Stitched Graphene Nanoplatelet Composites for Unitized Aerospace Structures

Lightweight composites play an important role in sustainability as their usage in aerospace vehicles translates to improved fuel consumption and reduced emissions. However, due to their low interlaminar strength, delaminations and microcracking degrade their strength and stiffness properties. Through-thickness stitching in composites enhances interlaminar properties but reduces the in-plane properties. Graphene nanoplatelets (GNPs) and carbon “thin plies” have been found to increase the mechanical properties of these composite structures. This study considers a hybrid composite that uses GNPs coupled with thin plies at the midplane to mitigate the reduction in the in-plane properties. Composite specimens [Formula: see text] were stitched with two different seam angles (0 and 90°) and tested under uniaxial tensile loading. Surface strain fields from digital image correlation measurements show a significant decrease in strain concentrations in the hybrid specimens compared to the baseline stitched composites. An increase of 17% in tensile modulus and a reduction of 15% in strain energy density are realized due to the hybrid architecture of the stitched composite.