N95- 29030

IMPACT OF COMPOSITES

ON FUTURE TRANSPORT AIRCRAFT

Robert H. Kinder

Douglas Aircraft Company

Direct Operating Cost Objective

In the current environment, new technology must be cost-effective in addition to improvingoperability. Various approaches have been used to determine the "hurdle" or "breakthrough" return

that must be achieved to gain customer commitment for a new product or aircraft, or in this case, a

new application of the technology. These approaches include retum-on-investment, payback period,and addition to net worth. An easily understood figure-of-merit and one used by our airline customers

is improvement in direct operating cost per seat-mile. Any new technology must buy its way onto theaircraft through reduction in direct operating cost (DOC).

Impact Measured by Aircraft

Direct Operating Cost

PRECEDING PAGE BLA_'_< I_!OT _L_",'IE'D 3

_:_,_11w_mt,_5_,q_ Direct Operating Cost Trends

Advanced technology has played a vital role in the continual productivity improvement of transportaircraft over the past 40 years. Speed, propulsion, aerodynamics, and capacity have contributed to

a continual decrease in DOC in each decade. With the introduction of the jet engine, improvement

was achieved through increased speed. In the 1970s, wide-body aircraft offered dramatic increases in

capacity and fuel efficiency. Over the past two decades, direct operating cost reductions have largelybeen the result of reduced fuel consumption derived from lower weight, reduced engine SFC, and

aircraft drag. But, as the chart shows, it is becoming increasingly difficult to achieve further reductionsin DOC.

Relative DOC

perSeat-Mile

U.S. Domestic Operations

3 l_ike DC-7 'Speed [

DC'6B_ I Capacity J

2 _ I _ DC-9-10 I

_ iDC.9.30_ I Ft_el EfficienclY

DC-8-10 _ O'_ DC 9 50 I

DC-8"5,0_"'",_ MD8o I ?1 oc-,

MD-11

. I1950 1960 1970 1980 1990 2000

Year of Initial Service

4

Operating Cost Distribution

The major component influencing direct operating cost is the ownership cost. Future advances in

aerodynamics, engine SFC, and structural weight will continue to shrink the fuel contribution to total

cost. However, reductions in ownership cost dominate the equation to justify the development of newaircraft.

DOC(%)

DOC

(%)

40353025201510

50

35

30

25

20

15

10

5

0

- 40%1

i

-'i

Ownership FlightCrew

Fuel Price $0.60/gal

4%

Cabin Fuel AF Eng Landing

Crew Maint Maint Fee

34%1

25%1

Fuel Price $1.50/gal

Ownership Flight Cabin Fuel AF EngCrew Crew Maint Maint

3%

F----3

LandingFee

M02105

5

U. S. Jet Kerosene Price

The forecast by McDonnell Douglas is that long-term fuel prices will remain fiat in constant dollar

terms at about 60 cents per gallon. This is based upon an abundant oil supply remaining (over 40 years

supply at present consumption) and the short-term nature of dramatic fluctuations due to political events.

Therefore, ownership costs are expected to continue as the largest element in the DOC equation.

Price

perU.S. Gallon

160

140

120

100

80

60

40

20

01970

t Hist°ry ] I I Forecast

- //_ Conlstant 1990 U.S. Cents j

_ /_ Current U.S. Ce_

I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I

1980 1990 2000 2010

6

Passenger Aircraft Deliveries

World passenger traffic is expected to grow at a 6.5% annual rate through 2010. During this period,intemational passenger traffic is projected to grow to 7.8% a year while domestic traffic is predicted to

increase 4.9% annually. Pacific/Asia will experience the fastest growth while North American traffic

growth will remain essentially constant. To meet the increased traffic demand, the world's jet aircraft

fleet is expected to more than double in the next 20 years (17,000 passenger aircraft by 2010 comparedto 8,000 today). The requirement for additional capacity combined with aircraft retirements results in

a McDonnell Douglas forecast of over 14,000 passenger jet aircraft deliveries during this time period.

