PSI - Issue 64

1322 Lingzhen Li et al. / Procedia Structural Integrity 64 (2024) 1318–1325 Author name / Structural Integrity Procedia 00 (2019) 000–000 5 stress-strain ( ) curve of the adherent can be regarded as a wine glass when plotted against the vertical axis ( - axis). In this analogy, the fracture energy of the adhesive bond divided by the thickness of the adherent strip ( / ) represents the wine poured into the glass. The height of the wine within the glass corresponds to the level of adherent tensile stress, with respect to the bond capacity. Therefore, this model is referred to as the "Wine Glass model". There are two methods to realize Equation (7), i.e., the Wine Glass model. The first method involves a graphical solution, as depicted in Fig. 3, incorporating an iterative numerical scheme. Section 5 showcases several examples of estimating bond capacity using this graphical solution. The second method requires a specific expression for the adherent stress-strain curve; substituting this expression into Equation (7) yields a closed-form solution for the bond capacity. Section 4 presents an example of the second method, incorporating a linear elastic adherent. Both methods can be easily implemented through either hand-calculation or using simple EXCEL/MATLAB coding. 4. Degrade to solution for linear adherents When the adherent has a linear stress-strain relationship, such as a CFRP strip, the solution of the bond capacity degrades to the well-known model for CFRP bonded joints (Equations (8) and (9)) (Fernando et al., 2014; Xia and Teng, 2005). It is not surprising. = � 2 (8) = � 2 (9) where and denote the bond capacity and corresponding adherent tensile stress, respectively; , , and represent the E-modulus, width, and thickness of the adherent strip, respectively; stands for the fracture energy of the adhesive bond. 5. Applications of the Wine Glass model This section demonstrates several examples of bond capacity estimation employing the proposed Wine Glass model, including Fe-SMA lap-shear joints and CFRP lap-shear joints. 5.1. Experiment overview Fig. 4 (a) schematically shows the dimensions of lap-shear joints tested by Li et al. (Li et al., 2023b). All adherent strips, namely Fe-SMA and CFRP strips, are 600 mm in length, 50 mm in width, and have a bond length of 300 mm. Non-prestrained and prestrained Fe-SMA strips have a thickness of 1.5 mm; their chord moduli, measured between 20 and 300 MPa, are 153.3 GPa and 137.5 GPa, respectively. CFRP strips have a thickness of 1.4 mm and an E modulus of 156 GPa. Fig. 4 (b) depicts the stress-strain curves of these adherents. A linear adhesive (SikaDur 30) and a nonlinear adhesive (SikaPower 1277), with a thickness of 0.5 mm, serve as bonding agents; their mode-II fracture energy are 1.2 and 12.5 MPa ⋅ mm, respectively. Fig. 5 and Fig. 6 demonstrate that bond capacities computed by the proposed Wine Glass model closely align with the experimental measurements.