Master Thesis defense presentation on September 5th, 2007. The goal of this project is to develop a preliminary design method of reinforcement around large cut-out in the composite fuselage and perform preliminary sizing of reinforcement around a transport plug door cut-out in a composite fuselage.

1. Design Methods for Large Cut-outsDesign Methods for Large Cut-outs
in Composite Fuselage Structuresin Composite Fuselage Structures
Supervisor: P. StockingSupervisor: P. Stocking
Presented by: Hassan JishiPresented by: Hassan Jishi
MSc thesis
Aerospace Vehicle Design

2. OverviewOverview
• Aerospace shell structures have cut-outs or openings that serve asAerospace shell structures have cut-outs or openings that serve as
windows, passenger doors, cargo doors, etc.windows, passenger doors, cargo doors, etc.
• These cut-outs or openings require some type of reinforcingThese cut-outs or openings require some type of reinforcing
structure to control local structural deformations and stresses nearstructure to control local structural deformations and stresses near
the cut-outthe cut-out
• Guides for preliminary sizing of members around the cut-out areGuides for preliminary sizing of members around the cut-out are
well developed for metallic structureswell developed for metallic structures
• Systematic approach to reinforcement design for large cut-outs inSystematic approach to reinforcement design for large cut-outs in
composite structure need to be developedcomposite structure need to be developed

3. OverviewOverview

4. Drive
• The introduction of large cut-outs represent a critical structural issue
• Several incidents have occurred were the passenger door or cargo
door have failed
• Next generation aircraft: reduce the structural weight of the fuselage
by 30%
• This is expected to be achieved using carbon fibre reinforced
plastics (CFRP).

5. Drive

6. ObjectivesObjectives
• Develop a preliminary design method of reinforcement around largeDevelop a preliminary design method of reinforcement around large
cut-outs in composite fuselage.cut-outs in composite fuselage.
• Perform preliminary sizing of reinforcement around a transport plugPerform preliminary sizing of reinforcement around a transport plug
type door cut-out in a composite fuselage.type door cut-out in a composite fuselage.
• Stress analysis of the reinforcement to substantiate the strength ofStress analysis of the reinforcement to substantiate the strength of
the fuselage with cut-out.the fuselage with cut-out.

7. MethodologyMethodology
• Analyze large cut-outs in metallic shell structure and its effect on theAnalyze large cut-outs in metallic shell structure and its effect on the
response of the shellresponse of the shell
• Study guides developed for preliminary sizing of reinforcementStudy guides developed for preliminary sizing of reinforcement
around the cut-outaround the cut-out
• Analyze the effect of large cut-outs on composite shell structureAnalyze the effect of large cut-outs on composite shell structure
• Utilize current practice for reinforcement in metallic structures andUtilize current practice for reinforcement in metallic structures and
then extend the work to cover composite structurethen extend the work to cover composite structure
• Utilize Software such as FUSEBEND, COALA, and Finite ElementUtilize Software such as FUSEBEND, COALA, and Finite Element
AnalysisAnalysis

8. Passenger Door
Reinforcing Structure
• Typical structure used for reinforcing passenger door cut-out in metallic
fuselage:
 Edge and adjacent frames
 Main and auxiliary sills
 Reinforcing doubler
 Intercostals
• Similar reinforcing structure is found in composite fuselage
• Composite designs are sized by ultimate strength whereas for an
aluminum fuselage these structures are typically driven by fatigue
considerations

9. Passenger Door
Reinforcing Structure

10. Cut-out
Case Study
• The A6 aircraft modeled during the group design project will be
utilized for the analysis of passenger door cut-out
• Based on loadng cases, Door #3 was the focus of the study
• Two load cases are considered:
 Load 1: Shear force and bending moment loads
 Load 2: Pressure differential load

11. Cut-out
Case Study

12. F.E.
Modeling
Approach
• Four main FE models were created (each loading case was
examined independently):
 Uncut Metallic, Uncut Composite
 Cut Metallic, Cut Composite
• Load 1 is achieved by applying a downward force at the free end of
the cylinder
• Load 2 is achieved by applying uniform pressure load on the internal
surface

13. F.E.
Modeling
Approach

14. • Initial metallic and composite uncut models consisted of skin only
 Maximum stress and deflection due to bending were verified
 Hoop and longitudinal stress due to pressure were verified
• Stiffened metallic and composite models
 FUSEBEND used to verify results
F.E. Modele
Verification

15. F.E. Modele
Verification

16. F.E. Modele
Verification

17. F.E. Modele
Verification

18. Metallic vs.
Composite
• Upon verification of the uncut models, the influence of introducing
the cut-out on metallic and composite fuselage are compared
• Similarities are observed between the metallic and composite
fuselage
 Deformation patterns around the cut-out
 Stress redistributions around the cut-out

19. Metallic vs.
Composite

20. Metallic vs.
Composite

21. Design of the
Reinforcement
• Guidelines to determine loads around a cut-out will be utilized and
extended for composite fuselage
• Method is obtained from Michael C. Y. Niu Book
• Design load cases:
 Case 1 Fuselage skin shear-flight conditions
 Case 2 Cut stringer loads- flight conditions
 Case 3 Fuselage Cabin Pressurization

22. Design of the
Reinforcement

23. Design of the
Reinforcement

24. Testing of the
Reinforcement
• FEA used to test of reinforcement around the cut-out of metallic
fuselage
• Stress levels of reinforced cut-out restored within 4% of un-cut
metallic fuselage
• Stress levels of reinforced cut-out restored in a similar pattern in
composite fuselage

25. Testing of the
Reinforcement

26. Testing of the
Reinforcement

27. Testing of the
Reinforcement

28. Conclusion
• Reinforcement methodology automated into FUSEBEND
• Reinforcement design methdology succsesfuly extended to
composites

29. Questions?Questions?
• Thank youThank you