共查询到18条相似文献,搜索用时 78 毫秒
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以氯化钠(NaCl)作为致孔剂与流变性能调节剂,碳纤维(CF)作为增强填料与流变性能调节剂,苯乙炔基封端聚酰胺酸溶液(PAA)作为基体树脂,配制适用于直书写3D打印的复合墨水,室温下打印成形后经热固化处理和NaCl刻蚀去除后制备了多孔热固性聚酰亚胺/碳纤维(TSPI/CF)复合材料. 研究表明:NaCl与CF对复合墨水的流变学性能具有好的调节作用;打印制备的TSPI/CF复合材料具有低的各向同性尺寸收缩和优异的耐热性能,且耐热性能随着CF含量的增加而提高;CF含量升高,TSPI/CF复合材料的孔隙率提高,平均孔径降低,力学性能增强;多孔TSPI/CF复合材料表现出优异的储油、出油性能以及浸油摩擦学性能. 相似文献
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为探寻非钻孔条件下露天爆破大块二次破碎形态的控制方法, 应用线性聚能射流对圆柱混凝土模型试件进行侵彻实验, 使用High-speed 3D DIC(高速三维数字图像相关方法)方法分析试件劈裂发展过程的全场三维形变特征。研究结果表明, 数据分析区内劈裂裂纹扩展速度在4个区间内呈阶梯式变化趋势, 峰值速度为235.52 m/s, 平均速度为140.89 m/s;线性聚能射流侵彻对劈裂裂纹扩展有明显导向作用, 应力集中作用使得劈裂裂纹围绕线性射流侵彻对称轴扩展, 扩展方向变化幅度较小;在劈裂裂纹扩展速度突变的3个时刻, 劈裂裂纹路径产生了3处明显拐点, 在拐点处伴随有支裂纹的产生, 支裂纹的扩展距离均未超过5 cm;主应变集中带形状及分布位置决定了裂纹扩展路径及趋势, 拉应变集中先于裂纹出现, 试件呈现准静态劈裂形态, 劈裂面平整度较高。 相似文献
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通过建立混凝土的3D细观模型,在细观尺度上分析动态压缩荷载作用下混凝土材料内部裂缝的产生和发展、损伤演化和动态强度及其影响因素。首先,基于传统的“生成-投放”法生成粒径、形状和空间分布均随机的凸多面体粗骨料模型,并通过骨料沉降和粒径缩放实现粗骨料的大体积率(达50%)和可调控;使用四面体网格划分骨料和砂浆表征其真实物理形状;使用界面粘结接触表征界面过渡区(ITZ)提升计算效率。进一步通过对比不同粗骨料粒径混凝土的分离式霍普金森压杆(SHPB)试验数据与模拟结果,如杆上应变时程、试件动态应力-应变曲线和试件损伤破坏模式,验证了建立的混凝土3D细观有限元模型、参数确定方法和数值仿真方法的准确性。最后,分析了30~100 s-1应变率范围内骨料粒径(4~8、10~14和22~26 mm)、体积率(20%、30%和40%)和类型(石灰岩、花岗岩和玄武岩)对混凝土动态压缩强度的影响。结果表明:粗骨料粒径增大,混凝土动态压缩强度先增大后减小;粗骨料体积率越高,混凝土动态压缩强度越大;混凝土动态压缩强度随粗骨料强度的增加而提高。 相似文献
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为了增强混凝土的抗侵蚀性能,对不同纤维掺量混凝土在硫酸镁侵蚀下的耐久性及力学性能进行了试验研究及分析。采用100mm×100mm×100mm的试块,纤维掺量分别为0%、0.05%、0.1%、0.2%、0.3%,浸泡于浓度为5.0%的硫酸镁溶液中,每30d观测表观裂缝、测试吸水率变化;每90d测定力学性能变化,并进行离子浓度测量。结果表明:玄武岩纤维对混凝土承载力及变形能力有一定的提高;玄武岩纤维混凝土与普通混凝土在硫酸镁溶液环境中相比,孔隙率增加速度较慢;但过量纤维反而对耐久性能产生不利影响;玄武岩掺量在0.1%左右时最为经济、合理。另外,针对玄武岩纤维离散困难的问题,提出了粉体颗粒玄武岩纤维离散法。本文研究可为玄武岩纤维混凝土的工程应用提供一定基础。 相似文献
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采用液压伺服试验系统,对120块不同聚丙烯纤维掺量的混凝土立方体试件进行高温后力学性能试验研究.分析了不同纤维掺量,不同目标温度对混凝土峰值应变、弹性模量、抗压强度等力学性能的影响,此外还探讨了高温后聚丙烯纤维混凝土的表观形态.试验结果表明,高温作用后混凝土试件物理结构发生了很大的变化.随着温度的升高聚丙烯纤维混凝土与普通混凝土一样,弹性模量与抗压强度都呈下降趋势,并且在300oC以后显著降低,而峰值应变上升.在相同温度下,随着纤维掺量的增加混凝土试件的抗压强度与弹性模量下降,峰值应变升高.通过对试验数据的统计分析,建立了不同掺量下聚丙烯纤维混凝土的相对抗压强度随温度变化的关系式,为聚丙烯纤维混凝土在各种实际工程中的应用提供了一定的参考价值. 相似文献
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新型混凝土桥面铺装材料的冲击力学性能 总被引:1,自引:0,他引:1
利用大尺寸Hopkinson压杆对新型混凝土桥面铺装材料钢纤维增强聚合物改性混凝土(steel fiber reinforced and polymer modified concrete,SFRPMC)进行了冲击实验,并且在相同基准配合比下,与普通混凝土、钢纤维混凝土的冲击性能进行了对比。观察了不同打击速度下三种材料的破坏形态,得到了在不同应变率下的应力应变关系,比较了三种材料的应变率敏感性,最后从机理上分析了掺加钢纤维和聚合物对混凝土材料冲击力学性能的影响。结果表明,钢纤维增强聚合物改性混凝土材料具有良好的冲击韧性,是一种理想的混凝土桥面铺装材料。 相似文献
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《Comptes Rendus Mecanique》2019,347(9):615-625
Polymers are commonly found to have low mechanical properties, e.g., low stiffness and low strength. To improve the mechanical properties of polymers, various types of fillers have been added. These fillers can be either micro- or nano-sized; however; nano-sized fillers are found to be more efficient in improving the mechanical properties than micro-sized fillers. In this research, we have analysed the mechanical behaviour of silica reinforced nanocomposites printed by using a new 5-axis photopolymer extrusion 3D printing technique. The printer has 3 translational axes and 2 rotational axes, which enables it to print free-standing objects. Since this is a new technique and in order to characterise the mechanical properties of the nanocomposites manufactured using this new technique, we carried out experimental and numerical analyses. We added a nano-sized silica filler to enhance the properties of a 3D printed photopolymer. Different concentrations of the filler were added and their effects on mechanical properties were studied by conducting uniaxial tensile tests. We observed an improvement in mechanical properties following the addition of the nano-sized filler. In order to observe the tensile strength, dog-bone samples using a new photopolymer extrusion printing technique were prepared. A viscoelastic model was developed and stress relaxation tests were conducted on the photopolymer in order to calibrate the viscoelastic parameters. The