On controlling interfacial heterogeneity to trigger bridging in secondary bonded composite joints: An efficient strategy to introduce crack-arrest features

Tao, Ran; Li, Xiaole; Yudhanto, Arief; Alfano, Marco; Lubineau, Gilles

doi:10.1016/j.compscitech.2019.107964

Cited by 32 publications

(14 citation statements)

References 39 publications

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“…The mechanical properties are reported in Table 2 . The adhesive is recommended for bonding both metals and composites and is characterized by very high peel and lap-shear strength [ 23 , 24 ]. The main mechanical properties are summarized in Table 1 .…”

Section: Methodsmentioning

confidence: 99%

Effect of Mechanical Pretreatments on Damage Mechanisms and Fracture Toughness in CFRP/Epoxy Joints

et al. 2021

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Adhesive bonding of carbon-fiber-reinforced polymers (CFRPs) is a key enabling technology for the assembly of lightweight structures. Surface pretreatment is necessary to remove contaminants related to material manufacturing and ensure bond reliability. The present experimental study focuses on the effect of mechanical abrasion on the damage mechanisms and fracture toughness of CFRP/epoxy joints. The analyzed CFRP plates were provided with a thin layer of surface epoxy matrix and featured enhanced sensitivity to surface preparation. Various degrees of morphological modification and fairly controllable carbon fiber exposure were obtained using sanding with emery paper and grit-blasting with glass particles. In the sanding process, different grit sizes of SiC paper were used, while the grit blasting treatment was carried by varying the sample-to-gun distance and the number of passes. Detailed surveys of surface topography and wettability were carried out using various methods, including scanning electron microscopy (SEM), contact profilometry, and wettability measurements. Mechanical tests were performed using double cantilever beam (DCB) adhesive joints. Two surface conditions were selected for the experiments: sanded interfaces mostly made of a polymer matrix and grit-blasted interfaces featuring a significant degree of exposed carbon fibers. Despite the different topographies, the selected surfaces displayed similar wettability. Besides, the adhesive joints with sanded interfaces had a smooth fracture response (steady-state crack growth). In contrast, the exposed fibers at grit-blasted interfaces enabled large-scale bridging and a significant R-curve behavior. While it is often predicated that quality composite joints require surfaces with a high percentage of the polymer matrix, our mechanical tests show that the exposure of carbon fibers can facilitate a remarkable toughening effect. These results open up for additional interesting prospects for future works concerning toughening of composite joints in automotive and aerospace applications.

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Section: Methodsmentioning

confidence: 99%

Effect of Mechanical Pretreatments on Damage Mechanisms and Fracture Toughness in CFRP/Epoxy Joints

et al. 2021

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“…These methods, however, induce architectural and mechanical shortcomings, such as fiber waviness, in-plane stiffness reduction (stitching or z-pinning [17,18]), manufacturing complexity [21], and are mostly applicable for co-cured CFRP rather than secondary bonding. Methods for improving delamination resistance for secondary bonded CFRP, so-called crack-stopping features, include a thermoplastic crack stopper [4], corrugation [22], staples [23], surface interfering [24], X-type arrester [25], formation of adhesive ligament [26], defect introduction [27] or adhesive bondline architecturing [28,29]. Nevertheless, most of these methods also incur manufacturing complexity, except adhesive bondline architecturing.…”

Section: Introductionmentioning

confidence: 99%

“…Adhesive bondline architecturing, which consists of introducing a specific heterogeneous morphology either at the adhesive-substrate interfaces or within the adhesive layer, presents a promising method since it is easily implemented, tailorable, effective (providing sufficient bridging traction for improving delamination resistance), and applicable for bonded repair (latest stage of implementation). In fact, very promising results have been obtained recently by in troducing patterns in the substrates that improve the adhesion properties of the adhesive-substrate interface [26]. In Ref.…”

Section: Introductionmentioning

confidence: 99%

“…In Ref. [26], the authors show that, although the adhesive layer is a purely bulk thermoset layer, controlling its adhesion with the substrates can trigger new mechanisms of dissipation, such as long-range bridging, that promotes an increasing R-curve response. Instead of patterning the substrates in order to modify the adhesion properties between the adhesive layer and the substrates, another option is to directly pattern the adhesive layer, for example, by inserting a crack-arrest feature inside the adhesive.…”

Section: Introductionmentioning

confidence: 99%

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Enhancement of fracture toughness in secondary bonded CFRP using hybrid thermoplastic/thermoset bondline architecture

Yudhanto

Almulhim

Kamal

et al. 2020

Composites Science and Technology

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“…Recently, similar concepts have drawn atten-61 tions to enhance the fracture resistance of secondary bonded joints 62 (Maloney and Fleck, 2019). Lubineau and coworkers designed a series of architectural bondline by patterning interface heterogeneity with laser to trigger large-scale ligaments bridging (Tao et al, 2020a;Tao et al, 2020b) or by embedding 3D printed thermoplastic nets in bondline (Yudhanto et al, 2020), which showed remarkable potential to control and tailor the fracture resistance curve.…”

mentioning

confidence: 99%

Snap-back instability of double cantilever beam with bridging

Lü

Lubineau

2021

International Journal of Solids and Structures

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Adhesive bonding community shows a continued interest in using bridging mechanisms to toughen the interface of secondary bonded joints, especially in the case of laminated composites. Due to snap-back instability that occurs during fracture, confusions may exist when identifying the toughening effect experimentally. The true toughening effect may be overestimated by lumping all energy contributions (kinetic energy included) in an overall effective toughness. Here, fundamentals for bridging to enhance fracture resistance are explored through the theoretical analysis of the delamination of a composite double cantilever beam (DCB) with bridging. Specifically, we establish a theoretical framework on the basis of Timoshenko beam theory and linear elastic fracture mechanics to solve the fracture response of DCB in the presence of discrete bridging phases. We elucidate the crack trapping and the snap-back instability in structural response during the crack propagation. We identify the contribution to the overall toughness observed numerically/experimentally of both the physical fracture energy and other types of dissipation.The associated toughening mechanisms are then unveiled. Furthermore, we study the effects of property of the bridging phases on the snap-back instability, based on which, we propose a dimensionless quantity that can be deployed as an indicator of the intensity of snap-back instability. Finally, we identify the role of geometrical properties, i.e. the substrate thickness and the arrangement spacing of the bridging phases, in the snap-back instability and the macroscopic fracture toughness of a DCB. This work provides, from a theoretical point of view, an essential insight into the physics related to the structural response of DCB with discrete toughening elements.

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On controlling interfacial heterogeneity to trigger bridging in secondary bonded composite joints: An efficient strategy to introduce crack-arrest features

Cited by 32 publications

References 39 publications

Effect of Mechanical Pretreatments on Damage Mechanisms and Fracture Toughness in CFRP/Epoxy Joints

Effect of Mechanical Pretreatments on Damage Mechanisms and Fracture Toughness in CFRP/Epoxy Joints

Enhancement of fracture toughness in secondary bonded CFRP using hybrid thermoplastic/thermoset bondline architecture

Snap-back instability of double cantilever beam with bridging

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