Generating dynamic crack growth resistance curves for fiber-reinforced concrete

Fiber-reinforced concrete is known to have a greater resistance to impact and impulsively applied loads than its plain counterpart. However, the exact mechanisms that contribute to this enhanced resistance are not known, and fundamental fracture tests are necessary to develop such an understanding. To this end, an instrumented drop weight impact machine was configured to perform dynamic fracture studies on fiber-reinforced concrete specimens. Cracks were allowed to open in Mode I under high rates of loading using contoured double cantilever beam specimens. The paper describes the test apparatus, instrumentation, calibration, and the data analysis. The technique was applied to investigate dynamic crack growth in two types of fiber-reinforced concrete composites: one with steel macrofiber and the other with polypropylene macrofiber. Companion tests were performed under quasi-static conditions. Test data indicate that the proposed technique can be successfully applied to study dynamic crack growth in cement-based composites and to further enhance their properties.