聚氨酯/环氧树脂互穿聚合物网络半硬泡沫的结构与性能

采用同步法合成了聚醚型聚氨酯/环氧树脂互穿聚合物网络半硬泡沫.通过FTIR,DMA,SEM研究了IPN半硬泡沫的化学结构、动态力学性能以及微观结构形态.FTIR分析表明了聚氨酯和环氧树脂的网络间存在接枝反应.很宽组成比范围内IPN半硬泡沫均显示出单一的宽温域玻璃化转变,而且该转变随着环氧树脂含量的增加向高温方向移动.通过SEM发现IPN半硬泡沫泡孔结构形状都比较均一.循环加载压缩发现所有IPN泡沫不仪压缩性能好而且具有很好的回弹性,大变形压缩后泡沫儿乎不变形,重复使用性能好.     

泡沫铝-聚氨酯复合材料制备及力学性能分析

目的研究泡沫铝相对密度、聚氨酯含量、聚氨酯硬段质量分数(硬段在热塑性聚氨酯弹性体橡胶中所占的质量分数)对泡沫铝-聚氨酯复合材料力学性能的影响。方法自行制备泡沫铝-聚氨酯复合材料,对制备的泡沫铝-聚氨酯样品进行准静态压缩实验。结果通过准静态压缩实验,得出了不同泡沫铝的相对密度、聚氨酯含量、聚氨酯硬段质量分数分别对应的应力应变曲线。当聚氨酯硬段质量分数和聚氨酯含量一定时,泡沫铝相对密度从5.4%提升到6.1%,泡沫铝-聚氨酯屈服强度增加了12.8%,流变应力增加了29.8%。当聚氨酯硬段质量分数和泡沫铝相对密度一定时,聚氨酯含量从9.21 g提升到13.19g,泡沫铝-聚氨酯屈服强度增加了32.6%,流变应力增加了10.9%。当聚氨酯含量和泡沫铝相对密度一定时,聚氨酯硬段质量分数从15%提升到25%,泡沫铝-聚氨酯屈服强度增加了95%,流变应力增加了55.5%。结论不同的泡沫铝相对密度、聚氨酯含量、聚氨酯硬段质量分数与泡沫铝-聚氨酯复合材料的力学性能成正相关的关系,泡沫铝相对密度、聚氨酯含量、聚氨酯硬段质量分数与泡沫铝-聚氨酯复合材料的缓冲吸能特性成正相关的关系。     

高模量树脂基体及高抗压复合材料的研究

以高密度的环氧树脂 TDE-85作为基体,选择不同的固化剂,研制出了三种高模量高强度的树脂体系,并对其力学性能、微观结构、自由体积进行了研究。论文取得了如下创造性的研究成果:(1)制备了拉伸模量大于5.0GPa,压缩模量大于6.0GPa,拉伸强度大于80MPa 的树脂体系,并对其力学性能进行了测试,系统研究了模量与密度之间的关系,同时对其微观断口形貌进行了观察。(2)研究了高模量基体对玻璃纤维增强复合材料单向板各项性能的影响。结果表明,随着基体模量的提高,复合材料的拉伸性能、压缩性能、弯曲性能、剪切性能显著提高。玻璃纤维复合材料的压缩强度达1337.5MPa,弯曲强度达2324.6MPa。(3)利用纳米材料 SiO_2、TiO_2、α-Al_2O_3、改性双酚 A 型环氧树脂,解决了纳米柱子均匀分散的技术难题。系统研究了纳米拉子对环氧树脂拉伸模量、强度、冲击韧性、热变形温度的影响。以纳米 SiO_2、高强玻璃纤维共同增强环氧树脂,制备了纳米纤维环氧树脂复合材料。这一研究在国内尚未见报道。(4)利用正电子淹没技术测试了自由体积,首次用实验验证了模量与自由体积的密切关系。对于 TDE-85/胺体系,在环氧基/胺摩尔比相同的条件下,浇铸体密度降低,自由体积的尺寸与浓度增大,浇铸体的模量与玻璃化温度降低。纳米粒子的加入,使自由体积尺寸增大,自由体积浓度降低,模量与玻璃化温度升高。     

