泡桐木夹层结构材料的力学性能

选用泡桐木为原料,制备出夹层结构用泡桐木绿色夹芯材料,其木质纤维具有天然蜂窝形状,结构类似于目前航空航天领域常用的蜂窝芯材;泡桐木芯材除密度略高于Balsa轻木外,其他力学性能测试指标均优于轻木,同时在价格上占有绝对的优势。采用真空导入成型工艺,成功制备出轻质高强的泡桐木夹层复合材料,通过不同跨高比试件的三点与四点弯试验,研究其典型受力破坏形态与机制;利用经典夹层梁理论预估试件抗弯刚度和受弯极限承载力,理论值与实测值符合较好,并以此为基础,提出了基于强度的优化设计方法。     

格构腹板式界面增强泡桐木夹芯复合材料梁的弯曲性能试验

复合材料及其夹层结构具有轻质高强、耐腐蚀、节能保温等特点,以玻璃纤维增强复合材料作为面层和格构腹板,以泡桐木为芯材,采用真空导入成型工艺,制备出格构腹板式界面增加泡桐木夹芯复合材料梁。在保持试件总尺寸不变条件下,对木梁、无格构木芯梁、格构木芯梁进行了平面、侧面四点受弯性能试验研究对比。得出如下结论:同一种构造试件平面受压时所受的极限承载力和刚度比侧面受压时所受的极限承载力和刚度高;无格构木芯梁、格构木芯梁试件所受的极限承载力和刚度比木梁试件所受的极限承载力和刚度有明显的提高;格构木芯梁试件所受的极限承载力和刚度比无格构木芯梁试件所受的极限承载力和刚度有一定的提高。     

剪跨比对腹板增强复合材料夹层梁受剪性能影响试验研究

对不同剪跨比(a/d)的纤维腹板增强复合材料夹层梁进行四点弯试验,得到其荷载-位移曲线和典型破坏模式,分析了不同剪跨比和纤维腹板厚度对其受剪机理影响规律。结果表明:剪跨比为1的试件承载力最大;随着剪跨比增加,腹板增强夹层梁极限承载力降低,延性性能降低,比强度降低;当夹层梁剪跨比小于3时,试件发生上面板压陷/芯材剪切破坏,当剪跨比大于3时,试件发生上面板受压屈服破坏;对具有相同剪跨比试件,纤维腹板能显著提高其极限承载力和延性性能,厚度越大,极限承载力提高效果越明显。     

面板厚度对复合材料夹层梁整体及局部弯曲力学性能影响

考虑芯材局部压陷效应,对泡沫夹芯复合材料夹层梁整体及局部弯曲力学性能进行研究。分析了上面板厚度对夹层梁整体及局部弯曲力学性能影响规律。首先,对三种不同厚度上面板夹层梁进行三点弯曲试验,结果表明,夹层梁破坏模式为芯材压陷破坏和芯材剪切破坏;上面板厚度越大,夹层梁极限承载力越大;增大上面板厚度能有效减弱加载点位置芯材局部压陷效应。其次,基于考虑芯材竖向压缩变形的高阶剪切变形理论,对试验梁整体及局部弯曲受力机理进行分析,得到夹层梁上、下面板不同位置挠度及应变的分布规律。最后,对不同试验梁极限承载力进行理论分析,并与试验结果对比。     

横向腹板增强复合材料夹层梁受弯性能试验研究

通过四点弯试验研究横向腹板增强复合材料夹层梁受弯性能,得到不同腹板间距、厚度对夹层梁弯曲破坏模式、刚度、极限承载力及延性性能的影响规律。结果表明:横向腹板能改变夹层梁的破坏模式,无腹板增强夹层梁破坏模式为芯材剪切破坏,横向腹板增强夹层梁破坏模式为多区格渐进破坏模式;相对于无腹板增强夹层梁,横向腹板能显著增强复合材料夹层梁的延性特性,最高达229%,腹板间距越小,夹层梁延性性能越好。     

格构腹板增强木芯复合材料短柱轴压性能试验与理论分析

格构腹板增强木芯复合材料短柱以玻璃纤维增强复合材料作为面层与格构腹板,以泡桐木作为芯材,采用真空导入工艺制作而成,具有轻质高强、耐腐蚀、延性好等显著优点。对具有不同格构腹板布置形式、纤维增强复合材料壁厚等参数的复合短柱进行轴压试验,研究了其破坏模式和机理。基于弹性分析法计算了短柱试件的极限承载力,计算值与试验值吻合较好。     

