Effects of Voids on Concrete Tensile Fracturing: A Mesoscale Study

Xu, Lei; Huang, Yefei

doi:10.1155/2017/7989346

Cited by 9 publications

(4 citation statements)

References 27 publications

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“…They found the aspect of brittle cavitation in an epoxy matrix for the transverse crack in fiber-matrix debond, also obtaining that due to voids transverse cracks arise in fiber epoxy composites. Xu and Huang proposed a mesoscale FE model with voids and illustrated a tensile fracture with a concrete’s continuum damage model [ 93 ]. They obtained that voids affect pre-peak and post-peak conditions, and two types of failure modes (single and two macro-scale crack) were summarized.…”

Section: Failure Theoriesmentioning

confidence: 99%

Review and Suggestion of Failure Theories in Voids Scenario for VARTM Processed Composite Materials

2021

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Fiber-reinforced composite structures are used in different applications due to their excellent strength to weight ratio. Due to cost and tool handling issues in conventional manufacturing processes, like resin transfer molding (RTM) and autoclave, vacuum-assisted resin transfer molding (VARTM) is the best choice among industries. VARTM is highly productive and cheap. However, the VARTM process produces complex, lightweight, and bulky structures, suitable for mass and cost-effective production, but the presence of voids and fiber misalignment in the final processed composite influences its strength. Voids are the primary defects, and they cannot be eliminated completely, so a design without considering void defects will entail unreliability. Many conventional failure theories were used for composite design but did not consider the effect of voids defects, thus creating misleading failure characteristics. Due to voids, stress and strain uncertainty affects failure mechanisms, such as microcrack, delamination, and fracture. That’s why a proper selection and understanding of failure theories is necessary. This review discusses previous conventional failure theories followed by work considering the void’s effect. Based on the review, a few prominent theories were suggested to estimate composite strength in the void scenario because they consider the effect of the voids through crack density, crack, or void modeling. These suggested theories were based on damage mechanics (discrete damage mechanics), fracture mechanics (virtual crack closure technique), and micromechanics (representative volume element). The suggested theories are well-established in finite element modeling (FEM), representing an effective time and money-saving tool in design strategy, with better early estimation to enhance current design practices' effectiveness for composites. This paper gives an insight into choosing the failure theories for composites in the presence of voids, which are present in higher percentages in mass production and less-costly processes (VARTM).

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Section: Failure Theoriesmentioning

confidence: 99%

Review and Suggestion of Failure Theories in Voids Scenario for VARTM Processed Composite Materials

2021

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“…After determining the gradation and volume fraction of the coarse aggregate along with the shape and size of the concrete specimen, the required concrete mesostructure can be randomly generated by employing the widely used parameterized modeling approach based on the take-and-place method [33]. In this study, the versatile mesostructure generator for concrete (MGC), developed using MATLAB, is used to generate the following required HFGC specimens and the wet-screened concrete specimens, and the detailed procedure and implementation of MGC can be referred to our previous work [34]. Figure 2(a) sketches an example of a hydraulic four-graded concrete specimen with the coarse aggregate volume fraction A F 50% and the proportions of the small, medium, large, and extra-large coarse aggregates set to 0.25, 0.25, 0.2, and 0.3, respectively, while an example of a hydraulic three-graded concrete specimen with the same coarse aggregate volume fraction and the proportions of the small, medium, and large coarse aggregates set to 0.3, 0.3, and 0.4, respectively, is illustrated in Figure 2…”

Section: Mesostructure Generation Of Hfgc and Wet-screened Concretementioning

confidence: 99%

“…en, the thin-layer four-node elements with a uniform thickness approximately set to 100 μm according to the experimental observation [35], which are used to model ITZs, are automatically inserted between coarse aggregate elements and their surrounding mortar elements. Following this strategy, a mesh generator is developed using MATLAB and Python, with the detailed procedure and implementation described in the previous study [34]. Moreover, in order to ensure the accurate representation of the geometric characteristics of coarse aggregates and meanwhile to generate a computationally less demanding FE model, the distance between two neighbouring seeds along the edges of coarse aggregates and the boundary of the specimen, which controls the average element size (or mesh density) to a great extent, is set to 0.4 times of the minimum size of the coarse aggregate.…”

