Understanding the effect of nano-modifier addition upon the properties of fibre reinforced laminates

This work presents a survey of the effect of three different commercially available nano-modifiers on the mechanical properties of an epoxy/anhydride unidirectional carbon fibre reinforced laminates. The nano-modifiers consisted of an organo-modified layered silicate, vapour grown carbon fibre (VGCF) and a triblock copolymer (SBM). The work has shown that tensile modulus exhibited little difference between the unmodified laminates while a modest decrease was observed for the tensile strength. Properties related to the toughness of the matrix, demonstrated improvements compared to the unmodified laminate such as the notch sensitivity under compression, ILSS and GIIC performance. The improvement of the GIIC for the VGCF modifier in particular was found to be over 100%. It was suggested that high aspect ratio of the nano-additive helped to constrain the growth of the micro-cracks which in turn delayed failure. Mode I GIC performance however, was found to decrease as a result of the fibre tows preventing optimum dispersion of the modifier. The effect of this was a very high “effective” clay concentration in the interlayer resin rich regions and a less than optimum fibre dispersion, results in promotion of the propagating crack rather than inhibition.