The influence of adhesive constitutive parameters in cohesive zone finite element models of adhesively bonded joints

Abstract

Keywords: Single lap joint Double cantilever beam End notch flexure Adhesive bond Parameter interaction Composite Computer experiments Fracture Kriging analysis Latin hypercube sampling Toughness Strength Sensitivity a b s t r a c tThe influence of adhesive parameters on the outcome of cohesive zone finite element simulations is reported. The simulations are of adhesively bonded joint configurations that are used to characterize joint performance (including the double cantilever beam, the end notch flexure, and the single lap joint). The coupon level experiments are often used individually to determine a single parameter in an adhesive constitutive model (such as a cohesive strength or toughness). In this study, the influence of strength, toughness, and other parameters are considered simultaneously in examining their effect on the finite element (FE) output for each test. In specifying input parameters, the assumed shape of the cohesive traction law is also considered. It is shown that the double cantilever beam model output is dependent primarily on one parameter, whereas the end notch flexure and single lap joint models are dependent on multiple adhesive parameters. By extension, these dependencies require consideration when mapping the results of physical experiments into a set of adhesive model inputs. It is also shown that the shape of the traction law appears insignificant to the outcome of the models. Sensitivities to input parameters are illuminated through kriging analysis of the finite element results; the parameter values are chosen via Latin hypercube sampling. Surrogate models are created and are used to quantify the sensitivities. A mapping technique is described for evaluating the output of physical tests.

Numerical analysis on load-bearing capacity and damage of double scarf adhesive joints subjected to combined loadings of tension and bending

“…The adhesive region is densely meshed using biasing effects while sparse meshes are used in other regions for higher computational accuracy. In addition, optional viscous damping is implemented between node pairs to improve convergence [15].…”

“…Based on the Traction-Separation (T-S) law, CZM is widely used to analyze the de-cohesion in composite structures [8][9][10][11][13][14][15]. It must be pointed out that the adhesive layer using CZM is a generalized interface phase rather than a material.…”

“…T-S curve can be considered as a representation of the constitutive relation of the equivalent interface [9]. A bilinear assumption model [25][26][27], in which a critical energy release rate G c and a cohesive strength s u are vital to capture the interface separation behavior [9][10][11]15,28], is employed in this study. Owing to the combined loadings, a complex stress state of the joint is present with mixed-mode (Mode I and II) damage propagation, as shown in Fig.…”

“…In addition, failure was demonstrated to take place progressively as energy dissipates gradually at the crack tip [4,[7][8][9][10][11]13]. Furthermore, failure generally occurs in the adhesive layer with a lower stiffness than that of the adherends, which has been proved by previous investigations [4,[8][9][10][11][14][15]. The onset of damage can be predicted without requiring any initial crack using the existing stress-or strain-based criteria [13].…”

“…Owing to the complex failure behavior of the adhesive joint, it is difficult to obtain a universal failure criterion to various situations. Alternatively, cohesive zone models (CZM) can simulate the damage onset and growth with mesh independence and dispensable initial crack, maintaining the possibility to characterize the behavior of the structure up to failure [7][8][9][10][11][12][13][14][15]. Especially, an efficient finite element computational method with the core of CZM was certified by Castagnetti et al [18], which showed that the socalled Tied Mesh method has the advantage of numerical precision and computational speed.…”