玻璃纤维复合材料层合板冲击后的压缩强度

对不同厚度的二维编织环氧玻璃纤维层合板进行落锤冲击试验及冲击后压缩破坏试验,以研究低速冲击对复合材料层合板剩余压缩强度(CAI)的影响。用透光描影及热揭层方法对冲击损伤形式进行描述。讨论了损伤宽度、损伤面积与冲击能量及剩余压缩强度、模量间的关系,并建立有限元模型,采用开口等效及软化夹杂等分析方法对材料的冲击后压缩强度值进行估算。     

冲击位置对挖补修理层合板冲击后压缩性能的影响

使用过程中的低速冲击损伤对修理后的复合材料结构同样会造成威胁.设计并进行了复合材料挖补修理结构的低速冲击及冲击后压缩试验,测量了试验件的损伤投影面积和剩余压缩强度,分析了不同冲击位置的影响.结果表明,挖补修理层合板冲击后压缩强度比未修补板的低,挖补层合板对低速冲击位置较为敏感.冲击点离开挖补区一定距离后,挖补对层合板的低速冲击及其继后压缩性能的影响消失.     

冲击方向对层合板低速冲击响应的模拟研究

利用有限元软件ABAQUS/Explicit,采用双线性本构法则和B–K断裂能准则,建立并验证了复合材料层合板的落锤式低速冲击损伤模型。在该验证模型的基础上,将冲头分别以30o,45o,60o和90o的冲击角度,以3.0 J和5.0 J的初始冲击能量对层合板进行冲击模拟试验。结果表明,冲头的冲击方向对层合板的冲击响应有着较大的影响,当冲击角度为45o时,冲击方向对层合板的能量耗散影响最大,当冲击角度为90o时,冲击方向对层合板能量耗散影响最小。     

CFRP层合板冲击后压缩失效分析数值模拟

复合材料层合板的损伤容限是复合材料结构设计的关键因素。针对碳纤维增强复合材料(CFRP)层合板低速冲击损伤和压缩破坏问题,本文基于连续损伤力学和粘结单元模型,在ABAQUS中对两种不同冲击能量下的层合板进行了低速冲击和冲击后压缩仿真分析,并对层内和层间损伤进行了研究,分析了层合板的冲击损伤与压缩失效行为,通过与试验结果进行对比,验证了该模型的有效性。研究结果表明:冲击损伤对层合板的剩余压缩强度有着重要影响,试件的破坏开始于冲击损伤区域,并逐渐扩展到层合板的边缘,压缩力快速下降,层合板最终失效。     

复合材料层合板低速冲击后的力学性能试验研究

对特定铺层的5224/CF3052平纹织物复合材料层合板进行了低速冲击和冲击后拉伸、压缩及弯曲试验。探讨了层合板在冲击试验过程中的损伤过程、特征和机理;分析了凹坑深度对层合板冲击后拉伸、压缩和弯曲强度的影响规律。结果表明:冲击后拉伸、压缩及弯曲强度降幅分别为60.9%、50.4%及28.4%,冲击后拉伸强度降幅最大,应引起注意。与冲击后压缩试验结果类似,凹坑深度与冲击后拉伸、弯曲剩余强度关系曲线存在拐点现象。     

CFRP层合板冲击后剩余强度及黏弹性能研究

通过对制备的环氧基碳纤维增强复合材料(CFRP)层合板进行低速冲击剩余压缩强度试验研究，分析了CFRP层合板的冲击后剩余性能，然后观察CFRP层合板的冲击凹坑回弹现象，分析CFRP层合板的黏弹性能，深入分析冲击过程中能量的吸收与转化。结果表明：当冲击能量越来越大时，CFRP层合板的损伤越来越严重，其剩余压缩强度越来越低；从凹坑边缘到凹坑中心处，CFRP层合板的应变能密度逐渐增大；凹坑回弹部位位于凹坑中心区域附近，呈现局部突起状，最终凹坑剖面近似于不规则“W”形。     

准静态压痕作用下复合材料层合板损伤阻抗与损伤容限实验研究

参照标准实验方法,开展了复合材料层合板对准静态压痕力的损伤阻抗和损伤容限实验研究,获取了接触力、压痕深度、压头位移等实验数据,并对含静压痕损伤层合板进行了剩余压缩强度试验。研究了压痕深度-接触力与剩余压缩强度-压痕深度的变化关系,并讨论了准静态压痕过程中的损伤演变过程和层合板的压缩破坏模式。结果表明:当层合板表面出现目视勉强可见压痕时,初始损伤发生,压痕深度随接触力增大而明显增大,同时剩余压缩强度随压痕深度增加而明显降低;当达到最大接触力时,层合板失去承载能力,背面可看到大量纤维断裂。对于含静压痕损伤的层合板,压缩破坏模式为贯穿损伤区域的层合板断裂。     

