Maturity assessment of the laminate variable stiffness design process

Variable stiffness (VS) laminate design methods allow to tailor the composite to a particular problem. This enlarged design space exploration is assisted by optimization algorithms and physics-based analyses. Although, the applicability of this methodology is at very early stages the search algorithms and analyses have evolved into sophisticated solutions. This survey aims to review the maturity of such models. However, a holistic approach must be formulated to account for all development activities like analysis, manufacturing, and certification. This survey classifies and reviews VS design papers over three decades of VS design methods to assess VS design maturity. Each paper is classified based on the research design criteria. We find that VS has evolved from a concept formulated in the early 1990s, proven through numerous feasibility studies that considered multiple performance criteria, mostly implemented into research-grade automated design tools considering fiber steering as the VS enabling mechanism, and extended into holistic-oriented multi-step design frameworks that incorporate efficient optimization algorithms, manufacturability and multidisciplinary analyses. However, certifiability considerations and more realistic structural representations have been found lacking in these frameworks. The latter is currently being researched, however the former has seen no investigative thrust.