Evaluation of interfacial debonding of fibre-reinforced polymer using variable angle peel test

This paper presents a new variable angle peel-test setup designed to investigate the interfacial bond of fibre-reinforced polymer (FRP) retrofitted diaphragms of a major Canadian bridge (Champlain bridge) that was in service for nearly six decades. In order to test the efficiency of the newly designed peel test, a total of eight 400 x 152.4 mm x 220 mm concrete blocks were fabricated and strengthened with carbon-FRP sheets on two adjacent sides. One side of each concrete substrate was used to evaluate the peeling force while the adjacent face is used for the determination of the interfacial bond strength through the standardized (ASTM D7522) direct tension pull-off test. The strengthened layer of the peel test was inspected with an infrared camera for signs of debonds at the interface. The peel test is scheduled to be conducted under variable angles from 30-90 degrees. Preliminary experimental results of the peel test at 45 degrees peel angle have shown promising results for a versatile test method for mixed-mode loading. High variation was noticed among the 40 direct tension pull-off samples. Differences in the peel force and direct tension pull-off test are discussed and the modes of failure of the two different tests are presented.