These aircraft are split almost evenly between narrow-body and wide-body units. In constant 1990

dollars, their value is almost one trillion dollars.

By Domiciled Region, 1991-2010

Middle East/

Latin Africa

America _---7601,

Middle East/Latin AfricaAmerica

14,022 Units $942.9 Billion(Constant 1990 Dollars)

*Excludes USSR

The Challenge to Technology

An improvement in any of the DOC parameters is very difficult to achieve. Consider that a ten percent

reduction in the cost/price of the aircraft is a very large reduction, but reduces DOC by only four percent.

However, a new aircraft should provide roughly a 10% improvement in operating cost to provide the

sales potential necessary for production commitment. To contribute to the achievement of that objective,

composite primary structure must provide a cost benefit as well as the expected weight savings. This

is the goal that must be achieved to realize the use of composite primary structure on a transport

(commercial or military) aircraft.

DOC Drivers

A IO-l'_,rce.t ltttl_roremt'ttt i. E.c'b l)ttrtl.telc,r

ll.s This lml.tcl o. DOC

4.0

DOG

(%)

3.0

2.0

1.0 -

oOwnershl

(Capllal

and Inlerest)

Fuel Price $0.60/gal

llll HnEngine Cruise Operating Alrh'ame Engine

SFC L/D Weight Malnlenance Maintenance

Empty

Direct Oi_et'tltitag Cost Objective

Relative DOCper Seat

(%)

0

-5

-10

¢,-

jf 9

J-15

-20 -15

/

J-10

P/

/

-5 0 5

Relative DOC per Trip (%)

Reductions in operating coststhat will justify inclusion in the product

8

MD-II, C-17, MD-12 Composite Construction

The extent of composites usage has continued to increase with time. Aircraft currently in production

utilize composites in numerous secondary structures such as fairings and control surfaces. Composites

account for 4 to 6 percent of the empty weight of these aircraft. The MD-12 will utilize composites forthe vertical and horizontal stabilizer boxes and floor beams, increasing the composite content to about

9 percent of empty weight.

Composites Applicatiott

itt Dottglas

7_'a.sport Aircraft

MD-11 Composite Cottstructiott

Wtnglet Trailing Edge _ No. 2 Engine Inlet

Access Panels _ //I

"_ Inlet Duct--_ _ /_t_._"/I 7-- Extended

//-"_ XN_ _/ Ta,, Cone

_ -f'k ......... lao _ -_¥._J /1---Elevators and

";_g'_,,_',l _ >_ __,nboa,d Vane," I _¢"AX/ _ _///_l.bo=d.,ap.

• _1_ / _'l_/'f/'_'/ f Inboard Aileron,'

/ ..,,ol) _ 1" 'r _ Lower

Radome

C-17 Composite Applications

NONS]RUCTURAL PARTS,

LINERS, TROOP SEATS

L -_ __1_ ib of

[_ Carbon/Kevlar/Epoxy

GFRP/Nomex Core

Kevlar/Foam Core

-_. _ Kevlar/Nomex

Carbon/Nomex

9

MD-12

Wide-Body Cross Section Comparison

MD-11237-in. Circular

747-400256 in. Wide

by309 in. High

MD-12291 in. Wide

by335 in. High c,,o.....

GI:VC0"t4-T

10

35,000 Ib ofComposites

MD-12 Composite ConstructionVert Stabilizer Box Rudders

Aft BodyFairings

Elevators and

Trailing EdgeOutboard andMid Flaps

FloorBeams

Horiz Stabilizer Box

Body Landing Gear Doors

Wing TrailingEdge Panels

Spoilers

Nose LandingGear Doors

RadomeWing/Fus Fillets

Main Landing Gear andStrut Doors

Inlet Duct

11

MD-XX Composite Construction

With composite wing and tail, the composite content of the MD-XX will grow to over 20 percent

of empty weight. If the MD-XX were to also have a composite fuselage, the percent composite wouldbe over 40% of aircraft empty weight.

