Cavitation in epoxies under composite-like stress states

Neogi, Anupam; Mitra, Nilanjan; Talreja, Ramesh

doi:10.1016/j.compositesa.2017.12.003

Cited by 27 publications

(10 citation statements)

References 29 publications

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“…It may be seen that the center line is more prone to tensile failure when the 80 mm region on the bottom face of the cube is in the free-boundary condition. In this regard, it should be pointed out that it is well known from the literature that tension in a sample results in cavitation or void nucleation in solid materials (Cristiano et al 2007;Dorfmann 2003;Gent and Lindley 1959;Neogi et al 2018). Therefore, it can be well expected that this tensile wave formed during shock loading of a material will result in void nucleation (cavitation) or an increase in the initial void volume fraction.…”

Section: Resultsmentioning

confidence: 99%

Microstructural Response of Shock-Loaded Concrete, Mortar, and Cementitious Composite Materials in a Shock Tube Setup

Deb

Samuelraj

Mitra

et al. 2019

J. Mater. Civ. Eng.

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Microstructural changes in concrete, mortar, and cementitious composite material were investigated to determine the efficacy of these materials subjected to shock loading. An experimental methodology with the ability to generate reproducible shock waves of specified blast pressure and decay time was used to perform repeatable experiments in the range of trinitrotoluene (TNT) explosion that is unsafe for concrete columns as specified in the FEMA (Federal Emergency Management Agency) guidelines (38 kg TNT at 3.7 m). The changes in the pore volume fraction of the samples before and after shock loading were used to determine the efficacy of the materials subjected to shock loading. The study reveals that even though percentage increase in pore volume fraction before and after shock loading is highest for cementitious materials, its absolute value is low compared to that of control samples, thereby justifying the better performance of cementitious composite materials. Moreover, the size of the pores is also observed to be lower for cementitious composite samples compared to those of the and concrete samples after shock loading in comparison to the control materials in the study. The reason for the better performance of cementitious composite materials can be attributed to an increase in tensile ductility of the sample as a result of fiber addition. Apart from development of a new cementitious material for blast load mitigation, the study also demonstrates the need to consider pore size distribution in equations relating pore volume fraction to strength.

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Section: Resultsmentioning

confidence: 99%

Microstructural Response of Shock-Loaded Concrete, Mortar, and Cementitious Composite Materials in a Shock Tube Setup

Deb

Samuelraj

Mitra

et al. 2019

J. Mater. Civ. Eng.

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“…Moreover, when a polymer matrix composite (PMC) is under external load, the constituent epoxy matrix is under triaxial stress state (or composite like stress state) (Asp et al., 1995, 1996), which is caused and enhanced by the following factors (Fiedler et al., 2001): (i) the difference in fiber and matrix Poisson's ratios causes a triaxial stress state; (ii) the random distribution of the fibers in a composite ply and the presence of thermal residual stresses in the epoxy matrix enhance the triaxial stress state. The presence of triaxial stress state causes the dependency of material strength on the hydrostatic pressure and reduces the ductility of the material significantly (Farbaniec et al, 2013). In specific to the epoxy matrix, the aforesaid statement is corroborated by the recent research work of Neogi et al (2018).…”

Section: Micromechanics Modeling Approachmentioning

confidence: 99%

Computational micromechanical modeling of transverse tensile damage behavior in unidirectional glass fiber-reinforced plastic composite plies: Ductile versus brittle fracture mechanics approach

