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1.
The plane problem of three-dimensional elastic stability is solved for a ribbon-reinforced composite under lateral compression if its initial state is nonuniform. The net approach is used to numerically solve the problem. The influence of the ratio of the elastic moduli of the matrix and the filler and the ribbon shape factor on the critical load of the material is studied 相似文献
2.
A solution in Cartesian coordinates to plane and spatial stability problems for composites is obtained within the framework of the second variant of the three-dimensional linearized theory of stability of deformable bodies. Two mechanical models are used: a homogeneous anisotropic medium with averaged mechanical characteristics and a piecewise-homogeneous medium with orthotropic linearly elastic components. To solve the problems, a mesh approach is applied. Discrete models are constructed using the concept of a base scheme. The calculated results are analyzed 相似文献
3.
An analysis is made of the results of investigations into the internal and surface instability of fibrous and laminated composites within the framework of the piecewise-homogeneous model and the equations of the three-dimensional linearized theory of stability. The possible buckling modes of the reinforcing elements in composites with either an elastic (polymeric) or elastoplastic (metallic) matrix are studied. The reliability domains of applied approximate design models are determined and some applications of results on fracture (due to structural instability) of unidirectional composites are presented 相似文献
4.
Behavior of Pin-loaded Laminated Composites 总被引:1,自引:0,他引:1
B. Okutan Baba 《Experimental Mechanics》2006,46(5):589-600
In this study, an investigation was carried out to determine the effects of joint geometry and fiber orientation on the failure
strength and failure mode in a pinned joint laminated composite plate. Behavior of pin-loaded laminated composites with different
stacking sequence and different dimensions has been observed experimentally. E/glass–epoxy composites were manufactured to
fabricate the specimens. Mechanical properties of the composites were characterized under tension, compression and in-plane
shear in static loading conditions. Laminated composites were loaded through pins. Single-hole pin-loaded specimens were tested
for their tensile response and width-to-hole diameter (W/D) and edge distance-to-hole diameter (E/D) ratios evaluated. A series
of experiments was performed with six different material configurations ([0/±45]s–[90/±45]s, [0/90/0]s–[90/0/90]s and [90/0]2s–[±45]2s), in all, over 120 specimens. E/D ratios and W/D ratios of plates were changed from 1 to 5 and 2 to 5, respectively. Failure
propagation and failure type were observed on the specimens. The influence of the joint geometry on the strength of the pin-loaded
composites was assessed. When laminated composite plates were loaded to final failure, three basic failure modes consisting
of net-tension, shear out and bearing failure were observed for the different geometric dimensions. All the connections tested
showed that the fiber orientations have a definite influence on the position around hole circumference at which failure initiated.
Net-tension failure occurred for specimens that had small width and large end distance. When the width was increased, the
specimens which had small end distances failed in the shear-out modes. When the end distance was increased, bearing failure
developed in addition to shear-out failure. The experimental results showed that the ultimate load capacities of E/glass–epoxy
laminate plates with pin connection were increased by increasing W and E. However, increasing the E/D and W/D ratios beyond
a critical value has an insignificant effect on the ultimate load capacity of the connection. 相似文献
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7.
A new asymptotic method is proposed to describe the free and forced transverse vibrations of elastic laminated beams of arbitrary
cross section using the three-dimensional elastic equations without additional hypotheses and constraints. For beams with
layers of equal Poisson's ratio, the zero-order natural frequencies are equal to the natural frequencies predicted by classical
beam theory based on the Bernoulli hypothesis. The method makes it possible to calculate the frequencies of free vibrations
and amplitudes of forced vibrations with prescribed accuracy for the first natural modes
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Translated from Prikladnaya Mekhanika, Vol. 41, No. 6, pp. 56–71, June 2005. 相似文献
8.
Two- and three-dimensional stability problems for a rectangular plate under uniaxial compression are solved by the mesh method. It is shown that the difference between the critical loads obtained in the three- and two-dimensional problems is not greater than 5% for arbitrary fixation conditions and arbitrary length and thickness ratio of the plate 相似文献
9.
The theory of microdamageability of multicomponent laminated composites is outlined through the simulation of microdamages in the components by pores filled with compression-resisting particles of the destroyed material. The damage criterion for a microvolume of a component is taken in the Schleicher–Nadai form, which allows for the difference between the ultimate tensile and compressive loads. The ultimate strength is a random function of Weibull-distributed coordinates. The stress–strain state and the efficient properties of the material are determined from the stochastic equations of the elastic theory for a laminated composite with porous components. The equations of deformation and microdamage are closed by the equations of porosity balance in the components. Nonlinear diagrams of the concurrent processes of deformation in the laminated material and microdamage in the matrix are plotted. The effect of the physical and geometrical parameters on them is studied 相似文献
10.
