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December 14, 2020
CAMX Paper Published: The Convergence of Composites & Topology Optimization
Ushering in the Next Era of Aircraft Lightweight Structures

Abstract

Although advanced composite material outperforms metal on material data sheets, actual composite structures often fail to provide a significant improvement. In part, this is due to the application of design approaches that were originally meant for metallic constructions. As a result, advanced composite structures have a redundant layup, with a quasi-isotropic stacking sequence that eliminates anisotropy instead of leveraging it, the so-called black aluminum. In today’s approach to taking better advantage of continuous carbon fiber’s mechanical properties, fibers are aligned based on the anticipated loading conditions. This can be achieved using hand layup or automated tape layup (ATL) / automated fiber placement (AFP) techniques. Though this provides a significant improvement over the “black aluminum” approach, it still falls short of realizing the full potential of continuous fiber anisotropy. Since carbon fibers perform best in tension, the part itself should be redesigned to take advantage of this effect. Though this exercise may seem intuitive for simple parts, in the aerospace industry, these coupled design activities easily become nonintuitive due to the complex loading conditions the aircraft structures are subjected to.

Arris Composites has developed a new process, Additive Molding(TM), capable of manufacturing complex geometries using continuous fiber. This paper presents optimizing topology and fiber orientation for an aerospace bracket, having complex 3D load cases. These optimized structures are shown to outperform current composite structures as well as structures machined and 3D printed from metal, making them ideal for next-generation aerospace brackets and joining structures.e

Introduction

The A350XWB and B787 programs are the first large-scale commercial programs to develop composite-intensive aircraft with a composition of about 80% composite materials by volume [1]. Reports on the costly investment of these clean-sheet designs [2] suggest that next-generation aircraft structures will likely be based upon derivatives of these models. Yet light-weighting challenges still abound within these programs and the upcoming ones. Particularly for brackets whose function is to transfer load from one mechanical interface to another. These aerospace applications still lack a complete advanced composites solution. While commercial support of simulation tools is currently emerging for metallic additive manufacturing processes, advanced composites manufacturing processes still lack such support. For instance, most leading vendors of finite element analysis packages have recently added topology optimization features for isotropic materials, yet topology optimization for fiber-reinforced composite structures is still not supported. 2 On the academic front, several research papers have already focused on topology optimization of continuous fiber-reinforced composites [3-4] and the academic community appears to have settled on a few benchmark problems, like the three-point flex problem, so-called the MesserschmittBölkow-Blohm (MBB) beam. However, these problems are simplified for purposes of benchmarking. Thus, the challenge of applying topology optimization and finite element analysis techniques to aerospace composite structures remain.

This paper aims to explore the potential benefits of applying a simultaneous topology and fiber orientation optimization toolset to 3D aerospace composite structures.

Read Whitepaper: compositesworld.com/cdn/cms/arris_composites_paper_camx_2020.pdf