분포형 광섬유 센서를 이용한 복합소재 DCB 시편의 균열 길이 측정

초록

Nowadays in the railway industry, composite structure is broadly applied to the car body, bogie frame and collision absorbtion structure and etc. To ensure the safety of these core composite structures, delamination characteristics must be considered first of all. The delamination, space debonding between layer and other layer, is dominated by resin and fragile part that has many possibilities of breakage due to its load bearing power that much less than the reinforced fiber. To evaluate the interlaminar fracture toughness, DCB(Double Cantilever Beam) test is normally conducted. In the conventional DCB test, test is usually conducted by observing the crack’s growth with a microscope, but in this paper, new technique is tried to measure the crack length in real time using optical fiber embedded in the kevlar/epoxy specimen. Crack tip position was monitored using strain distribution field data from the optical fiber and compared with the microscope data. BOCDA (Brillouin Optical Correlation Domain Analysis) technique was used to measure the strain distribution of the optical fiber and spatial resolution, strain accuracy were about 9mm, ±20 each.