玻璃纤维/环氧层合板低冲击能量与凹坑深度量化研究

使用试件为单向层合板和多向层合板两种类型的玻璃纤维增强环氧树脂基复合材料层合板,采用自由落体式冲击试验机进行低能量冲击,以及超景深显微镜对损伤形貌进行特征描述。引入低能量冲击关系因子K,建立冲击能量与损伤凹坑深度量化关系,该量化关系可使冲击能量与损伤形貌特征相对应。所建立的凹坑深度与冲击能量的关系,既可以根据测量冲击凹坑深度反推出冲击时的能量值,也可以根据冲击能量预判结构的损伤情况。     

金属网对玻璃纤维增强复合材料低速冲击损伤特性的影响

为研究304不锈钢网对玻璃纤维编织复合材料低速冲击损伤特性的影响,利用落锤试验机分别对2 mm厚的不含、含一层和含三层304不锈钢网的玻璃纤维编织复合材料板进行5 J、20 J、40 J和60 J能量下的冲击实验,从层合板载荷峰值、最大凹陷位移、能量吸收和损伤机理等方面,分析不锈钢网对层合板抗冲击性能的影响规律。研究结果表明,当冲击能量未达到层合板击穿能量阈值前,载荷峰值和最大凹陷位移随着冲击能量的增大而增大。三层不锈钢网的加入使得层合板在较小凹陷位移时就能达到最大载荷,具有良好的抗冲击性能。层合板损伤形状呈十字形,损伤程度沿着厚度方向逐渐加深,背面中心点处损伤最为严重。当冲击能量超过层合板能量阈值时,中心区域损伤呈花瓣开裂状,主要损伤模式为纤维拉伸断裂和基体破碎、金属丝拉伸断裂。     

复合材料层合板冲击损伤剩余强度分析

民用飞机复合材料结构设计时必须考虑复合材料层合板的冲击损伤.通过试验测量和数值模拟两种方法分析碳纤维增强复合材料层合板低速冲击损伤后的剩余压缩强度,试验采用标准试验规范进行测量,数值模拟分析采用层内渐进损伤模型和层间Cohesive模型模拟分析层合板冲击损伤以及剩余压缩强度.数值模拟与试验结果对比表明,该数值模拟分析方...     

氢气纯度分析方法准确性的探讨

ONACCURACYOFANALYSISOFOFHYDROGEN1前言我公司目前应用的氢气纯度分析方法有两种,一种是爆炸反应法,另一种是焦性没食子酸吸收法。几年来,人们对两种分析方法的准确性曾有过褒贬不一的评论。这里我们也谈谈自己粗浅的观点。2爆炸法测定氢气纯度一定量的氢气样品与适量的空气之均匀混合物因反应后生成液体水而引起气体体积减少,减少的体积等于参加反应气体体积之和。其中l／3为氧气,2／3为氢气。根据氢气取样量和反应前后混气体体积之差,以及氢气在反应中的体积比例关系,可计算出样品的氢气纯度。计算公式式中：A一混…     

COMPARISON OF METHODS OF ANALYSIS OF GYPSUM1

The different analytical methods proposed for the evaluation of gypsum have been subjected to an experimental test. A combination method, consisting of a fusion with KHCO₃ and determination of CaO by KMnO₄ titration, the SO₃ by Andrews method of titration of BaCrO₄ has been found to give very reliable results with the least consumption of time.     

SEDIMENTATION OF BINARY MIXTURES OF PARTICLES OF UNEQUAL DENSITIES AND OF DIFFERENT SIZES

A model is developed for the sedimentation from a suspension of two particle species of unequal densities and of different sizes. The composition and the thickness of various layers in the sediments are predicted using graphical and analytical methods. The model predictions were in excellent agreement with experimental results, when the particle size ratio was ≥ 108. When size ratio of the particles was 2.60 and 4.31 the agreement occurred in about 50 percent of the cases.     

HEASUREHENT OF INSTANTANEOUS RATES OF LOSS OF VOIATILE COMPOUNDS DURING DRYING OF DROPS

A novel technique serves to monitor instantaneous rates of loss of a volatile solute from a suspended drop during drying. A highly sensitive electron capture detector is used to monitor concentrations of SF6 released into a flowing gas stream from a suspended, drying drop. Simultaneously, the appearance and morphological development of the drop are monitored with a video camera. This provides the wherewithal of relating instantaneous rates of loss of the volatile solute to particular events during the development of particle morphology.

