Separation failure of composite materials

Kachanov, L. M.

doi:10.1007/bf00856347

Cited by 47 publications

(24 citation statements)

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“…Therefore, delamination is regarded as a fracture mechanism. The paper [61] was the first to study delamination. Since then, there have been numerous studies on the subject.…”

Section: Buckling (Delamination) Of Elastic and Viscoelastic Pates Wimentioning

confidence: 99%

Three-dimensional instability problems for viscoelastic composite materials and structural members

Akbarov

2007

Int Appl Mech

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Investigations of viscoelastic composite materials and structural members carried out using the TDLTSDB and initial-imperfection method are reviewed. The investigations address the internal and surface loss of stability of layered and fibrous composites, the loss of stability of plates, and the delamination (buckling) of plates with cracks. Each of these problems is reviewed separately. New areas of further research are proposed. The review focuses on the investigations carried out by the author and his students Keywords: buckling, crack, delamination, plate, instability, viscoelastic composite material 1. Introduction. As in [33,[41][42][43][44][45] and many other publications, by three-dimensional instability problems will be understood here instability problems investigated employing the three-dimensional linearized theory of stability of deformable bodies (TDLTSDB). The investigations regarding the construction of the TDLTSDB are detailed in the paper [46] and in the monographs [33,[41][42][43]45]. It was noted there that the tendencies to construct the theory, which allows us (i) to describe the buckling phenomenon for a well-defined three-dimensional stress-strain state and (ii) to obtain reliable data on the critical parameters for thin-walled and massive structural elements, contributed to the creation of the TDLTSDB. Historically, the TDLTSDB began to be developed in the first half of the 20th century, and the basic TDLTSDB relations were obtained in [30, 31-33, 35, 38, 45, 63, 71-73, 80, 84, 85] using either a strict and exact approach based on the linearization of the exact and strict relations of the nonlinear three-dimensional theory or an approximate approach based on a physical and, in part, linearization of certain relations. Development and detailed analyses of the results from these investigations were presented in the monographs [41,42,45].In the second half of the 20th century, the main attention of researchers was focused on the solution to separate classes of TDLTSDB problems. At the same time, general aspects of the TDLTSDB were also developed. It should be noted that the results of these studies were the subject of many monographs such as [41][42][43][44][45] and were reviewed in many papers such as [28,46,47,49,52,55,56,58].It follows from the search of the foregoing and other numerous inquiries that the TDLTSDB was mainly applied to analyze the stability of structural members made of time-independent materials. Moreover, these investigations used the bifurcation (Euler) approach. The Euler approach is known to be generally unsuitable for investigating instability problems for structural elements made of time-dependent materials and subjected to external static loading. This is why a dynamic investigation method was suggested in [40,45] to examine these problems. Note that this method represents the sought quantities with a multiplier exp(iWt) and determines the critical parameters of the problems from the requirement ImW = 0. However, if the dynamic investigation method is applied with...

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“…Therefore, delamination is regarded as a fracture mechanism. The paper [61] was the first to study delamination. Since then, there have been numerous studies on the subject.…”

Section: Buckling (Delamination) Of Elastic and Viscoelastic Pates Wimentioning

confidence: 99%

Three-dimensional instability problems for viscoelastic composite materials and structural members

Akbarov

2007

Int Appl Mech

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“…However, it seems unnecessary to present a more precise description of postcritical deformation, since the energy approach used to describe the process of composite delamination is itself approximate in nature [3].…”

Section: ~O ~O (4)mentioning

confidence: 99%

“…To derive this equation, the energy approach is used [3] based on the comparison of compression energy of a composite bar in the precritical state with the total energy in the elements of a split bar in the postcritical state. It is assumed that failure is possible if the energy of precritical compression is not smaller than the sum of the postcritical energy and the work of failure, which is necessary for splitting a bar into strips.…”

Section: The Failure Of Unidirectional Composite Tubes In the Chinesementioning

confidence: 99%

Failure of composite tubes in the Chinese lantern mode under a weight-type load

Smerdov¹

1999

Mech Compos Mater

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In [1], an equation is derived for calculating the critical stress of failure of unidirectional composite tubes in the form of a Chinese lantern (splitting of a tube into strips with subsequent loss of stability):where ~ is the specific work of failure upon splitting along the fibers, E is the elastic modulus in the direction of the axis of a thin-walled tube, R is the radius, and L is the length of the tube. Equation (1) is widely used both for scientific-methodical purposes and for calculating certain composite structures. Thus, for example, in [2] this equation was used to choose the optimum sizes of elements of a multisectional tubular structure subjected to bending and to calculate the stem of bamboo.However, when applying Eq.(1), we should bear in mind that it is valid only in some special conditions of loading, which is very seldom realized in actual structures. To derive this equation, the energy approach is used [3] based on the comparison of compression energy of a composite bar in the precritical state with the total energy in the elements of a split bar in the postcritical state. It is assumed that failure is possible if the energy of precritical compression is not smaller than the sum of the postcritical energy and the work of failure, which is necessary for splitting a bar into strips. In [1], the energy balance is given bywhere U 0 is the energy of precritical compression, U 1 is the energy of compression in the new state, U z is the energy of bending of strips, and F is the work of failure. The equality in the last expression leads to formula (1). Expression (2) is valid only when, upon failure of the bar, there is no additional displacement of its edges, i.e., at loading of the so-called "press" type. Such loading can be realized, for example, in a testing machine. However, for machine-building constructions, the action of a load of "weight" type is more characteristic when the acting force retains its magnitude after splitting of a tube. For such loads, Eq. (2) must be modi-

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“…Whitcomb concluded that for some cases it might be possible to overlook the effect of contact or overlapping of sublaminates in the delamination zone. Kachanov [2] treated as a thin film problem to the single delamination assumed to be near surface and through width. Chai et al [3] established an analytical one dimensional model for the analysis of delamination buckling of beam-plates.…”

Section: Introductionmentioning

confidence: 99%