Abstract 

Reducing emissions of pollutants is a key priority to fight again the climatic changes that we are going to face over the 21st century.  More and more pressing environmental constraints are shaping the new technological solutions in the transportation sector, from personal cars up to mass air transport. Automotive and aerospace industries are then seeking new solutions to create lighter structures to reduce fuel consumption or make easier the transition to electrical vehicles.

Extreme lightweight structures can today be obtained by using high-performance composites based on continuous fibers and polymeric matrices. These materials that were reserved before to high tech industries, will become even more common tomorrow with the expected cut in the production cost of carbon fibers. Assembling composite parts is however still a challenge that often jeopardizes the energy efficiency of structures. Classical joining techniques, such as bolting and riveting, add to the total structural weight and require hole drilling. These result in extra cost due to manufacturing and to extra weight (due to rivets/bolt and locally increased composite thickness to ensure integrity of the substrate). Designers have thought for a long time about replacing the “bolted” solution with integral adhesive bonding. In such joints, the mechanical cohesion between parts is only ensured by an intermediary adhesive layer. This would minimize the additional work and weight needed to realize the assembly.

However, integral adhesive bonding is not used for primary structure today, because of its extreme sensitivity to the quality of the substrate preparation that can largely modify the intrinsic performance of the joint. More important for us, the failure of adhesive joints is often unstable: the joint behaves well until the development of a catastrophic crack that would propagate throughout the whole joint, resulting in the loss of the application. In a sense, adhesive-based-design is missing today the “crack arrest” function that is fulfilled by bolts. There are arresting the cracks even in case of premature failure, providing enough time to repair the structure before catastrophic failure.

Our objective is here to introduce new strategies to equip by design adhesive interfaces with crack arrest features. From a practical point of view, we are manipulating the R-curve of the interface by introducing non-local dissipative mechanisms, such as bridging, that will add to the classical cohesive energy of the adhesive.

References

[1] R. Tao, M. Alfano and G. Lubineau (2018). Laser-based surface patterning of composite plates for improved secondary adhesive bonding. Composites Part A: Applied Science and Manufacturing, v. 109, pp. 84-94.

[2] R. Tao, M. Alfano and G. Lubineau (2019). In situ analysis of interfacial damage in adhesively bonded composite joints subjected to various surface pretreatments. Composites Part A, v. 116, pp. 216-223.

[3] R. Tao, X. Li, A. Yudhanto, M. Alfano and G. Lubineau (2020). On controlling interfacial heterogeneity to trigger bridging in secondary bonded composite joints: An efficient strategy to introduce crack-arrest features. Composites Science and Technology, v. 188, 107964

[4] A. Yudhanto, M. Almulhim, F. Kamal, R. Tao, L. Fatta, M. Alfano, G. Lubineau (2020). Enhancement of fracture toughness in secondary bonded CFRP using hybrid thermoplastic/thermoset bondline architecture. Composites Science and Technology, v. 199, 108346

[5] R. Tao, X. Li, A. Yudhanto, M. Alfano, G. Lubineau (2020), Laser-based interfacial patterning enables toughening of CFRP/epoxy joints through bridging of adhesive ligaments. Composites Part A, v. 139, 106094.

[6] A. Wagih and G. Lubineau (2021). Enhanced mode II fracture toughness of secondary bonded joints using tailored sacrificial cracks inside the adhesive.   Composites Science and Technology, 204, 108605.‏

[7] A. Wagih, R. Tao and G. Lubineau (2021). Bio-inspired adhesive joint with improved interlaminar fracture toughness. Composites Part A, v. 149, 106530.

[8] P. Hu, D. Pulungan, R. Tao and G. Lubineau (2021), Influence of curing processes on the development of fiber bridging during delamination in composite laminates. Composites Part A: Applied Science and Manufacturing. v. 149,106564

[9] R. Tao, X. Li, A. Yudhanto, M. Alfano and G. Lubineau (2022). Toughening adhesive joints through crack path engineering using integrated polyamide wires. Composites Part A: Applied Science and Manufacturing. 158(8), 106954

[10] M. Hashem, A. Wagih and G. Lubineau (2022). Laser-based pretreatment of composite T-joints for improved pull-off strength and toughness. Composite Structures.  291(1), 115545

[11] A. Wagih, M. Hashem and G. Lubineau (2022). Simultaneous strengthening and toughening of composite T-joints by microstructuring the adhesive bondline. Composites Part A: Applied Science and Manufacturing. 162(1-4), 107134

[12] A. Wagih, H. Mahmoud, R. Tao and G. Lubineau, Towards tough thermoplastic adhesive tape by microstructuring the tape using tailored defects. Polymers, 2023, 15(2), 259

Biography

Pr. Gilles Lubineau is professor of Mechanical Engineering in the Physical Science and Engineering Division and Director of ENERCOMP, a Technology Consortium for Composites in Energy Applications. He is principal investigator of the Laboratory of Mechanics for Energy and Mobility, an integrated environment for composite engineering that he created in 2009 when joining KAUST).

Following his “aggregation” in theoretical mechanics, Pr. Lubineau earned a PhD degree in Mechanical Engineering from École Normale Supérieure de Cachan (ENS-Cachan), France.  Before joining KAUST, Pr. Lubineau was a faculty member at the École Normale Supérieure of Cachan, and a non-resident Instructor at the École Polytechnique, France. He also served as a visiting researcher at UC-Berkeley and as Interim Dean of the Physical Science and Engineering Division at KAUST.

His fields of research include: integrity at short and/or long-term of composite materials and structures, inverse problems for the identification of constitutive parameters, multi-scale coupling technique, nano and/or multifunctional materials. He covers a wide expertise related to most fields of composite materials, with over 200 published papers in journal spanning from material science (Advanced Materials, Macromolecules, etc..), Composites Engineering,  all the way to theoretical mechanics (JMPS, CST, Scientific Reports) and applied maths (IJNME, CMAME, etc..).

He is an editor for Mechanics of Materials and a board member for various journals. Prof. Lubineau is an elected Member of the European Academy of Sciences and Arts. He is an elected Fellow of the International Association of Computational Mechanics (IACM), and recipient of the Daniel Valentin Amac Award.