Composite Wing and Tail GroupPrimary and Secondary Structure

0000000000000000000

Composite Nose and TailCones, Fairings, FloorPanels, Doors, and Nacelles

12

Wing Box Data Projection

Conventional composite construction reduces weight but at increased cost. McDonnell Douglas

studies of a wing box unit show a 25 percent weight savings but a 50 percent or greater cost increase

for a conventional composite unit. Using the ICAPS methodology, the weight savings will be retained

with a goal of achieving better than a 40 percent improvement in cost compared to the conventional

composite unit.

Ob.jectives of DAC Co,iposites

l',-ogr,,a With NASA

Develop Primary Structure Technology

Below the Cost of Metal

Wi.g Box Cost Data Projectio.

PercentCost

150

100:;>':.:

>>>>:_.

::::::T:.

_iiiiii!iii

:i:):!:!:i:i:.>::.:.:.

50 ...........,.....

?!:i:?:i:i::::::;:::::::

::.:+::.:

.:.::::.:.

0C WMetal

;ii!i!i!iiiii::;::::::::::

: >'+>.

i:!:[:i:?:[:::::::::::::

:::::::::::'::

:::::::::::::

!i!i)i!ii!:i

iiii!i?!ii!i

::::::::;:: : '

i iiiiiilill:":::::::::::: ':.:.:.:.:.; :.ii!::!://:::::::::::::T:

ili?iii!:!:!i

ii::iiiii::_is_.:.:.:.:.:.:..... T'I

C WDouglas

Composite Unit

iiiiiiiiiiii!

i!i!ii!ii_iil--::::::::5:::

_i:!:i:i:i:i:!

:.::.::.:.:

i:i:i:i:i:i:i

_!iiiiiiii!;i

:.:.:.::.:.:

iiiiii_[_)!ii.....-.

::::::.::::::.:::;::;:;::::::::I .......

C WleAPS

Unit

150

100

PercentWeight

50

0

13

Aircraft Cost Distribution

Ownership costs (to the operator) are directly related to the vehicle price which, in turn, depends

on the manufacturer's cost. Structure costs are larger than propulsion, avionics, or equipment costs.

The largest components of structure costs are the fuselage and wing. These two components providethe largest potential for a significant impact on ownership cost and total operating cost. McDonnell

Douglas has elected to focus its initial effort on the wing. Success with a composite wing will yieldtwo benefits: reduced weight and reduced drag. Reduced drag results from the stiffness characteristics

of composite which allows higher aspect ratio without attendant weight penalties.

1990 Technology Aircraft

Fraction ofAircraft Cost

(%)

35

30

25

20

15

10

5

0

29%

Wlno

_ _,

_ Fuse-lage

///,,/,

///-,

?>,_:

Airframe

25%

/,d(/

_/////

?7//.÷

Engine

14%

8%

Systems Avionics Interior

4%

Gear

MD-XX Composite Wing Technology

_>,,', /-- Composite Secondary

(A) _O X Structure

_/__///_ INCREASE ASPECT /_ -2.5% Fuel Burn 7. Relative To "A"

-. • / _ _A h.. _ Composite Secondary

Aluminum / _ _ _1 _:_ // Structure

grt 'rm:t_re J C CHANGEgBOo X _ (B)_'_ ._

L,.._-//-- Composite Secondary

I_ "// Structure Aluminum /Itl:gtttt_ ./ _ primary /

(C) _ _._ Structure _ -

Primary Structure

14

One-Third Reduction in Fuel Burned

It is possible, through incorporation of several new technologies, to achieve a one-third reduction in

aircraft fuel consumption. However, a full one-third reduction in fuel burned exclusively is not enough

to achieve a ten percent reduction in DOC. An all-new aircraft with a thirty-three percent reduction in

fuel burned would provide an economic benefit of only four to eight percent in DOC depending on fuel

price.

Relative DOCper Seat

(%)

o.J I

Re at" p "p ( )

15

DOC Using Conventional vs. ICAPS Wing Box

The benefit of the ICAPS wing on the total direct operating cost has been calculated for an MD-XX

aircraft. Reducing the cost of the wing by just ten percent provides an additional two percent reductionin DOC.

