scholarly journals Hierarchical Composites with Electrophoretically Deposited Carbon Nanotubes for In Situ Sensing of Deformation and Damage

Nanomaterials ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 1262
Author(s):  
Colleen M. Murray ◽  
Sagar M. Doshi ◽  
Dae Han Sung ◽  
Erik T. Thostenson
Keyword(s):  
Carbon Nanotubes ◽  
Electrical Response ◽  
Crack Density ◽  
Aqueous Dispersion ◽  
Transverse Cracks ◽  
Damage State ◽  
Transverse Cracking ◽  
Hierarchical Composites ◽  
Acoustic Emission Sensors ◽  
In Situ Sensing

As composites are used increasingly in structural components, novel techniques for detecting micro-scale damage are required. Their nanoscale size and high aspect ratio allow carbon nanotubes to create electrically conductive pathways that enable sensing. In this work, carbon nanotubes are deposited onto glass fabric using electrophoretic deposition to create hierarchical composites. Polyethylenimine functionalized carbon nanotubes are deposited from an aqueous dispersion using an electric field. Symmetric cross-ply composites are investigated as a model system to demonstrate the ability to detect incipient damage and transverse microcracks. The specimens are subjected to tensile loading, and a resistance increase is observed because of two key mechanisms—A reversible change in nanotube-nanotube tunneling gaps due to elastic straining of the network and a permanent severing of paths in the conducting network due to formation of transverse cracks in the 90° plies. By analyzing the electrical response, the damage state can be identified. Acoustic emission sensors are used to validate the results. The strength and Young’s modulus of the composites with integrated carbon nanotubes are similar to the control specimens. Crack density measurements using edge replication reveal that transverse cracking can be suppressed, demonstrating multi-functionality with improved damage tolerance and integrated sensing.

scholarly journals Influence of Maleic-Anhydride Polypropylene on Transverse Cracking in Glass Fibre-Reinforced Polypropylene Cross-Ply Laminates

1994 ◽  
Vol 3 (5) ◽  
pp. 096369359400300 ◽  
Author(s):  
M.J.A. van den Oever ◽  
T. Peijs
Keyword(s):  
Maleic Anhydride ◽  
Glass Fibre ◽  
Saturation Level ◽  
Shear Lag ◽  
Transverse Cracks ◽  
Damage State ◽  
Transverse Cracking ◽  
Glass Fibre Reinforced ◽  
Polypropylene Matrix ◽  
Fibre Matrix

This study investigates the influence of improved adhesion, resulting from maleicanhydride modification of the polypropylene matrix, on transverse cracking in 0/906/0 glass fibre-reinforced polypropylene laminates. It was shown that the characteristic damage state in cross-ply polypropylene/glass laminates, i.e. the saturation level of transverse cracks, is independent of fibre-matrix adhesion and corresponds very well with a predicted value using a shear-lag analysis.

Evolution of Crack Density in Cross-Ply Laminates - Application of a Coupled Stress and Energy Criterion

2016 ◽  
Vol 713 ◽  
pp. 262-265
Author(s):  
Maria Kashtalyan ◽  
I.G. García ◽  
Vladislav Mantič
Keyword(s):  
Composite Laminates ◽  
Crack Density ◽  
Great Influence ◽  
Energy Criterion ◽  
Matrix Cracking ◽  
Transverse Cracks ◽  
Transverse Cracking ◽  
Finite Fracture Mechanics ◽  
Equivalent Constraint Model ◽  
Constraint Model

The first damage mode to appear in continuous fibre-reinforced composite laminates subjected to in-plane loading is usually transverse cracking, i.e. matrix cracking in the off-axis plies of the laminate. Since the density of transverse cracks has a great influence on the subsequent failure steps like delaminations, it is important to be able to predict it accurately. In this paper, the evolution of crack density with increasing external load is predicted using a combination of the Coupled Criterion of Finite Fracture Mechanics and the Equivalent Constraint Model.

scholarly journals A Study of Matrix Crack Tip Delaminations and their Influence on Composite Laminate Stiffness

1999 ◽  
Vol 8 (4) ◽  
pp. 096369359900800 ◽  
Author(s):  
Maria Kashtalyan ◽  
Costas Soutis
Keyword(s):  
Transverse Crack ◽  
Crack Density ◽  
Crack Tip ◽  
Implicit Functions ◽  
Transverse Cracks ◽  
Transverse Cracking ◽  
Stiffness Properties ◽  
Equivalent Constraint Model ◽  
Constraint Model ◽  
Stiffness Loss

