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In this article, a continuum-based constitutive model is developed to predict the mechanical behavior of 5052 resin epoxy reinforced by multiwalled carbon nanotubes (MWCNTs) based on experimentally generated data. For this purpose, MWCNTs/epoxy specimens with various percentages of functionalized and nonfunctionalized MWCNTs are prepared. The SEM graphs indicate that functionalization leads to a better bound between epoxy and MWCNTs and a higher level of dispersion. The specimens are then tested under standard ASTM D638-02 a procedure and their true plastic stress–strain curves are extracted. Investigations on experimentally generated data reveal that a wt% dependent equation which is obtained using any two series of these data can be successfully implemented for others. The equation is then implemented into a finite element software using a developed user material subroutine in which is utilized based on a particular solution algorithm. In order to verify the accuracy of the model some tensile as well as load-unload-reload tension tests are performed according to standard conditions and acceptable agreement between the numerical and experimental results are observed. Results also indicate that the proposed empirical model can precisely predict the stress–strain behavior of 5052 resin epoxy containing arbitrary wt% of MWCNTs in the range 0–1 wt%. [ABSTRACT FROM AUTHOR]

This study describes an experimental investigation of the degradation of the tensile properties of basalt fibers and epoxy-based composites in various corrosive environments, including alkaline, acid, salt and water solutions, and clarifies the corresponding degradation mechanisms. Carbon and glass fibers and their composites are adopted as references. Accelerated experiments were conducted at temperatures of 25℃ and 55℃ and the variation in tensile properties was studied by means of tension testing, mass loss weighing, scanning electron microscope imaging and energy spectrum analysis. The experimental results show that basalt fibers posses relatively strong resistance to water and salt corrosion, moderate resistance to acid corrosion and severe degradation in an alkaline solution. The tensile properties of basalt FRP composites are much better than those of basalt fibers. The degradation mechanism of basalt fibers involves damage by etching in salt, water and alkaline solutions and by change in the chemical composites in an acid solution. The fracture properties of basalt FRP composites are controlled by the failure of corroded interfaces between the fibers and the resin, making the interface the critical factor, rather than the fiber itself. [ABSTRACT FROM PUBLISHER]

The overall objective of the investigation presented in this paper was to study the effect of dispersion of core-shell polymer (CSP) particles within the ply interfaces on damage evolution of glass/epoxy laminates under impact loading. These laminates were fabricated with the CSP particle dispersion controlled to 14 % of the total weight of the used prepreg. A series of impact experiments were done with instrumental drop tower device at all probable impact energies within a practical low velocity impact range. The damage phenomena occurring in the internal microstructure of the laminates were analysed with the help of scanning electron microscope and correlated to the structural response of the laminate. The predominant damage modes were dependent on the magnitude of the applied impact energy. The CSP particle incorporation does not change the sequence of the fracture events but it delays and mitigates the damage creation. The deformation of the CSP particles and the tearing of their outer shells absorb most of the impact energy thereby preventing initiation of matrix cracks at lower impact energies and delaying fibre damage at higher energies. The crushed particles along with their nano-size rubber cores impede crack propagation requiring the cracks to follow torturous paths consequently dissipating additional amount of energy. These particles also promote elastic energy absorption of the laminates minimizing their tendency to fracture easily under impact. The ultimate load bearing capability of the modified laminate showed 60 % improvement and the deflection characteristics indicated lower proneness to impact. [ABSTRACT FROM AUTHOR]