by Hatamleh, Omar; Beek, Joacim; Forman, Royce; Shivakumar, Venkataraman; Lyons, Jed

A new numerical method based on the strip yield analysis approach was developed for calculating the Crack Tip Opening Displacement (CTOD). This approach can be applied to any crack geometry, of either infinite or finite extent, with arbitrary applied loading conditions. The technique is an adaptation of the dislocation-density based boundary element method to obtain crack-face opening displacements at any point on a crack, and succeeds in obtaining the requisite values as a series of definite integrals, the functional parts of each of which are evaluated exactly in closed form. The power of the technique is demonstrated by obtaining solutions to several crack configurations of practical interest.

DOI: 10.1007/s10704-005-0746-8
Print publication date: 8/1/2005
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by Xie; Chung, Jaeung; Waas, Anthony M.; Shahwan, Khaled W.; Schroeder, Jessica A.; Boeman, Raymond G.; Kunc, Vlastimil; Klett, Lynn B.

This paper presents a predictive methodology and verification through experiment for the analysis and failure of adhesively bonded, hat stiffened structures using coupon level input data. The hats were made of steel and carbon fiber reinforced polymer composite, respectively, and bonded to steel adherends. A critical strain energy release rate criterion was used to predict the failure loads of the structure. To account for significant geometrical changes observed in the structural level test, an adaptive virtual crack closure technique based on an updated local coordinate system at the crack tip was developed to calculate the strain energy release rates. Input data for critical strain energy release rates as a function of mode mixity was obtained by carrying out coupon level mixed mode fracture tests using the Fernlund–Spelt (FS) test fixture. The predicted loads at failure, along with strains at different locations, were compared with those measured from the structural level tests. The predictions were found to agree well with measurements for multiple replicates of adhesively bonded hat-stiffened structures made with steel hat/adhesive/steel and composite hat/adhesive/steel, thus validating the proposed methodology for failure prediction.

DOI: 10.1007/s10704-005-0646-y
Print publication date: 8/1/2005
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by Nègre, P.; Steglich, D.; Brocks, W.

Ductile tearing of laser welded Al sheets is studied both experimentally and numerically. The mechanical behaviour and the microstructure of the various zones of the weld are characterised. Mechanical tests on compact tension (C(T))-specimen are carried out, with the position of the initial crack in the heat affected zone. Due to the asymmetry of the configuration, crack path deviation towards the softer fusion zone is observed. The topography of the non-planar fracture surface is measured using laser equipment. This work is focussed on the prediction of the fracture resistance and the simulation of crack path deviation for the respective configuration. The numerical simulations are based on two different models for ductile damage: the micromechanical Gurson–Tvergaard– Needleman (GTN) model and the phenomenological cohesive model. In the case of the GTN-model, the crack front may follow an arbitrary path. In contrast, the crack propagation direction for the cohesive model is prescribed by the morphology of the finite element mesh. The GTN-model is used to investigate crack path deviation and to derive limits for simplifications used together with the cohesive approach. The latter allows for a cost-efficient 2D simulation. Good agreement between experimental results and numerical simulations could be achieved in all cases

DOI: 10.1007/s10704-005-0523-8
Print publication date: 8/1/2005
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by Enderlein, M.; Ricoeur, A.; Kuna, M.

This paper deals with numerical methods, developed to analyze plane stationary cracks in piezoelectric structures under dynamic electromechanical loading conditions. In the first part an explicit finite element scheme is presented, which has been developed to solve the transient coupled electromechanical boundary value problem. A special technique is implemented in the algorithm, accounting for the limited electrical permeability of the crack. In contrast to well known algorithms for static calculations it does not require any iteration. In order to calculate dynamic stress and electric displacement intensity factors for arbitrary crack configurations, the interaction integral is generalized for electromechanical problems. The efficient applicability and the high accuracy of the implementations are demonstrated by numerical examples, giving insight into several effects occuring with dynamically loaded cracks in piezoelectrics

DOI: 10.1007/s10704-005-0522-9
Print publication date: 8/1/2005
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by Guz, A. N.; Lapusta, Y.; Samborskaya, A. N.

A 3D model and an estimation of fiber interaction effects during internal instability n non-linear composites are presented Results are based on a micrornechanies solution for a series of fibers embedded in an infinite non-linear incompressible matrix. An ideal bonding between the fibers and the matrix is assumed. Comparison with a limiting case in which the distance bet’ween the neighboring fibers tends to infinity is carried out. It shows the significance of the fiber interaction effects in the considered problem.

DOI: 10.1007/s10704-005-4104-7
Print publication date: 8/1/2005
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by Levin, Valery; Sevosticmov, Igor

A new analytical approach for’ micromechanical modeling of the effective viscoelastic behavior of a’ composite material is presented. Fractionexponential operators are. used to describe the viscoelastic properties of the constituents. To construct the corresponding elastic solution, effective field method is used. Effective viscoelastic operators are obtained from the Volter ra’s elasticity-viscoelasticity correspondence principle. Incompatible deformation that often occurs during the manufacturiig process is taken intp account. All the formulas are obtained in explicit ready-to-use form.

DOI: 10.1007/s10704-005-4103-8
Print publication date: 8/1/2005
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by

DOI: 10.1007/s10704-005-4102-9
Print publication date: 8/1/2005
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by

DOI: 10.1007/s10704-005-4101-x
Print publication date: 8/1/2005
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by Peng, Nan-Ling; Yang, Juan; Wang, Min-Zhong

In this paper, a cooled composite interface corner consisting of two bonded dissimilar materials is considered as a plane problem. With the complex variable method, the thermal residual stress field is studied analytically. It is found that the regular stress term possesses the singularity either of lnr or ln2r. The exact expressions for the corresponding singular stress field are presented.

DOI: 10.1007/s10704-005-3179-5
Print publication date: 8/1/2005
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by Shi, Dong-Li; Feng, Xi-Qiao; Jiang, Hanqing; Huang, Yonggang Y.; Hwang, Keh-Chih

Due to the enormous difference in the scales involved in correlating the macroscopic properties with the micro- and nano-physical mechanisms of carbon nanotube-reinforced composites, multiscale mechanics analysis is of considerable interest. A hybrid atomistic/continuum mechanics method is established in the present paper to study the deformation and fracture behaviors of carbon nanotubes (CNTs) in composites. The unit cell containing a CNT embedded in a matrix is divided in three regions, which are simulated by the atomic-potential method, the continuum method based on the modified Cauchy–Born rule, and the classical continuum mechanics, respectively. The effect of CNT interaction is taken into account via the Mori–Tanaka effective field method of micromechanics. This method not only can predict the formation of Stone–Wales (5-7-7-5) defects, but also simulate the subsequent deformation and fracture process of CNTs. It is found that the critical strain of defect nucleation in a CNT is sensitive to its chiral angle but not to its diameter. The critical strain of Stone–Wales defect formation of zigzag CNTs is nearly twice that of armchair CNTs. Due to the constraint effect of matrix, the CNTs embedded in a composite are easier to fracture in comparison with those not embedded. With the increase in the Young’s modulus of the matrix, the critical breaking strain of CNTs decreases.

DOI: 10.1007/s10704-005-3073-1
Print publication date: 8/1/2005
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