Advanced grid-stiffened composite shells for heavy-lift helicopter blade spars

Sreenivas N. Nampy, Edward Smith, Charles E. Bakis

Research output: Contribution to conferencePaper

Abstract

Heavy-lift helicopter blades are estimated to be large and heavy (upwards of 360 kg per blade) when the spars are constructed as monocoque structures. It is proposed to replace these conventional spar designs with lighter grid-stiffened composite shells. Composite stiffened shells have been known to provide superior strength to weight ratio and damage tolerance with a great potential to reduce weight. The design space for grid-stiffened rotor blade spar structures is new and the behavior of these structures under axial, bending, and torsion loads needs to be accurately predicted. The overall objective of the present research is to develop and integrate the necessary design analysis tools to conduct a feasibility study in employing grid-stiffened shells for heavy-lift rotor blade spars. A new analytical model was developed to accurately model various grid stiffening configurations and the results were compared with current state-of-the-art analysis, finite element analysis (FEA) and in certain cases, experiments. Parametric studies of grid density, stiffener angle, and aspect ratio of stiffener cross section showed excellent correlation (within 5-7%) between FEA and the new model. On the other hand, differences in the range of 26-60% between current state-of-the-art analysis and FEA were seen for certain designs. A preliminary design study was conducted to evaluate the weight saving potential of a simple cylindrical grid-stiffened rotor blade spar structure compared to a baseline monocoque design. Discretized design variables were stiffener density, stiffener angle, shell laminate, and stiffener aspect ratio and the design constraints were stiffness, material strength, and stability. For the range of the design variables explored, a weight saving of 9% compared to the baseline was obtained without violating any of the design constraints.

Original languageEnglish (US)
DOIs
StatePublished - Feb 28 2014
Event55th AIAA/ASMe/ASCE/AHS/SC Structures, Structural Dynamics, and Materials Conference - SciTech Forum and Exposition 2014 - National Harbor, MD, United States
Duration: Jan 13 2014Jan 17 2014

Other

Other55th AIAA/ASMe/ASCE/AHS/SC Structures, Structural Dynamics, and Materials Conference - SciTech Forum and Exposition 2014
CountryUnited States
CityNational Harbor, MD
Period1/13/141/17/14

Fingerprint

Helicopters
Composite materials
Turbomachine blades
Rotors
Finite element method
Aspect ratio
Damage tolerance
Torsional stress
Laminates
Analytical models
Loads (forces)
Stiffness

All Science Journal Classification (ASJC) codes

  • Civil and Structural Engineering
  • Mechanics of Materials
  • Building and Construction
  • Architecture

Cite this

Nampy, S. N., Smith, E., & Bakis, C. E. (2014). Advanced grid-stiffened composite shells for heavy-lift helicopter blade spars. Paper presented at 55th AIAA/ASMe/ASCE/AHS/SC Structures, Structural Dynamics, and Materials Conference - SciTech Forum and Exposition 2014, National Harbor, MD, United States. https://doi.org/10.2514/6.2014-1062
Nampy, Sreenivas N. ; Smith, Edward ; Bakis, Charles E. / Advanced grid-stiffened composite shells for heavy-lift helicopter blade spars. Paper presented at 55th AIAA/ASMe/ASCE/AHS/SC Structures, Structural Dynamics, and Materials Conference - SciTech Forum and Exposition 2014, National Harbor, MD, United States.
@conference{86cfa5219f7e44dc8ec4a09f7cb921d1,
title = "Advanced grid-stiffened composite shells for heavy-lift helicopter blade spars",
abstract = "Heavy-lift helicopter blades are estimated to be large and heavy (upwards of 360 kg per blade) when the spars are constructed as monocoque structures. It is proposed to replace these conventional spar designs with lighter grid-stiffened composite shells. Composite stiffened shells have been known to provide superior strength to weight ratio and damage tolerance with a great potential to reduce weight. The design space for grid-stiffened rotor blade spar structures is new and the behavior of these structures under axial, bending, and torsion loads needs to be accurately predicted. The overall objective of the present research is to develop and integrate the necessary design analysis tools to conduct a feasibility study in employing grid-stiffened shells for heavy-lift rotor blade spars. A new analytical model was developed to accurately model various grid stiffening configurations and the results were compared with current state-of-the-art analysis, finite element analysis (FEA) and in certain cases, experiments. Parametric studies of grid density, stiffener angle, and aspect ratio of stiffener cross section showed excellent correlation (within 5-7{\%}) between FEA and the new model. On the other hand, differences in the range of 26-60{\%} between current state-of-the-art analysis and FEA were seen for certain designs. A preliminary design study was conducted to evaluate the weight saving potential of a simple cylindrical grid-stiffened rotor blade spar structure compared to a baseline monocoque design. Discretized design variables were stiffener density, stiffener angle, shell laminate, and stiffener aspect ratio and the design constraints were stiffness, material strength, and stability. For the range of the design variables explored, a weight saving of 9{\%} compared to the baseline was obtained without violating any of the design constraints.",
author = "Nampy, {Sreenivas N.} and Edward Smith and Bakis, {Charles E.}",
year = "2014",
month = "2",
day = "28",
doi = "10.2514/6.2014-1062",
language = "English (US)",
note = "55th AIAA/ASMe/ASCE/AHS/SC Structures, Structural Dynamics, and Materials Conference - SciTech Forum and Exposition 2014 ; Conference date: 13-01-2014 Through 17-01-2014",

