Basalt fiber is a kind of high performance fiber material prepared from basalt ore by melting wire drawing process, which has the advantages of non-toxic, excellent mechanical properties, corrosion resistance and so on. It is used to produce fiber reinforced polymer composites (FRP), and has great application value in transportation, construction and other fields. In FRP, the area formed between the fiber surface and the matrix is called the interface. Its main function is to transfer the external load from the polymer matrix to the fiber through the interface, so that the macro properties of FRP can be significantly improved. The structure and properties of the interface are particularly important for the stress transfer process, and the interface debonding between fiber and matrix is the main factor leading to the failure of FRP structure. Therefore, it is of great significance to establish an early warning and monitoring technology for the interface debonding of FRP materials to evaluate the life and service behavior of materials.
Recently, the Environmental Science and Technology Laboratory of Xinjiang Institute of Physics and Chemistry, Chinese Academy of Sciences has established a new method for monitoring interfacial debonding of basalt fiber-reinforced polymer composites. Researchers surveyed the literature and found that the small organic molecule four -(4-nitrobenzene) ethylene (TPE-4N) with aggregation induced luminescence (AIE) effect has the characteristics of fluorescence "switch switching" : The material hardly emits light when it exists in crystalline form, but it emits strong green fluorescence when it is transformed into amorphous state after grinding, and the small molecule has excellent film forming performance on glass, metal and other surfaces. Based on the above phenomena, the basalt fiber coated with TPE-4N was prepared by a simple dip coating process. When the researchers observed the surface morphology of the fibers, they found that TPE-4N molecules formed a uniform coating on the fiber surface, and the fibers glowed bright green fluorescence. After heat treatment at 150 ° C, the TPE-4N coating on the surface of the fiber underwent a phase transition from amorphous state to crystalline state, and the fluorescence was almost completely quenched. The basalt fiber samples after tensile heat treatment were studied, and it was found that there was almost no fluorescence in the sample before tensile treatment, but when the fiber partially fractured under the action of stress, the TPE-4N crystalline coating coated on the fiber surface was damaged and transformed into an amorphous state, which made the sample emit obvious green fluorescence again (Figure A).
Basalt fiber-reinforced FRP (BFRP) samples were prepared by embedding these fibers in a flexible polymer matrix (PDMS), and the fluorescence behavior of BFRP samples under tensile conditions was investigated. The study shows that the debonding strain of TPE-4N/BFRP sample (6.29%) is basically the same as that of BFRP sample (6.93%) (FIG. B), indicating that the introduction of TPE-4N at the interface has little effect on the mechanical properties of BFRP. When the tensile strain of the TPE-4N/BFRP sample reaches 5.25%, the gray value of the sample shows a sudden change (Figure C), which is earlier than the strain of the complete debonding (6.29%), indicating that TPE-4N can be used for early interface debonding warning detection of BFRP materials. The health status of BFRP materials can be evaluated by detecting the intensity of fluorescence signal. This method provides a new way to predict the life of materials in real time.
The research was published in Composites Communications and supported by the Xinjiang Natural Science Foundation.
Using TPE-4N molecule with AIE effect for health monitoring of basalt fiber reinforced composites (A. Changes in fluorescence signal of basalt fiber coated with TPE-4N molecule under different stress conditions; B. Stress-strain curves of different BRFRP materials; C, fluorescence signal changes of TPE-4N and BFRP under different strain conditions).
The article source: - Chinese Academy of Sciences
- China Composite Expo
Post time: Aug-18-2022