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排序方式: 共有265条查询结果,搜索用时 15 毫秒
1.
This paper concentrates on the experimental investigation of the self-reinforced all-polypropylene composites. There exists an optimum processing condition to produce high quality specimens by injection–compression molding. Tensile and 3-point bending properties of the virgin PP materials were nearly unaffected by the introduction of reinforcing knit layer(s) due to very low fibre content of the knitted fabrics used. 3-point bending properties were also unaffected by the surface of indentation-flexure. The applied impact energy was maintained at 5 J for the homo-PP and 27 J for the block-PP materials, respectively, to cause penetration during drop-weight impact tests. It is interestingly noteworthy that the self-reinforced homo-PP composites exhibited superior energy absorption capability when compared with the virgin matrix materials. The corresponding plate bending performances of the self-reinforced homo-PP composites also revealed consistent improvement as compared to their virgin counterparts. On the other hand, although virgin block-PP material exhibited better impact performances than its composite reinforced by the homo-PP knitted fabric, a notably small increase in the reinforcement fibre content revealed considerable improvement in the impact properties comparable to those of the virgin block-PP matrix materials. These self-reinforced homo-PP/block-PP materials have clearly indicated that they have the potential to out-perform the block-PP materials via modification and/or manipulation of the reinforcement knit structural/geometrical parameters and the content of reinforcement fibres. Both static and dynamic impact properties are likely to be affected by the local area properties of the tested face under indentation, and thereby contributing to the improved performances of the composite specimens with the knit face under the impact. 相似文献
2.
本文通过对织物透湿性的定性分析,应用灰色系统理论,建立了织物透湿率的灰色动态预测模型,经实验验证,该模型具有很高的预测精度。 相似文献
3.
陈健 《浙江理工大学学报》1997,(4)
和式纹样近年来常被西方服装、装饰界作为东方文化的典型屡屡采用,并浸润到我国相关领域。本文试对和式纹样的生成背景及其特色略作分析,以引起设计界的重视和关注。 相似文献
4.
Stress Dilatancy and Fabric Dependencies on Sand Behavior 总被引:2,自引:0,他引:2
A stress dilatancy model with embedded microstructural information, originally developed by the writers, is used to illustrate the pivotal importance of dilatancy and fabric on the behavior of sand. Fabric, as a second-order tensor, enters into the stress dilatancy equation obtained from a microscopic analysis of an ensemble of rigid particles. Model simulations of sand behavior are carried out in triaxial stress conditions along strain paths with varying degrees of controlled dilation (or compaction) including isochoric deformations as a particular case. Under particular strain paths and fabric conditions, it is shown that a relatively dense sand can succumb to instability or liquefaction under other than isochoric (undrained) conditions. This phenomenon is in accord with laboratory experiments in which dilation or compaction is controlled by modulating the amount of water flowing in or out of a sand specimen during shearing. Mixed drained–undrained loading paths are also simulated with particular reference to fabric dependence at a fixed void ratio. Model simulations capture most of the observed characteristics of sand response, such as instability and asymptotic behavior under various conditions. 相似文献
5.
6.
The influence of the natural (or artificially induced) structure of a geomaterial on its compression behavior is investigated. An approach for modeling this influence for various structured geomaterials is proposed by using the disturbed state concept. An isotropic compression model is formulated on three basic assumptions. A special version of the proposed model is also described for situations where the compression is one-dimensional. The proposed compression model is used to simulate the behavior of a variety of structured geomaterials such as clays, sands, calcareous soils, clay-shale, soft rock, unsaturated soils, and soils artificially treated by adding chemical agents or mechanical reinforcement, and the model is evaluated on the basis of these simulations. A general discussion on the influence of the structure of geomaterials on their mechanical properties is also presented. 相似文献
7.
The present study focuses on the characterisation and evaluation of the fatigue behaviour of flax–epoxy composites. A better understanding of this behaviour allows the prediction of long-term properties to assess the viability and long-term durability of these materials. The purpose of this work is to systematically compare the tension–tension fatigue behaviour of flax fibre composites for one random mat, six textile architectures and two laminate configurations, which are used in a wide range of applications. The fibre architecture was found to have a strong effect on the fatigue behaviour, where higher static strength and modulus combinations present the best fatigue characteristics. They have a delayed damage initiation and increased fatigue life as well as a reduced damage propagation rate combined with higher energy dissipation in the early stages of fatigue loading. 相似文献
8.
Changes in the internal structure of nonwoven mats during tensile testing were investigated in situ with micro X-ray computer tomography (CT). Fiber orientation and volume fraction, as well as fiber–fiber contact, were quantitatively characterized at several strain levels. These parameters are apt to change under tensile loading and are important in determining the mechanical properties of nonwoven mats. The reorientation of fibers along the tensile direction was restricted at large deformations due to interlocked structures, which formed as a result of inherent entanglements in the nonwoven mats. In addition, contact efficiency, which describes the relative degree of fiber–fiber contact and was shown to be a suitable geometrical parameter for characterizing the microstructure of nonwoven mats, decreased at low strain and then increased with increasing strain until failure. 相似文献
9.
This paper presents a linear discretized theoretical model on the basis of the ideal theoretical model to evaluate elastic constants of plain-weave composite by using the statistics of the feature parameters of yarn measured from Micro CT data. A finite element method is utilized to calculate the elastic constants of the composite using the modified and global mean feature parameters of yarn, respectively. Uniaxial tensile and in-plane shear experiments are then completed to measure in-plane elastic constants of the composite. Finally, comparisons among the predictions of two theoretical models, FEM and experimental results are conducted. The results show that the stochastic fluctuations of yarn feature parameters decrease the in-plane elastic moduli and increase the in-plane shear moduli and Poisson’s ratios of the plain-weave composite. The discretized theoretical model with taking account of real yarn stochastic features can predict more accurate elastic constants of the composite than deterministic models. 相似文献
10.
We report an in situ analysis of the microstructure of woven composites using carbon nanotube (CNT)-based conductive networks. Two types of specimens with stacking sequences of (0/90)s (on-axis) and (22/85/−85/−22) (off-axis) were manufactured using ultra-high-molecular-weight polyethylene fibers and a CNT-dispersed epoxy matrix via vacuum-assisted resin transfer molding. The changes in the electrical resistance of the woven composites in response to uniaxial loading corresponded to the changes in the gradient of the stress–strain curves, which is indicative of the initiation and accumulation of microscopic cracking and delamination. The electrical resistance of the woven composites increased due to both elongation and microscopic damage; interestingly, however, it decreased beyond a certain strain level. In situ X-ray computed tomography and biaxial loading tests reveal that this transition is due to yarn compaction and Poisson’s contraction, which are manifest in textile composites. 相似文献