HYDROTHERMAL AGEING OF AIRCRAFT COMPOSITESHydrothermal Ageing of Aircraft Composites Kolesnik Kirill...

HYDROTHERMAL AGEING

OF AIRCRAFT COMPOSITES

Kolesnik Kirill

Junior researcher

The Central Aero-Hydrodynamic Institute

Postgraduate student

Moscow Institute of Physics and Technology

Russia

The Central Aerohydrodynamic Institute named after N.E. Zhukovsky (TsAGI)

Hydrothermal Ageing of Aircraft Composites Slide 2Kolesnik Kirill

─ theoretical and applied aerospace research facility

– primary carbon fiber composites

– secondary carbon fiber composites

– glass fiber composites

– FRP floor panels

– metals

• 34% composites

• 132 – 211 passengers

• up to 6 400 km range


Modern russian jet Irkut MC-21

A

B

D

Plan of the presentation

1. Hydrothermal effects

2. Qualification of composite structures

3. Maximum operating temperature

4. Operating moisture content

5. Realistic hydrothermal factors


Hydrothermal effects on composites

On the resin:• Plastification

• Swelling

• Destruction

• Secondary curing

On the lamina:

• Reduction of properties, mainly matrix governed

On the laminate:

• Internal hydrothermal stress

On the construction:

• Moisture affects bond-line (adhesive) - may lead to disbondings

• Moisture ingress in the honeycomb core

• Galvanic corrosion, mainly Al and carbon-epoxy


Structural materials handbook - Part 1: Overview and material properties and applications, ECSS‐E‐HB‐32‐20, 2011.

Longitudinal tensile strength Transverse tensile strength

Mechanical lamina properties as a function

of temperature and moisture content


Mechanical lamina properties as a function

of temperature and moisture content

Moisture content, %

Rel

ativ

e in

terl

amin

arsh

ear

stre

ng

th

Test temperature, ºCC

om

pre

ssiv

e st

ren

gth

, M

Pa

TürkmenD. Compressive behaviour of CFRP

laminates exposed in hot-wet environments – 1996.MardoianG.H., EzzoM.B. Flight service evaluation of

composite helicopter components – 1990.


Lamina properties degradation model

0

0 TT

TTg

g

g

−

−=

0

5.00

1212

5.00

22

04.00

11

=

=

=

=

gGG

gEE

gEE

Shan, Meijuan, et al. "A progressive fatigue damage model for composite structures

in hygrothermal environments." International Journal of Fatigue 111 (2018): 299-307.

5.00

1212

5.00

5.00

54.00

04.00

gSS

gYY

gYY

gXX

gXX

CC

TT

CC

TT

=

=

=

=

=

Tg – glass transition temperature

T – temperature

index 0 – reference data

A S Maxwell at. al. Review of accelerated ageing methods and lifetime prediction

techniques for polymeric materials, NPL Report DEPC MPR 016, 2005


Test conditions

for hydrothermal qualification of composite structures

High temperature

Moisture conditioning

High realism

Time consuming

Special equipment

High temperature

Dry

Time efficient

Building-block approach

Special equipment

Room temperature

Dry

Time efficient



Test-bench

Hydraulic/Electric Ram

Lever-Loading System

Test Object

Dynamometer


Control surfaces test set up

Climatic cabinet

Hot-wet and cold conditions

Infrared heating



Overload Factors:𝐾𝑊𝑇 , 𝐾𝑣𝑎𝑟 , 𝐾𝑑𝑎𝑚

Overload Factors assure

structural strength in all

operating conditions



Test conditions for

hydrothermal qualificationTest elements

𝐾𝑊 =𝑋𝑊𝑋

𝐾𝑇 =𝑋𝑇𝑋

𝐾𝑊𝑇 =𝑋𝑊𝑇

𝑋

Environmental

compensation factor

Air flow velocity

for take off scenario

Maximum operation temperature

Rolfes, R., J. Tessmer, and K. Rohwer. "Models and tools for heat

transfer, thermal stresses, and stability of composite aerospace

structures." Journal of thermal stresses 26.6 (2003): 641-670.

"Static Strength Substantiation of Composite

Airplane Structure"

PS-ACE100-2001-006, December 2001

For most paint colorsa default critical structural

temperature is 82°C (180°F)


40

45

50

55

60

65

70

75

80

85

-300 -200 -100 0 100 200 300

Surface temperature, ºC

верх. обш. снаружи

верх. обш. внутри

нижн. обш. внутри

нижн. обш. снаружи

Taxi Start phaseStop

Transient cooling of wing box during take off scenario

16°C


t, s

l1 = l2 = 8 mm, qс = 1082 W·m–2,

A = 0.45, Tair = 56 ºС,

h0 = 8.5 W·m–2°K–1, Ag = 0.73,

Tg = 75 ºС, q12 ≠ 0, h12 = 0

Top skin outside

Top skin inside

Bottom skin inside

Bottom skin outside

Ultimate load

0

20

40

60

80

100

0 5 10 15 20

Su

rfac

e te

mp

erat

ure

, ºC

l, mm

t = –300 сек.

t = 120 сек.


