Effect of Strain Rate on Compression Behavior of Vinyl Ester Resin Casting

Quasi-static and high strain rate compressive experiments on vinyl ester casting were carried out by means of MTS (Material Test System) and Hopkinson bar. The behaviors of the compressed unstable and fracture of the resin casting at different strain rates were investigated.The results indicate that the response behavior of the resin casting is controlled by different mechanisms at different strain rate, and some mechanical properties of vinyl ester casting are rate-dependent: the casting are destroyed in toughness model under strain rate 3.3×10 -4～6.6×10 -3/s, while the casting are destroyed in brittleness model under strain rate 950～5800/s. The yield stress, yield strain energy density are all increased with the increasing strain rates at quasi-static as well as at high strain rates. What is interesting is that the yield strain decreased with the strain rates increasing at quasi-static while increased at high strain rates. It is considered that the casting occurred forcing high elastic deformation at high strain rates. The damage of the specimens is mainly controlled by axial stress before unstable deformation, while mainly controlled by shear stress after unstable deformation, and then developed to fracture finally. This progress is rate-dependent: the development of the cracks inside the castings increased with the strain rate increasing.

Toughening of vinyl ester resins by two-dimensional MXene nanosheets

Two-dimensional nanosheets are highly effective tougheners for vinyl ester resins.The toughening effect is related to the high specific surface area and unique two-dimensional planar structure of the nanosheets.In this study,a coupling agentγ-(2,3-epoxypropoxy)propytrimethoxysilane(Kh-560)was used to modify MXene nanosheets(M-MXene)for use in toughening vinyl ester resin.The mechanical properties,including the tensile strength,flexural strength,Young’s modulus and elongation,of neat vinyl ester resin and vinyl ester resin modified with MXene and M-MXene were investigated.The results showed that modification significantly improved the mechanical properties of the vinyl ester resin.The tensile and flexural strengths of the MXene-nanosheet-modified vinyl ester resin were 27.20%and 25.32%higher,respectively,than those of the neat vinyl ester resin.The coupling agent improved the interfacial compatibility between the MXene nanosheets and vinyl ester resin,which resulted in the tensile and flexural strengths of the M-MXene-nanosheet-modified vinyl ester resin being 52.57%and 54.60%higher,respectively,than those of the neat vinyl ester resin for a loading quantity of nanosheets of only 0.04 wt%,which is economically viable.The main mechanisms by which the nanosheets toughen the resin are crack deflection and crack pinning.

The Effect of Fibre Length on Flexural and Dynamic Mechanical Properties of Pineapple Leaf Fibre Composites

The present paper deals with the effect of loading different pineapple leaf fibre(PALF)length(short,mixed and long fibres)and their reinforcement for the fabrication of vinyl ester(VE)composites.Performance of PALF/VE composites was investigated through three-point bending flexural testing and viscoelastic(dynamic)mechanical properties through dynamic mechanical analysis(DMA).DMA results revealed that the long PALF/VE composites displayed better mechanical,damping factor and dynamic properties as compared to the short and mixed PALF/VE composites.The flexural strength and modulus of long PALF/VE composites were 113.5 MPa and 14.3 GPa,respectively.The storage(E′)and loss(E″)moduli increased to 2000 MPa and 225 MPa respectively for PALF/VE composites.Overall result analysis indicated that increasing the length of the reinforcement fibre results in satisfactory mechanical performance and dynamic properties of composites.