}

Nampy, SN, Smith, E & Bakis, CE 2014, 'Advanced grid-stiffened composite shells for heavy-lift helicopter blade spars' Paper presented at 55th AIAA/ASMe/ASCE/AHS/SC Structures, Structural Dynamics, and Materials Conference - SciTech Forum and Exposition 2014, National Harbor, MD, United States, 1/13/14 - 1/17/14, . https://doi.org/10.2514/6.2014-1062

Advanced grid-stiffened composite shells for heavy-lift helicopter blade spars. / Nampy, Sreenivas N.; Smith, Edward; Bakis, Charles E.

2014. Paper presented at 55th AIAA/ASMe/ASCE/AHS/SC Structures, Structural Dynamics, and Materials Conference - SciTech Forum and Exposition 2014, National Harbor, MD, United States.

Research output: Contribution to conferencePaper

TY - CONF

T1 - Advanced grid-stiffened composite shells for heavy-lift helicopter blade spars

AU - Nampy, Sreenivas N.

AU - Smith, Edward

AU - Bakis, Charles E.

PY - 2014/2/28

Y1 - 2014/2/28

N2 - Heavy-lift helicopter blades are estimated to be large and heavy (upwards of 360 kg per blade) when the spars are constructed as monocoque structures. It is proposed to replace these conventional spar designs with lighter grid-stiffened composite shells. Composite stiffened shells have been known to provide superior strength to weight ratio and damage tolerance with a great potential to reduce weight. The design space for grid-stiffened rotor blade spar structures is new and the behavior of these structures under axial, bending, and torsion loads needs to be accurately predicted. The overall objective of the present research is to develop and integrate the necessary design analysis tools to conduct a feasibility study in employing grid-stiffened shells for heavy-lift rotor blade spars. A new analytical model was developed to accurately model various grid stiffening configurations and the results were compared with current state-of-the-art analysis, finite element analysis (FEA) and in certain cases, experiments. Parametric studies of grid density, stiffener angle, and aspect ratio of stiffener cross section showed excellent correlation (within 5-7%) between FEA and the new model. On the other hand, differences in the range of 26-60% between current state-of-the-art analysis and FEA were seen for certain designs. A preliminary design study was conducted to evaluate the weight saving potential of a simple cylindrical grid-stiffened rotor blade spar structure compared to a baseline monocoque design. Discretized design variables were stiffener density, stiffener angle, shell laminate, and stiffener aspect ratio and the design constraints were stiffness, material strength, and stability. For the range of the design variables explored, a weight saving of 9% compared to the baseline was obtained without violating any of the design constraints.

AB - Heavy-lift helicopter blades are estimated to be large and heavy (upwards of 360 kg per blade) when the spars are constructed as monocoque structures. It is proposed to replace these conventional spar designs with lighter grid-stiffened composite shells. Composite stiffened shells have been known to provide superior strength to weight ratio and damage tolerance with a great potential to reduce weight. The design space for grid-stiffened rotor blade spar structures is new and the behavior of these structures under axial, bending, and torsion loads needs to be accurately predicted. The overall objective of the present research is to develop and integrate the necessary design analysis tools to conduct a feasibility study in employing grid-stiffened shells for heavy-lift rotor blade spars. A new analytical model was developed to accurately model various grid stiffening configurations and the results were compared with current state-of-the-art analysis, finite element analysis (FEA) and in certain cases, experiments. Parametric studies of grid density, stiffener angle, and aspect ratio of stiffener cross section showed excellent correlation (within 5-7%) between FEA and the new model. On the other hand, differences in the range of 26-60% between current state-of-the-art analysis and FEA were seen for certain designs. A preliminary design study was conducted to evaluate the weight saving potential of a simple cylindrical grid-stiffened rotor blade spar structure compared to a baseline monocoque design. Discretized design variables were stiffener density, stiffener angle, shell laminate, and stiffener aspect ratio and the design constraints were stiffness, material strength, and stability. For the range of the design variables explored, a weight saving of 9% compared to the baseline was obtained without violating any of the design constraints.

UR - http://www.scopus.com/inward/record.url?scp=84894462857&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84894462857&partnerID=8YFLogxK

U2 - 10.2514/6.2014-1062

DO - 10.2514/6.2014-1062

M3 - Paper

ER -

Nampy SN, Smith E, Bakis CE. Advanced grid-stiffened composite shells for heavy-lift helicopter blade spars. 2014. Paper presented at 55th AIAA/ASMe/ASCE/AHS/SC Structures, Structural Dynamics, and Materials Conference - SciTech Forum and Exposition 2014, National Harbor, MD, United States. https://doi.org/10.2514/6.2014-1062