Fiber Steering for Mass-Efficient Thin Plate Structures

In the development of next-generation air and space vehicles mass efficiency is a key design driver [1]. As aerostructures become thinner, their stability becomes an increasing concern. Traditionally, industrial design has followed a linearized approach where instabilities are viewed as a ‘failure’ mode. If instead methodologies can embrace nonlinearity, postbuckling can be safely exploited for enabling additional structural capability [2]. In this work we utilize the postbuckling regime to design mass-efficient thin laminated plates for aerospace applications. This work optimizes the stacking sequences (fiber orientation and number of layers) of both conventional straight fiber and novel fiber-steered laminates to minimize for a target axial compression and load-carrying capacity. Fiber-steered structures [3], those in which the fiber orientations follow curvilinear reference paths, have been identified as a route towards improved structural lightweighting by engineering stiffness variations to redistribute prebuckling stresses [4].

This work investigates the design of a simply supported plate under uniaxial compression whilst applying nonlinear design constraints: load carrying capacity, static strength and manufacturability in response to a prescribed end-shortening strain. Genetic algorithms in MATLAB are used to determine the optimal layups for minimum mass problems using the Finite Element Method (FEM). Three optimizations are conducted to demonstrate the increasing tailor-ability achievable by fiber-reinforced materials. A Quasi-Isotropic structure is first presented that serves as the baseline for angle-ply and fiber-steered optimizations to outperform.

Overall, the proposed work aims to progress towards the safe and controlled use of instabilities in future design methodologies and further the application of structural nonlinearity in aerospace applications.

REFERENCES:
[1] L. Zhu, N. Li and P. Childs, Prop. Pow. Res., vol. 7, no. 2, pp. 103-119, 2018.
[2] A. Champneys, T. Dodwell, R. Groh, G. Hunt, R. Neville, A. Pirrera, A. Sakhaei, M. Schenk and M. Wadee, Front. Appl. Math. Stat., vol. 5, 2019.
[3] M. W. Hyer and R. F. Charette, AIAA 30th Structures, Structural Dynamics, and Materials Conference, Mobile, 1990.
[4] C. McInnes, A. Pirrera, B. Kim and R. Groh, AIAA SciTech 2023, National Harbor, 2023.