The Journal of Adhesion

An, Le; Jin, Chenyu; Li, Xiuzhao; Ren, Tengfei; Wang, Cunxian

doi: 10.1080/00218464.2025.2477019pmid: N/A

Welded joints resulting from bond exchange reactions (BERs) can achieve a strong and repeatable joining of thermoset composites. However, the current research on BER-induced welded joints is still at a preliminary stage and no study has been performed for the shear strength under dynamic loadings. In this work, epoxy composites are welded with the extrinsic welding method, and then the single lap – shear tests of the BERs-induced welded joint are conducted in the electromagnetic split Hopkinson tensile bar (ESHTB) system. The loading velocity is ranged from 5 m/s to 9 m/s by controlling the applied voltage, and the corresponding failure forces and shear strengths, etc. are obtained. Results show that the shear strength increases considerably under dynamic loadings compared with those under quasi – static loading. An obvious linear relationship between shear strengths and loading velocities is obtained, which is capable of predicting the shear strength over a wide range of loading velocities. Moreover, the failure surfaces of BER-induced welded joints under dynamic loadings are analyzed and compared with that under quasi-static loading.

Lorkiewicz, Jerzy; Barlak, Marek; Wyszkowska, Edyta; Okrasa, Sebastian; Kosińska, Anna; Wilczopolska, Magdalena; Marchlewski, Paweł; Nowakowska-Langier, Katarzyna

doi: 10.1080/00218464.2025.2478991pmid: N/A

The procedure for preparing superconducting electron gun Nb-Pb photocathodes, composed of a lead layer deposited on the niobium surface should ensure their sufficient adhesion due to mandatory cleaning of the gun in ultrapure water under high pressure. It is a real challenge since Nb and Pb neither form solid solutions nor present good mutual wettability. So far adequate adhesion has not been achieved. We present a new approach to increase adhesion by preliminary lead implantation into niobium before depositing the final photoemissive Pb layers by magnetron sputtering and in a cathodic arc. The purpose of this study is to demonstrate the effectiveness of such a procedure. The scope of the article includes a description of experiments carried out on 10 trial Nb-Pb photocathodes, showing the impact of using pre-implanted niobium substrates on the adhesion strength of lead layers measured in scratch tests. The results of these tests are interpreted based on the nanoindentation of the transition zones between the layers and substrates. Increased adhesion was reached at a graded change in nanomechanical properties between film and substrate. The way to achieve such gradual transition is proposed for the future work. The presented results serve as a guideline in preparing superconducting Nb-Pb photocathodes.

Wick, Adrian; Lehmann, Martin; Volkmer, Thomas

doi: 10.1080/00218464.2025.2481107pmid: N/A

Modern timber engineering is based on homogenised, strength-graded timber elements, mainly bonded with different types of adhesives. The actual development and increasing meaning of the wood construction would not have been possible without the adhesive technology. The following paper presents some of the results of a comprehensive study of the impact of a number of selected process parameters on the formation, quality and performance of glue lines. To ensure consistent production quality, the bonding geometry (glue line thickness) should be kept constant. The tested adhesive joint quality based on tensile shear tests according to EN 302–1, supported by microscopic analyses, shows that the pressing pressure leads to the overpressing of unevenness, compaction of the adhesive and suppression of blistering in one-component polyurethane adhesives. The penetration depth of the adhesive is not affected by the variation of the pressure. Delamination tests according to EN 302–2 to assess durability in combination with the prevailing pressure distribution show no obvious correlation. However, it does provide an indication that the surface preparation and treatment exert a crucial influence on the bond geometry and therefore on durability.

Yang, Yongming; Hou, Junkai; Khabaz-Aghdam, Ata; da Silva, Lucas F.M.; Zhang, Shishun

doi: 10.1080/00218464.2025.2482714pmid: N/A

Constant loads with various magnitudes, i.e. 25%, 35%, 45%, 55%, 65%, 75%, and 85% of the ultimate tensile load (UTL) were imposed to adhesive coupons until their fracture. It was found that even at low-load magnitudes of 25−45% of the UTL, the adhesive could still accumulate significant creep strain (average creep coefficient: 2.98) or even fracture after about 4,200 hours of continuous loading. Under the high-load magnitudes of 65−85% of the UTL, the adhesive specimens broke during the primary creep stage with a minimum creep coefficient of only 0.09. It was also found that the ultimate strain in creep tests at load magnitudes of 55% and 65% of the UTL was roughly 1.5%, approximately 1.4 times higher than the tensile ultimate strain. SEM pictures showed that the adhesive rupture at high-load magnitudes displayed a brittle fracture mode, whereas plastic fracture mode was at low-load magnitudes. A threshold value between the load magnitudes of 45% and 55% of the UTL was determined, below which the adhesive exhibited linear viscoelasticity. The creep propagation of adhesive specimens under a full range of load magnitudes and until failure was precisely parameterised, simulated, and prediction of creep rupture life were performed.