双向格构腹板增强泡沫夹层复合材料梁弯曲性能试验

复合材料夹层结构具有比强度高、比刚度高、可设计性强、耐腐蚀等特点,以聚氨酯泡沫为芯材,以玻璃纤维增强复合材料为面板和格构腹板,采用真空导入成型工艺,制备双向格构腹板增强泡沫夹层复合材料梁。对无格构泡沫夹芯复合材料梁,不同腹板高度、腹板间距双向格构增强泡沫夹层复合材料梁进行三点弯曲试验,研究其破坏模式和机理。基于泡沫填充矩形蜂窝芯材的等效十字模型,预估试件的抗弯刚度和挠度,计算值与试验值吻合较好。     

芯材密度对复合材料夹层梁弯曲力学性能影响

研究了聚氨酯泡沫密度对复合材料夹层梁弯曲力学性能的影响。首先,对5种不同密度(48~413kg/m3)泡沫芯材复合材料夹层梁进行三点弯试验研究,结果表明,夹层梁极限承载力随芯材密度的增大而增大;当芯材密度大于等于199kg/m3时,继续增大泡沫密度,夹层梁极限承载力增加速度变慢;随着芯材密度的增加,夹层梁破坏模式由芯材压陷变为面板受压屈服破坏。其次,基于考虑芯材竖向压缩变形的高阶剪切变形理论,对不同试验梁弯曲受力机理进行弹性分析,得到夹层梁上、下面板挠度变化及应变分布规律,并与试验结果对比,验证了理论分析方法的正确性。最后,对试验过程中夹层梁典型的破坏模式进行极限承载力分析,提出其极限承载力计算公式,并与试验结果对比,结果吻合良好。     

齿槽增强泡桐木夹层结构界面性能试验

采用在芯材表面开槽并注入树脂的方法,可以有效提高泡桐木夹层结构的玻璃纤维树脂面板与泡桐木芯材之间的黏结性能.为比较齿槽的界面增强效果,使用真空导入工艺制备了多个不同槽宽、槽深及间距的试件,应用双悬臂梁(DCB)方法,测试了夹层梁发生层间断裂时的能量释放率,发现齿槽构造可以显著地提高泡桐木夹层结构的界面性能.同时,分析了影响夹层结构界面性能的关键因素,齿槽的增强作用可体现在工艺和界面构造两方面.     

无腹筋BFRP筋玄武岩纤维混凝土深梁抗剪性能试验研究

为研究玄武岩纤维对无腹筋BFRP筋混凝土深梁裂缝开展、破坏形态、跨中挠度、剪切开裂承载力及抗剪极限承载力的影响,以玄武岩纤维体积掺率和纤维长度为参数,设计并制作了5根试验梁,通过四分点集中力加载研究深梁的抗剪性能。结果表明:随着纤维特征参数的增大,构件破坏形态出现由斜压破坏向剪压破坏转变的趋势;与普通混凝土深梁相比,相同荷载作用下,玄武岩纤维混凝土深梁跨中挠度和裂缝宽度均随着纤维特征参数的增大而减小;构件剪切开裂承载力和抗剪极限承载力随着纤维特征参数的增大均有所提高。在考虑玄武岩纤维增强作用的基础上,参照GB 50010—2015规范对玄武岩纤维混凝土深梁抗剪极限承载力进行计算,实测值与计算值基本吻合。     

塑钢纤维磷渣混凝土弯曲性能研究

以不掺塑钢纤维的磷渣混凝土为基准,对纤维长度为30 mm、40 mm、55 mm和纤维掺量为3 kg/m³、6 kg/m³、9 kg/m³的塑钢纤维磷渣混凝土进行四点弯曲试验,研究不同纤维长度和纤维掺量对磷渣混凝土弯曲性能的影响规律。研究结果表明:随着塑钢纤维长度和掺量的增加,磷渣混凝土的抗弯强度随之增加,塑钢纤维长度为55 mm,掺量为3 kg/m³时,对磷渣混凝土抗弯强度增强效果最佳,抗弯强度比基准组提高了56%;随着塑钢纤维长度和掺量的增加,磷渣混凝土弯曲韧性指数不断增大,弯曲韧性不断提高,塑钢纤维长度为55 mm,掺量为9 kg/m³时,弯曲韧性指数I₂₀比基准组提高了9.8倍。     

焊接试板面弯,背弯与侧弯的比较

焊接工艺评定试板和产品焊接试板,按标准要求都要进行弯曲试验.根据计算和经验,侧弯伸长率小,且焊缝表面经过加工,不受表面质量影响,所以试验结果更接近实际,更为准确.     

纬编双轴向多层衬纱织物增强复合材料的弯曲性能研究

本文主要对高性能纤维的纬编双轴向多层衬纱织物增强复合材料的弯曲性能进行研究分析.本文所用的增强纤维为玻璃纤维和高强聚乙烯纤维两种,增强织物包括玻璃纤维织物、高强聚乙烯纤维织物及玻璃纤维/聚乙烯纤维层间混合织物三种,基体为乙烯基酯树脂,文中着重对几种复合材料的弯曲性能进行测试和分析比较.分析结果表明,该类复合材料有很好的弯曲性能,含有玻璃纤维的横向弯曲破坏有其特点,玻璃纤维为脆性破坏,而聚乙烯纤维表现为屈曲破坏.     

