportional to the applied stress level. A new fatigue life prediction equation as a function of applied stress is proposed. The prediction was verified experimentally using cross‐ply carbon/epoxy laminate (CFRP) tube under torsional fatigue loading. It is shown that the proposed equation has wide applicability and agrees well with experimental data.     

Design and characterization of polypropylene matrix/glass fibers composite materials

In this article, polymer composites based on polypropylene (PP) matrix reinforced with short glass fibers type E (GF‐type E) were obtained. However, to ensure good interfacial adhesion and stress transfer across the interface, the influence of the chemical functionalization of the phases was analyzed. The better interfacial adhesion is assured by the use of maleic anhydride grafted PP and amino‐functionalized GF. The obtained composite materials were tested from the point of view of composition, morphology, and mechanical properties. It can conclude that the chemical functionalization of the two phases is beneficial from the point of view of compatibility of the phases and consequently higher mechanical properties are obtained. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42163.     

Electrospun nanofiber: Emerging reinforcing filler in polymer matrix composite materials

The rapidly developing technique of electrospinning has gained surging research interest since the 1990s due to its capability of yielding continuous fibers with diameters down to the nanometer scale. Despite enormous efforts devoted to explore applications of electrospun nanofibers, such as separation, catalysis, nanoelectronics, sensors, energy conversion/storage, and biomedical utilization, there are limited attempts to employ these nanofibers for reinforcement in polymer composites. Electrospun nanofibers, however, possess comprehensive advantages not typically shared by other nanoscale composite fillers/reinforcing agents, such as continuity, diverse material choice, controlled diameter/structure, possible alignment/assembly, mass production capability and so forth. Therefore electrospun nanofibers have great potential as promising reinforcement fillers for next-generation polymer composites. This is a comprehensive and state-of-the-art review of the latest advances made in development of electrospun nanofiber reinforced polymer composite materials with intention to stimulate interests in both academia and industry.     

Accurate permeability characterization of preforms used in polymer matrix composite fabrication processes

The permeabilities of fabrics composed of carbon and glass fibers have been determined by utilizing both simple 1-dimensional and 2-dimensional radial flow measurements using silicone oil and motor oil as permeants. The carbon fabric is typical of that used in fabrication of aerospace grade polymer matrix composites, while the glass fabric is a 3-dimensional woven fabric that has been proposed as a standard reference material for permeability characterization. Our results indicate that reliable permeability data for fiber preforms with varying architectural complexity can be obtained provided that the experiments are performed with utmost care and that appropriate equations are used to analyze the data. In-plane permeabilities for the carbon fiber preforms from transient unidirectional constant flow rate and constant pressure experiments agreed within 5%, regardless of the preform orientation to the flow direction. Steady-state results on the same preforms showed agreement within 2% between constant flow rate and constant pressure experiments. The capillary pressure effect was shown to be negligible for the transient experiments. The maximum difference between the transient and steady state permeability values was 3%. The maximum difference between a permeability measured with unidirectional flow and the same permeability measured with radial flow is less than 10%.     

Preparation and characterization of RDX based composite energetic materials with a cellulose matrix

Cyclotrimethylenetrinitramine (RDX)-based high-energy explosives are widely used in weapon warheads, propellants, and ammunition. Many studies have explored different supporting structures for RDX; however, the use of natural materials have rarely has been reported. Natural cellulose is widely known for its excellent compatibility and loading capacity. In this study, cellulose was used as a supporting structure and insensitive material for RDX composites. Cellulose/RDX composite aerogels (RCAs) were prepared using 1-allyl-3-methyl imidazole (AMIMCl) as the solvent, and their properties were characterized. The results show that the content of nitrogen in cellulose/RCAs was 34.5%, and the content of RDX was as high as 94.3%. Moreover, RDX particles were attached to the fibers inside the cellulose aerogels (CAs), forming a homogeneous protective layer on the surface of the cellulose matrix. Compared with the raw RDX material, the thermal stability of the cellulose/RDX energetic aerogels was greatly increased. The porosity of the CAs was reduced due to RDX particles growing inside the CAs. The impact sensitivity increased from 35 to 78 cm.     

