Aerospace series - Definitions of imperfections and defects in organic matrix composite materials

This document provides a list of terms with their definitions illustrated by typical photographs, in order
to define a common vocabulary on the imperfections and damage that may occur during the
manufacture of organic matrix composite materials (which will be called “resin” in this document).
Some types of damage may also be encountered in use.
This document is restricted to their definitions and does not give any acceptance criteria. The word
“imperfection” will be preferred to the word “defect”, although the word “defect” might be usually used.
Defect acceptance criteria to be discussed between the user and customer and documented
appropriately between the two parties.

Luft- und Raumfahrt - Definitionen von Unvollkommenheiten und Defekten in der organischen Matrix Kompositmaterialien

Série aérospatiale - Définitions des imperfections et défauts dans les matériaux composites à matrice organique

Aeronavtika - Definicije napak poškodb v organskih matričnih kompozitnih materialih

General Information

Status
Published
Publication Date
28-Jun-2021
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
24-Jun-2021
Due Date
29-Aug-2021
Completion Date
29-Jun-2021

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SLOVENSKI STANDARD
SIST EN 4866:2021
01-september-2021
Aeronavtika - Definicije napak poškodb v organskih matričnih kompozitnih
materialih

Aerospace series - Definitions of imperfections and defects in organic matrix composite

materials
Luft- und Raumfahrt - Definitionen von Unvollkommenheiten und Defekten in der
organischen Matrix Kompositmaterialien
Série aérospatiale - Définitions des imperfections et défauts dans les matériaux
composites à matrice organique
Ta slovenski standard je istoveten z: EN 4866:2021
ICS:
49.025.99 Drugi materiali Other materials
SIST EN 4866:2021 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 4866:2021
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SIST EN 4866:2021
EN 4866
EUROPEAN STANDARD
NORME EUROPÉENNE
June 2021
EUROPÄISCHE NORM
ICS
English Version
Aerospace series - Definitions of imperfections and defects
in organic matrix composite materials

Série aérospatiale - Définitions des imperfections et Luft- und Raumfahrt - Definitionen von

défauts dans les matériaux composites à matrice Unvollkommenheiten und Defekten in der organischen

organique Matrix Kompositmaterialien
This European Standard was approved by CEN on 19 August 2019.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this

European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references

concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN

member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by

translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management

Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,

Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 4866:2021 E

worldwide for CEN national Members.
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SIST EN 4866:2021
EN 4866:2021 (E)
Contents Page

European foreword ...................................................................................................................................................... 5

1 Scope .................................................................................................................................................................... 6

2 Normative references .................................................................................................................................... 6

3 Terms and definitions ................................................................................................................................... 6

3.1 General................................................................................................................................................................ 6

3.2 Bonding imperfections ................................................................................................................................. 7

3.3 Presence of foreign substance .................................................................................................................... 8

3.4 Surface imperfections ................................................................................................................................... 8

3.5 Cavities.............................................................................................................................................................. 10

3.6 Fibres arrangement imperfection .......................................................................................................... 10

3.7 Imperfection specific to sandwiches...................................................................................................... 11

3.8 Stitching imperfections ............................................................................................................................... 12

3.9 Damage ............................................................................................................................................................. 13

3.10 Other .................................................................................................................................................................. 14

Annex A (informative) List of definitions and figures .................................................................................... 16

Annex B (informative) Pictures of bonding imperfections ........................................................................... 18

B.1 Absence of adhesive ..................................................................................................................................... 18

B.2 Absence of contact ........................................................................................................................................ 18

B.3 Adhesive joint colour heterogeneity...................................................................................................... 18

B.4 Adhesive rupture .......................................................................................................................................... 19

B.5 Debonding ....................................................................................................................................................... 19

B.6 Excessive adhesive bead ............................................................................................................................ 19

B.7 Insufficient adhesion ................................................................................................................................... 19

B.8 Junction imperfection ................................................................................................................................. 20

B.9 Lack of adhesive ............................................................................................................................................ 20

Annex C (informative) Pictures of presence of foreign substances ........................................................... 21

C.1 Foreign object................................................................................................................................................. 21

C.2 Inclusion ........................................................................................................................................................... 22

C.3 Pollution ........................................................................................................................................................... 23

Annex D (informative) Pictures of surface imperfections............................................................................. 24

