Digital Composite Sparse Structures for Lightweight Airframes

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Solution Overview

Problem

Conventional aircraft manufacturing methods rely on large, monolithic composite parts, which are complex to assemble and repair, and lack the ability to efficiently distribute loads, leading to high mass densities and limited structural redundancy.

Innovation Solution

A digital material composed of small, fiber-reinforced composite units connected by elastic links, allowing for the creation of strong, lightweight sparse structures that can be assembled into complex geometries with automated processes, enabling tunable mechanical properties and redundancy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If large monolithic composite parts are used, then structural strength is achieved, but mass density increases and assembly complexity increases

Engineering Contradiction:

Improvestructural strengthVSAvoidmass density

Core Design Contradiction:

StrengthVSWeight of stationary object

Solution Approach 1:

The structure is divided into many small discrete units (digital material units) that are assembled into a sparse structure. Each unit is a complete structural element with embedded fibers, and multiple units connect to form the overall structure. This segmentation allows the structure to achieve required strength through distributed load paths while reducing mass density by eliminating unnecessary material in non-loading regions.

Inventive Principle:

Principle #1Segmentation

2Weight of stationary object

If many small discrete units are assembled, then mass density is reduced and reconfigurability is improved, but connection strength becomes the weak link

Engineering Contradiction:

Improvemass densityVSAvoidconnection strength

Core Design Contradiction:

Weight of stationary objectVSStrength

Solution Approach 1:

The connections between discrete units are created using composite material techniques, specifically continuous fibers that run through multiple units. These fiber-reinforced connections have strength comparable to or exceeding the units themselves, eliminating the weak link problem. The composite connection material provides both structural continuity and high strength-to-weight ratio.

Inventive Principle:

Principle #40Composite materials

3Device complexity

If conventional monolithic parts are used, then assembly is simplified, but structural redundancy is limited and repairability is poor

Engineering Contradiction:

Improveassembly complexityVSAvoidstructural redundancy

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The modular discrete unit design enables individual units to be easily removed, replaced, or repaired without affecting the entire structure. Damaged units can be discarded and new units installed, providing excellent repairability and structural redundancy. The standardized connection interfaces facilitate quick replacement operations.

Inventive Principle:

Principle #34Discarding and recovering

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The approach results in structures that are as strong as monolithic parts but with lower mass densities, offering improved assembly precision, reconfigurability, and enhanced resistance to localized damage, while allowing for the integration of sensing and monitoring capabilities.

Implementation Method 1

The units are reversibly joined by elastic connections. The connections allow force to be transferred among linked units.

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

Each unit comprises fiber-reinforced composite material. In some implementations, the digital material is reinforced with carbon fibers.

Methodology Applied

Scientific EffectComposite materials: Composite Materials

Implementation Method 3

Each unit comprises fiber-reinforced composite material. In these laminates, there may be multiple layers, with fibers oriented in different directions in different layers.

Methodology Applied

Scientific EffectFiber reinforcement:

Implementation Method 4

In exemplary implementations, the digital material is anisotropic. This anisotropy may be due to different fiber orientations within each unit.

Methodology Applied

Scientific EffectAnisotropy: Anisotropy

Data Source

PatentUS8986809B2Methods and apparatus for digital composites

Publication Date: 2015.03.24 MASSACHUSETTS INST OF TECH

AI summary

In exemplary implementations of this invention, a digital material comprising many discrete units is used to fabricate a sparse structure. The units are reversibly joined by elastic connections. Each unit comprises fiber-reinforced composite material. Each unit is small compared to the sparse structure as a whole. Likewise, in a sparse structure made from this digital material, the number of types of units is small compared to the total number of units. The digital material is anisotropic. This anisotropy may be due to different fiber orientations within each unit. Furthermore, different units in a single sparse structure may be oriented in different directions and in different, non-parallel planes. In some cases, the digital material is reinforced with carbon fibers, and connections between units are stronger than the units themselves. The small discrete units may be assembled into a strong, lightweight sparse structure, such as an airframe.