Sharma

Daggumati

2019

International Journal of Damage Mechanics

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A detailed micromechanical finite element analysis methodology is presented to predict the transverse tensile (fiber perpendicular) failure behavior of a unidirectional (UD) glass fiber-reinforced plastic composite ply. In order to understand the constituent-level stress–strain and damage behavior, finite element analysis is accomplished using representative volume element (RVE) that consists of random fiber distribution as observed in the microscopic image of an actual composite ply. For modeling the fiber/matrix interface failure behavior, cohesive zone module (cohesive surface/cohesive element) of Abaqus® is used. In order to capture the epoxy matrix stiffness and strength degradation, the following two different approaches are used: (i) initially, the linear Drucker–Prager plasticity model in combination with a ductile fracture criterion is used; (ii) later, a brittle failure approach such as the quadratic normal stress criterion within the framework of eXtended finite element method is used. From the detailed micromechanical analysis of the RVE, it is observed that the initial damage in the RVE occurs in the form of fiber/matrix interface decohesion. With increasing tensile load, interface crack propagates and creates a stress concentration region in the matrix material, adjacent to the crack tip. Further load application causes both interface crack tip and matrix stress concentration to move away from the load application direction. As soon as the interface crack tip reaches approximately 60° to 70° away from the load application direction, the conjunction of the matrix damage with the interface crack leads to the RVE final failure. The predicted average stress–strain curves from the above-mentioned two different epoxy matrix failure criterions (ductile and brittle) correlate very well with the experimental results, indicating that the brittle failure behavior of a UD fiber-reinforced plastic composite ply under transverse tensile load is mainly controlled by the fiber/matrix interface properties.

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“…The damage that typically develops in a composite laminate upon being impacted originates from nano-scale defects, and Clyne & Hull [4] have demonstrated very clearly how the fibre/matrix interface in a composite, and the polymeric matrix immediately surrounding the individual fibres, can lead to nano-scale cracks being present. Furthermore, from a study by Neogi et al [5], it appears that the triaxial stress-state near a fibre-matrix interface plays a significant role in such cracking processes, leading to cavitation on a nano-scale. Features on the fibre, due to its surface roughness, with a length-scale of the order of 50-100 nm, and the presence of sizing on the fibre surface can also play a role in the initiation processes of nanoscale cracks [6].…”

Section: Introductionmentioning

confidence: 99%

“…As described above, the numerical model is meso-scale in nature, in which cracks initiate in the CFRP at a nanoscale but then develop into meso-scale damage. Such nano-scale cracks and defects [5][6][7] have been shown to initiate in the matrix around fibres, etc. and these then trigger sub-micrometre intralaminar matrix cracks that initiate and propagate around the impact point.…”

Section: (D) Impact Damage (I) Introductionmentioning

confidence: 99%

“…Furthermore, from a study by Neogi et al . [5], it appears that the triaxial stress-state near a fibre-matrix interface plays a significant role in such cracking processes, leading to cavitation on a nano-scale. Features on the fibre, due to its surface roughness, with a length-scale of the order of 50–100 nm, and the presence of sizing on the fibre surface can also play a role in the initiation processes of nano-scale cracks [6].…”

Section: Introductionmentioning

confidence: 99%

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Experimental and numerical investigations on the impact behaviour of pristine and patch-repaired composite laminates

Liu

Brooks

Hall

et al. 2022

Phil. Trans. R. Soc. A.

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The present paper investigates the impact behaviour of both pristine carbon-fibre-reinforced-plastic (CFRP) composite laminates and repaired CFRP laminates. For the patch-repaired CFRP specimen, the pristine CFRP panel specimen has been damaged by cutting out a central disc of the CFRP material and then repaired using an adhesively bonded patch of CFRP to cover the hole. Drop-weight, impact tests are performed on these two types of specimens and a numerical elastic-plastic, three-dimensional damage model is developed and employed to simulate the impact behaviour of both types of specimen. This numerical model is meso-scale in nature and assumes that cracks initiate in the CFRP at a nano-scale, in the matrix around fibres, and trigger sub-micrometre intralaminar matrix cracks during the impact event. These localized regions of intralaminar cracking then lead to interlaminar, i.e. delamination, cracking between the neighbouring plies which possess different fibre orientations. These meso-scale, intralaminar and interlaminar, damage processes are modelled using the numerical finite-element analysis model with each individual ply treated as a continuum. Good agreement is found between the results from the experimental studies and the predictions from the numerical simulations. This article is part of the theme issue ‘Nanocracks in nature and industry’.

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Cavitation in epoxies under composite-like stress states

Cited by 27 publications

References 29 publications

Microstructural Response of Shock-Loaded Concrete, Mortar, and Cementitious Composite Materials in a Shock Tube Setup

Microstructural Response of Shock-Loaded Concrete, Mortar, and Cementitious Composite Materials in a Shock Tube Setup

Computational micromechanical modeling of transverse tensile damage behavior in unidirectional glass fiber-reinforced plastic composite plies: Ductile versus brittle fracture mechanics approach

Experimental and numerical investigations on the impact behaviour of pristine and patch-repaired composite laminates

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