Transverse strength enhancement of carbon fiber reinforced polymer composites by means of magnetically aligned carbon nanotubes

Advanced polymer composites are used in various fields such as light-weight automobile, aerospace and bio-implant engineering owing to their extraordinary mechanical properties. Carbon fiber reinforced polymer (CFRP) composites have outstanding mechanical properties in the longitudinal direction due to their light weight and excellent strength. However, they have poor transverse mechanical properties which limit their use in many structural applications. It will be very beneficial to improve the transverse stiffness of CFRP composites. This paper presents a new technique which will substantially enhance the transverse mechanical properties of CFRP composites. Multi-wall carbon nanotubes (CNTs) were added to the CFRP composite specimen and aligned in the transverse direction by means of a magnetic field. The CNTs alignment process was aided by the addition of magnetic nanoparticles which adhered to the carbon nanotubes by surface adsorption during the curing process. This resulted in a significant increase in the transverse stiffness of the CFRP composites. In order to assess the impact of this technique on the mechanical properties, three-point bending tests according to (ASTM – D790-02) were carried out. The results showed that the aligned CNTs increased the stiffness by 46% whereas the nonaligned CNTs increased the stiffness by 20%. Additionally, the maximum load carrying capacity was increased by 33% for the aligned CNTs case and 15% for the nonaligned case.

► This paper presents a new technique to enhance the transverse mechanical properties of composite materials.
► Adding transversely aligned carbon nanotubes to the composite increased the load carrying capacity and the stiffness of the composite.
► The added carbon nanotubes were aligned in the transverse direction by means of applying a magnetic field and the addition of magnetic nanoparticles.
► The flexure modulus was increased by 30% and the maximum load carrying capacity by 15%.