Experimental Investigation of the Effect of CNT Addition on the Strength of CFRP Curved Composite Beams

Abstract

Carbon nanotubes (CNT) have been attracting attention as a toughening material in composite matrix due to their excellent mechanical properties. However, superior properties of CNTs have not yet been realized in the strengthening of composites against fracture. This study focuses on investigating the effect of CNT variation in the epoxy resin on the strength of curved composite beams. Specimens are [0/90] fabric carbon/epoxy composite laminates manufactured by hand layup technique 3 % wt CNT fractions in the epoxy resin. Curved beam composite laminates were subjected to four point bending loading according to ASTM D6415/D6415M–06a and the load displacement plot is recorded. Digital Image Correlation technique is used to obtain deformation field in the laminate at the curved region just before delamination failure initiates. A high speed camera at 28,000 fps was used to capture the deformation sequence after initiation of failure. For the CNT added laminate, both CBS and failure load is found to decrease with the load-displacement behavior found to change from single load drop to multiple load drops. In addition, delamination is found to be constrained to the curved region for the CNT added laminate in contrast to the base laminate where delamination extends to the arms.