Probabilistic optimisation of mono-stringer composite stiffened panels in post-buckling regime

Abstract

In this paper, a multi-objective probabilistic design optimisation approach is presented for reliability and robustness analysis of composite structures and demonstrated on a mono-omega-stringer stiffened panel. The proposed approach utilises a global surrogate model of the composite structure while accounting for uncertainties in material properties as well as geometry. Unlike the multi-level optimisation approach which freezes some parameters at each level, the proposed approach allows for all parameters to change at the same time and hence ensures global optimum solutions in the given parameter design space (for both probabilistic and deterministic optimisations) within a certain degree of accuracy. The proposed approach is used in this study to conduct extensive multi-objective probabilistic and deterministic optimisations (without considering safety factors) on a mono-stringer stiffened panel. In particular, a global surrogate model is developed utilising the computational power of a highperformance computing facility. The inputs of the surrogate model are the omega-stringer geometry and the mechanical properties of the composite material, while the outputs are the fundamental linear buckling load (LBL) and the nonlinear postbuckling strength (NPS). LBL and NPS are obtained via detailed parametric finite element models of the mono-stringer stiffened panel; in the nonlinear model, the interface between the skin and the omega-stringer is modelled via cohesive elements to allow for debonding in the post-buckled regime. Extensive multi-objective optimisations are conducted on the surrogate model using deterministic and probabilistic approaches to examine the omega-stringer geometric parameters mostly affecting the system robustness and reliability. The differences between deterministic and probabilistic designs are highlighted as well.

A novel multi-fidelity modelling-based framework for reliability-based design optimisation of composite structures

“…1. The conventional RBDO methodology uses computationally intensive models or high-fidelity based surrogate models [4,5,8,27]. In this framework, multi-fidelity models are constructed using both HFM and LFM before RBDO process is carried out.…”

“…The composite panel considered in this work is shown in Fig. 2 [27]. The geometry of this composite panel is parametrised by X1, X2, X3 and X4 which are stringer foot length, stringer height, horizontal distance between top and foot, and stringer top length, respectively.…”

Reliability-based bottom-up manufacturing cost optimisation for composite aircraft structures

“…Although it is important to take into account manufacturing cost when designing a composite part, the safety/ reliability of the part is also a very important consideration to take into account as well, especially for parts used in aircraft. There are many examples in which the reliability of a structure is optimised under the presence of uncertainties (Farokhi et al 2020;Yoo et al 2020;Bacarreza et al 2014;Lopez et al 2016;Simoes et al 2006;Hu et al 2016). One notable example is (Farokhi et al 2020) in which the geometric design of an aircraft mono-stringer compositestiffened panel was optimised based on reliability.…”

“…There are many examples in which the reliability of a structure is optimised under the presence of uncertainties (Farokhi et al 2020;Yoo et al 2020;Bacarreza et al 2014;Lopez et al 2016;Simoes et al 2006;Hu et al 2016). One notable example is (Farokhi et al 2020) in which the geometric design of an aircraft mono-stringer compositestiffened panel was optimised based on reliability. Reliability was estimated based on buckling behaviour and under the presence of uncertainties in composite material properties.…”

Multi-fidelity probabilistic optimisation of composite structures under thermomechanical loading using Gaussian processes

“…Lopez et al [8] proposed a new RBDO algorithm that combined reliability analysis with deterministic optimisation process and demonstrated using a composite stiffened panel. Farokhi et al [9] introduced a global multi-objective probabilistic design optimisation approach, including reliability analyses of composite structures. Chen and Qiu [10] developed a reliability assessment for composite laminate structures with correlated elastic mechanical parameters that consider the correlations between different parameters.…”