Reduction of the stiffness properties of cross-ply [0m/90n]s laminates due to delaminations, growing at the 0/90 interface from the tips of transverse cracks in the 90° plies and splits in the 0° plies, is analysed by means of a theoretical approach based on the Equivalent Constraint Model (ECM). Reduced stiffness properties of the damaged lamina are derived as explicit functions of the crack density and relative delamination area associated with that lamina and implicit functions of the two damage parameters associated with the neighbouring laminae. Transverse crack tip delaminations are found to cause significant reduction in the laminate shear modulus and Poisson's ratio. Contribution of each damage mode (transverse cracking, transverse crack tip delaminations, splitting and split tip delaminations) into stiffness loss is established.

Cohesive Finite Element Based Modeling of Damage in Composite Materials

2002 ◽  
Author(s):  
Rajesh S. Kumar ◽  
Ramesh Talreja
Keyword(s):  
Finite Element ◽  
Composite Materials ◽  
Composite Laminates ◽  
Damage Evolution ◽  
Crack Density ◽  
Cohesive Zone Modeling ◽  
Cohesive Law ◽  
Transverse Cracks ◽  
Damage State ◽  
Viscoelastic Composite

Damage in composite laminates affects its overall viscoelastic response. Constitutive equations have been developed for composite laminates considering a fixed damage state. A complete description, however, requires suitable damage evolution laws. This paper is focused on studying damage evolution in viscoelastic laminates using a cohesive finite element approach. A two dimensional, four nodded finite element is developed incorporating a rate-independent traction-displacement cohesive law. This element is used in conjunction with plane strain bulk elements behaving in a linear viscoelastic manner to simulate crack evolution between two existing transverse cracks in symmetric cross-ply laminates. The effects of loading strain-rate, ply constraint and initial crack density are studied. This study shows expected trends in the behavior and indicates the suitability of cohesive zone modeling to study damage evolution in viscoelastic composite materials.

Electrical self-sensing of strain and damage of thermoplastic hierarchical composites subjected to monotonic and cyclic tensile loading

2019 ◽  
Vol 30 (10) ◽  
pp. 1527-1537 ◽  
Author(s):  
O Rodríguez-Uicab ◽  
C Martin-Barrera ◽  
A May-Pat ◽  
A Can-Ortiz ◽  
PI Gonzalez-Chi ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Carbon Nanotube ◽  
Electrical Response ◽  
Multiwall Carbon Nanotubes ◽  
Tensile Loading ◽  
Multiwall Carbon Nanotube ◽  
Aramid Fibers ◽  
Hierarchical Composites ◽  
Polypropylene Matrix ◽  
Multiwall Carbon

Electrical monitoring of strain and damage in multiscale hierarchical composites comprising unidirectional aramid fibers modified by multiwall carbon nanotubes and polypropylene as matrix is investigated. The key factor for electrical self-sensing in these thermoplastic composites is the formation of a multiwall carbon nanotube network, which is achieved by using two material architectures. In the first architecture, the multiwall carbon nanotubes are dispersed within the polypropylene matrix, while aramid fibers remain unmodified. The second architecture uses also multiwall carbon nanotube-modified polypropylene matrix, but the aramid fibers are also modified by depositing multiwall carbon nanotubes. Under tensile loading, the electrical response is nonlinear with strain ( ε), and the piezoresistive sensitivity was quantified by gage factors corresponding to low ( ε < 0.25%) and high ( ε > 0.3%) strain regimes. Such gage factors were 4.83 (for ε < 0.25%) and 13.2 (for ε > 0.3%) for composites containing multiwall carbon nanotubes only in the polypropylene matrix. The composites containing multiwall carbon nanotubes in the matrix and fibers presented higher piezoresistive sensitivity, with average gage factors of 9.24 ( ε < 0.25%) and 14.0 ( ε > 0.3%). The higher sensitivity to strain and damage for a specific material architecture was also evident during cyclic and constant strain loading programs and is attributed to the preferential localization of multiwall carbon nanotubes in the hierarchical composite.

