Stiffened Composite Panel Design Based on Improved genetic

Stiffened Composite Panel Design • Based on “Improved genetic algorithm for the design of stiffened composite panels, ” by Nagendra, Jestin, Gurdal, Haftka, and Watson, Computers and Structures, pp. 543 -555, 1996. • Standard genetic algorithm did not work well enough even with simplified structural model (finite strip). • Algorithm was improved based on simplified version of the panel design problem (e. g. fixed blade height, single laminate).

Geometry and loading

Modeling in PASCO • Finite strip model assume that in one direction we can use sine solution, while in the other the displacement can have general shape. • Panel Analysis and sizing code (Stroud and Anderson) based on analysis code by Wittrick and Williams.

Optimization problem •

Optimization formulation •

Material properties • Today’s graphite-epoxys can do much better.

Genetic code

Selection and Crossover • Rank based fitness and roulette wheel selection. • Original crossover is a 2 -point crossover applied to entire genome. • Two children produced. • Improved crossover applied individually to each of the three substrings. • Crossover applied with 95% probability. If not, first parent copied into next generation.

Mutations • Mutation applied to one child with each gene mutated with 3% probability to random new gene. • Improved mutation separates orientation mutations from deletion and addition mutations. • Stack deletion: First select randomly skin or blade. Then stack closest to mid-plane deleted with Probability of 2 -3%. • Stack addition: Skin or blade selected randomly, then random stack added at mid-plane. • New: Permutation, intra-laminar swap, inter-laminar swap.

Results with original GA • What is the main difference between rounded continuous optimum and GA design?

Tuning the algorithm •

Improved GA designs • What is different?

Comparison