Intrinsic fracture toughness of fiber reinforced and functionally graded concretes: An innovative approach

Elakhras, A. A.; Seleem, M. H.; Sallam, Hossam El-Din M.

doi:10.1016/j.engfracmech.2021.108098

Cited by 20 publications

(8 citation statements)

References 44 publications

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“…Unfortunately, such previous work was not only a waste of time and effort but also led the scientific research compass in this field in the wrong direction for solving such problems. The first attempt in the right direction for predicting the fracture toughness of fibrous composite materials was made by Salam and colleagues [34,[36][37][38][39]. Sallam and co-workers [36,39] successfully correlated the mode I fracture toughness of FRC using MC specimens, i.e., correlating a vectorial problem with a crack path independent of the initial crack length by scalar parameters such as Griffith's energy release rate..…”

Section: Hypothesismentioning

confidence: 99%

“…The first attempt in the right direction for predicting the fracture toughness of fibrous composite materials was made by Salam and colleagues [34,[36][37][38][39]. Sallam and co-workers [36,39] successfully correlated the mode I fracture toughness of FRC using MC specimens, i.e., correlating a vectorial problem with a crack path independent of the initial crack length by scalar parameters such as Griffith's energy release rate.. The dilemma of the proposed work is that mixed-mode fracture toughness is a vectorial problem with a crack path dependent on either initial crack length or M e , as shown in Fig.…”

Section: Hypothesismentioning

confidence: 99%

“…Recently, the MC specimen was used to find the intrinsic value of K IC in FRC and FGC for mode I cracked specimens. Elakhras et al [36] used MC specimens to study the size effect on fracture toughness for FRC and FGC. They compared their results with Hillerborg's concept.…”

Section: Introductionmentioning

confidence: 99%

“…As aforementioned, the MC specimen approach could consider the contribution of fiber bridging during the mode I crack propagation in FRC [36][37][38][39]. Checking this potential in mixed-mode MC specimens is an interest leading to a generalized realistic experimental approach.…”

Section: Introductionmentioning

confidence: 99%

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Mixed-mode fracture toughness of high strength FRC: a realistic experimental approach

Hussien

Moawad

Seleem

et al. 2022

Archiv.Civ.Mech.Eng

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Unfortunately, fibrous composite materials' mixed-mode fracture toughness (Keff) was measured using inappropriate through-thickness cracked (TTC) specimens. The problem with such specimens is the ignorance of the fibers in the pre-notch surfaces, i.e., no fiber bridging behind the crack tip. In the present paper, a real Keff of fiber-reinforced concrete (FRC) was experimentally determined using matrix cracked (MC) specimens. Traditional (TTC) specimens were also adopted for comparison. The effect of fiber length (35 mm, 50 mm, and hybrid fibers, 50% from each length) and mode of mixity (Me), Me = 0, 1/4, and 1/2 were studied. Hooked end steel fibers of a volume fraction equal to 1% were used. All cracked beams with a crack-length-to-beam-depth ratio equal to 0.3 were tested under three-point bending in mode I and mixed-mode. The span/depth ratio was equal to two for all specimens. Since there is no equation to predict the Keff of MC specimens and the inapplicability of Griffith's theory to predict the Keff due to the difference in crack paths, new realistic procedures were suggested to overcome this dilemma. The results indicated that MC specimens recorded a lower crack initiation load than the peak load. In contrast, the crack initiation load coincides with the peak load in the case of TTC specimens. This reflected the role of steel fibers behind the crack tip in retarding the specimens to reach their ultimate capacity after crack initiation. Keff increased with increasing Me. Although long fibers recorded higher peak load and energy, their effect on Keff of MC FRC specimens was marginal due to the minor effect of fiber length on the crack initiation loads. The MC specimen is a realistic approach for estimating the Keff of FRC.

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Section: Hypothesismentioning

confidence: 99%

Section: Hypothesismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Mixed-mode fracture toughness of high strength FRC: a realistic experimental approach

Hussien

Moawad

Seleem

et al. 2022

Archiv.Civ.Mech.Eng

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“…Fiber-reinforced concrete has received extensive attention from researchers and engineers, mainly because of its good mechanical and deformation properties. However, the distribution of fibers in concrete has been uniform in the studies on fiber-reinforced concrete thus far [17][18][19][20]. Lai Jianzhong [21] studied the penetration resistance and explosion-proof performance of ultrahigh-performance concrete (UHPC) with a single-layer and functionally graded structure.…”

Section: Introductionmentioning

confidence: 99%

Durability Investigation of Fiber-Reinforced Functionally Graded Concretes in Cold Regions

Jiang¹,

Jin

2022

Applied Sciences

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Introducing the differential design concept of functional gradient into mass concrete structures is a feasible design concept that can meet the requirement of crack resistance and internal hydration heat reduction for mass concrete in cold regions. This study analyzed functionally graded concrete’s long-term performance and durability behavior through experimental tests. Based on various concrete mix proportion designs, six concrete groups were selected to test. The shrinkage performance tests were conducted according to the specifications, and early crack resistance tests were also carried out. In addition, the crack development characteristics of concrete with different mix proportions were compared and analyzed, and the impermeability, frost resistance, and carbonation resistance tests were conducted. The test results show that concrete’s long-term performance and durability can be effectively improved by adopting the functional gradient concrete design. The functional gradient concrete adds an anti-freezing polycarboxylate superplasticizer, steel fiber, and polypropylene fiber. Therefore, it can better meet the actual needs of mass concrete structures in cold regions. The drying and autogenous shrinkage rates of mass concrete structures mixed with a composite water reducer were significantly reduced. As a result, this method effectively improved the microporous structure, reduced the loss of dynamic elastic modulus, and improved the anti-freezing performance of concrete of various strength grades. Furthermore, adding steel-like fiber and monofilament polypropylene fiber to the concrete outside the structure can improve the crack resistance of concrete and effectively inhibit the occurrence and development of dry shrinkage and early cracks. Therefore, it can better meet the actual needs of mass concrete structures in cold areas.

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Effect of micro‐sized luffa cylindrica fibers on the mechanical properties of epoxy epikote 828

Trung,

Huu,

Anh

et al. 2023

Vietnam Journal of Chemistry

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Micro‐sized luffa cylindrica fibers (MLCFs) are made from raw luffa natural fibers from Vietnam and are environmentally friendly while possessing good mechanical strength. This work focuses on the mechanical properties of composite based on epoxy epikote 828 reinforced with MLCFs, particularly the fracture toughness. The results show that the MLCFs content has a great influence on the fracture toughness, especially the critical‐stress intensity factor (KIC) and izod impact strength of composite. Specifically, when using MLCFs reinforced from 0 to 2.0 wt.%, the critical‐stress intensity (KIC) increased from 1.89 to 4.60 MPa.m1/2, while the izod impact strength increased from 3.6 to 7 KJ/m2, respectively. The thermal behavior of the composite reinforced with MLCFs at different contents was determined using thermogravimetric analysis (TGA). The surface fracture structure of the composite samples was determined using scanning electron microscopy (SEM) method.

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Intrinsic fracture toughness of fiber reinforced and functionally graded concretes: An innovative approach

Cited by 20 publications

References 44 publications

Mixed-mode fracture toughness of high strength FRC: a realistic experimental approach

Mixed-mode fracture toughness of high strength FRC: a realistic experimental approach

Durability Investigation of Fiber-Reinforced Functionally Graded Concretes in Cold Regions

Effect of micro‐sized luffa cylindrica fibers on the mechanical properties of epoxy epikote 828

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