Mode I fracture of adhesive joints using tailored cohesive zone models

Abstract

Cohesive zone models are explored in order to study cleavage fracture in adhesive bonded joints. A mode I cohesive model is defined which correlates the tensile traction and the displacement jump (crack faces opening) along the fracture process zone. In order to determine the traction-separation relation, the main fracture parameters, namely the cohesive strength and the fracture energy, as well as its shape, must be specified. However, owing to the difficulties associated to the direct measurement of the fracture parameters, very often they are obtained by comparing a measured fracture property with numerical predictions based on an idealized traction separation relation. Likewise in this paper the cohesive strength of an adhesive layer sandwiched between elastic substrates is adjusted to achieve a match between simulations and experiments. To this aim, the fracture energy and the load-displacement curve are adopted as input in the simulations. In order to assess whether or not the shape of the cohesive model may have an influence on the results, three representative cohesive zone models have been investigated, i.e. exponential, bilinear and trapezoidal. A good agreement between experiments and simulations has been generally observed. However, a slight difference in predicting the loads for damage onset has been found using the different cohesive models.

Numerical evaluation of mode I/II SIF of quasi-brittle materials using cracked semi-circular bend specimen

“…It was experimentally noticed that crack extension occurred in mode I rather than shear mode or mixed mode. Many investigations were typically focused in opening mode failure for crack growth (Alfano et al, 2009;Erdogan & Sih, 1963;Fowell et al, 1995;Lim et al, 1994;Yoshihara & Kawamura, 2006;Zhang, 2002;Zhou et al, 2012). The cracks in brittle materials are often vulnerable to compressive loading rather than tensile loading (Ke et al, 2008).…”

Delamination-Debond Behaviour of Composite T- Joints in Wind Turbine Blades

“…Cohesive layer is then assumed to be damaged according to a considered cohesive law which relates interface tractions to interface displacements. Some of the generally used cohesive laws are bilinear [7,8,18], exponential [15] and trapezoidal [16, Figure 2, where, t i 0 is the interfacial strength and δ i 0 is the interfacial displacement for damage initiation, δ i C is the critical displacement for crack growth and δ i S is the softening displacement for trapezoidal law; i=I, II, III stands for fracture modes I, II and III. Bilinear cohesive law is used in this study.…”

Cohesive Zone Model Identification With DCB Test Parameter Estimation Sensitivity

“…Alfano and Fugiuele [1] have compared experimental data from mode-I crack test of adhesively bonded joints, with those obtained by modeling adhesive layer with exponential intrinsic cohesive zone model, bi-linear and trapezoidal. A good agreement be-tween experiments and simulation has been obtained and show that energy release rate is the only influencing parameter during propagation phase.…”