Cohesive behaviors of hydrogel under large-scale bridging

It has been recently revealed that large-scale bridging mechanism can be invoked to drastically improve the debonding resistance of hydrogel adhesion, but the optimization of the improvement remains elusive. Aiming at shedding light on the optimization, the present paper investigates the cohesive behaviors of hydrogel under the condition of large-scale bridging in 90-degree peel. A quasi-static model is established based on the principle of minimum potential energy, with the traction-separation law determined from experiments. The model is proved reliable in predicting the force-displacement response and the backing profile up to the peak peel force. Further theoretical analyses indicate that, within the range of interest, the peak peel force decreases with the extended length, increases with the Young's modulus of backing, increases then plateaus with the adhesion length and the thickness and bending stiffness of backing. In addition, the vertical displacement at peak peel force escalates with the extended length, remains mostly constant with varying adhesion length, declines with the Young's modulus of backing, and declines then stabilizes with increasing thickness and bending stiffness of backing. These theoretical insights may help tailor the material properties and geometric parameters for on-demand design of hydrogel adhesion as well as other soft adhesives for biomedicine and engineering.

Study the Influence of Processing Oil on the Physical Mechanical and Adhesion Properties of Ethylene Propylene Diene Monomer/Chlorobutyl Blend to Polyester Fabric

In this paper, the influence of paraffinic oil on the physical mechanical, thermal and adhesion properties of three blends of EPDM Buna EP T.6465, Keltan 5260Q and Keltan 6160 D and CIIR have been investigated. The results showed that the tensile strength values and elongation at break of keltan 5260Q/CIIR and keltan 6160 D/CIIR with 10 wt.% paraffinic oil represent the improvement of 57.8%, 57.6% and 71% to 81% respectively, compared with one without oil. The mean peel force of EPDM keltan 6260D with 10% oil loaded is about 36% and 32.5% higher than that of EPDM keltan 5260Q and EP.T 6465 blends respectively. With suitable oil content, in this case is 10% wt., the thermal resistance of keltan 5260 Q and 6160D seems to be higher than that of without processing oil and suitable for thermal resistance rubber application.

Study on the Influence of Processing Oil on the Physical Mechanical Properties and Adhesion of Ethylene Propylene Diene Monomer (EPDM) Rubbers to Polyester Fabrics

In this paper, the influence of paraffinic oil on the physical mechanical and thermal properties of three EPDM rubbers types Buna EP T.6465, Keltan 5260Q and Keltan 6160 D have been investigated. The results showed that the tensile strength and the elongation at break of Keltan 5260Q and Keltan 6160 D with 10 phr paraffinic oil represent the improvement of 57.8% to 57.6% and 71% to 81% respectively, compared to EPDM rubbers without paraffinic oil. The mean peel force of EPDM keltan 6260D with 10 phr paraffinic oil loaded is about 36% and 32.5% higher than that of keltan 5260Q and EP.T 6465 respectively. Beside that at the suitable paraffinic oil contents, the thermal resistance of Keltan 5260 Q and 6160D seems to be a little higher than that of without processing oil and these EPDM rubbers are suitable for application to high thermal resistance rubber products.

Bonding Strength of FRP-Metal Hybrids

The lightweight credo “the right material in the right place” raises an interesting concern once different materials are meant to provide a watertight bond. Therefore, we investigate the bonding behavior of metals with Fiber-Reinforced-Plastic (FRP) materials. In order to optimize the bond, the major influencing factors and their interactions are studied.In order to identify the above interactions, FRP-metal hybrid specimens were investigated with regard to peel forces and shear strengths. During manufacturing the influencing factors such as sheet metal and FRP type, surface treatments, and bonding processes were varied.Considering the peel force, a thermoset plastic matrix adhesively bonded to steel provided the best results, along with the use of a novel surface etching method by Kobelco. The latter yielded the highest shear strengths within this investigation. No bond could be obtained applying thermoset plastic matrices for in-operandi connections.Using adhesives or surface treatments introduced additional production costs. Hence, in-operandi bonding would be a favorable option, however, one requiring further research. Compared to the material costs, the additional production costs could prove to be insignificant once the bonding process has been properly robustified and automated.

Swelling effects on localized adhesion of an elastic ribbon

We investigate the adhesion mechanism between an elastic strip of vinylpolysiloxane bent in a racquet-like shape, and a thick elastomeric substrate with the aim to understand how local swelling modifies adhesion. Using a modified loop–tack adhesion test, we place a droplet of silicone oil in between the two materials, vary the dwell time and measure the force required to separate the two interfaces. The experiments are then compared with an analytical model that describes how the critical peel force is modified as the interfacial surface energy changes over time. Our study reveals that in certain circumstances swelling can enhance adhesion. More specifically, strong adhesion is obtained when most of the droplet is absorbed by the solid. By contrast, when the droplet remains at the interface a small adhesive force is measured.

Peel strength characterisation on ply/ply interface using wedge and T-peel/pull-type tests

Thermoplastic tapes have found a prominent place in automated tape placement (ATP), due to their reduced processing time. ATP also offers significant reduction in labour; however, the most attractive aspect is the use of its welding properties. Welding or diffusion bonding is necessary for two thermoplastic materials to bond to each other through the combined effect of heating and consolidation pressure. The work published in this article shows how various thermoplastic tape materials with different material properties are bonded to each other using a direct flame-type ATP process. Contact angle and differential scanning calorimetry measurements help understanding of the processing needs of the considered materials. The samples obtained after ATP are sent for peel testing using a wedge peel test principle, so that the force required to separate the bonding is identified. A T-peel test/pull test is also employed to cross-compare peel results obtained through wedge peel testing. The main aim of the work is to study the quality of connection between the two plies with different material interfaces and also how friction might contribute to peel force when wedge peeling is used. A numerical model is also implemented to show the effects of this friction.

Effect of Cohesive Zone Size on Peeling of Heterogeneous Adhesive Tape

The interaction between the cohesive zone and the elastic stiffness heterogeneity in the peeling of an adhesive tape from a rigid substrate is examined experimentally and with finite element simulations. It is established in the literature that elastic stiffness heterogeneities can greatly enhance the force required to peel a tape without changing the properties of the interface. However, much of these concern brittle materials where the cohesive zone is limited in size. This paper reports the results of peeling experiments performed on pressure-sensitive adhesive tapes with both an elastic stiffness heterogeneity and a substantial cohesive zone. These experiments show muted enhancement in the peeling force and suggest that the cohesive zone acts to smooth out the effect of the discontinuity at the edge of the elastic stiffness heterogeneities, suppressing their effect on peel force enhancement. This mechanism is examined through numerical simulation which confirms that the peel force enhancement depends on the strength of the adhesive and the size of the cohesive zone.