Studies On The Pulling Sensibility And Applications Of Carbon Fiber/Silicone Rubber Composites

As a new sensor material, silicone rubber composite has the potential applications in the transport field to monitor and judge small internal deformation of roads and bridges, which could avoid curing after being destroyed and greatly save maintenance costs. In this paper, the electrical properties, mechanical properties, pulling sensibility characteristics and the deformation monitoring in concrete of carbon fiber/silicone rubber composites were studied by experiments and theories, which is beneficial to the development of new sensors through providing experimental and theoretical support. Short carbon fiber is used as conductive filler and two-component room temperature curing liquid silicone rubber is used as matrix. The composite materials were prepared by solvent dilution supplemented assisted by ultrasonic dispersion. It is proved that uniformly dispersed composites with the smooth surface can be prepared by surface pretreatment of carbon fiber.It is shown from the electrical, mechanical and pulling sensibility tests that under normal temperature, there is a significant phenomenon of percolation conductivity and the percolation threshold is only 0.8vol%. When the applied voltage is lower than 10V, the CV curves of composites showed good linearity, obeying Ohm's law. Also, as the temperature increases, the conductivity of composite materials firstly decrease slowly and then sharply drops, and it decreases up to 3~5 orders of magnitude near the critical temperature. The filling of carbon fiber improves their conductive properties as well as the mechanical properties. Dosage of 1.26vol%, the elastic modulus of only 3.3MPa, lower elastic modulus of composite materials ensure that remarkable features of pulling sensibility. Near the percolation threshold, composite materials exhibit the best characteristics of pulling sensibility, pulling sensibility coefficient as high as 25.88. With the number of stretching cycles increasing, pulling sensibility feature is relatively stable.Through theoretical analysis of the relationship between conductive properties and pulling sensibility of composite materials, it is concluded that near the percolation threshold, the conductivity obeysσ=5.6×104(1.008Φ-0.008)2.2136 in law, which provides the theoretical basis for the establishment of pulling sensibility model. Pulling sensibility feature is caused by the change of the percolation threshold in tension. Combining with the conductive mechanism and tests, the conductivity of composite materials obey the law of lg(σ/σ0)=Aεin the small deformation range, which prove that it is a qualified pulling sensibility material.Finally, the deformation monitoring of the composite material in the concrete was studied. It is shown that the resistance-pulling variation of composites and the stress-pulling relationship of the concrete is almost synchronous in uniaxial compression and three-point bending tests. Furthermore different empirical formulas were established to predict the deformation of concrete structures and internal injury. Results show that carbon fiber/silicone rubber composite can serve as an excellent sensor for the deformation monitoring of concrete materials.