Twisted Flexbeam Unit for Rotor Blade Control

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Solution Overview

Problem

Existing flexbeam units for multi-blade rotor aircrafts face challenges in efficiently transferring high oscillating forces while maintaining aerodynamic performance and durability, often resulting in increased drag and complex manufacturing processes due to the arrangement of virtual flapping and torsion axes in series, leading to undesired distortional buckling and limited mechanical stress distribution.

Innovation Solution

A flexbeam unit comprising torsion-elastic and flexible elements with a twisted area, allowing for lead-lag, flapping, and pitch angle control movements, featuring a helically shaped design with separated fiber-reinforced polymer layers and shear-soft separation materials, which reduces shear stiffness influence and enables large displacements, thus improving aerodynamics and manufacturing simplicity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If virtual flapping hinge and torsion axis are arranged in series in the flexbeam element, then the flexbeam element can provide the required virtual hinges and torsion functionality, but the flexbeam element becomes unnecessarily prolonged and aerodynamic performance decreases

Engineering Contradiction:

Improvevirtual hinge and torsion functionalityVSAvoidflexbeam element length

Core Design Contradiction:

ReliabilityVSLength of moving object

Solution Approach 1:

The patent combines the virtual flapping hinge and torsion axis functions into a single integrated region where the fiber reinforcement changes orientation. This merging of functions eliminates the need for separate series arrangements, thereby reducing the overall length of the flexbeam element while maintaining both virtual hinge and torsion capabilities.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent transitions from a one-dimensional series arrangement to a two-dimensional integrated region where fiber reinforcements are oriented at different angles (0° and 90°) within the same cross-sectional plane. This dimensional change allows both virtual hinge and torsion functions to coexist in a compact space, reducing the longitudinal length of the flexbeam element.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Object-affected harmful factors

If torsion weak region has small cross section to reduce drag, then aerodynamic drag is reduced, but resistance against lead-lag and flap shear forces is compromised

Engineering Contradiction:

Improveaerodynamic dragVSAvoidresistance against shear forces

Core Design Contradiction:

Object-affected harmful factorsVSStrength

Solution Approach 1:

The patent employs composite material construction with fiber reinforcements oriented at 0° and 90° to the longitudinal direction within the twisted area. This composite arrangement provides anisotropic mechanical properties that maintain high resistance against lead-lag and flap shear forces even with a reduced cross-sectional area, thereby reducing aerodynamic drag while preserving structural strength.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies different fiber reinforcement orientations (0° and 90°) in specific local regions of the twisted area to optimize performance. The 0° fibers provide resistance against lead-lag shear forces while the 90° fibers resist flap shear forces, allowing the torsion weak region to have reduced drag while maintaining necessary strength through localized quality variations.

Inventive Principle:

Principle #3Local quality

3Strength

If flexbeam element uses fiber reinforced composite material for flexibility and strength, then mechanical performance is improved, but manufacturing complexity increases

Engineering Contradiction:

Improveflexibility and strengthVSAvoidmanufacturing process complexity

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The patent segments the fiber reinforcement into distinct layers with specific orientations (0° and 90°) within the twisted area. This segmentation allows for modular manufacturing where pre-fabricated fiber layers can be stacked and cured separately before final assembly, reducing overall manufacturing complexity while maintaining the mechanical benefits of fiber reinforced composite materials.

Inventive Principle:

Principle #1Segmentation

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 proposed flexbeam unit achieves enhanced aerodynamic performance, increased durability, and reduced maintenance needs by allowing large blade movements with minimal bending moments at the rotor hub, while maintaining high stiffness and fatigue resistance, thus overcoming the limitations of conventional designs.

Implementation Method 1

at least one twisted area in which the at least one flexbeam element is twisted in the associated longitudinal direction by a predetermined twist angle that is at least comprised between 90° and 270°

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Data Source

PatentUS10005552B2Flexbeam unit with at least one twisted flexbeam element

Publication Date: 2018.06.26 AIRBUS HELICOPTERS DEUT GMBH

AI summary

A flexbeam unit for a multi-blade rotor of a rotary wing aircraft, the flexbeam unit comprising a plurality of flexbeam elements defining a predetermined number of torsion elements that are connectable with associated rotor blades of the multi-blade rotor, at least one of the predetermined number of torsion elements comprising at least one flexbeam element having an associated longitudinal direction, the at least one flexbeam element comprising at least one twisted area in which the at least one flexbeam element is twisted in the associated longitudinal direction.