Modified pendulum hammer in impact tests of adhesive, riveted and hybrid lap joints

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Abstract

This paper presents a modified pendulum hammer adapted to test the impact strength of lap joints. The impact tests of lap specimens exhibited greater repeatability in terms of the results, compared with the tests of block specimens (specimens used in Block Shear Test (ISO 9653)). The modified testing device also allowed for testing of rivet and hybrid rivet–adhesive joints. The comparative tests showed that the impact strength of the hybrid connections was greater than the sum of the impact strengths of the adhesive and rivet joints. Our research demonstrated the significant effect of the impact speed on the measured impact strength; this effect appeared to be related to the deformation energies of the test device and connected elements, which were more deformed at a lower load speed. We also showed a serious influence of adhesive forces on the impact strength of glued joints.

Section snippets

Introduction - research methodology

Adhesive joints are widely used in several applications, including aircraft and vehicle construction [1], [2], [3], [4], [5]. The extent of damage to such objects in the event of emergency landings or collisions with other objects depends on the properties of the materials from which they are built (e.g. some car body sheets are characterised by a large range of plastic deformations, although this strongly depends on the area of application in the car body, and for the a and b pillar high

Influence of the Young's modulus of the adhesive and method of processing bonded surfaces on the impact strength of adhesive joints

For the tests it was adhesively bonded 15 identical specimens, among which 5 were designed for static-strength testing and 10 for the impact tests. The overlap length of the samples was 13 ± 0.15 mm. The adherends of AW 2024T3 alloy were 2 mm thick and 20 mm wide (Fig. 7a). The specimens were adhesively bonded with the epoxy based Epidian 57 two-stage-cured Z1 hardener (24 h at ambient temperature and 5 h at 80 °C) and epoxy based Belzona 1111, which was cured at ambient temperature for one

Numerical analysis of stresses in dynamically loaded adhesive layer

Numerical calculations were performed in the ANSYS 16.2 system using the Explicit Dynamics module. The numerical model of the sample (Fig. 9) mounted in the testing device was dynamically loaded with a speed of 2960 mm/s. The FEM model was built on the basis of hexagon elements with dimensions of 0.5 mm. The 0.1 mm thick adhesive layer was modeled with one layer of elements. The validity of this method of modeling the adhesive joints was demonstrated in the work [21] and checked in numerous

Comparative tests of adhesively bonded, riveted, and hybrid specimens

All specimens were bonded with an overlap lz = 24.5 mm (Fig. 13), which resulted from the length of the rivet joint having two rivets with a diameter d = 3.5 mm (lz = 2d + 3d + 2d). The joined sheets of AW 2024T3 alloy were 2 mm thick and 20 mm wide. Rivets with countersunk heads were used.

The surfaces of the adhesively bonded and hybrid samples were prepared by abrasive blasting and washing using extraction gasoline. Epidian 57/Z1 was used to bond these specimens. The hybrid specimens were

Conclusions

The built-up test stand allowed us to conduct impact tests on lap joints. The dispersion of the results of the tests on the adhesive joints, which were conducted according to the proposed methodology, proved to be smaller than that in the impact tests of block samples [22], validating the usefulness of the proposed test method. An additional advantage of this method concerned with the method of loading the adhesive layer during the tests, which was identical to that used in shear-strength

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