PSI - Issue 41

M.R.M. Aliha et al. / Procedia Structural Integrity 41 (2022) 87–93 Aliha et al. / Structural Integrity Procedia 00 (2022) 000 – 000

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Nomenclature a

crack length

a/W crack length ratio ABJs adhesively bonded joints BR biaxiality ratio Bi-ASB bi-material asymmetric short beam d thickness of the adhesive layer DCB double cantilever beam E modulus of elasticity ENF end-notch flexural F applied load K I mode I stress intensity factor K II mode II stress intensity factor MMB mixed mode bending S

distances between fixed bottom span support and crack edge fixed span ratio S ′ distances between movable bottom span support and crack edge S ′ /L movable span ratio t thickness of the adherents T T-stress T * non-dimensional form of T-stress W width of the beam Y I mode I geometry factor Y II mode II geometry factor Greek symbols θ direction of fracture initiation ν Poisson's ratio 1. Introduction S/L

Structural adhesively bonded joints (ABJs) are used in various industries such as aerospace, automotive, civil construction, electronics, biology and medicine. This is due to their ability to bond similar and dissimilar materials, high fatigue and corrosion resistance, ability to present a uniform distribution of stress at the joint region, good damping properties, and efficiently bonding of thin plates. Variables such as insufficient surface cleaning and the presence of voids in the adhesive layer lead to the formation of cracks at the bonding region under applied loads. As a result, the fracture characteristics of cracked ABJs subjected to a variety of loading conditions should be assessed in order to assure the structure's health [1]. Double Cantilever Beam (DCB) [2], End-Notch Flexural (ENF) [3], and Mixed Mode Bending (MMB) [4] are some examples of well-known specimens that can be utilized to evaluate the fracture parameters of cracked ABJs subjected to mode I, mode II, and mixed-mode I/II loading conditions, respectively [5]. The mentioned testing techniques have some drawbacks, including the incapacity to present the full range of mode mixities, the need for extensive testing jigs and fixtures to conduct the experiments, the significant experimental costs, substantial deformations that occur during the test, non-linearity caused by the weight and curve of the lever, and comparatively large size of the test specimen [6]. As a result, proposing a suitable testing technique for analyses of mixed-mode I/II fracturing of adhesively bonded joints is still a necessary subject. As a result, Aliha et al. [6,7] offered the bi-material inclined notch short bend beam (BISBB) specimen for fracture analysis of ABJs with similar or dissimilar adherent types. This suggested specimen have some advantages including testing convenience using a typical three-point bend fixture, generating complete ranges of in-plane mode mixities, and small size of final test sample. However, when employing the BISBB test setup for mixed-mode I/II testing of ABJs, the specimen must be built with varied crack inclination angles [6] and this issue can be mentioned as a serious disadvantage for the BISBB specimen.