TECHNOLOGY CFRP Reinforcing composites - carbon nanotubes break new ground Hamburg University of Technology has analysed hotmelt epoxy prepreg systems modified by an industrially-available masterbatch containing single-wall carbon nanotubes. Ultra-low loadings of 0.01 and 0.05 wt.% of nanotubes significantly improved the fracture properties of modified CFRP. JEns schnEiDEr Development and Support Leader, Adhesives and Composites OCSiAl T he use of composite materials is driven by their high strengthto-weight ratio and rigidity in comparison to traditional materials. However, unlike the latter, the performance of composites depends very much on the methods and conditions of fabrication. To compensate for a high defects ratio, engineers have generally had to incorporate up to 40% more material as a safety margin to ensure the required reliability level. Carbon fibre-reinforced plastics (CFRP) involve a number of issues, a crucial one being a low damage resistance that can be attributed to the nature of the matrix and its interface to the fibre. Impact load pressure causes cracking and delamination, leading to a major decrease in performance. It has been found that reinforcing the polymer with the addition of nanomaterials significantly improves composites performance. The potential of nanotubes in reinforcing composites A recent study by the Institute of Polymers and Composites at Hamburg University of Technology (TUHH) that compared neat and single-wall carbon nanotube-modified unidirectional CFRP prepregs showed great potential for the emergence of materials with enhanced performance parameters. Based on the advantages and the exceptional characteristics of single-wall carbon nanotubes, a 120°C-TG industrial prepreg was developed. The study analysed a hotmelt epoxy prepreg system that was modified by an industrially-available masterbatch containing 1 wt.% TUBALL™ single-wall carbon nanotubes for ease of use and safe handling. The unidirectional carbon fibre prepreg contained Mitsubishi carbon fibres type Grafil 34-700. Improved fracture properties The results of the study clearly demonstrated that the key benefits of TUBALL nanotube modification of CFRP laminates centre around fracture properties. Even at very low concentrations of 0.01 wt.% and Fig. 1: Ultrasonic C-scan (defect echo) of impacted specimens for delamination area determination: neat (left), 0.01 wt.% (middle) and 0.05 wt% (right) 64 jec composites magazine / No112 April - May 2017