170 / 2022-04-30 13:46:45

Experimental study on mechanical properties of FRP-ECC super tough composite material

Engineered Cementitious Composites (ECC); FRP-ECC super tough composite; FRP sheet-ECC interface performance; Optimized design; Tensile test

Fiber Reinforced Polymer (FRP) is widely used in repairing and strengthening concrete structures due to its light weight, high strength, good corrosion resistance, earthquake resistance and durability. However, in the use of FRP, organic resin is often used as binder, which is easy to occur degradation and other problems, resulting in poor bonding performance of the interface between FRP and concrete, and easy to be deboned. Engineered Cementitious Composites (ECC) is a kind of high ductility material with multi-crack development mode, which can be used as inorganic binder. A new fiber reinforced material can be formed by compounding with FRP. In previous studies, FRP is usually compounded with ECC in the form of grid or braided net. In these two forms, the constraint of latitudinal fiber on meridional fiber exists, which leads to high interface adhesion between FRP and matrix ECC, limiting the ductility of ECC.



In this paper, FRP sheets are used to replace the traditional FRP mesh fabrics and grids. After reasonable calculation and design, the slip of FRP sheets in ECC matrix can be realized under certain conditions. The mechanical properties of FRP and ECC interface were studied and the axial tensile tests were carried out on the designed composite plate (Fig. 1, Fig. 2, Fig. 3, and Fig. 4). Thirteen groups of specimens were designed to study the interface bond performance between fiber and ECC matrix, and to study the influence of different fiber types and different embedding lengths on the drawing load. The test results show that the peak pull-out load increases with the increase of fiber embedment length under the same cross-sectional area and a certain embedment depth, but the fiber breaks when the embedment length exceeds a certain length. The critical embedment length of carbon fiber reinforced composites (CFRP) is 90mm, that of basalt fiber reinforced composites (BFRP) is 30mm, and that of glass fiber reinforced composites (GFRP) is 70mm. When the elastic modulus of fiber increases, the peak drawing load increases.



Seven groups of specimens were designed to study the axial tensile mechanical properties of FRP slate-ECC composites, and the effects of the number of FRP, bond length and FRP reinforcement form (carbon fiber mesh fabric and carbon fiber sheet) were investigated (Fig. 5). The results show that for the number of FRP sheets, the best composite effect is 2 pieces of FRP sheet specimens, 4 pieces of FRP sheet spacing is too small to produce vertical cracks, resulting in matrix damage (Fig. 6).



Through pull-out test, this topic explored the influence of FRP types and embedded length on the interface bond performance, combined with the results of previous tests (ECC configuration, FRP mesh fabric-ECC composite mechanical properties test), carried out theoretical analysis, designed the layout of FRP sheet, proposed technical points. The tensile test of a new type FRP-ECC super tough composite plate was carried out. This research has enriched the theory of FRP-ECC composite materials, and has a good application prospect for reducing the waste of materials in the FRP grid-ECC composite system in engineering. At the same time, as part of the raw materials are replaced by the industrial by-products of fly ash in ECC, ECC raw materials are sustainable and conform to the concept of green ecological ECC, which responds to the task of the building sector under the carbon neutral policy.