玻璃微珠/环氧树脂复合泡沫材料的力学性能及其理论分析

以环氧树脂(EP)为基体,空心玻璃微珠(HGM)为填料制备复合泡沫,并对其开展压缩、拉伸和低速冲击试验,探究不同微珠体积分数和冲击能量对微珠泡沫复合材料破坏形态、强度、模量和冲击吸能效应的影响.结果表明:当微珠体积含量从50％增加到75％时,微珠泡沫的抗压强度和模量分别降低了65％和55％,抗拉强度和模量分别降低了39％和30％,材料得到很大程度的轻量化.在43 J和49 J的冲击能量作用下,复合泡沫吸收的能量随着微珠体积分数的增大而增加,而当冲击能量进一步增大,微珠体积比为70％的复合泡沫比吸能(SEA)最高.过多微珠导致的团聚以及材料之间界面作用减弱对复合泡沫力学性能产生较大影响.基于复合材料细观力学理论,通过夹杂方法计算出微珠泡沫复合材料的有效模量,其理论值与试验值吻合较好.     

相对密度对泡沫铝力学性能和能量吸收性能的影响

对不同相对密度的两种胞孔结构--开孔和闭孔泡沫铝进行了单轴压缩试验,研究了相对密度对泡沫铝力学性能和能量吸收性能的影响.结果表明:随着相对密度的增大,泡沫铝的屈服强度与流动应力也相应增加,通过对本实验结果进行拟合,得出泡沫铝的屈服强度与相对密度的关系式.泡沫铝材料吸收的能量随着应变量的增大而增加,在相同应变量下,高密度开孔泡沫铝的吸收能比低密度闭孔材料多.吸能效率反映材料本身的一种属性,高的理想吸能效率表明泡沫铝是一种优良的吸能材料.     

全厚度缝合复合材料泡沫芯夹层结构力学性能研究与损伤容限评定

探索了全厚度缝合复合材料闭孔泡沫芯夹层结构低成本制造的工艺可行性及其潜在的结构效益。选用3 种夹层结构形式, 即相同材料和工艺制造的未缝合泡沫芯夹层和缝合泡沫芯夹层结构及密度相近的Nomex 蜂窝夹层结构, 完成了密度测定、三点弯曲、平面拉伸和压缩、夹层剪切、结构侧压和损伤阻抗/ 损伤容限等7 项实验研究。结果表明, 泡沫芯夹层结构缝合后, 显著提高了弯曲强度/ 质量比、弯曲刚度/ 质量比、面外拉伸和压缩强度、剪切强度和模量、侧压强度和模量、冲击后压缩(CAI) 强度和破坏应变。这种新型结构形式承载能力强、结构效率高、制造维护成本低, 可以在飞机轻质机体结构设计中采用。      

静态载荷下丝瓜络的能量吸收性能研究

为了深入了解丝瓜络的力学性能、能量吸收特性及其规律,对丝瓜络进行了轴向静态压缩试验,再通过拟合试验数据得到丝瓜络的单位体积的吸能量与密度的关系式。试验结果表明:丝瓜络的应力-应变曲线有3个阶段,即弹性阶段、屈服平台阶段和密实化阶段,屈服平台阶段的平台应力在0.15~0.50 MPa之间,密实化应变在70%左右,且其平台区较长,是一种理想的吸能材料;丝瓜络是一种对密度敏感的材料,其屈服强度、平台应力和单位体积的吸能量均随密度的增加而增加,密实化应变随密度增加而减小;丝瓜络单位质量的吸能量可以与泡沫铝材料相媲美。研究结果可作为设计基于丝瓜络结构的新型超轻仿生材料结构的基础数据     

