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Ceramics and Composites
Published in Yip-Wah Chung, Monica Kapoor, Introduction to Materials Science and Engineering, 2022
Here, a second phase is introduced into the ceramic matrix in the form of fibers or particulates (Figure 6.11). The second-phase material increases the fracture toughness through three mechanisms: Crack deflection: If the second-phase material is stronger than the matrix, it will deflect cracks. With sufficient concentration of second-phase particles, cracks zigzag within the material, thus increasing the energy required to propagate the crack through the matrix.Fiber pull-out: During tensile deformation, fibers may fracture or be pulled out of the matrix. Depending on the bonding characteristics between the matrix and fibers, the pull-out process requires either overcoming the friction or breaking bonds at the fiber-matrix interface.Crack bridging: Second-phase fibers can form bridges across the opening crack. In order for the crack to propagate, additional energy must be dissipated to break the fibers, or pull them out of the matrix.
An experimental study on the effects of introducing carbon nanotube on low velocity impact behavior of carbon/aramid fiber reinforced intra-ply hybrid composites
Published in The Journal of The Textile Institute, 2023
Farzin Azimpour-Shishevan, M.A. Mohtadi-Bonab
All failure types in fabricated CAFRP composite are only observed at the contact region of the impactor to the specimen because of low velocity impact. In low velocity impact, the damage extension occurs by nucleation and propagation of the matrix crack (Aslan et al., 2003; Soutis & Curtis, 1996; Zhang et al., 2021). It is worth-mentioning that the existence of the matrix crack does not influence the toughness and stiffness of the composite. The delamination which is considered as the critical failure mode after impacting propagates in the region of the impacted surface due to the presence of the transverse shear stresses (Hajikazemi et al., 2020; Ouyang et al., 2021; Zhou et al., 2021). The nucleation and propagation of delamination degrades the stiffness and eventually it results in the failure of the composite structure. The damage will later join with other failure types with the introduction of considerable fiber damage, which begins with fiber cracking and develops into fiber fracture and fiber pullout (Hajikazemi et al., 2020). As shown in Figure 8a and b, the delamination, fiber pull and fiber breakage are recognized as the important failure modes in these materials. It should be implied that the delamination occurred due to mode II of interlaminar shear stresses which was generated by the bending of the laminate. Moreover, the fiber-pull out happened because of low adhesion of fibers and matrix and fiber breakage is produced by the high through thickness stresses. It should be considered that fiber debonding was occurred between aramid yarns during the energy dissipation of low velocity impact test.
Effects of Shrinkage Reducing Admixture and Polypropylene Fiber Utilization on Some Fresh State, Mechanical and Durability Properties of Khorasan Mortar
Published in International Journal of Architectural Heritage, 2022
Tuğçe İsafça-Kaya, Kemal Karakuzu, Süleyman Özen, Ali Mardani, Adem Doğangün
Different results were obtained in the literature by using fiber and SRA together. Yoo et al. (2015) stated that the SRA utilization leads to an increase in the porosity in the zone between the fiber and matrix. Thus, the flexural strength of high-strength concrete mixtures was negatively affected. In addition, as the SRA reduced the shrinkage, the radial confinement pressure forming the frictional bond between the fiber and the matrix decreased. This situation significantly reduces the resistance to fiber pull-out and adversely affects the strength. In contrast to these findings, some researchers (Soliman and Nehdi 2014; Wang et al. 2013) reported that the compressive strength of mixtures containing fiber and SRA was higher than that of the mentioned materials separately. Because the SRA reduces the contact angles between the fibers and the solution. This situation leads to improve wettability by allowing the fiber to make better contact with the matrix. This helps to keep compact the zone between fibers and matrix. As indicated in Figure 9, the flexural and compressive strengths obtained in mixtures containing fiber and SRA differ from the strength results shown in Figures 6 and 8. The addition of fiber and SRA in some mixtures improved the strength of specimens. However, voids formed in some mixtures where fiber agglomeration was dominant had a negative effect on strength. For these reasons, the strengths of the specimens containing fiber and SRA were found to be incompatible with the results of the specimens containing fiber and SRA separately.
Composite material from waste poly (ethylene terephthalate) reinforced with glass fiber and waste window glass filler
Published in Green Chemistry Letters and Reviews, 2023
Biruk Gedif Worku, Tessera Alemneh Wubieneh
The process of fiber pull-out accounts for a sizeable portion of the energy absorption during impact in the majority of fiber-filled composites. The work required to debond the fibers from the matrix and the work required to pull the fibers out of the matrix against friction together make up the fracture energy. When the energy was transferred to the composite, the weak surface adhesion between the fiber and matrix caused the crack to begin. Due to inadequate interfacial adhesion between the fiber and matrix, the impact strength drops (21,35,36).