Effective Elastic and Plastic Properties of Interpenetrating Multiphase Composites

In interpenetrating phase composites, there are at least two phases that are each interconnected in three dimensions, constructing a topologically continuous network throughout the microstructure. The dependence relation between the macroscopically effective properties and the microstructures of interpenetrating phase composites is investigated in this paper. The effective elastic moduli of such kind of composites cannot be calculated from conventional micromechanics methods based on Eshelby's tensor because an interpenetrating phase cannot be extracted as dispersed inclusions. Using the concept of connectivity, a micromechanical cell model is first presented to characterize the complex microstructure and stress transfer features and to estimate the effective elastic moduli of composites reinforced with either dispersed inclusions or interpenetrating networks. The Mori–Tanaka method and the iso-stress and iso-strain assumptions are adopted in an appropriate manner of combination by decomposing the unit cell into parallel and series sub-cells, rendering the calculation of effective moduli quite easy and accurate. This model is also used to determine the elastoplastic constitutive relation of interpenetrating phase composites. Several typical examples are given to illustrate the application of this method. The obtained analytical solutions for both effective elastic moduli and elastoplastic constitutive relations agree well with the finite element results and experimental data.     

高支化环三磷腈型苯并噁嗪的合成表征及性能

以自制的六(4-羟基苯氧基)环三磷腈(I)、苯胺、甲醛为原料,甲苯为溶剂合成了高支化环三磷腈型苯并噁嗪(II),收率68.9%。采用傅里叶变换红外光谱、核磁氢谱、差示扫描量热法、热重分析、极限氧指数(LOI)和水平-垂直燃烧试验对(II)及其固化物(III)的结构和性能进行了表征,并对比了其与传统苯并噁嗪的热性能与阻燃性能。结果表明,(II)的开环聚合起始温度为186.0℃,峰值温度为235.4℃,具有比传统苯并噁嗪更低的开环聚合起始温度;(III)的5%和10%热失重温度分别为344.1℃和392.7℃,800℃残炭率为64.97%,LOI值可达43.5%,UL-94等级为V-0,具有比传统苯并噁嗪更为优异的热稳定性和阻燃性,可应用于阻燃要求较高的场合。     

新型阻燃剂-2-羧乙基苯基次膦酸及其阻燃共聚酯的制备、表征及热性能研究(英文)

制备了一种新型的含磷阻燃剂-2-羧乙基苯基次膦酸(CEPPA),并用FTIR、HNMR表征了其结构。当磷含量为0.6wt%时,其阻燃共聚酯的LOI可达29.4%。同时利用DSC、TGA研究了不同磷含量共聚酯的热性能。结果表明,共聚酯的玻璃化转变温度(Tg)、熔点(Tm)、热结晶温度(Tmc)、起始分解温度(Tid)随着磷含量的增加而降低,而冷结晶温度(Tcc)、最大分解速率(Tmax)、燃烧后炭层含量则随之增加。为了更好地解释阻燃剂的阻燃机理,利用FTIR研究了TGA测试后生成炭层的结构,结果表明燃烧后的炭层主要由含磷碎片组成。     

The influence of CH4 addition on composition, structure and optical characteristics of SiCN thin films deposited in a CH4/N2/Ar/hexamethyldisilazane microwave plasma

Amorphous silicon carbonitride (a-SiCN) thin films were synthesized in a microwave plasma assisted chemical vapor deposition system using N₂, Ar, CH₄ and hexamethyldisilazane vapor (HMDSN). Composition, morphology and optical constants of the layers have been studied as a function of CH₄ rate in the range 0 to 9%. It was found that films are mainly composed of silicon nitride like compound whatever the CH₄ rate. However, CH₄ addition leads to less hydrogenated and denser films. In addition, a refractive index augmentation from 1.7 to 2.0 and a Tauc gap decrease from 5.2 eV to 4.8 eV is measured with CH₄ rate increase. It is believed that the refractive index augmentation is due to higher thin film density whereas hydrogen bonds decrease is assumed to contribute to the band gap narrowing. Besides, CH₄ addition to the gaseous mixture increases thin film oxidation resistance. These results show the ability of varying composition, structure and optical constants of a-SiCN films by modifying CH₄ rate in a N₂/Ar/HMDSN plasma.