Peiliang Cong

Silane coupling agent grafted graphene oxide and its modification on polybenzoxazine resin

Abstract Graphene oxide (GO), as a two-dimensional carbon material with excellent properties including strong mechanical properties and good thermal resistance, can be used to modify the polybenzoxazine (PBZ) resins. Unfortunately, the poor dispersity of GO is still the main obstacle restricting the effects of GO in PBZ resin. Silane coupling agent, 3-aminopropyltriethoxy-silane (APTS), is a good choice to modify the surface of GO to improve the dispersity and the bridging action between GO and PBZ resin. In this way, not only the poor dispersion of GO in benzoxazine can be overcome, but also the potential of GO, such as good thermal resistance and strong mechanical properties, can be explored during the modification of PBZ resin.

Influence of thickeners on cement paste structure and performance of engineered cementitious composites

Hydroxypropyl methylcellulose (HPMC) and amphoteric polyacrylamide (ACPAM) were respectively used to prepare engineered cementitious composite (ECC) which exhibits strain-hardening behavior under uniaxial tension. The connections between cement paste structure and the performance of the composite in fresh and hardened state were investigated, aiming at achieving the desirable workability at a given solids concentration. The experimental results of viscosity and microstructure of cement pastes show that the intimate connections between flocculation groups lead to the growing increase in viscosity. The results of deformability and fiber dispersion demonstrate that fiber dispersion coefficient is a comprehensive index which can reflect the performance of deformability as well as uniformity. And the desirable fresh mixture can be achieved by optimizing the viscosity of cement paste. At last, the ductile strain-hardening performance of the ECC prepared with HPMC or ACPAM was investigated through uniaxial tensile test.

Damage evolution model of strain hardening cementitious composites under the uniaxial stress state

The deformation and damage behaviors of strain hardening cementitious composites (SHCC) under the uniaxial stress state were investigated in this paper. Two ductile failure-based constitutive models were introduced to describe the uniaxial tension and compression properties of SHCC only using a few parameters. The computation method of model parameters was developed to ease the simulation procedures. Damage evolution of the SHCC was simulated by the formulation of continuum damage mechanics subsequently. The results show that the proposed models fit the stress-strain curves reasonably well, and the damage variables show different growth rules under uniaxial tension and compression. It is concluded that the proposed method can not only simply simulate the constitutive behavior of SHCC with the reasonable accuracy but also capture the characteristic of material degradation.