Journal ArticleDOI
Determination of cohesive laws of composite bonded joints under mode II loading
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In this article, a data reduction scheme based on equivalent crack length concept was used to obtain the evolution of the fracture energy during the test and a trapezoidal cohesive law was fitted to the experimental one in order to perform numerical simulations using finite element analysis.Abstract:
In this work, mode II cohesive laws of carbon–epoxy composite bonded joints were obtained using the direct method applied to the end notched flexure (ENF) test. The direct method is based on the differentiation of the relation between the evolution of the fracture energy ( J II ) and the crack tip opening displacement in mode II (CTOD II ) during the test. A data reduction scheme based on equivalent crack length concept was used to obtain the evolution of the fracture energy during the test. The method allows overcoming problems related to identification of crack tip in mode II tests and the presence of a non-negligible fracture process zone (FPZ), which both difficult the right estimate of J II . The digital image correlation technique (DIC) was used to monitor the CTOD II , which was synchronized with the load–displacement data. A trapezoidal cohesive law was fitted to the experimental one in order to perform numerical simulations using finite element analysis. The main goal was to validate all the procedure used to get the cohesive laws. The good agreement obtained between the numerical and experimental load-CTOD II curves and between the cohesive laws demonstrates the adequacy of the proposed procedure concerning the evaluation of the composite bonded joints cohesive laws under mode II loading.read more
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Journal ArticleDOI
An investigation of hygrothermal effects on adhesive materials and double lap shear joints of CFRP composite laminates
Abstract: This paper was aimed to investigate the hygrothermal effects on the mechanical behavior of the double lap shear joints of Carbon/Epoxy composite laminates, which were bonded using epoxy adhesive film SY14. First, experimental method was used to evaluate the hygrothermal dependent properties of the adhesive and the static response of composite laminate double lap joints at various environment conditions. The specimens were grouped into room temperature/dry (RD), room temperature/wet (RW), elevated temperature/dry (ED) and elevated temperature/wet (EW). The wet specimens were immersed in deionized water at temperature of 90 °C for 60 h and the elevated temperature is 95 °C. Tensile tests were carried out at room temperature and elevated temperature (95 °C) in a controlled chamber. Results showed that the elastic modulus and tensile strength decreased about 24% and 27% respectively after exposure to humidity environment. And a large degradation was found when exposure to high temperature while the plasticity became notable. The failure modes of the double lap shear joints were studied by visual inspection. It was found that both adhesive and cohesive failure happened for dry specimens at room temperature. While failure modes were dominated by cohesive failure after moisture exposure and adhesive failure at elevated temperature. Second, a finite element model was utilized to simulate the damage evolution of the double lap joints. The moisture diffusion process, swelling stress and thermal stress were included. And hygrothermal dependent cohesive law was considered to study the damage evolution. It revealed that failure modes were highly dependent on the weaker strength of adhesive and cohesive. Moisture absorption caused large degradation in cohesive strength, so the failure modes were mostly cohesive failure. Elevated temperature decreases strength of adhesive seriously, so adhesive failure dominates. Good agreement was achieved between the predicted failure loads and experimental results. And the predicted failure modes were also consistent with the experimental phenomenon.
Journal ArticleDOI
Rate dependent behavior of crash-optimized adhesives – Experimental characterization, model development, and simulation
Michael May,Olaf Hesebeck,Stephan Marzi,Wolfgang Böhme,Jörg Lienhard,Sebastian Kilchert,Markus Brede,Stefan Hiermaier +7 more
TL;DR: In this article, the authors developed a fully rate-dependent constitutive law for cohesive interface elements considering both, the strain rate dependency of the initiation stress and the strain ratio dependency of fracture toughness.
Journal ArticleDOI
A Survey of Computational Models for Adhesion
TL;DR: This work presents a survey of computational methods for adhesive contact focusing on general continuum mechanical models for attractive interactions between solids that are suitable for describing bonding and debonding of arbitrary bodies.
Journal ArticleDOI
Mode-I, mode-II and mixed-mode I+II fracture behavior of composite bonded joints: Experimental characterization and numerical simulation
TL;DR: In this article, the fracture behavior of composite bonded joints subjected to mode-I, mode-II and mixed-mode I+-II loading conditions was characterized by mechanical testing and numerical simulation.
Journal ArticleDOI
Mode II fracture toughness of CFRP as a function of temperature and strain rate
TL;DR: In this article, the influence of temperature and strain rate on the fracture energy in G IIC of composite plates was investigated. And significant influence of the strain rate and temperature on composite materials was found.
References
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Journal ArticleDOI
Two-dimensional digital image correlation for in-plane displacement and strain measurement: a review
TL;DR: In this article, a review of the 2D digital image correlation (2D DIC) technique for displacement field measurement and strain field estimation is presented, and detailed analyses of the measurement accuracy considering the influences of both experimental conditions and algorithm details are provided.
Book
Image Correlation for Shape, Motion and Deformation Measurements: Basic Concepts,Theory and Applications
TL;DR: In this paper, a comprehensive overview of image correlation for shape, motion and deformation measurements is provided. But, the authors do not discuss the effect of out-of-plane motion on 2D measurements.
Journal ArticleDOI
On the Analysis and Design of the End Notched Flexure (ENF) Specimen for Mode II Testing
TL;DR: In this article, an end notched flexure (ENF) specimen is examined as a candidate for measuring interlaminar fracture toughness in skew symmetric loading and a simple design study for sizing the ENF specimen to minimize geometric nonlinear response and to avoid nonlinear material behavior or flexural failure is presented.
Journal ArticleDOI
The use of full-field measurement methods in composite material characterization: interest and limitations
TL;DR: An overview of the use of full-field measurement techniques for composite material and structure characterization reported in the recent literature is presented in this article, where the features of the main types of measurement techniques are first briefly described.
Journal ArticleDOI
Numerical simulations of adhesively-bonded beams failing with extensive plastic deformation
TL;DR: In this article, an embedded process zone (EPZ) model was used to study the coupling between fracture of the interface and plastic deformation of the adherends in an adhesively-bonded joint.