Analytical design of in-plane and through-the-thickness auxetic composite laminates

Auxetic composite laminates, i.e. laminates with a NPR (Negative Poisson’s Ratio), are regarded as a promising solution to combat LVI (Low-velocity impact) delamination BVID (Barely visible internal damage) and ensuing property degradation, a cause for concern in aerospace components, mainly inflicted by fortuitous accidents during handling operations. In order to potentiate the auxetic effect through the minimization of the Poisson’s ratio, a thorough analysis of material properties and stacking sequences is required, as only a restricted domain of combinations can generate the desired effect, either in an IP (In-plane) or TTT (Through-the-thickness) configuration. This paper focuses on a MATLAB program developed for IP and TTT auxetic laminate design, based on the CLT (Classical Lamination Theory). Cases studies on NPR domain definition of C/E (Carbon/epoxy), G/E (Glass/epoxy) and hybrid C-G/E (Carbon-Glass/epoxy) laminates are presented. Moreover, the influence of fibre volume fraction on C/E and G/E laminates is analysed.