聚合物基PTC热敏材料的研究

综述了聚合物基PTC热敏材料的PTC效应机理、PTC效应影响因素以及PTC效应稳定化的途径。     

Use of solid residue from olive kernel pyrolysis for polymer matrix composite manufacturing: Physical and mechanical characterization

This study is aiming at the production of carbon material from agricultural residues by pyrolysis and their further use for the production of green polymeric composites. The development of an agricultural‐based polymer matrix compatible with olive pits and consequently a fully biodegradable composite system is the future and ultimate goal of the undertaken research. In this study, pyrolysis of olive kernels was conducted at 800°C for 1 h. Furthermore, elemental, proximate, and metal analyses were performed for to the raw material and the produced char. The analyses showed that the pyrolytic char from olive kernel is a carbon rich material with significant concentration in metals, which can be further studied as additive for the production of green materials. For that purpose, samples made out of epoxy matrix, reinforced with pyrolytic char from olive kernel at different concentrations, were manufactured and mechanically characterized at three point bending conditions. A maximum increase of 60% in bending modulus in comparison to the net matrix modulus was achieved. The new material developed in the present investigation is a green composite with an elastic modulus 60% higher than that of the pure matrix. Results were also compared with predictions derived by the application of a theoretical model previously developed by the first author for the evaluation of the elastic modulus in particulate composites taking into account not only the effect of filler‐matrix adhesion but also the degree of dispersion of fillers into the matrix. It was found that predicted values as derived from the application of the model were in very good agreement with experimental findings. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Evaluation of polymer matrix composite manufacturing routes for production of an oxide/oxide ceramic matrix composite

The use of manufacturing methods commonly used for polymer matrix composites (PMCs) in the production of ceramic matrix composites (CMCs), as opposed to more traditional ceramic manufacturing methods, has the potential to reduce the cost of components. This work focuses on three typical PMC manufacturing methods and assesses their suitability for the production of an oxide-oxide porous matrix ceramic composite, starting from a commercially available pre-impregnated Nextel 610®/aluminium oxide material. While all the techniques can be used to produce CMCs, results showed that compared with vacuum bagging and warm pressing, autoclave processing produced the best outcome. It resulted in the most uniform thickness laminates and the lowest macro-porosity, as well as the highest flexural strength.     

微胶囊型自修复聚合物复合材料研究进展

介绍了聚合物复合材料自修复的概念和机理,自修复体系的组成和要求以及自修复材料的评价方法。综述了最近几年对影响复合材料自修复效果的4个方面因素(微胶囊的含量及粒径、修复剂的种类、催化剂的用量和粒子尺寸以及体系混合次序)的研究进展。     

树脂基复合材料成型工艺的发展

树脂基复合材料具有质轻、力学性能优异等优点,在航天航空等领域逐步取代金属成为主要结构制件,并在民用领域得到了快速的发展．本文着重介绍树脂基复合材料的优点,缠绕、拉挤、液体模塑成型工艺的发展以及树脂体系固化工艺。     

Development of characterisation methodologies for macroporous materials

The exceptional property sets of macroporous materials are leading to an increasing number of applications, particularly in the biomedical sector. Apart from the underlying material properties, it is the characteristics of the porous structure that dictate the properties of fabricated devices. Conventional methods of examining the pore structure have a number of inherent disadvantages such as low sampling volume, laborious and frequently destructive sample preparation, tedious and subjective image analysis. Recently, industrial microtomographic methods have become important tools for interrogating porous materials. However, one of the limitations of micro-CT methods is the non-specific nature of commercially available image analysis software coupled with the complicated nature of the key parameters. This paper presents some progress towards the development of a novel analysis tool that aims to characterise specific parameters over a wide range of macroporous materials. This paper focuses on aspects directly relevant to the characterisation of Hydroxyapatite macroporous (HA) foams and demonstrates the capability to obtain statistically meaningful parameters essential for process development and pre-implantation quality assurance.     

Moisture uptake and hygroexpansion of wood fiber composite materials with polylactide and polypropylene matrix materials

Effects of butantetracarboxylic acid (BTCA) modification, choice of matrix, and fiber volume fraction on hygroexpansion of wood fiber composites have been investigated. Untreated reference wood fibers and BTCA‐modified fibers were used as reinforcement in composites with matrices composed of polylactic acid (PLA), polypropylene (PP), or a mixture thereof. The crosslinking BTCA modification reduced the out‐of‐plane hygroexpansion of PLA and PLA/PP composites, under water‐immersed and humid conditions, whereas the swelling increased when PP was used as matrix material. This is explained by difficulties for the BTCA‐modified fibers to adhere to the PP matrix. Fiber volume fraction was the most important parameter as regards out‐of‐plane hygroexpansion, with a high‐fiber fraction leading to large hygroexpansion. Fiber‐matrix wettability during processing and consolidation also showed to have a large impact on the dimensional stability and moisture uptake. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Conductive polymer composite materials and their utility in electromagnetic shielding applications

