Laminated shells with debonding between laminas in temperature field

A heat-conduction problem is formulated for laminated plates and shells with a heat-conducting layer and debonding between laminas. The approach consists in analyzing how the layer thickness changes in the process of debonding of laminas and deformation of plates and shells. The three-dimensional thermoelastic and heat-conduction equations are expanded into polynomial Legendre series in thickness. The first-order, Timoshenko’s, and Kirchhoff-Love equations are examined. A numerical example of laminated shells with a heat-conducting layer is considered Published in Prikladnaya Mekhanika, Vol. 42, No. 7, pp. 135–141, July 2006.     

Thin plate bending problem of dissimilar strips with two bond lines

Summary A solution to the thin plate bending problem of partially bonded dissimilar strips with two bond lines is presented. The two strips are symmetrically bonded with respect to the interface which is on theX-axis. The complex stress functions approach together with the rational mapping function technique are used in the analysis. A concentrated bending moment applied at each strip is considered. Distributions of bending and torsional moments, as well as the stress intensity of debonding (SID) at the debonding tips are obtained, and the debonding extension is investigated.     

STUDY ON DEBONDING FAILURE MODEL OF POLYUREA-BASED COATING WITH HIGH VELOCITY WATER FLOW BASED ON COHESIVE ZONE MODEL

冲磨和空蚀破坏是水利水电设施最为常见的病害之一,严重影响水利水电设施的安全运行和效益发挥. 泄洪建筑物通常喷涂聚脲基涂层来提高抗冲耐磨性能,但在泄洪高速水流速度作用下抗冲磨聚脲基涂层的剥离破坏机理的研究尚属空白. 本文基于高速水流的流态形式,提出了高速水流对泄洪建筑物的力学作用模型,水流作用对泄洪建筑物的载荷主要包括拖曳力、冲击力、脉动力和上浮力;采用内聚力模型表征聚脲基涂层与泄洪建筑物防护体界面的剥离破坏过程,建立了高速水流聚脲涂层的剥离破坏模型, 给出了模型的有限元形式方程、本构关系以及损伤起始原则、演化原则和接触碰撞模型. 通过聚脲涂层与混凝土基底的剥离破坏试验,分析了不同剥离倾角下界面剥离破坏的拉应力与倾角之间的变化规律,得到了聚脲涂层剥离破坏过程中应力-$\!$-位移变化关系. 根据剥离破坏试验计算了界面剥离破坏断裂模型参数,采用数值方法对模型进行了验证,试验结果与模型计算结果吻合良好,为泄洪建筑物的抗冲耐磨设计提供理论依据.     

微粒填充流变材料界面开裂的局部临界应力及尺寸效应的理论分析

研究了以等轴粒子填充流变材料的边界开裂机理，采用能量准则导出了以界面能表示的界面开裂局部临界应力的简洁表达式。由于临界应力正比于１√α，从而可以非常方便地研究粒子开裂的尺寸效应，以碳酸钙微粒填充的聚丙烯复合材料为例进行了理论分析，通过比较界面开裂的能量准则和张应力准则得出结论：即使按照保守的方法估算，即在界面强度等于基体强度的条件下，只要粒径不超过０．２微米，若能量准则得到满足，则张应力准则也会得     

Effect of Coulomb friction on the fiber/matrix debonding and matrix cracking in unidirectional fiber-reinforced brittle-matrix composites

A model for a macroscopic crack transverse to bridging fibers is developed based upon the Coulomb friction law, instead of the hypothesis of a constant frictional shear stress usually assumed in fiber/matrix debonding and matrix cracking analyses. The Lamé formulation, together with the Coulomb friction law, is adopted to determine the elastic states of fiber/matrix stress transfer through a frictionally constrained interface in the debonded region, and a modified shear lag model is used to evaluate the elastic responses in the bonded region. By treating the debonding process as a particular problem of crack propagation along the interface, the fracture mechanics approach is adopted to formulate a debonding criterion allowing one to determine the debonding length. By using the energy balance approach, the critical stress for propagating a semi-infinite fiber-bridged crack in a unidirectional fiber-reinforced composite is formulated in terms of friction coefficient and debonding toughness. The critical stress for matrix cracking and the corresponding stress distributions calculated by the present Coulomb friction model is compared with those predicted by the models of constant frictional shear stress. The effect of Poisson contraction caused by the stress re distribution between the fiber and matrix on the matrix cracking mechanics is shown and discussed in the present analysis. Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 43, No. 2, pp. 171–190, March–April, 2007.     

Universal relations between dynamic and static interfacial stress intensity factors

Universal relations between dynamic and static interfacial stress intensity factors are derived for both in-plane and anti-plane cases under rate independent loading. Explicit and analytical form of the universal function is provided for the simple case of mode III fracture.Sponsored jointly by the National Natural Science Foundation of China and the State Education Commission of China.     

Dynamic self-similar debonding of interface at very high velocity: Anti-plane case

This paper analyzes the anti-plane problem of dynamic self-similar debonding of interface at very high velocity. The debonding is modeled as an interface crack propagating self-similarly from zero-length. The extending speed is assumed to be transonic or supersonic. We first consider the dynamic debonding under moving concentrated loads. The moving dislocation model of self-similar propagation of an interface crack is used to formulate the problem to a singular integral equation which is solved analytically. The singularity of stresses near the crack tip is discussed and the dynamic stress intensity factors are presented. Finally the solution of dynamic debonding underx ²-type loads is obtained by using the superposition method.     

界面超高速自相似动态分层分析：反平面情况

对材料界面超高速自相似动态分层的反平面问题进行了解析分析。分层模拟为界面裂纹由零长度自相似扩展，扩展速度为蹭音速或超音速。首先考虑运动集中载荷作用下界面动态分层的情况，利用界面裂纹自相似扩展的运动位错模型将问题归结为奇异积分方程，并求得解析解，分析了裂纹尖端的应力奇性，获得了动应力强度因子。最后，利用叠加原理给出了ｘ＾ｎ型载荷作用下界面动态分层的解。     

微纳米尺度膜/基结构界面性能的实验研究

为了研究铜膜/有机玻璃结构的界面性能,首先对沉积在有机玻璃基底上300nm厚的铜膜进行了单轴压缩实验,部分区域的薄膜因屈曲而脱离基底。选择在膜/基粘接良好区域、膜/基脱粘区域分别进行等位移纳米压痕实验。利用膜/基粘接良好区域处硬度/弹性模量与压痕位移的关系来确定膜/基结构的临界脱粘位移。基于宏观力学中表征界面性能的能量法,利用两个区域等位移的塑性功差值来确定界面能量释放率。研究结果表明:当压痕位移约450nm时,膜/基结构开始出现界面脱粘,实验测得铜膜/有机玻璃结构的界面能量释放率值在6.81~10.32J/m2之间。     

颗粒增强复合材料相界面的动态应力分析

针对硬微粒填充高聚物复合材料因相界面脱粘开裂生成微孔洞的微损伤成核机制,取材料的代表体积单元进行动力分析,通过对粘弹性基体本构关系作Laplace变换建立了基本方程,并引入Hankel变换,得到了球对称动荷载作用下相界面应力变化规律的解析解,据此分析了惯性效应和粘性效应对界面脱粘的影响。