A = 0,2 (white)

A = 0,45 (gray)

A = 0,9 (black)

Composite skin temperatures

due to solar heating and takeoff cooling

Takeoff cooling reduces

the maximum operating temperature of thin components

Before take of

Ultimate load

0

0.2

0.4

0.6

0.8

1

0 10 20 30 40 50

Relative

moisture

content

t, years

l = 2

l = 8

l = 12

l = 20


0.00

0.04

0.08

0.12

0.16

0 100 200 300

Moisture content, %

t, days

образец

численное моделирование

Calculated and experimental moisture contents

Experimental data

Numerical calculation

6 mm laminate

Moisture absorption modeling for diff. thicknesses

Moisture absorption in hot-wet climate (Sochi, Russia)

Moisture diffusion obeys the Fick’s law

0

0.2

0.4

0.6

0.8

1

0 5 10 15 20

Relative moisture content

l, mm

Порт-Харкорт, Нигерия

Гуам

Сингапур

Мухаррак, Бахрейн

Сочи

Вудбридж, Англия

Шлезвиг-Гольштейн, Германия

Владивосток

Москва

Магадан


Port Harcourt, Nigeria

Guam

Singapore

Bahrain

Sochi, Russia

Woodbridge, UK

Schleswig, Germany

Vladivostok, Russia

Moscow, Russia

Magadan, Russia

Moisture content resulting 30 years of operation

Equivalent to RH = 85%

More than 10 mm thick laminates does not reach the equilibrium moisture level

The effect of stiffener

on moisture distribution

Stiffener

Stiffener core has lower

moisture concentration

Relative

moisture

content


(Port Harcourt, Nigeria)

a bc

Pure resin

filler

The effect of fiber fraction V f

and radius of the stiffener

on total moisture content

0

0.2

0.4

0.6

0.8

1

0 5 10 15 20 25 30

Rel

ativ

e m

ois

ture

conte

nt

Radius, mm

Vf = 0.6

Vf = 0

0

0.2

0.4

0.6

0.8

1

0 0.1 0.2 0.3 0.4 0.5 0.6

Rel

ativ

e m

ois

ture

conte

nt

V f

Radius = 10 mm

Radius = 30 mm



0

20

40

60

80

0 4 8 12 16 20 24

Surf

ace

tem

per

atu

re,ᵒ

C

t, hour

White paint

No heating

Black paint

0

20

40

60

80

100

0 4 8 12 16 20 24

Rel

ativ

e h

um

idit

y, %

t, hour

White paint

No heating

Black paint

Typical daily surface temperatures

Corresponding relative humidity

0

0.2

0.4

0.6

0.8

1

0 5 10 15 20

Rel

ativ

em

ois

ture

conte

nt

l, mm

Black paint

White paint

No heating

The effect of color on the moisture content

of a horizontal panel

The effect of solar heating




Exposure to the sun reduces final moisture content

The effect of operation


0

0.2

0.4

0.6

0.8

1

0 5 10 15 20

Rel

ativ

e m

ois

ture

conte

nt

l, mm

Day 8 hour flights, without solar heating

Two 4 hour day flights, white paint

Night 8 hours flights, black paint



Flight exposure disperses the total moisture content

Application of operational temperature and moisture content


Numerical method: Laminated theory

Material: CYCOM 977

Lay-up configuration: {–45/0/45/0/0/90/0/0/45/0/–45}n

Failure criterion: Tsai-Hill

Thickness, mm Temperature °C Moisture content

2 54 0.84

8 60 0.83

20 65 0.70

-100

-50

0

50

100

150

0 10 20 30 40

σ11

τ12


Initial failure

-100

-50

0

50

100

150

0 10 20 30 40

σ11

τ12

normal conditions

high temperature and moisture content

realistic temperature and moisture for top surface

realistic temperature and moisture for bottom surface

Failure envelopes for 2 mm laminate

Ultimate failure

Application of operational temperature and moisture content


Thickness, mm Temperature °CMoisture

content

𝐾𝑊𝑇 Average

degradation𝜎11𝑇 𝜏12 𝜎11𝐶

2 54 0.84 0.93 0.78 0.76 17%

8 60 0.83 0.93 0.73 0.72 21%

20 65 0.70 0.90 0.69 0.68 24%

Standard case 82 0.85 0.85 0.63 0.63 30%


Summary

• Takeoff cooling reduces the maximum

operating temperature of thin components

• Thick laminates does not reach the equilibrium

moisture level over the operational lifetime

• Realistic temperature and moisture content

may reduce structural test’s overload factors

Thank you for your attention!

HYDROTHERMAL AGEING OF AIRCRAFT COMPOSITESHydrothermal Ageing of Aircraft Composites Kolesnik Kirill...

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