Commercial electronic devices require shielding solutions that ensure electromagnetic compatibility (EMC) while accounting for effects of specific enclosure structural features such as seams, vents, and port dimensions. In practice, suitable EMC materials combine with the device operating characteristics to determine an overall shielding response. To optimally couple plastic design practices with EMC requirements, both polymer materials science and electrical engineering concepts, must be considered. Use of extrinsically conductive polymer (ECP) formulations for electronic applications has advantages in that they can be directly molded to a desired shape and serve to provide the necessary shielding while also meeting mechanical integrity requirements. Shielding and mechanical performance can be varied via filler loading or altered through wall thickness changes to satisfy demands associated with a particular device. Injection‐moldable ECP polycarbonate‐based formulations can attain average shielding effectiveness (SE) levels of ～50–60 dB through 2 GHz at 2‐mm thickness as measured using ASTM D 4935 procedures. These values vary with thickness, and SE improvements of ～10–20 dB are observed when increasing from 1 to 2 mm. Additionally, resultant mechanical properties of shielding composites are strong functions of overall fiber content. These interrelated material and shielding characteristics, which form the basis for filled conductive polymer use within practical enclosure shielding designs, are described. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

复合导电高分子材料的改性及应用研究进展

介绍了复合导电高分子材料的主要构成和分类,综述了碳系复合导电高分子材料[如炭黑(CB)填料型、碳纳米管(CNTs)填料型和石墨烯填料型等]、金属系复合导电高分子材料和金属氧化物系复合导电高分子材料的改性进展。最后对复合导电高分子材料的应用和发展前景进行了展望。     

TiO_2/ACF复合材料的制备及表征

采用浸渍-提拉法和溶胶-凝胶法制备TiO2/ACF复合光催化材料,用BET、XRD和SEM等进行表征。结果表明,溶胶-凝胶法制备的复合材料由于负载了大量TiO2,其比表面积明显低于浸渍法;浸渍法制备的复合材料随着粘结剂添加量的增加,比表面积呈减小趋势。溶胶-凝胶法制备的复合材料的表面TiO2锐钛晶型较明显,浸渍-提拉法无明显的锐钛晶型。采用浸渍-提拉法制备的TiO2/ACF复合材料,TiO2以粒状负载于ACF表面;溶胶-凝胶法中TiO2在ACF表面形成一层薄膜,由于焙烧,薄膜产生裂隙,暴露出ACF,有利于吸附和催化作用的同时进行。     

DMC/MVQ绝缘复合材料的制备及性能表征

针对硅橡胶力学性能差的特点,本工作以硅橡胶（MVQ）为基相,以团状模塑料（DMC）为增强相,以丁苯橡胶（SBR）为相容剂来制备DMC/MVQ绝缘复合材料,研究了SBR的用量对MVQ性能的影响。结果表明：SBR和MVQ共混制得的并用胶性能要比纯MVQ的性能好,其最佳配比为DMC 60phr,SBR 25phr,MVQ 75phr;制备的复合材料体积电阻率都在4.9×1012Ω.m以上,复合材料的绝缘性能良好;通过扫描电镜分析（SEM）和动态热机械分析（DMA）,研究了复合材料的相容性,SBR的加入改善了DMC/MVQ绝缘复合材料的相容性,增加了界面相互作用,提高了DMC/MVQ绝缘复合材料的性能。     

改性水滑石/PVC复合材料的合成及性能表征

通过接枝共聚工艺,对纳米水滑石进行表面处理,生成无机核、有机壳的核-壳结构,研究了经表面处理和未经表面处理的水滑石对PVC复合材料力学性能、耐热性能、阻燃性能的影响。结果表明,经表面处理后的水滑石对复合材料力学性能的影响要好于未改性的水滑石;未经处理的水滑石对复合材料维卡软化温度有较大的提高;加入水滑石后,复合材料阻燃性能得到较大提高。     

Deformation and fracture characterization of inelastic composite materials using potentials

An approach using strain energy-like potentials to characterize deformation and fracture of inelastic, nonlinear composite materials is described. The inelasticity may be due to various causes, including microcracking, microslipping, and rate processes responsible for fading memory (viscoelasticity). The concept of work potentials is introduced first, and then arguments are given for their existence for inelastic materials. Emphasis in the paper is on elastic composite materials with changing or constant states of distributed damage. Experimental results on polymeric composites are subsequently presented to illustrate this approach to deformation and fracture characterization. Finally, extension to viscoelastic behavior is discussed.