5

0

Relative DOC

per Seat -5(%)

-10

9/

9f

/

.__ So.6o,ga,i_

-15-15

-20 -10 -5 0 5

Relative DOC per Trip (%)

16

DOC Using ICAPS Wing and Fuselage

Extending the use of the ICAPS methodology (i.e., weight and cost reduction) to include the fuselageimproves the total operating cost picture even further.

Relative DOC

per Seat(%)

"'_-_'0 -,', " .',0 .E _ ",Relative DOC per Trip (%)

17

DOC Using Current Composite Construction Costs

Extensive application of composites at today's cost of construction is prohibitive. The resultingincreased cost of ownership has offset nearly all the fuel consumption benefits associated with the

application of several new technologies.

)'" pRelative DOC _e ./

per oSeat 4/ .G\@_'/ $1"5°/g__J

"°1/ I _ I /"

" -20 -15 -10 -5 0 5

Relative DOC per Trip (%)

18

Innovative Composite Aircraft Primary Structure

The following charts depict the schedule and some of the results to date of the Douglas compositeprimary structure program. The program will conclude with the construction and testing of a full scale

(approximately 60 ft.) semi-span. The wing stub box is currently under construction. Single andmulti-needle sewing machines are shown making performed parts prior to RTM. These machines will

potentially replace expensive drivematic riveting machines used in manufacturing metal wings.

I Phase A _ Phase B

./_ , J Semispan Wing

__ / [Wing Stub Boxl ' ,F---| Coupons _" I Major Load Point and Local Detail Testsfll I "---3

_ [I l_J _'__ _ SCaP;r_ A -I Attachment

_E,eme nts _ _ ptY_aOcnh_ %_

t__.__._._......__._/_ "_OX Specimens

Subcom! Repair Panel Tests

4 by 6 Foot Stitched Preform

ORIGINAE PAGE

L_LACK AND WHITE PHOTOGRAPI.-r

19

Stitching Machine Operation

128 Needle Stitching Machine

2O ORIGINAL F/-,,GC.

BLACK AND WHITE PHOTOGRAPH

Witlg Sectiota, hi, Drivemat, ic

21

Damage Area Comparison for Blade-Stiffened Panel

While composite laminates have excellent properties in the plane of the layers, they are weak in the

through-the-thickness direction. Stitching provides a means for suppressing the types of delamination

failures arising from that weakness. One advantage provided by stitching is the reduction in theincidence and size of damage from impacts and the subsequent reduction of maintenance and repair

costs. Weight saving is realized because the working allowable stress levels for damaged compressionstructure is increased.

3 Times Area 1"

Typical Toughened-Resin

High-Strength Fiber

Area 1: Stitched/RTM

22

Typical Compression Test

Composite panels loaded in compression typically fail with extensive splitting apart of the laminate

layers. This mode of failure can be totally suppressed when high-density stitching is used. Stitched

compression panels fail on a 45 ° shear plane in a manner much more typical of that expected fromhomogeneous metal panels.

Brooming Failure of Toughened Resin and High Strength Fibers(Prepreg Panel-Unstitched)

Compression Failure at 45-deg Shear on

Blade Stiffener and Skin (Stitched/RTM-Blade Stiffened)

Wing Compression Test Panel

O_'-_[GiNAL PAGE

BLACK AND W_ITE PHOTOG_,_PI-4

23

Summary

In summary, there is a requirement for a large number of new conventional aircraft over the next

20 years. Sales of these aircraft will go to the builders who can offer the best operating economics.

Ownership costs will continue to dominate the economics equation. To find application on these new

transport aircraft, composite primary structure must provide production cost reduction as well as fuel

consumption and maintenance benefits.

Conventional subsonic transports will continue todominate the market.

Ownership cost will continue to increase as a percentageof total operating cost.

Composite primary structure can benefit several elements

of the operating cost picture - ownership, fuel, maintenance.

A well-conceived and implemented ICAPS plan will provide

major benefit to the next transport aircraft..

24