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Masoomeh Eskandarian - One of the best experts on this subject based on the ideXlab platform.

  • a simple surface treatment and characterization of aa 6061 aluminum alloy surface for adhesive bonding applications
    Applied Surface Science, 2012
    Co-Authors: N Saleema, Royston W. Paynter, Dilip K. Sarkar, Danick Gallant, Masoomeh Eskandarian
    Abstract:

    Structural adhesive bonding of aluminum is widely used in aircraft and automotive industries. It has been widely noted that surface preparation of aluminum surfaces prior to adhesive bonding plays a significant role in improving the strength of the adhesive bond. Surface cleanliness, surface roughness, surface wettability and surface chemistry are controlled primarily by proper surface treatment methods. In this study, we have employed a very simple technique influencing all these criteria by simply immersing aluminum substrates in a very dilute solution of sodium hydroxide (NaOH) and we have studied the effect of varying the treatment period on the adhesive bonding characteristics. A bi-component epoxy adhesive was used to join the treated surfaces and the bond strengths were evaluated via single lap shear (SLS) tests in pristine as well as degraded conditions. Surface morphology, chemistry, crystalline nature and wettability of the NaOH treated surfaces were characterized using various surface analytical tools such as scanning electron microscopy and energy dispersive X-ray analysis (SEM/EDX), optical profilometry, infrared reflection absorption spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction and contact angle goniometry. Excellent adhesion characteristics with complete Cohesive Failure of the adhesive were encountered on the NaOH treated surfaces that are comparable to the benchmark treatments such as anodization, which involve use of strong acids and multiple steps of treatment procedures. The NaOH treatment reported in this work is a very simple method with the use of a very dilute solution with simple ultrasonication being sufficient to produce durable joints.

David H Pashley - One of the best experts on this subject based on the ideXlab platform.

  • relationship between surface area for adhesion and tensile bond strength evaluation of a micro tensile bond test
    Dental Materials, 1994
    Co-Authors: Hidehiko Sano, Tsunekazu Shono, Hidekazu Sonoda, T Takatsu, B Ciucchi, Ricardo M Carvalho, David H Pashley
    Abstract:

    Abstract Objectives . The purpose of this study was to test the null hypothesis that there is no relationship between the bonded surface area of dentin and the tensile strength of adhesive materials. Methods . The enamel was removed from the occlusal surface of extracted human third molars, and the entire flat surface was covered with resin composite bonded to the dentin to form a flat resin composite crown. Twenty-four hours later, the bonded specimens were sectioned parallel to the long axis of the tooth into 10–20 thin sections whose upper part was composed of resin composite with the lower half being dentin. These small sections were trimmed using a high speed diamond bur into an hourglass shape with the narrowest portion at the bonded interface. Surface area was varied by altering the specimen thickness and width. Tensile bond strength was measured using custom-made grips in a universal testing machine. Results . Tensile bond strength was inversely related to bonded surface area. At surface areas below 0.4 mm 2 , the tensile bond strengths were about 55 MPa for Clearfil Liner Bond 2 (Kuraray Co., Ltd.), 38 MPa for Scotchbond MP (3M Dental Peoducts), and 20 MPa for Vitremer (3M Dental Products). At these small surface areas all of the bond Failures were adhesive in nature. Significance . This new method permits measurement of high bond strengths without Cohesive Failure of dentin. It also permits multiple measurements to be made within a single tooth.

Omer Said Toker - One of the best experts on this subject based on the ideXlab platform.

  • Minimising the environmental footprint of industrial-scaled cleaning processes by optimisation of a novel clean-in-place system protocol
    Journal of Cleaner Production, 2015
    Co-Authors: İbrahim Palabiyik, Mustafa Tahsin Yilmaz, Peter J. Fryer, Phillip T Robbins, Omer Said Toker
    Abstract:

    Cleaning of food fouling deposits in processing equipment is costly and time consuming. Fouling deposits form as a result of adhesion of species to the surface and cohesion between elements of the material. Cleaning can result from either or both adhesive and Cohesive Failure. In this study, the aim was to investigate the removal kinetics of an adhesive material and to design a novel cleaning in place (CIP) protocol for these kinds of materials at industrial scale to reduce environmental impact of cleaning processes. It was detected that different variables controlled the cleaning process in removal of adhesive deposit. Temperature was not found as a significant variable in the initial stage of cleaning. Velocity of cleaning water controlled the cleaning at this stage when top layers of the deposit were removed by fluid mechanical removal due to breakdown of weak Cohesive interaction. In the later cleaning stage, both velocity and temperature significantly contributed to cleaning, which suggested that both hydrodynamic forces and rheological changes are needed to overcome adhesion forces between the deposit and surface. Hence, a novel "two step CIP protocol" was proposed due to existence of different mechanisms in cleaning. When compared with conventional one step CIP protocols currently used in the processing plants, the proposed CIP protocol reduced the energy consumption by 40% without decreasing the cleaning efficiency.

Qingru Tang - One of the best experts on this subject based on the ideXlab platform.

  • a study of laser surface treatment in bonded repair of composite aircraft structures
    Royal Society Open Science, 2018
    Co-Authors: Shaolong Li, Wenfeng Yang, Qingru Tang
    Abstract:

    Surface pre-treatment is one of the key processes in bonded repair of aircraft carbon fibre reinforced polymer composites. This paper investigates the surface modification of physical and chemical properties by laser ablation and conventional polish treatment techniques. Surface morphology analysed by laser scanning confocal microscopy and scanning electron microscopy showed that a laser-treated surface displayed higher roughness than that of a polish-treated specimen. The laser-treated laminate exhibited more functional groups in the form of O 1 s/C 1 s atomic ratio of 30.89% for laser-treated and 20.14% for polish-treated as evidenced by X-ray photoelectron spectroscopy observation. Contact angle goniometry demonstrated that laser treatment can provide increased surface free energy and wettability. In the light of mechanical interlocking, molecular bonding and thermodynamics theories on adhesion, laser etching process displayed enhanced bonding performance relative to the polishing surface treatment. These properties resulted in an increased single lap shear strength and a Cohesive Failure mode for laser etching while an adhesive Failure mode occurred in polish-treated specimen.

Karel Matous - One of the best experts on this subject based on the ideXlab platform.

  • multi scale modeling of heterogeneous adhesives effect of particle decohesion
    Mechanics of Materials, 2009
    Co-Authors: Mohan G Kulkarni, Philippe H Geubelle, Karel Matous
    Abstract:

    Abstract We examine the microscopic toughening mechanisms and their effect on the macroscopic Failure response of heterogeneous adhesives made of stiff particles embedded in a more compliant matrix. The analysis relies on a multi-scale Cohesive framework first described in Matous et al. [Matous, K., Kulkarni, M., Geubelle, P., 2008. Multiscale Cohesive Failure modeling of heterogeneous adhesives. Journal of the Mechanics and Physics of Solids 56, 1511–1533]. Two microscopic constitutive Failure models are incorporated: an isotropic damage model to capture the fracture response of the matrix and a Cohesive law to model the inclusion-matrix interfacial debonding. A detailed study of the RVE size is presented followed by a set of examples that illustrate the effect of filler size, volume fraction and particle–matrix interface properties on the macroscopic effective traction-separation law of heterogeneous adhesives.

  • multiscale Cohesive Failure modeling of heterogeneous adhesives
    Journal of The Mechanics and Physics of Solids, 2008
    Co-Authors: Karel Matous, Mohan G Kulkarni, Philippe H Geubelle
    Abstract:

    A novel multiscale Cohesive approach that enables prediction of the macroscopic properties of heterogeneous thin layers is presented. The proposed multiscale model relies on the Hill's energy equivalence lemma, implemented in the computational homogenization scheme, to couple the micro- and macro-scales and allows to relate the homogenized Cohesive law used to model the Failure of the adhesive layer at the macro-scale to the complex damage evolution taking place at the micro-scale. A simple isotropic damage model is used to describe the Failure processes at the micro-scale. We establish the upper and lower bounds on the multiscale model and solve several examples to demonstrate the ability of the method to extract physically based macroscopic properties.