A Damage Model Containing Delamination in Composite Laminates

2006 ◽  
Vol 324-325 ◽  
pp. 43-46
Author(s):  
Yu Pu Ma ◽  
Xin Zhi Lin ◽  
Qing Fen Li ◽  
Zhen Li
Keyword(s):  
Composite Laminates ◽  
Damage Model ◽  
Laminated Composite ◽  
Shear Lag ◽  
Analysis Model ◽  
Transverse Cracks ◽  
Transverse Cracking ◽  
Stiffness Reduction ◽  
Laminated Composite Materials ◽  
Modulus Reduction

When stress is high, delaminate damage can be induced by transverse cracks. A complete parabolic shear-lag damage model containing delamination induced by transverse cracks is therefore proposed and applied to predict the stiffness reduction by transverse cracking in cross-ply laminated composite materials. The predictions of the complete parabolic shear-lag analysis model, the incomplete parabolic shear-lag analysis model, and the complete parabolic shear-lag damage model containing delamination proposed in this paper have been compared. Results show that the young’s modulus reduction values obtained by our analysis model are better agreement with the experimental ones than other models.

scholarly journals The Piezoresistive Highly Elastic Sensor Based on Carbon Nanotubes for the Detection of Breath

Polymers ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 713 ◽  
Author(s):  
Romana Daňová ◽  
Robert Olejnik ◽  
Petr Slobodian ◽  
Jiri Matyas
Keyword(s):  
Carbon Nanotubes ◽  
Flexible Substrate ◽  
Thermoplastic Polyurethane ◽  
Aqueous Dispersion ◽  
Portable Devices ◽  
Multiwalled Carbon ◽  
Novel Technique ◽  
Subsequent Application ◽  
Wearable Electronic ◽  
Type Frequency

Wearable electronic sensor was prepared on a light and flexible substrate. The breathing sensor has a broad assumption and great potential for portable devices in wearable technology. In the present work, the application of a flexible thermoplastic polyurethane/multiwalled carbon nanotubes (TPU/MWCNTs) strain sensor was demonstrated. This composite was prepared by a novel technique using a thermoplastic filtering membrane based on electrospinning technology. Aqueous dispersion of MWCNTs was filtered through membrane, dried and then welded directly on a T-shirt and encapsulated by a thin silicone layer. The sensing layer was also equipped by electrodes. A polymer composite sensor is capable of detecting a deformation by changing its electrical resistance. A T-shirt was capable of analyzing a type, frequency and intensity of human breathing. The sensitivity to the applied strain of the sensor was improved by the oxidation of MWCNTs by potassium permanganate (KMnO4) and also by subsequent application of the prestrain.

Stress Distribution on the Cracked Sandwich Plate with Non Linear Thermal and Moisture Concentration

2021 ◽  
Vol 32 ◽  
pp. 45-62
Author(s):  
Mohamed Khodjet Kesba ◽  
Noureddine El Meiche ◽  
A. Benkhedda
Keyword(s):  
Stress Distribution ◽  
Concentration Distribution ◽  
Sandwich Plate ◽  
Crack Density ◽  
Transverse Cracks ◽  
Linear Distribution ◽  
Moisture Concentration ◽  
Linear Temperature ◽  
Stiffness Reduction ◽  
Non Linear

The influence of linear and non-linear temperature and moisture concentration distribution on the stress distribution was studied for metal/ceramic sandwich plate with transverse cracks. An interlaminar adhesive layer between two different layers is taken into account which transferring the normal stress and the interlaminar shear stress. The validation of the used model was done with the comparison of the stiffness reduction as a function of crack density and the experimental data. A comparison showed that a satisfactory qualitative and quantitative agreement was obtained. The temperature and moisture concentration variation are studied using the linear and non-linear distribution around the cracks to predict the stress distributions along the axis x. Finally, it observed through this study that the variations of the thermal and moisture concentration distribution largely impact the stress distribution for a sandwich plate with transverse cracks in the central layer and also with different mechanical properties of each layers.

Stabilized aqueous dispersion of multi-walled carbon nanotubes obtained by RF glow-discharge treatment

2009 ◽  
Vol 11 (7) ◽  
pp. 1817-1822 ◽  
Author(s):  
Leron Vandsburger ◽  
Edward J. Swanson ◽  
Jason Tavares ◽  
Jean-Luc Meunier ◽  
Sylvain Coulombe
Keyword(s):  
Carbon Nanotubes ◽  
Glow Discharge ◽  
Aqueous Dispersion ◽  
Discharge Treatment ◽  
Multi Walled Carbon Nanotubes ◽  
Rf Glow Discharge ◽  
Walled Carbon Nanotubes
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