Composite delamination models

R. Khoshravan and C. Bathias, Delamination test and EDEB and ENF composite specimens model and mode 2, annual report, VAMAS WGS, 1990. 

The earliest works of trying to model different length scales of damage in composites were probably those of Halpin [235, 236] and Hahn and Tsai [237]. In these models, they tried to deal with polymer cracking, fiber breakage, and interface debonding between the fiber and polymer matrix, and delamination between ply layers. Each of these different failure modes was represented by a length scale failure criterion formulated within a continuum. As such, this was an early form of a hierarchical multiscale method. Later, Halpin and Kardos [238] described the relations of the Halpin-Tsai equations with that of self-consistent methods and the micromechanics of Hill [29],... 

D.H. Allen et al A cumulative damage model for continuous fiber composite laminates with matrix cracking and interply delaminations. ASTM Sp. Tech. Pub. 972, 57-80 (1988)... 

Allix O, Leveque D, Perret L, Identification and forecast of delamination in composite laminates by an interlaminar interface model. Comp. Sci Tech., 58, 1998, 671-678. 

The delamination of UD composites in the presence of large-scale bridging has been modelled and studied experimentally rather well, and the list of some references can be found in [1, 2]. 

In the present paper, the methodology of testing and modelling the delamination. jf UD composites in the presence of large-scale bridging is adapted for the delamination stud> in 3D woven materials, The following four key alterations used in this study are essential ... 

It is clear, from the examples cited above, that lower crustal delamination takes place. What is less certain is the relative importance of this process, for the number of convincing examples of lower crustal delamination is small. Kramers and Tolstikhin (1997) argued on the basis of their Pb-isotope forward transport model that lower crustal delamination is a minor process and not important in modifying crustal compositions. In contrast, Plank (2005) argued that between 40 and 50% lower crustal loss is required over geological time, to achieve the present-day Th/La ratio of the bulk crust. Whilst this volume equates to only 0.3% of the mantle mass, and less than 10% of the mass of subducted slabs over geological... 

Katerelos DG, Paipetis A, Kostopoulos V. A simple model for the prediction of the fatigue delamination growth in impacted composite panels. Fatigue Fract Eng Mater Struct 2004 27 911-22. http //dx.doi.org/10.1111)5.1460-2695.2004.00798.x. 

The degradation of the composite laminates can be modelled as simple strength criteria for fibres or matrix, before delamination occurs. Eigure 9.19 shows the test force history for a 200 x 200 mm plate and the various numerical EE (77) predictions (Davies et al. [42]), The hnear elastic case does get the time of the event but underestimates the peak force by a factor of 3. The damaged EE prediction overestimates the force but does get the departure from the linear solution correctly. The fuUy degraded solution (with much fibre failure) does match the experimental history. Delamination was confined to one interface near the mid-plane as the C-scan image indicates. 

Greve L, Pickett AK. Delamination testing and modelling for composite crash simulation. Compos Sci Technol 2006 66 816-26. 

A future trend in composite bolted joint design is the use of more advanced continuum damage mechanics approaches to model joint failure, so that non-linear shear behaviour and gradual stiffness degradation can be implemented. An important element of joint failure is delamination, and many efforts are being undertaken to implement delamination in finite element models. However, for bolted joints analysis this poses many problems due to the large number of delamination interfaces in thick laminates. 

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