Mohammad R. Irshidat

Utilizing Vacuum Bagging Process to Prepare Carbon Fiber/CNT-Modified-epoxy Composites with Improved Mechanical Properties

ABSTRACT In this work, the effects of carbon nanotube-modified epoxy and carbon nanotube-enriched sizing agent on the tensile properties and failure mode of unidirectional carbon fiber/epoxy composites were investigated. Laminates of carbon fiber/epoxy composites at different concentrations of carbon nanotube and sizing agent were fabricated by hand layup vacuum bagging process. Scanning electron microscopy analysis was conducted to unveil the relation between the macroproperties and the composites’ microstructure. Experimental results showed that the carbon nanotube-modified epoxy/carbon fiber composite showed 20% enhancements in the Young’s modulus compared to the pristine epoxy/carbon fiber composite. The scanning electron microscopy analysis of the fracture surfaces revealed that incorporating carbon nanotube into the epoxy matrix with utilizing the vacuum improves the interfacial bonding and minimizes the voids that act as crack initiators. This microstructure enhances the interfacial shear strength and load transfer between the matrix and the fabrics and consequently the tensile characteristics of the formulated composite. GRAPHICAL ABSTRACT

Effect of Nanoclay on Expansive Potential of Cement Mortar due to Alkali-Silica Reaction

The impact of partial substitution of cement particles with nanoclay on the expansive potential of cement mortar due to alkali-silica reaction (ASR) was investigated. Portland cement was replaced by 0.5%, 1%, and 2% montmorillonite nanoclay. The effect of ASR on compressive strength, chemical composition, and microstructure of nanoclay-cement composites was evaluated. The accelerated mortar-bar method was followed to perform the ASR test according to ASTM C1567. The experimental results showed that the expansion of cement mortar due to ASR can be reduced by the addition of nanoclay. Two percent nanoclay was the only dosage among others used in this study that can mitigate the expansion. Furthermore, the ASR caused a marginal enhancement in compressive strength of mortar compared to the specimens cured in water. The gain in strength reached up to 10% for mortars contacting 2% nanoclay. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis did not detect the formation of any secondary products due to the ASR, revealing the similarity between ASR and the pozzolanic reaction for the first 14 days of the reaction. However, the microstructure of the mortars became denser and more homogeneous when a part of cement was replaced by nanoclay.

Effect of viscosity reducing agent on the properties of CNT/epoxy nanocomposites

Abstract Epoxy nanocomposites that are produced in a solvent-free environment suffer from the inadequate dispersion of nanofiller and poor interfacial interaction between the nanofiller and polymer matrix. In this work, the effect of replacing a portion of the epoxy resin with a viscosity reducing agent (VRA) on the structure, electrical and mechanical properties of carbon nanotube (CNT)/epoxy nanocomposite have been investigated. Optical microscopy (OM) and transmission electron microscopy (TEM) were used to characterize the structure of the nanocomposite at the microscale and nanoscale, respectively. For nanocomposites without VRA, it was found that the addition of CNT degrades the tensile strength and toughness; meanwhile, it enhances the flexural modulus, Young’s modulus and electrical conductivity of the nanocomposite. However, the addition of VRA retained the tensile strength of the epoxy system and maintained the improvements in flexural strength and electrical conductivity that have been achieved due to CNT addition.