Section: Mesh Discretizationmentioning

confidence: 99%

Comparisons of Tensile Fracturing Behaviors of Hydraulic Fully Graded and Wet‐Screened Concretes: A Mesoscale Study

Jin

Jing

et al. 2018

Advances in Materials Science and Engineering

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e widely used wet-screening method in the experimental testing of hydraulic fully graded concrete inevitably results in a gap between the real mechanical parameters of hydraulic fully graded concrete specimens and those of the corresponding wet-screened specimens and therefore necessitates the comparative study on their mechanical behaviors. To this end, a two-dimensional mesoscale modeling methodology is developed for simulating the tensile fracturing behaviors of hydraulic fully graded and wet-screened concretes, and extensive Monte Carlo simulations are performed. e individual effects of specimen size variation, variation of gradation and volume fraction of coarse aggregates, and the weaker interfacial transition zones surrounding the large coarse aggregates to be removed by wetscreening are detailed followed by the discussion on the combined effect of these three main factors. All the mean values of the macroscopic mechanical parameters related to tensile fracturing behaviors are found to show significant change in response to wetscreening, and the underlying differentiation mechanism and governing factor(s) are identified. Furthermore, it is shown that the randomness of the investigated parameters can be roughly described by the Gaussian distribution, and the dispersion of each of the investigated parameters of hydraulic fully graded concrete is higher than that of the corresponding wet-screened concrete.

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“…At first, concrete heterogeneity is considered as three phases, namely coarse aggregate, mortar, and ITZ [2,3]. The geometry [4][5][6], volume ratio [7,8], and size distribution [9,10] of coarse aggregates affect the mechanical behavior of concrete. The geometry of coarse aggregate was considered to be circular, elliptical, or polygonal, which was found to be sensitive to the tensile strength of concrete [6].…”

Section: Introductionmentioning

confidence: 99%

The Effects of Stochastic Circular Pores on Splitting Tensile Behavior of Concrete Based on the Multifractal Theory

Wang,

Tao

2023

Fractal Fract

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Concrete naturally contains a large number of circular-like stochastic pores which weaken the tensile strength of concrete and change the crack propagation path. This study investigates the influences of the size distribution and the spatial distribution of stochastic pores on the fracture behavior of concrete based on the splitting tensile test. The mesoscale model of concrete containing coarse aggregate, mortar, interface transition zone (ITZ), and circular pores is established to simulate the crack initiation, propagation, and coalescence of concrete. Concrete samples with a single hole are prepared to verify the effectiveness of the numerical simulation method. Numerical tests are conducted on numerous mesoscale concrete samples with various porosities, pore size distributions, and pore spatial distributions. The numerical simulation results indicate that the tensile strength decreases with the increase of pore size at the same porosity. Based on multifractal theory, a quantitative indicator to describe the spatial distribution uniformity of concrete stochastic pores is proposed. There is a positive correlation between the spatial distribution uniformity of stochastic pores and the tensile strength. The stochastic circular pores can have a profound effect on the concrete’s fracture pattern, which results in three typical macro-crack patterns in the numerical simulation of the splitting tensile test. The presented results deepen the understanding of the influence of stochastic circular pores on the tensile mechanical properties of concrete and provide a reference for the design of concrete structures.

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Effects of Voids on Concrete Tensile Fracturing: A Mesoscale Study

Cited by 9 publications

References 27 publications

Review and Suggestion of Failure Theories in Voids Scenario for VARTM Processed Composite Materials

Review and Suggestion of Failure Theories in Voids Scenario for VARTM Processed Composite Materials

Comparisons of Tensile Fracturing Behaviors of Hydraulic Fully Graded and Wet‐Screened Concretes: A Mesoscale Study

The Effects of Stochastic Circular Pores on Splitting Tensile Behavior of Concrete Based on the Multifractal Theory

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