中等应变率下泡沫铝的吸能特性

进行了不同密度、高度和压缩方向下泡沫铝的准静态压缩试验和中等应变率下(＜100 s-1)的冲击试验,研究了具有不同密度的闭孔泡沫铝在准静态压缩和冲击工况下的吸能特性.结果表明,泡沫铝是一种近似的各向同性结构,具有较高的单位质量吸能特性,是一种较好的吸能材料.在准静态和中等应变率冲击条件下,泡沫铝对应变率不敏感,其应力应变关系与应变率关系不大.不同的泡沫铝,其平台应力与密度之间的关系不同,在研究其性能时,必须测量应力-应变关系.泡沫铝的致密区对其吸能特性有很大的影响.     

梯形格栅结构增强泡沫夹芯复合材料平压性能

设计了一种梯形格构增强泡沫夹芯板,并采用真空辅助树脂灌注(VARI)工艺制备了多种不同结构参数的格构增强泡沫夹芯板。实验研究了夹芯板在平面压缩载荷下的失效模式与力学性能,考察了夹芯板结构参数(试样尺寸、格构腹板角度、格构腹板厚度)对夹芯板比压缩强度、比压缩模量与比吸能的影响规律。结果表明:格构增强泡沫夹芯板主要破坏模式为格构腹板的断裂与屈曲;夹芯板中泡沫芯材与格构腹板协同增强;60°夹角格构增强夹芯板相对于无格构增强夹芯板的比压缩强度、比压缩模量和比吸能分别提高了89.4%、137.9%、45.2%;格构增强泡沫夹芯板压缩性能随着格构腹板角度、格构腹板厚度的增加而提高。这类夹芯板的设计为船舶与海洋工程领域轻质夹芯复合材料的应用提供了指导。     

闭孔EVA泡沫类静态缓冲性能的研究

目的 研究密度与应变率对闭孔EVA泡沫材料类静态缓冲性能的影响规律。方法 基于包装用缓冲材料静态压缩试验法和能量吸收图法,对密度为80、95、106、124和180kg/m³的闭孔EVA泡沫试样在不同应变率下进行类静态压缩试验,得到应力-应变曲线,基于此进一步处理得到相应的单位体积能量吸收、能量吸收效率、缓冲系数和最大比吸能等曲线,同时绘制试样类静态压缩过程中的能量吸收图。结果 闭孔EVA泡沫材料的密度越高,密实化应变越小,最大单位体积能量吸收越大;在压缩应变相同时,应变率越大,应力、单位体积能量吸收、能量吸收效率、最大比吸能越大;得到了5种密度闭孔EVA泡沫材料的本构方程和闭孔EVA泡沫材料的能量吸收图及其斜率与应变率的关系式;通过分析密实化应变与相对密度的关系,得到相关拟合公式。结论 密度与应变率对闭孔EVA泡沫材料的缓冲性能有着非常大的影响,在一定的应力水平下会有一个最佳的密度使得刚好能吸收完能量,并保护产品不破损,该最佳密度受应变率的影响,因此可以通过能量吸收图进行相关的缓冲包装优化设计。     

Fiber-reinforced composite foam from expandable PVC microspheres

The properties of composite foam based on PVC expandable microspheres reinforced with continuous aramid fibers are described. The foam was fabricated by infiltrating low-density non-woven fiber webbing with PVC microspheres. The assembly was subsequently heated to expand the foam. The resulting composite foam consisted of 10 wt% aramid fibers and had a density of 100 kg/m³. Mechanical properties, crack propagation, and microstructure of composite foams were evaluated and compared with properties of similar unreinforced foam and with commercial PVC foam of comparable density. The influence of fiber concentration, fiber architecture and bonding was investigated also. Properties were measured in tension, shear, compression, and flexure using standard ASTM test methods. The composite foam performance equaled or surpassed the performance of most thermoplastic foams commercially available. The tensile strength and modulus of the composite foam increased by factors of 6 and 8, respectively, and the shear strength and modulus increased by factors of 1.8 and 2.4. The composite foam also exhibited improved strain energy density and damage tolerance, and reduced notch sensitivity.     

