Study On The Low Velocity Impact Of Carbon Fiber/Epoxy Laminates Based On FBG Sensor

Carbon fiber reinforced composites have been widely used in the field of aerospace and other civilian areas. However the internal structures of the composites prone to cause damage such as matrix cracking and delamination by the low velocity impact. And these damages, which cannot easily been found in the routine testing, would weak the structural strength and short the life span significantly. Therefore efficient non-destructive testing methods for the real-time monitoring of the internal structure are importment. Due to Fiber Bragg Grating (FBG) sensors’advantages, such as low cost、 small size and good anti-interference, they have been more and more widely used in the non-destructive testing of carbon fiber reinforced composites.In this paper, carbon fiber/epoxy laminates are made by the method of autoclave molding. And in this process, Fiber Bragg Grating (FBG) sensors are embedded in composite laminates. Besides, the tests of mechanical properties of the composite laminates, such as tensile and bending are carried out. The results show that the compatibility between FBG sensors and composite laminates is good, and FBG sensors can accutately reflect the changes of the internal stress of composite laminates.In order to study the affects of low velocity impact to carbon/epoxy laminates using FBG sensors, first composite laminates are impacted with different impact energies, the result shows that FBG sensors’wavelength shift differently as the impact energies are different. That is to say, changes of wavelength of the FBG sensors can reflect the degree of damage in composite laminates. Then the influence of the distances between FBG sensors and impacting location have been studied, the conclusions can been summarized that the location of impact can be determined by the changes of wavelength of FBG sensors. Besides cumulative impact on the carbon/epoxy laminates has been studied in this paper, and FBG sensors can effectively determine the internal damage of carbon/epoxy laminates. In conclusion, FBG sensors are an effective means of non-destructive testing of carbon fiber reinforced composites.