Direct tension and fracture resistance curves of ultra high performance marine composite materials

Fracture behavior is one of the most important,yet still little understood properties of ultra-high performance cementitious composites(UHPCC),a new marine structural engineering material. Research on the fracture and direct tension behavior of UHPCC was carried out.The constitution law of UHPCC was divided into three phases:pre-partial debonding,partial debonding,and pullout phases.A direct tension constitution law was constructed based on the proposed fiber reinforcing parameter as a function of fiber volume fraction,fiber diameter and length,and fiber bonding strength.With the definition of linear crack shape,the energy release rate of UHPCC was derived and the R-curve equation was calculated from this.Loading tests of UHPCC using a three-point bending beam with an initial notch were carried out.The predictions from the proposed R-curve were in good agreement with the test results, indicating that the proposed R-curve accurately describes the fracture resistance of UHPCC.Introduction of a fiber reinforcement parameter bridges the fracture property R-curve and micro-composites' mechanics parameters together.This has laid the foundation for further research into fracture properties based on micro-mechanics.The proposed tension constitution law and R-curve can be references for future UHPCC fracture evaluation.