Softness evaluation of keratin fibers based on single‐fiber bending test

The evaluation of single‐fiber softness by bending is an ingenious and vital approach for the basic investigation of both the fiber bending properties and the textile softness. The bending behavior and bending modulus of wool, alpaca and silk fibers have been measured by an axial‐buckling method developed by the authors, which uses the fiber compression bending analyzer (FICBA). The bending properties of single fibers were quantified by calculating the equivalent bending modulus and the flexural rigidity by measuring the protruding length and diameter of fiber needles and the critical force, P_cr, obtained from the peak point of the force‐displacement curve. The measured data showed that the equivalent bending modulus of the alpaca fiber is higher than that of wool fiber, and even the rigidity is 10 times as high as wool, but its friction coefficient is lower than that of wool, which means that the soft handle of alpaca fabrics is mainly due to the smooth surface and low friction coefficient of alpaca fibers in contrast to that of wool fiber. For the silk fiber, despite high equivalent bending modulus, the smoother handle of silk should be mainly due to the thin fiber diameter in contrast to that of keratin fibers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 701–707, 2006     

拉挤成型复合材料夹芯桥面板弯曲性能试验研究

拉挤成型复合材料夹芯桥面板系采用拉挤成型工艺制作的轻木夹芯复合材料板材,具有质量轻、强度高、刚度大、耐久性好、生产效率高等优点。本文以杨木、无碱玻璃纤维以及不饱和聚酯树脂为原料,采用拉挤成型工艺制作了复合材料夹芯桥面板,对其进行了三点弯试验,得到了其破坏模式和弯曲力学行为。试验结果表明,与带肋腹板空心桥面板相比,拉挤成型复合材料桥面板弯曲承载力提高了87%,抗弯刚度提高了24%。     

H2 response characteristics for sol–gel-derived WO3-SnO2 dual-layer thin films

This paper describes the deposition of SnO₂ and WO₃ thin films and WO₃-SnO₂ dual-layer thin films using the sol-gel process. The microstructure and morphology of these three thin films were analyzed with FE-SEM and X-ray diffraction. The H₂ response characteristics, including response magnitude, time and transients of the three samples, were investigated at different operation temperatures and H₂ gas concentrations. Although the maximum response magnitude of 29.31 towards 1000 ppm H₂ gas appeared at 225 °C,the WO₃-SnO₂ dual-layer films still had a response magnitude of 24.23 at 175 °C, which is much higher than those of the SnO₂ (4.19) and WO₃ (6.73) thin films. The linear response magnitude profile of the WO₃-SnO₂ dual-layer thin films toward H₂ gas concentration was obtained. The mechanism of the enhanced gas response characteristics was explained by the band bending theory.     

Misalignment-Induced Bending in Pin-Loaded Tensile-Creep Specimens

In this paper, we have examined the possibility that elastic bending induced by load misalignment can affect creep measurements on pin-loaded tension specimens of silicon nitride (Si₃N₄). We have shown that elastic bending at room temperature can be as great as 42% of the axial strain when clean pins were used but was reduced to ∼3% when lubricated pins were used. Creep tests at the same applied stress and temperature were conducted on two groups of Si₃N₄ test specimens: one group used clean pins, and the other group used lubricated pins. By measuring the shapes of the specimens before and after the creep tests, we have determined that the loading holes were slightly misaligned before the creep tests and that small amounts of bending were induced by the creep tests. Bending occurred both in the gauge section of the specimen and in the transition region between the gauge section and the heads of the specimen (the latter phenomenon is defined as hinge bending). Our study indicated that the secondary creep rate, the hinge bending, and the bending of the gauge section was not dependent on pin lubrication, because the results from the clean and lubricated groups were statistically indistinguishable. Hinge bending was dependent on initial misalignment of the loading holes, whereas bending of the gauge section was independent of such factors.     

论复合材料弯曲实验

本文通过一系列的实验比较和分析研究，客观地评论了复合材料弯曲性能测定的两种主要实验方法－－三点弯曲和四点弯曲方案的优缺点，测定复合材料弯曲性能时参考。     

穿孔位置对单向层板弯曲刚度的影响

对不同穿孔位置单向板分别在筒支和固支约束方式下的弯曲刚度进行试验研究，并进行了有限元建模和数值计算。有限元计算结果和试验结果吻合良好。研究结果表明，穿孔面积比相同时，在不同的约束条件下穿孔位置对弯曲刚度的影响不同；在弯矩最小处穿孔的单向层板具有最大的弯曲刚度。