developed computational model of nano reinforced polymer composite takes into account the nanostructure and the dispersion of the nanoparticles. Hyper and viscoelastic phenomena was considered to validate and analyse the stress–strain relationship in the cases of filler concentrations of 8%, 9%, and 10%. In order to represent the nanostructure, a 3D representative volume element (RVE) was utilized and subsequent simulations were run in the commercial finite element package ABAQUS. The results acquired in this study could lead to a better understanding of the mechanical characteristics of the nanoparticle reinforced composite, manufactured using a new photopolymer extrusion 5-axis 3D printing technique. 相似文献
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为研究温度、加载速率、纤维掺量对玄武岩纤维增强混凝土(BFRC)动态压缩强度和冲击韧度的影响,利用?100 mm分离式霍普金森压杆(SHPB)装置,对经历不同温度作用后的BFRC进行冲击加载实验。结果表明:高温后BFRC的动压强度及冲击韧度在同一温度下随平均应变率的上升近似线性增大;温度的升高总体上导致BFRC在同一加载速率下的动压强度及冲击韧度减小、应变率敏感性减弱;同一工况下,BFRC的动压强度和冲击韧度较素混凝土普遍提高,且当纤维体积掺量为0.2%时强韧化效果相对最佳。由此可见,高温后BFRC的冲击压缩特性受温度、加载速率、纤维掺量的综合作用影响,掺入玄武岩纤维可以有效降低高温后BFRC的损伤劣化程度。 相似文献
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Geometrically structured interfaces in nature possess enhanced, and often surprising, mechanical properties, and provide inspiration for materials design. This paper investigates the mechanics of deformation and failure mechanisms of suture interface designs through analytical models and experiments on 3D printed polymer physical prototypes. Suture waveforms with generalized trapezoidal geometries (trapezoidal, rectangular, anti-trapezoidal, and triangular) are studied and characterized by several important geometric parameters: the presence or absence of a bonded tip region, the tip angle, and the geometry. It is shown that a wide range (in some cases as great as an order of magnitude) in stiffness, strength, and toughness is achievable dependent on tip bonding, tip angle, and geometry. Suture interfaces with a bonded tip region exhibit a higher initial stiffness due to the greater load bearing by the skeletal teeth, a double peak in the stress–strain curve corresponding to the failure of the bonded tip and the failure of the slanted interface region or tooth, respectively, and an additional failure and toughening mechanism due to the failure of the bonded tip. Anti-trapezoidal geometries promote the greatest amplification of properties for suture interfaces with a bonded tip due the large tip interface area. The tip angle and geometry govern the stress distributions in the teeth and the ratio of normal to shear stresses in the interfacial layers, which together determine the failure mechanism of the interface and/or the teeth. Rectangular suture interfaces fail by simple shearing of the interfaces. Trapezoidal and triangular suture interfaces fail by a combination of shear and tensile normal stresses in the interface, leading to plastic deformation, cavitation events, and subsequent stretching of interface ligaments with mostly elastic deformation in the teeth. Anti-trapezoidal suture interfaces with small tip angles have high stress concentrations in the teeth and fail catastrophically by tooth failure, whereas larger tip angles exhibit a shear failure of the interfaces. Therefore, larger tip angles and trapezoidal or triangular geometries promote graceful failure, and smaller tip angles and anti-trapezoidal geometries promote more brittle-like failure. This dependence is reminiscent of biological systems, which exhibit a range of failure behaviors with limited materials and varied geometry. Triangular geometries uniquely exhibit uniform stress distributions in its teeth and promote the greatest amplification of mechanical properties. In both the bonded and unbonded cases, the predictions from the presented analytical models and experimental results on 3D printed prototypes show excellent agreement. This validates the analytical models and allows for the models to be used as a tool for the design of new materials and interfaces with tailored mechanical behavior. 相似文献