均匀化有限元法预测复合材料层合板宏观有效弹性性能

首先由等效能量原理提出复合材料有效弹性模量定义,再由小参数渐进展开均匀化理论,推导出复合材料层合板等效弹性张量。同时结合有限元方法,建立复合材料层合板的多尺度模型,预测碳纳米管以及纳米薄膜增强复合材料层合板的宏观有效弹性模量。由均匀化方法来求得弹性模量的宏观平均值,将其输入商业软件ANSYS系统进行计算,由此把宏、细观两个尺度耦合起来,可以对复合材料层合板进行等效弹性性能分析。这对新材料的研究、发展具有一定的指导作用。     

基于数字图像相关方法的复合材料层间剪切性能研究

层间剪切强度是评价复合材料层合板层间力学性能的一项重要指标。首先,按照ASTM D 2344开展了复合材料层合板短梁剪切试验,研究了CCF300/5228复合材料层合板层间剪切性能。其次,基于数字图像相关方法得到了不同载荷作用下层间全场位移和应变分布。最后,利用ABAQUS建立了复合材料层合板有限元模型,分析了复合材料层合板层间位移及应变分布,并与数字图像相关计算结果进行了对比。研究表明,数字图像相关方法试验结果与有限元分析结果具有较好的一致性。数字图像相关方法能够实时监测层合板层间应变分布,进而预测层间剪切破坏位置,为复合材料层间剪切性能研究提供有效的全场应变监测手段。     

纤维曲线铺放的变刚度复合材料层合板的屈曲

本文介绍了一种纤维曲线铺放的变刚度复合材料层合板的概念,利用这种新的铺放方法所引起的复合材料层合板面内应力的重新分布,提高了复合材料层合板的屈曲载荷.并且利用ABAQUsTM软件对这种纤维曲线铺放的复合材料层合板进行了建模计算,验证了其面内受力情况下,屈曲载荷显著提高,幅度达14%左右.     

复合材料层合板低速冲击承载能力的细观力学有限元模型

将复合材料细观力学桥联模型与有限元软件ABAQUS结合,用于分析层合板受低速冲击作用的极限承载能力.通过确定组分材料是否破坏来判断单层板是否破坏,对破坏后的单层实施一种常系数刚度衰减.将细观力学本构模型、针对组分材料的破坏判据以及刚度衰减模式编制成用户子程序VUMAT,为ABAQUS求解层合板的极限冲击响应提供一种自定义材料模型.只需要输入纤维和基体的材料参数、纤维体积含量等有限数据并且无须单层板的实验数据,就能顺利实施复合材料层合板结构的冲击承载能力分析.所计算的层合板的挠度-时间曲线以及横向冲击力-时间曲线与实验值吻合良好,说明本文的方法是有效的.     

纤维分布对复合材料固化变形的影响

本文分析了复合材料层合板纤维分布不均匀的产生原因,提出了纤维分布不均匀度的表征参数Id,采用图像处理技术测定了层合板的纤维分布不均匀度,用实验和有限元方法研究了纤维分布不均匀对复合材料固化变形的影响规律。结果表明,复合材料的固化变形随着纤维分布不均度增加而增大,变形量随着层合板层数增多而减小,研究还表明,固化变形程度与层合板的铺层方式相关。     

基于SPH方法的鸟撞复合材料层合板数值分析

采用光滑粒子流体动力学法(SPH)耦合有限元法对复合材料层合板受鸟撞击的过程进行了数值模拟。复合材料层合板采用渐进损伤模型,鸟体采用SPH粒子建立模型,利用ANSYS/LS-DYNA显示动力分析模块分析了复合材料层合板结构非线性接触。分析了鸟撞层合板过程中鸟体损伤及层合板单层纤维失效和基体失效情况,分析了鸟体的入射角方向及层合板采用不同铺层时对层合板吸能效果的影响。计算结果表明,合理设计层合板铺层可以提高层合板的吸能效果。     

热塑性复合材料本构方程及应用

近年来,许多新型复合材料不断涌现,如热固性复合材料和热塑性复合材料等。这些材料在航空、航天、建筑等领域得到日益广泛的应用。因此,对这些材料力学性能的研究已引起国内外高度重视。本文根据弹性理论,考虑到流体不可压缩的条件,分析热塑性复合材料的力学性能,得出粘性各向异性、横观各向同性材料本构关系;通过细观力学研究,导出材料的粘性参数η11,η12,η22,η23;通过对层合板力学变形的研究,导出粘性各向异性层合板的膜应力和应变速率之间的关系及其实际粘性参数η-ij′,并对所得结果进行讨论。     

复合材料螺旋弹簧的刚度预测及分析

针对实心结构截面形式的玻璃纤维复合材料螺旋弹簧,基于复合材料宏观力学层合板理论,提出一种玻璃纤维复合材料螺旋弹簧的静刚度理论预测方法,并分析了该方法中弹簧各参数对弹簧刚度的影响,明确了各参数对弹簧刚度的敏感程度。     

非连续大线长纤维增强复合材料宏观弹性常数预测方法

基于Tandon-Wend模型对单向非连续纤维增强复合材料的宏观弹性常数进行了预测,然后采用纤维长度和纤维取向两个特征变量,结合层合板理论预测纤维随机分布的非连续纤维增强复合材料的宏观弹性常数。最后通过实验验证了文中所述方法的准确性。结果表明,本文方法可以准确地预测纤维随机分布的非连续大线长纤维增强复合材料的宏观弹性常数。     