Initial experiments have been carried out with drops of aqueous solutions of glucose, sucrose, maltodextrin and coffee extract. The results clearly display the onset of the volatiles-retentive selective diffusion phenomenon. There is also substantial loss of the volatile component later in the drying process, when the drops undergo repeated ex ansion, bursting and cratering due to the formation of internaf bubbles. These experiments appear to be the first quantitative demonstration of major losses accompanying changes in drop morphology.     

几种针状焦性能对比

针状焦分石油系和煤系两大类,这主要取决于针状焦的原料来源。在同一系列中由于原料不同和工艺条件不同 ,针状焦的各自性能也不相同。针状焦是生产超高功率石墨电极和高功率石墨电极的主要原料 ,针状焦的性能对石墨电极的质量有至关重要的影响。所以对针状焦性能以及其对石墨电极质量影响的研究十分必要的。以下是常用的几种进口针状焦和国产针状焦的性能对比。１原料性能分析对比原料试样包括４种针状焦 ,其中两种为进口针状焦：三菱针状焦和新日化针状焦;另两种为国产针状焦：鞍山针状焦和锦州针状焦。其中除锦州针状焦是石油系针状焦外…     

茶多酚提取方法进展

本文综述了国内外现有茶多酚提取方法的现状以及近期的研究进展，并对其优缺点进行了评价。这将有助于中低档茶的综合利用和茶多酚的进一步开发应用。     

ANALYSIS OF RECENT MEASUREMENTS OF THE VISCOSITY OF GLASSES

Viscosity of Simple Soda-Silicate 500° to 1400°C Comparison of the results given by English with those of Washburn, Shelton and Libman, indicates a discrepancy in the absolute values of log₁₀ viscosity amounting to 0.6, those of Washburn et al., being relatively too high. If correction for this is made, the isothermal curves of log₁₀ viscosity as a function of soda content are smooth up to 50% Na₂O, showing no inflection. The observations as a function of temperature T are all represented within accidental error by an equation of the type where all three constants vary regularly with the composition. Change of Viscosity of Glass (6SiO₂, 2Na₂O) due to Molecular Substitution of CaO, MgO and Al₂O₃ for Na₂O The effect is clearly brought out by plotting (from the results of English) the change of log₁₀η due to the substitution as a function of temperature. The curves each show a sharp bend at a temperature between 840° and 1050°C, which is designated the aggregation temperature T_a. If we divide these curves by the corresponding percentage substituted, we get curves for each oxide which are straight and parallel below the aggregation temperatures, the slopes (increase of change of log₁₀η per 100°C) being −0.056 (CaO), −0.055 (MgO), −0.018 (A1₂O₃) per per cent oxide substituted. For substitution of 1/2 molecule the slopes are −0.325 (CaO), −0.23 (MgO) and −0.18 (Al₂O₃) per 100°. At the aggregation temperature the change of log₁₀η per per cent is a minimum, 0.03 to 0.06 for CaO, 0.12 for MgO, 0.07 for Al₂O₃. Evidence of Aggregation in Glasses, from viscosity Measurements The sharp bends in the plots of change of log₁₀η due to substitution of an oxide for Na₂O, suggest the beginning of molecular aggregation at these temperatures. These aggregation temperatures are close to the devitrification temperatures, but the effect on the viscosity curves cannot be due to actual devitrification since it does not change with time. Taking the aggregation temperatures as equal to devitrification temperatures, additional isotherms are roughly sketched into the equilibrium triangle of the system Na₂O-CaO-SiO₂. Change of Viscosity of Glass (4SiO₂, 2Na₂O) due to of Substitution of B₂O₃ for SiO₂ The change of log₁₀η (from the results of English) is plotted as a function of temperature, and also the change of log₁₀η per per cent B₂O₃. The curves are more complex than for the substitution for Na₂O.     

环氧树脂羟基值测定方法的研究

利用乙酸酐、吡啶和浓硫酸混合的乙酰化试剂测定环氧树脂中羟基值含量的方法具有操作简便、滴定终点明显和分析结果误差小等优点。     

骑式摩托车油箱喷涂工艺的改进

面对日益激烈的市场竞争,摩托车油箱外观质量越来越成为影响销售的因素之一。文章介绍了改进工艺后的油箱涂装,该涂装体系提高了油箱外观的丰满度,降低了油箱涂装的生产成本。     

聚酰亚胺的合成法

本文评述了缩聚型聚酰亚胺的主要合成方法和近年来国际上在合成中所做的探索。