Tolerance management during the design of composite structures considering variations in design parameters

Abstract

Composite structures play an important role in realising resource-efficient products. Their high lightweight potential and improved manufacturing technologies lead to an increased use in high-volume products. However, especially during the design and development of high-volume products, the consideration of uncertainties is essential to guarantee the final product quality. In this context, the use of modern lightweight materials, such as fibre reinforced plastics (FRP), leads to new challenges. This is due to their high number of design parameters, which are subject to deviations from their nominal values. Deviating parameters, e.g. ply angles and thicknesses, influence the manufacturing process as well as the structural behaviour of a composite part. To consider the deviating design parameters during the design process, a new tolerance optimisation approach is presented, defining tolerance values for laminate design parameters, while ensuring the functionality of the composite structure. To reduce the computational effort, metamodels are used during this optimisation to replace finite element simulations. The proposed approach is applied to a use case with different key functions to show its applicability and benefits.

Estimation of Composite Laminate Ply Angles Using an Inverse Bayesian Approach Based on Surrogate Models

“…Surrogate models can greatly decrease the computational time especially when using sampling strategies where the model is executed many times. One kind of mathematical surrogate model, which has been used recently by many researchers (Avendaño-Valencia et al, 2020;Franz et al, 2021;Gentile & Galasso, 2020;Kong et al, 2018), are Gaussian processes (GP). Equation 5shows the definition of a GP consisting of a mean function 𝑚(𝑥) and a covariance function 𝑘(𝑥, 𝑥 ′ ), which typically consist of some free parameters-also called hyperparameters (Rasmussen & Williams, 2008).…”

Tolerance Optimization of Patch Parameters for Locally Reinforced Composite Structures

“…Beside the mechanical properties of the laminate, loads and geometry are important parameters of the macro scale [8,10]. A more detailed view on the classification of parameters to the different scales and investigations on the effects of uncertainties is given in [11].…”

“…In this context, it is common to differ between design tolerances on the part geometry to ensure the functionality and machine tolerances, which are needed to meet the design tolerances during manufacturing [19]. Tolerances for the laminate design parameters such as ply angle, ply thickness or fiber volume fraction, as well as the dimensional parameters of the reinforcements are most likely to be categorized as design tolerances [11]. Nonetheless, they have not been tackled in tolerance analysis of composite structures extensively.…”

“…The author estimates the tolerance costs using the fuzzy multi attribute theory (FMAUT) and minimizes them using a nonlinear programming optimization algorithm [39]. A current tolerance optimization approach is presented by the authors in [11]. Herein tolerances for laminate design parameters are allocated using a least-cost approach in combination with a meta model based tolerance analysis.…”

“…Therefore, the investigated measures which are subject to variations from manufacturing are defined. Beside the ply angles, thickness and fiber volume fraction, which already have been presented in [11], the focus is set to geometrical variations of the local reinforcement patches in this work. This includes the patch dimensions, the position and orientation.…”