Mechanical properties of graphene platelets reinforced syntactic foams

Graphene platelets (GPs) are two-dimensional thin plates containing few layers of graphene sheets. Compressive and tensile behaviors of epoxy-based syntactic foams with pristine GPs as additives are discussed in this article. Four sets of syntactic foams containing 0, 0.1, 0.3, and 0.5 vol.% of GPs were fabricated and tested. The volume fraction of microballoons in all syntactic foam samples was kept constant at 30%. Results indicated that the compressive and tensile moduli of the syntactic foams were significantly improved as compared to samples that did not contain GPs. The addition of GPs also enhanced the tensile strength while the compressive strength was only slightly increased. Optimal property improvements were obtained for very low filling fraction of approximately 0.3 vol.%. Samples with higher volume fraction of GPs (0.5%) showed deterioration in mechanical properties when compared to other GP containing samples. Transmission microscopy study indicated formation of voids enclosed by undispersed GPs in the samples which could explain the decline of the properties. High matrix porosity could also play an important role in this observation. Utilizing surface modified GPs could allow incorporation of higher volume fraction of GPs homogeneously, thus improving the mechanical properties of the syntactic foams.     

Comparison of tensile and compressive characteristics of vinyl ester/glass microballoon syntactic foams

The present study is focused on the synthesis and characterization of vinyl ester/glass microballoon syntactic foams. Tensile and compressive properties of vinyl ester matrix syntactic foams are characterized. Results show that the compressive strength and moduli of several syntactic foam compositions are comparable to those of the neat matrix resin. Due to the lower density of syntactic foams, the specific compressive properties of all compositions are higher than those of the neat resin. Similar trends are observed in the tensile properties. Mechanical properties of vinyl ester matrix syntactic foams are compared to well-documented mechanical properties of epoxy matrix systems. The comparison shows that low cost vinyl ester resins, which are extensively used in marine applications, can result in syntactic foams with comparable performance to epoxy matrix systems. In addition, tensile modulus is found to be 15–30% higher than the compressive modulus for all syntactic foam compositions. This difference is related to the possibility of particle fracture in the stress range where modulus is calculated in the compressive stress–strain curves.     

Production and properties of micro‐porous glas bubble zinc and aluminium composites

Micro‐porous syntactic foams were produced by means of integration of glass bubbles into aluminium and zinc matrices. Preforms of glass bubbles were pressure infiltrated with the alloys AlSi9Cu9 ans ZnAl4Cu using squeeze casting. The preforms were sintered thermically without the use of bonding agents. Using the combination of different sintering steps syntactic foams with locally different densities could be produced. The mechanical properties of the foams were tested indicating a high compression strength of the foams and a very good compression energy absorption. Furthermore, corrosion behaviour and behaviour at higher temperatures were investigated.     

不同密度聚酰亚胺泡沫的制备与性能

制备了基于3,3’-4,4’-二苯甲酮四酸二酐(BTDA)、多苯基多亚甲基多异氰酸酯(PAPI)及二苯甲烷二异氰酸酯(MDI)的聚酰亚胺泡沫,通过改变发泡时的环境压力,制备了不同密度的泡沫;利用红外光谱和扫描电镜对所制备的聚酰亚胺泡沫进行了结构与形貌表征,并对泡沫热性能和压缩强度行了表征。结果表明,所制备的泡沫密度随着制备压力的增大而增加,泡沫密度为7.3~160kg/m~3,红外光谱确认了目标聚合物的合成,泡沫T_g不低于250℃,且具有良好的热稳定性,经过250℃处理的泡沫的T_g达到270℃,T_(d5%)达到404℃,均高于230℃处理得到的泡沫的性能。压缩性能测试表明所制备泡沫压缩强度随着密度增加而增加,当密度为160kg/m~3时,压缩强度达到1.88 MPa。     

