Study on the Self-Monitoring of Bending Fatigue Cumulative Damage for Carbon Nanofiber Polyurethane Cement

Abstract

Polyurethane cement (PUC) is a kind of high-strength composite bending and strengthening material that is made by adding an appropriate amount of super fine aggregate, such as cement, into the polyurethane matrix. Carbon nanofiber polyurethane cement (CNFPUC) prepared by adding an appropriate amount of carbon nanofiber (CNF) can significantly reduce the resistivity of PUC. In order to reveal the change regulation of electrical resistivity of CNFPUC under fatigue load, the four-point bending fatigue life test of CNFPUC under different temperatures and stress levels was conducted by using a multifunction test device on a mixture of UTM-30 asphalt. The results showed that the resistivity increased slightly with the increase of bending strain in the process of the CNFPUC bending test, which presented a two-stage trend of a small increase and a sharp increase, and the maximum bending tensile stress was up to 26.65 MPa. Under periodic load, the resistivity increased with the increase of stress level and cycle times. When the damage amount reached 90%, the fatigue resistivity increased sharply, and with the increase of stress level, the effect of temperature on resistivity decreased gradually. This study may provide a theoretical basis for practical engineering applications.

Experimental Study on the Bending Resistance of Hollow Slab Beams Strengthened with Prestressed Steel Strand Polyurethane Cement Composite

“…Although existing reinforcement methods [7][8][9][10][11][12][13] could effectively improve the bearing capacity of old bridges, there are still some limitations in controlling the self-weight of the structure, shortening the reinforcement period and simplifying the reinforcement process. In recent years, polyurethane cement composite, a lightweight and high strength corrosion resistant material [14][15][16][17], has become a hot research topic in the field of bridge reinforcement.…”

Self‐Monitoring of Reinforced Concrete Beam Bending with Carbon Nanofiber Polyurethane Composite

“…(2) e stress-strain curve of the steel bar is based on a double-line model, which is expressed as ε p � ε p (λ) � 6.38λ + 198(0 < λ ≤ 400), 2.53 × 10 − 4 λ + 2λ + 1480(400 < λ ≤ 3000). 􏼨 (8) Substituting formula (8) into formula (7) can obtain M � M(λ), and from adjusting the value of the corresponding variable for the different failure modes, the moment value with the resistance change rate λ as the independent can be obtained. After the CPUC reinforcement, the selfmonitoring function of the beam body can be realized by monitoring the changes in the resistance change rate.…”

“…As people prioritize structural safety and comfort, intelligent materials have attracted increasing attention in the field of civil engineering, and the detection and monitoring of structural health and safety have become an important part of civil engineering, specifically, disaster prevention and mitigation [5][6][7][8].…”

Special Issue on “New Materials and Techniques for Environmental Science”

“…Based on their previous study on the synthesis of CNFPUC materials [10], Yang and Sun contribute another paper on the self-monitoring of bending fatigue cumulative damage of CNFPUC [13], in which detailed characterizations on the resistivity of CNFPUC by adjusting bending strain, stress level, cycle times, and temperate were performed. In addition, the relationship between the fatigue cumulative damage and the change of the resistivity of materials was further analyzed.…”