ORCID Profile
0000-0001-7393-4363
Current Organisation
Delft University of Technology
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Publisher: Elsevier BV
Date: 04-2015
Publisher: SAGE Publications
Date: 21-12-2011
Abstract: This article presents progressive failure analysis of double-notched carbon/epoxy composite laminates with different scales. A numerical analysis strategy based on material property degradation method (MPDM) and cohesive elements (CE) is developed to model progressive failure of scaled double-notched composite laminates, where the material property degradation method is used to model the intralaminar failure and the cohesive elements are employed to account for the delamination at the interfaces. Different failure theories are considered in the material property degradation method–cohesive element approach and a comparative study of these failure theories is presented. The mesh dependency of the material property degradation method–cohesive element approach is investigated with different notch and element types for the double-notched composite laminates. Size scaling effects are also studied by traditional fracture models and the material property degradation method–cohesive element approach, significantly revealing a trend in strength reduction of notched composites with increasing specimen size. The predictions are compared with the experimental results and reasonably good agreement is observed.
Publisher: Elsevier BV
Date: 08-2016
Publisher: Elsevier BV
Date: 03-2014
Publisher: Elsevier BV
Date: 04-2017
Publisher: Elsevier BV
Date: 09-2014
Publisher: Elsevier BV
Date: 02-2017
DOI: 10.1016/J.ULTRAS.2016.09.019
Abstract: Linear ultrasonics methods based on the principle of reflection, transmission, dissipation of sound waves have been traditionally used to detect delaminations in composite structures. However, when the delamination is in very early stages such that it is almost closed, or closed due to a compressive load, the linear methods may fail to detect such cases of delaminations. Nonlinear acoustics/ultrasonics have shown potential to identify damages in composite structures which are difficult to detect using conventional linear ultrasonic methods. The nonlinear method involves exciting the structure with a sinusoidal signal of certain (or multiple) frequency and observing the vibrations of the structure. The vibrations of the damage region differ significantly from intact regions and can be used to identify the damage. However due to the complex and varying nature of the nonlinear phenomena created by the interaction between the exciting signal and the damage, there are many variables at play which can lead to success or failure of the method. While experiments lead to the establishment of the method to be used as a damage detection technique, numerical simulations can help to explain the various phenomena associated with nonlinearity. This work presents a quick approach to model the nonlinear behavior caused by closed delaminations. The model is validated with a previously available approach for nonlinear vibrations modeling and a comparison is made between the two. The local nature of the nonlinearity enables to map out the area of damage in the structure. Additionally, a few parametric studies are performed to study the effect of various parameters related to the nonlinear phenomenon.
Publisher: SAGE Publications
Date: 15-07-2016
Abstract: The strength prediction of open-hole fibre-reinforced composite laminate under compression is very important in the design of composite structures. The modelling of fibre, matrix damage and delamination plays an important role in the understanding of the damage mechanics of laminate under open-hole compression. In this article, a progressive damage model for open-hole compression that is based on continuum shell elements and cohesive elements is established to model in-plane damage and delamination, respectively. The damage mechanics of sublaminate-scaled laminates with ply sequence [45/0/−45/90] ms and ply-level-scaled laminates with ply sequence [45 n /0 n /−45 n /90 n ] s are investigated by our proposed model. The Tsai-Wu and Hoffman failure criteria are employed for the determination of matrix damage initiation. Compared with the experiments, the numerical results using the Tsai-Wu criterion exhibit better accuracy regarding open-hole compression strength prediction and failure modes simulation.
Publisher: Elsevier BV
Date: 11-2016
Publisher: Elsevier BV
Date: 04-2015
Publisher: Elsevier BV
Date: 04-2013
Publisher: Acoustical Society of America (ASA)
Date: 04-2017
DOI: 10.1121/1.4981133
Abstract: Vibro-acoustic modulation (VAM) is a form of a non-destructive testing technique used in nonlinear acoustic methods for the detection of defects. It comprises of exciting the structure with a dual frequency sinusoidal signal and studying the interaction of this wave with the underlying defect. In this work a theoretical study on the mechanics of VAM is presented for a generic material body. The roles of different types of defect on the response of the material are analyzed. The theoretical analysis shows the origins of the nonlinear frequencies in the form of higher harmonics and sidebands commonly observed in the output response of VAM excitation. In addition, the analysis provides insights on the relationships between the magnitudes of the nonlinear responses and those of the input vibrations, and on the physical origins of the nonlinear responses. For a physical visualization of the nonlinear vibrations associated with the theory a finite element analysis of VAM is also performed. The model looks into the plausibility of using VAM for the mapping of damage in physical structures. The model is also used to investigate the effects of the defect size and defect depth on the nonlinear mechanism of VAM.
Publisher: SAGE Publications
Date: 28-07-2016
Abstract: In this paper we employ a nonlinear acoustic method, namely, the vibro-acoustic modulation method, for the detection of delamination and kissing bond in composites. Both a (large- litude and low-frequency) pumping wave and a (low- litude ultrasound) probing wave are used to vibrate the structure. Permanently bonded piezoceramic transducers are used for both excitation and measurement. A side-band ratio is used to estimate the extent of nonlinear interactions between the two input waves in the structure. Current results show that the proposed method successfully differentiates the intact specimens from both the delamination and the kissing bond specimens used in this study.
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Boyang Chen.