Reconsidering Laminate Nonsymmetry

Abstract

Nonsymmetric laminates are commonly precluded from composite design due to perceptions of reduced performance arising from in- and out-of-plane coupling. This coupling introduces warpage during cure—leading to raised stresses, together with diminished buckling and load carrying capacity. However, these reduced performance characteristics are rarely quantified and included in the design process; instead the symmetric-only paradigm remains pervasive at the cost of a significantly reduced design space. Warpage is largely driven by mismatch in the coefficients of thermal expansion between sublaminates located above and below the midplane and can be predicted by the classical laminate theory. Acknowledging that all symmetric laminates in multipart structures have build stresses from assembly, it is proposed that subsets of nonsymmetric laminates that translate to similar raised stress levels be considered for design. Challenging this symmetric-only design paradigm would permit greater design freedom and offer new routes to elastically tailor composite structures. Further analysis of structural performance is assessed in terms of reduced loading and buckling capacity.