Aluminium foams for transport industry

Foamed materials are widespread in transportation industry applications. While polymeric foams have been applied for many years foamed metals are now beginning to move into the focus of interest. A powder metallurgical method which allows the production of aluminium foams with porosity levels up to 90% is described. The foams typically have closed pores and densities ranging from 0.4 to 1 g cm⁻³, so that this foamed metals float on water. The unique mechanical properties of metal foams are described. The density dependence of metal foam properties is shown with the Young's modulus, flexural strength and compression strength as examples. A non-linear dependency of these properties on the density is found and discussed. The discussion then focuses on the energy absorption properties of aluminium foams and tools to select appropriate foams for a given energy absorption task.     

The mechanical behavior of foamed aluminum

Experiments have been carried out to investigate the mechanical behavior of foamed aluminum with different matrixes and states. It is found that the matrix composition has a significant influence over the deformation, failure and fracture of foamed aluminum. Like other cellular solid materials, Al foam shows a smooth compression stress–strain curve with three regions characteristic of plastic foams: linear elastic, plastic collapse and densification. AlMg10 foam has a serrated plateau and no densification, characteristic of brittle foams. AlMg10 foam has higher compressive and tensile strength but lower ductility than Al foam. The difference in the mechanical properties between Al foam and AlMg10 foam decreases as the relative density decreases, and when it is lower than roughly 0.15, no difference can be discerned. The mechanical properties in compression are clearly higher than those in tension, which can be explained in terms of dislocation theory and stress concentration behavior.     

聚氨酯和聚乙烯基酯为基的聚合物互穿网络泡沫

合成了聚氨酯和聚乙烯基酯的基的全水发泡聚合物互穿网络软质泡沫。各配方泡沫的聚氨酯对聚乙烯基酯的比例和／或水量各不同相同，在同等水量和相同密度的两组泡沫中，ＰＵ／ＰＶＥ＝９０／１０的泡沫的均呈现拉伸强度最高值。随乙烯基酯含量的增加，所有泡沫的落球回弹降低，同时压缩滞后增加。这种能量吸收能力的提高也反映在动态力学谱上，即聚氨酯软段和聚乙烯基酯的玻璃化温度间的高阻尼区明显变宽。聚氨酯软段Ｔｇ的显著移高表     

Elastic moduli of a lean and a pavement quality concrete under uniaxial tension and compression

Results are given of strain measurements taken during a limited proramme of tests on a lean concrete and a pavement quality concrete to compare the elastic moduli under direct tension and compression. For each type of concrete differences of less than 10% were found between the tensile and compressive tangent moduli. In tension tests deviation from linearity, indicating commencement of microcracking, occurred at a lower percentage of the ultimate tensile strength for the concrete having the higher cement content. Modulus values were higher for the lean concrete than for the richer pavement quality concrete.     

聚氨酯/环氧树脂互穿网络硬泡静态压缩塑性变形模式

采用同步法合成聚氨酯/环氧树脂互穿网络硬泡,通过FTIR和SEM研究其化学结构及微观结构形态,为研究其压缩响应及变形模式,对其进行静态压缩试验。结果表明:IPN硬泡的压缩行为表现出各向异性。平行发泡方向的压缩应力-应变曲线表现出三个变形阶段,其中平台阶段的显著特征是应变软化和局部变形。垂直发泡方向的压缩曲线则单调增加,平台阶段没有产生应变软化,整个压缩过程中试样变形均匀分布。IPN硬泡的静态压缩存在明显的应变率效应,环氧树脂含量对压缩性能影响显著。描述IPN硬泡压缩局部变形理论模型,变形带厚度和变形带前沿传播速度的理论值与试验值吻合较好,采用该模型分析研究IPN硬泡的压缩变形机理。