Yu. V. Kokhanenko 《International Applied Mechanics》2000,36(8):1067-1076
The concept of basic schemes is employed to construct discrete problems that approximate the basic three-dimensional problems of the elastic theory of composites in circular cylindrical coordinates for domains of arbitrary connectivity and complex geometry 相似文献
11.
IntroductionWhencompositecylindricalshellsareundertheactionofdynamicloading ,theymayfallindynamicbucklingordynamicinstability .Ifthedynamicloadissuddenlyapplied ,oritischanginginstantaneously ,suchasimpulsiveloading ,then ,dynamicbucklingwillhappenforthesh… 相似文献
12.
A piecewise-homogeneous-medium model is used to consider a stability problem for layered elastoplastic coatings under plain strain. The theory of small elastoplastic strains is used. Characteristic equations are derived in an explicit form for a power dependence between the strain and stress intensities. The effect of the inelastic properties of layers on the phenomenon being studied is demonstrated by a specific example 相似文献
13.
The stability of a laminated elastic coating with a polymeric bonding layer is considered within the framework of a piecewise-homogeneous model. The principle of critical strains is used in combination with the Volterra principle to account for the viscoelastic properties of polymers. Explicit expressions for determination of critical loads and time are derived. The range of variation in these parameters within which the coating does not buckle is found numerically 相似文献
14.
基于双目立体视觉原理的三维数字图像相关方法已被广泛应用于平面或曲面物体的表面形貌和三维变形测量。然而因相机自热、环境温度变化等内外部因素的影响,同一三维数字图像相关测量系统在不同时间,其内部参数会不可避免地发生微小改变,从而或多或少地引起额外的形貌和变形测量误差。为获得高精度的测量结果,需对由相机自热或环境温度变化引起的变形测量误差进行表征,并采用措施予以减小或消除此类误差。本文以石英玻璃平板为研究对象,利用三维数字图像相关测量系统对其位移和应变分布进行了连续5小时的测量,分析了测量结果随相机温度变化的关系曲线。研究结果显示,本文所用相机通电后其机壳温度一般约上升8~10℃甚至更高,所搭建的三维数字图像相关测量系统因相机温度变化所引起的应变测量误差在50~200με(约15~21με/℃)之间。本文还给出了相应建议来减小和消除相机或环境温度变化对三维变形测量的影响。 相似文献
15.
两级载荷下复合材料层板疲劳与寿命预测 总被引:4,自引:0,他引:4
研究了复合材料层板疲劳过程中的累积应变演化规律,建立了以累积应变为基础的非线性积累损伤法则,实验结果表明:文中提出的累积应变方法能够较好地反映加载次序效应,准确地预测了复合材料层板在两级载荷下的疲劳寿命。 相似文献
16.
A microdamage theory is constructed for laminated fibrous materials with transversely isotropic fibers and a porous isotropic matrix under thermal actions. Microdamages in the matrix are simulated by pores, empty or filled with particles of the damaged material that resist compression. The fracture criterion for a microvolume of the matrix is assumed to have the Nadai–Schleicher form, which takes into account the difference between the tensile and compressive ultimate loads, with the ultimate strength being a random function of coordinates with a power or Weibull distribution. The stress–strain state and the effective properties of the material are determined from the thermoelastic equations for laminated fibrous materials with a porous matrix. The deformation and microdamage equations are closed by the porosity balance equations corrected for the thermal effect. For various types of loading, nonlinear relations are derived for the coupled processes of deformation of a laminated fibrous material and microdamage of the matrix due to the thermal macrostrain. The effect of physical and geometrical parameters on these processes is studied. 相似文献
17.
The stability of laminated elastomer coatings at normal and high temperatures is considered in a three-dimensional formulation. The problem is formulated and the basic characteristic equations are derived. Graphs of the physicomechanical parameters of some elastomers against temperature are experimentally obtained. Specific examples for a three-layer coating are considered 相似文献
18.
IntroductionComputinganalysisfortheproblemsofthethree_dimensionalsolid ,eachtypeofplatesandshellsetc .,numericalalgorithmincommonusehasfinitedifferencemethod ,finiteelementmethod ,weightedresidualsmethodandBEMetc.Owingtocomplexityofthethree_dimensionalpro… 相似文献
19.
Equivalent generalized problems are obtained for new spectral problems described by ordinary differential equation of the fourth order with conjugation conditions. High-accuracy discretization algorithms are developed based on classes of piecewise-polynomial functions that may have a discontinuous first derivative at the point where the conjugation conditions are specified 相似文献
20.
利用叶开源和刘人怀提出的修正迭代法 ,导出了两端铰支、对称正交铺层的浅拱在均布载荷作用下的三次近似特征关系式 ,进而分析了结构几何参数、铺层数等对于‘跳跃失稳’临界载荷的影响 ,并通过与‘动力失稳’临界载荷的比较 ,讨论了两个‘失稳’概念的区别。 相似文献