复合材料加筋层合板阶梯式挖补修理的稳定性分析研究

基于有限元方法,研究了复合材料加筋层合板阶梯式挖补修理的稳定性问题。利用商用有限元分析软件MSC.Patran/Nastran,建立了复合材料层合板阶梯式挖补修理结构稳定性三维有限元分析模型。并通过所得屈曲特征值计算出修补结构临界失稳载荷,拟合出临界失稳载荷图,分析得出不同筋距、加筋数、挖补阶数和胶层厚度对复合材料层合板阶梯式挖补修理结构稳定性的影响规律。     

Sapindaceae,cyanolipids, and bugs

Scentless plant bugs (Heteroptera: Rhopalidae) are so named because adults of the Serinethinae have vestigial metathoracic scent glands. Serinethines are seed predators of Sapindales, especially Sapindaceae that produce toxic cyanolipids. In two serinethine species whose ranges extend into the southern United States,Jadera haematoloma andJ. sanguinolenta, sequestration of host cyanolipids as glucosides renders these gregarious, aposematic insects unpalatable to a variety of predators. The blood glucoside profile and cyanogenesis ofJadera varies depending on the cyanolipid chemistry of hosts, and adults and larvae fed golden rain tree seeds (Koelreuteria paniculata) excrete the volatile lactone, 4-methyl-2(5H)-furanone, to which they are attracted.Jadera fed balloon vine seeds (Cardiospermum spp.) do not excrete the attractive lactone. Loss of the usual heteropteran defensive glands in serinethines may have coevolved with host specificity on toxic plants, and the orientation ofJadera to a volatile excretory product could be an adaptive response to save time.Mention of a commercial product does not consititute an endorsement by the USDA.     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Many Drugs of Abuse May Be Acutely Transformed to Dopamine,Norepinephrine and Epinephrine In Vivo

It is well established that a wide range of drugs of abuse acutely boost the signaling of the sympathetic nervous system and the hypothalamic–pituitary–adrenal (HPA) axis, where norepinephrine and epinephrine are major output molecules. This stimulatory effect is accompanied by such symptoms as elevated heart rate and blood pressure, more rapid breathing, increased body temperature and sweating, and pupillary dilation, as well as the intoxicating or euphoric subjective properties of the drug. While many drugs of abuse are thought to achieve their intoxicating effects by modulating the monoaminergic neurotransmitter systems (i.e., serotonin, norepinephrine, dopamine) by binding to these receptors or otherwise affecting their synaptic signaling, this paper puts forth the hypothesis that many of these drugs are actually acutely converted to catecholamines (dopamine, norepinephrine, epinephrine) in vivo, in addition to transformation to their known metabolites. In this manner, a range of stimulants, opioids, and psychedelics (as well as alcohol) may partially achieve their intoxicating properties, as well as side effects, due to this putative transformation to catecholamines. If this hypothesis is correct, it would alter our understanding of the basic biosynthetic pathways for generating these important signaling molecules, while also modifying our view of the neural substrates underlying substance abuse and dependence, including psychological stress-induced relapse. Importantly, there is a direct way to test the overarching hypothesis: administer (either centrally or peripherally) stable isotope versions of these drugs to model organisms such as rodents (or even to humans) and then use liquid chromatography-mass spectrometry to determine if the labeled drug is converted to labeled catecholamines in brain, blood plasma, or urine samples.     

2008～2009年世界塑料工业进展

收集了2008年7月～2009年6月世界塑料工业的相关资料,介绍了2008～2009年国外塑料工业的发展情况,提供了世界塑料产量、消费量及全球各类树脂的需求量及产能情况。按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(尼龙、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、特种工程塑料(聚苯硫醚、液晶聚合物、聚醚醚酮)、通用热固性树脂(酚醛、聚氨酯、环氧树脂、不饱和聚酯树脂)不同品种的顺序,对树脂的产量、消费量、供需状况及合成工艺、产品应用开发、树脂品种的延伸及应用的进一步扩展等技术作了详细介绍。     

Methyl 2,4,6-decatrienoates Attract Stink Bugs and Tachinid Parasitoids

Halyomorpha halys (Stål) (Pentatomidae), called the brown marmorated stink bug (BMSB), is a newly invasive species in the eastern USA that is rapidly spreading from the original point of establishment in Allentown, PA. In its native range, the BMSB is reportedly attracted to methyl (E,E,Z)-2,4,6-decatrienoate, the male-produced pheromone of another pentatomid common in eastern Asia, Plautia stali Scott. In North America, Thyanta spp. are the only pentatomids known to produce methyl 2,4,6-decatrienoate [the (E,Z,Z)-isomer] as part of their pheromones. Methyl 2,4,6-decatrienoates were field-tested in Maryland to monitor the spread of the BMSB and to explore the possibility that Thyanta spp. are an alternate host for parasitic tachinid flies that use stink bug pheromones as host-finding kairomones. Here we report the first captures of adult and nymph BMSBs in traps baited with methyl (E,E,Z)-2,4,6-decatrienoate in central Maryland and present data verifying that the tachinid, Euclytia flava (Townsend), exploits methyl (E,Z,Z)-2,4,6-decatrienoate as a kairomone. We also report the unexpected finding that various isomers of methyl 2,4,6-decatrienoate attract Acrosternum hilare (Say), although this bug apparently does not produce methyl decatrienoates. Other stink bugs and tachinids native to North America were also attracted to methyl 2,4,6-decatrienoates. These data indicate there are Heteroptera in North America in addition to Thyanta spp. that probably use methyl 2,4,6-decatrienoates as pheromones. The evidence that some pentatomids exploit the pheromones of other true bugs as kairomones to find food or to congregate as a passive defense against tachinid parasitism is discussed.