Structural strengthening and damage behaviors of hybrid sprayed fiber-reinforced polymer composites containing carbon fiber cores

With advantages in sustainability, low thermal conductivity, and self-weight, the foamed cement-based composites have captured tremendous attention in various low strength structural and nonstructural applications. This paper aimed to investigate the effects of the short polypropylene fibers on the quasi-static compression performance of the ultra-low-weight foamed cement-based composites. The results show that the elasticity modulus, peak strength, and ultimate linear strength of the fiber-reinforced composites are increased by 208%, 42%, and 71%, respectively. The plateau stress and the densification strain energy of fiber-reinforced composites are improved by up to 49% and 47%. Simultaneously, the failure mode of the fibrous sample is altered from a brittle behavior to plastic behavior. The significance of this work shows that short synthetic fibers can improve the compressive capacity considerably, turning out to be an effective strategy for obtaining higher mechanical strengths associated with ultra-low-weight typical cement-based elements. According to the experiment results, a constructive damage model is carried out to describe the compressive properties of short PP fiber-reinforced composites. Thus, such theoretical curves can describe the compression behavior successfully and can be potentially applied in practical project and numerical simulation. This work can also be useful toward the foundation of optimal design for toughening behavior in fiber-reinforced lightweight cement elements.

Section: Introductionmentioning

confidence: 99%

Compressive behaviors of ultra-low-weight foamed cement-based composite reinforced by polypropylene short fibers

Yang

Zhou

Deng

et al. 2020

“…Fire accidents present challenges to the safety and operation of civil engineering structures during construction and services, such as high-rise buildings and underground structures (Chen et al, 2016;Ju and Wu, 2015;Kale and Ostoja-Starzewski, 2016;Park et al, 2016;Wu and Ju, 2016;Yan et al, 2017). Mechanical degradation of concrete exposed to high temperatures has been taken into consideration on the fire-resistant design of fiber-reinforced composites (Xiao and Ko¨nig, 2004;Ziao et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

A novel multi-scale model for predicting the thermal damage of hybrid fiber-reinforced concrete

Zhang

Zhu

et al. 2019

A multi-scale micromechanical model is proposed to predict the damage degree of hybrid fiber-reinforced concrete under or after high temperatures. The thermal degradation of hybrid fiber-reinforced concrete is generally composed of the damage of the cement paste caused by thermal decomposition and thermal incompatibility, the deterioration of aggregates and fibers, and the interfacial damage between aggregates and the matrix. In this multi-scale model, four levels of hybrid fiber-reinforced concrete structures are considered when the thermal damage degree is derived; namely, the equivalent calcium silicate hydrate (C–S–H) product level, the cement paste level, the concrete level, and the hybrid fiber-reinforced concrete level. At the cement paste level, thermal decompositions of C–S–H product and calcium hydroxide are taken into account. In addition, a dimensionless parameter of the crack density is introduced to represent the thermal cracking of the matrix. At the concrete level, the interfacial damage of aggregates is simulated by a spring–interface model, in which the interfacial parameters are assumed to be functions of temperature. Moreover, at the cement paste level and the hybrid fiber-reinforced concrete level, a sub-stepping homogenization method is proposed to determine the effective properties. Comparisons between previously published experimental data and predictions and discussions illustrate the feasibility of the proposed multi-scale model in predicting thermal damage of concrete and hybrid fiber-reinforced concrete.

“…However, for frozen soils, few attempts were made to consider the microstructures by means of continuum micromechanics and homogenization theory of heterogeneous materials. During the last decades, many researchers have made investigations on unfrozen reinforced composite materials, mainly focusing on the interactions between the matrix and inclusions in micro-scale perspective to simulate the macroscopic stress–strain responses (Ayadi et al., 2018; Chen et al., 2017; Damiani and Sun, 2017; Diamantopoulou et al., 2017; Egner and Ryś, 2017; Ganjiani, 2018; Hassanifard and Feyzi, 2017; Jin and Arson, 2018; Mizuno, 2017; Park et al., 2017; Pupurs and Varna, 2017; Wu and Ju, 2017; Zhang et al., 2017). Sun et al.…”

Section: Introductionmentioning

confidence: 99%

A micromechanics-based elastoplastic constitutive model for frozen sands based on homogenization theory

Liu

2019

A micromechanics-based constitutive model is formulated to describe the nonlinear elastoplastic behaviors of frozen sands. In the model, frozen soils are conceptualized as two-phase materials, in which the first phase is regarded as virgin/undamaged frozen soil specimen including the components of soil particles, ice crystals, and partial water with elastic–brittle behaviors (bonded elements), and the second phase is treated as fully damaged soil sample including soil particles and unfrozen water with elastoplastic behaviors (frictional elements). The interactions between bonded elements and frictional elements are well considered in the representative volume element within the framework of continuum micromechanics and homogenization theory. Moreover, the non-uniform distribution of strain is taken into account and the breakage process is considered due to the structural degradation/loss of ice crystals in the representative volume element. It is found that the ice crystals are gradually breaking up and then melting into unfrozen water with the increase of external loads, so at the moment the bonded elements are considered to transform into frictional elements and then both elements bear the external loads collectively. A novel binary-medium constitutive model is established by the Mori–Tanaka technique and then validated by two groups of laboratory tests about frozen soils and unfrozen sands under conventional triaxial compression conditions. Eventually, the predictions demonstrate that the theoretical calibrations are well in agreement with the available experimental stress–strain responses.