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Nima Beheshtizadeh - One of the best experts on this subject based on the ideXlab platform.

  • three Point Bending Test of glass epoxy composite health monitoring by acoustic emission
    alexandria engineering journal, 2019
    Co-Authors: Nima Beheshtizadeh, Amir Mostafapour, Saman Davoodi
    Abstract:

    Abstract As glass epoxy composites have special properties, they are used in different structures. Health monitoring of this kind of composite is very important due to its use in many industries. Acoustic emission technique is one of the best methods for health monitoring. Since flexural loading is widespread in utilization of this type of composite, in this research acoustic emission method was used to monitor and check the different failure mechanisms of glass epoxy composite flexural loading. In order to determine different failure mechanisms, the wavelet transform and Choi-Williams transform analysis was used to process acoustic signals. Three types of dominant failure mechanisms (matrix fracture, debonding and fiber breakage) in this composite were identified and the frequency ranges corresponding to these failure mechanisms were determined. Wavelet transform results showed that, this three type of dominant failure mechanisms (matrix fracture, debonding and fiber breakage) in flexural loading have frequency range of 62.5–125 kHz, 125–187.5 kHz and 187.5–250 kHz respectively. Also energy distribution of each frequency ranges obtained and fitted with fracture mechanisms. Finally the observations of scanning electron microscope from fracture surface of specimen validated the obtained results. This research showed the possibility of acoustic emission technique as a monitoring tool of glass/epoxy composite in flexural failure.

Alvaro Della Bona - One of the best experts on this subject based on the ideXlab platform.

  • flexural strength and weibull analysis of a microhybrid and a nanofill composite evaluated by 3 and 4 Point Bending Tests
    Dental Materials, 2008
    Co-Authors: Sinval Adalberto Rodrigues, Jack L Ferracane, Alvaro Della Bona
    Abstract:

    Abstract Objectives The aim of the present study was to evaluate the flexural strength and the Weibull modulus of a microhybrid and a nanofill composite by means of 3- and 4-Point Bending Tests. Methods Thirty specimens of Filtek Z250™ (3M/ESPE) and Filtek Supreme™ (3M/ESPE) were prepared for each Test according to the ISO 4049/2000 specification. After 24 h in distilled water at 37 °C the specimens were submitted to 3- and 4-Point Bending Tests using a universal Testing machine DL2000 (EMIC) with a crosshead speed of 1 mm/min. Flexural strength data were calculated and submitted to Student's t -Test ( α  = 0.05) and Weibull statistics. The fractured surfaces were analyzed based on fractographic principles. Results The two composites had equivalent strength in both Test methods. However, the Test designs significantly affected the flexural strength of the microhybrid and the nanofill composites. Weibull modulus ( m ) of Supreme™ was similar with both Tests, while for Z250™, a higher m was observed with the 3-Point Bending Test. Critical flaws were most often associated with the specimen's surface (up to 90%) and were characterized as surface scratches/grooves, non-uniform distribution of phases, inclusions and voids. Significance Flexural strength as measured by the 3-Point Bending Test is higher than by the 4-Point Bending Test, due to the smaller flaw containing area involved in the former. Despite the large difference in average filler size between the composites, the volume fraction of the filler in both materials is similar, which was probably the reason for similar mean flexural strength values and fracture behavior.

Jafar Razmi - One of the best experts on this subject based on the ideXlab platform.

  • Fracture toughness of bonds using interfacial stresses in four-Point Bending Test
    Mechanics of Materials, 2011
    Co-Authors: Ousama M. Abdelhadi, Leila Ladani, Jafar Razmi
    Abstract:

    Abstract Bond strength is an important factor in electronic and photonic packaging. Measuring bond characteristics, strength, and fracture toughness is particularly difficult in microelectronic devices where miniaturized bonds are used (e.g., wafer bonding and 3 dimensional integrated circuits). Since applying load directly to the bonds is proven difficult, four-Point Bending Test with notched specimen has been typically used to facilitate fracture toughness measurements at small scale. This method is based on experiencing large peeling and shear stresses at the interface of two layers of different materials at the notch. However, there is a lack of analytical solution that can be used to determine the peeling and shear stresses at the interface of four-Point bend specimen. This manuscript presents analytical modeling of peeling and shear stresses in tri-layer four-Point bend specimens. Strength of materials approach with the assumption of small strains, within elastic region, is adopted in this study for evaluation of stresses and displacements. Furthermore, beam theory is utilized to develop equations that describe the moments and shear forces in the assembly due to the four-Point Bending loads. Second and fourth order differential equations are derived for shear and peeling stresses respectively at the interfaces of the assembly. Boundary conditions are determined based on load, supports and shear force and moment diagrams of the assembly. The problem solution is obtained by solving the governing differential equations instantaneously using standard methods. Finite-Element-based simulation is used to compare with and verify the analytical solution. This work also presents an alternative approach where the stresses at the notch are used to determine the fracture toughness. An experiment is conducted on a specimen with intermetallic material as bond material. The analytical approach is then verified with the results of four-Point Bending experiment and is validated using the conventional technique (which is based on energy equilibrium and presented by Eq. (60) ).

Aufray Maëlenn - One of the best experts on this subject based on the ideXlab platform.

  • Assessment of interface failure behaviour for brittle adhesive using the three-Point Bending Test
    'Elsevier BV', 2021
    Co-Authors: Birro Thiago, Aufray Maëlenn, Paroissien Eric, Lachaud Frederic
    Abstract:

    International audienceIn the framework of the adhesive bonding, the assessment of interfacial properties has an essential role in determining the adhesive joints' global responses. Various surface preparations are available for each type of metallic substrate. There are plenty of Tests widely used for mechanical characterisation to determine the adhesive properties and few Tests to assess interfacial properties. For such a case, a specific three-Point Bending Test can be applied to examine the interactions between adhesive and substrate. On the other hand, a direct comparison of the critical force is not always possible because of geometrical incompatibility. A practical solution for the last issue is applying a coupled stress-energy criterion (CC) since the interface properties are independent of the substrate thickness. Hence, CC and the macro-element technique were applied to determine the interfacial properties using an aluminium alloy 2024-T3 as substrate and the adhesive DGEBA/DETA™ under many preparation conditions. As a result, the three-Point Bending Test's overall behaviour was established in terms of interface strength (adherence), including incremental energy release rate and critical stress. Thus, this paper can be read as the first work towards the ability to predict the interface failure in the frame of three-Point Bending Test using different geometries. In conclusion, the occurrence of an adhesive or cohesive failure and the unstable or a stable failure propagation of the bonded joints were sorted and classified as a function of interface properties

  • Assessment of interface failure behaviour for brittle adhesive using the three-Point Bending Test
    'Elsevier BV', 2021
    Co-Authors: Birro Thiago, Aufray Maëlenn, Paroissien Eric, Lachaud Frederic
    Abstract:

    In the framework of the adhesive bonding, the assessment of interfacial properties has an essential role in determining the adhesive joints' global responses. Various surface preparations are available for each type of metallic substrate. There are plenty of Tests widely used for mechanical characterisation to determine the adhesive properties and few Tests to assess interfacial properties. For such a case, a specific three-Point Bending Test can be applied to examine the interactions between adhesive and substrate. On the other hand, a direct comparison of the critical force is not always possible because of geometrical incompatibility. A practical solution for the last issue is applying a coupled stress-energy criterion (CC) since the interface properties are independent of the substrate thickness. Hence, CC and the macro-element technique were applied to determine the interfacial properties using an aluminium alloy 2024-T3 as substrate and the adhesive DGEBA/DETA™ under many preparation conditions. As a result, the three-Point Bending Test's overall behaviour was established in terms of interface strength (adherence), including incremental energy release rate and critical stress. Thus, this paper can be read as the first work towards the ability to predict the interface failure in the frame of three-Point Bending Test using different geometries. In conclusion, the occurrence of an adhesive or cohesive failure and the unstable or a stable failure propagation of the bonded joints were sorted and classified as a function of interface properties

  • Using the Finite Element Analysis Method to Study the 3-Point Bending Test for the Characterization of the Adherence
    'Geophysical Center of the Russian Academy of Sciences', 2019
    Co-Authors: Sauvage Jean-baptiste, Chalandon Pierre, Poquillon Dominique, Nardin Michel, Aufray Maëlenn
    Abstract:

    International audienceAn elastic finite element analysis was conducted to evaluate the stress distribution in the initiation zone of the adhesive rupture during the 3-Point Bending Test. This Test is used to measure the adherence between a polyepoxy adhesive and aluminum alloy with different surface treatments. The purpose is to compare, in the high stress concentration areas, the stress fields calculated using finite element method with the experimental data obtained in different configurations. Focusing on the load level at crack initiation, on the localization and the size of adhesive failure initiation, a local criterion for adhesive fracture is proposed based on the value of the stress normal to the interface

  • Practical adhesion measurements of protective coatings on bronze by three-Point Bending Test
    'Springer Science and Business Media LLC', 2019
    Co-Authors: Aufray Maëlenn, Josse Claudie, Balbo Andrea, Monticelli Cecilia, Švara Fabjan Erika, Škrlep Luka, Kosec Tadeja, Gartner Nina, Martini Carla, Masi Giulia
    Abstract:

    International audienceWhen attempting to sufficiently protect outdoor bronze monuments from corrosion, searches for an effective solution are usually based on coating applications which have a high anticorrosive efficiency. In order to correctly assess the level of protection provided by such coatings, adherence (practical adhesion) measurements need to be performed for the proper evaluation of the deterioration of coating systems with aging. Although a coupled study of adherence with aging would be of great interest, very few such studies are available. In this work, a methodological approach is proposed for the evaluation of coatings applied to metallic cultural heritage monuments of, based on the use of a three-Point Bending Test. Adherence characterization of different protective coatings has been performed both on bare and on traditionally black-patinated bronze coupons (Cu–Sn alloy with 5.9 wt% Sn), which were used as basic model substrates. The investigated coatings were Incralac®, silane, sol–gel oxysilane, and a silane-modified polymethacrylate (an adhesion promoter for fluoropolymer). The results of measurements which were obtained before and after accelerated aging in concentrated acid rain made it possible to more easily differentiate between the various adherence levels of different coating systems. Coupled with adherence measurements, the results of systematic optical and SEM observation of the different failure morphologies are also presented. In the case of the coated bare alloy, adhesive failures were mainly observed. The silane (PropS-SH) coating showed the best adherence. In the case of the patinated bronze Test specimens, only cohesive failures occurred. Adherence is directly related to the cohesion of the black patina rather than that of the applied coating. It was observed that aging reduces the level of the adherence

  • Prediction of Adhesion Failure of Bonded Joints using 3-Point Bending Test and Stress-Energy Coupled Criterion
    HAL CCSD, 2018
    Co-Authors: Birro Thiago, Aufray Maëlenn, Paroissien Eric, Lachaud Frederic
    Abstract:

    International audienceIn the recent years, a coupled energy and stress approach has been used successfully to treat problems involving stress concentration since the stress-based criteria only are no more valid near a singularity. For the adhesive failure characterization, Roche et al. [4] have developed a 3-Point Bending Test which has a similar stress concentration condition, and thus the coupled criterion can be applied to predict the failure of the adhesively bonded joint. For mechanical properties determination, the semi-analytical approach Macro-element technique is used, and the results will be compared with Cohesive Zone Model (CZM) based on damage mechanics

Dongjoo Kim - One of the best experts on this subject based on the ideXlab platform.

  • improvement of the biaxial flexure Test method for concrete
    Cement & Concrete Composites, 2013
    Co-Authors: Jihwan Kim, Dongjoo Kim
    Abstract:

    Abstract The biaxial flexure Test (BFT) method for the biaxial tensile strength of concrete has been improved. To ensure the equi-biaxial stress condition during the Test, the geometry of the specimen, proper treatment of the specimen surface, and the support conditions were proposed. The biaxial flexural strength of concrete was measured with the improved biaxial flexure Test method. The coefficient of variation (c.o.v) of the biaxial flexure Test method is comparable to that of the four-Point Bending Test and ASTM C 1550. The improved biaxial flexure Test provides a practical and reliable means of determining the biaxial flexural strength of concrete. The biaxial tensile strength given by the biaxial flexure Test method and the ASTM C 1550 method is greater than the uniaxial tensile strength using the four-Point Bending Test method.