PSI - Issue 41

9

A.R.F. Soares et al. / Procedia Structural Integrity 41 (2022) 48–59 Soares et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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Table 1. Adherend properties for the SPECIMEN-DCB component. Steel PM300

Adhesive Araldite ® AV 138/HV 998

Young’s modulus (MPa) Shear modulus (MPa)

210000 80770 290-330

Colour

Grey ca. 1.7

Specific gravity

Hardness (HB)

Viscosity

Thixotropic > 11 MPa

Compressive yield strength R c0.2 (MPa) Yield strength Rp0.2 at 20°C (MPa)

1000 900

Lap shear strength at 25°C Pot life (100g at 25°C)

30 min

4.2. Joint fabrication

In this study, eight test specimens were used. The steel adherends were obtained from PM300 steel in a milling process made up of 11 steps using 5 different mills and 3 drills. The adhesive Araldite ® AV138 was mixed according to the technical sheet using a weight ratio of 5:2 of adhesive to hardener. The test specimens were manufactured according to the joint geometry represented in Fig. 7 . The steel adherends’ surface was prepared by grit blasting using corundum sand followed by degreasing using acetone. The bonding procedure was accomplished in a steel jig that assured the proper alignment between adherends by using guide pins. To assure the correct adhesive thickness, calibrated steel shims were used at both ends of the adhesive layer. Moreover, at the adhesive layer’s edge corresponding to the initial crack, the calibrated sh im was composed of outer steel shims glued to a middle sharp blade, to produce a sharp crack for crack initiation. After the curing time of one week, the excessive adhesive was removed from the joints, one of the specimens’ sides were painted with white co rrector fluid and a printed scale was glued at the same face to facilitate the reading of crack length during the test. 4.3. Testing The joint tests were performed on eight test specimens, two specimens for each test configuration. After the time required for adhesive curing, all specimens were loaded to failure to obtain the different P -  curves. The test procedure is similar for each configuration since the developed MMB equipment allows easy assembly and configuration. The tests were performed at room temperature in a Shimadzu ® AG-X 100 UTM. For measurement of a , the side face of the specimen was recorded through a sequence of photographs, with five seconds interval, by using a digital camera with a fixed focal distance of 100 mm to the side face of the specimen, approximately. The test speed indicated for Araldite ® AV 138/HV 998 adhesive is about 0.5 mm/min, so it was defined for all tests.

Fig. 8. Different configurations used for the tests.

Fig. 8 presents the different test configurations selected for this work. The configurations DCB_01 and DCB_02 refer to pure mode I loading, while ENF_01 and ENF_02 refer to pure mode II loading. On the other hand, configurations P2_01, P2_02, P3_01 and P3_02 represent two combinations of mixed-mode loading. The MMB