D.1 Fern .................................................................................................................................................................... 24

D.2 Flaking .............................................................................................................................................................. 25

D.3 Wrinkle ............................................................................................................................................................. 26

D.4 Imprint .............................................................................................................................................................. 27

D.5 Indentation (dent/punching) ................................................................................................................... 27

D.6 Line flash .......................................................................................................................................................... 28

D.7 Marbling ........................................................................................................................................................... 28

D.8 Nick .................................................................................................................................................................... 29

D.9 Pill ....................................................................................................................................................................... 29

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SIST EN 4866:2021
EN 4866:2021 (E)

D.10 Projection ........................................................................................................................................................ 30

D.11 Resin flash ....................................................................................................................................................... 30

D.12 Scratch .............................................................................................................................................................. 31

D.13 Surface porosities ......................................................................................................................................... 31

Annex E (informative) Pictures of cavities ......................................................................................................... 33

E.1 Insufficient impregnation/dry area....................................................................................................... 33

E.2 Porosities ......................................................................................................................................................... 34

E.3 Voids .................................................................................................................................................................. 34

Annex F (informative) Pictures of fibres arrangement imperfections ..................................................... 35

F.1 Bird eyes .......................................................................................................................................................... 35

F.2 Gap/overlap .................................................................................................................................................... 35

F.3 Off-centring ..................................................................................................................................................... 36

F.4 Ply misorientation ........................................................................................................................................ 36

F.5 Resin accumulation ...................................................................................................................................... 36

F.6 Undulation....................................................................................................................................................... 38

Annex G (informative) Pictures of imperfections specific to sandwiches ............................................... 39

G.1 Accidental filling of honeycomb cells .................................................................................................... 39

G.2 Core crushing (honeycomb or foam) ..................................................................................................... 39

G.3 Cut honeycomb .............................................................................................................................................. 40

G.4 Deformed honeycomb cells ....................................................................................................................... 41

G.5 Edge filling imperfections .......................................................................................................................... 41

G.6 Insufficient meniscus on honeycomb .................................................................................................... 42

G.7 Lack of densification .................................................................................................................................... 43

G.8 Separation of the honeycomb nodal joints .......................................................................................... 43

G.9 Slope deformation (chamfer) ................................................................................................................... 44

G.10 Telegraphing .................................................................................................................................................. 45

Annex H (informative) Pictures of stitching imperfections ......................................................................... 46

H.1 Incorrect stitching depth ........................................................................................................................... 46

H.2 Loop ................................................................................................................................................................... 46

H.3 Missing stitching ........................................................................................................................................... 46

H.4 Non-conforming spacing ............................................................................................................................ 46

H.5 Non-conforming angle ................................................................................................................................ 46

Annex I (informative) Pictures of damages ........................................................................................................ 47

I.1 Burn ................................................................................................................................................................... 47

I.2 Crack .................................................................................................................................................................. 47

I.3 Cut ply ............................................................................................................................................................... 48

I.4 Decohesion ...................................................................................................................................................... 48

I.5 Delamination .................................................................................................................................................. 49

I.6 Microcrack ...................................................................................................................................................... 50

I.7 Perforation ...................................................................................................................................................... 50

I.8 Tearing-off of the material ........................................................................................................................ 51

I.9 Whitening of the resin ................................................................................................................................ 51

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SIST EN 4866:2021
EN 4688:2021 (E)

Annex J (informative) Pictures of other imperfections .................................................................................. 52

J.1 Excessive resin flow ..................................................................................................................................... 52

J.2 Feather duster ................................................................................................................................................ 52

J.3 Geometry imperfection ............................................................................................................................... 52

J.4 Non-conforming number of plies ............................................................................................................ 52

J.5 Non-conforming stacking sequence ....................................................................................................... 53

J.6 Non-conforming thickness ........................................................................................................................ 53

J.7 Pinching ............................................................................................................................................................ 53

Bibliography ................................................................................................................................................................. 54

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SIST EN 4866:2021
EN 4866:2021 (E)
European foreword

This document (EN 4866:2021) has been prepared by the Aerospace and Defence Industries

Association of Europe — Standardization (ASD-STAN).

After enquiries and votes carried out in accordance with the rules of this Association, this

document has received the approval of the National Associations and the Official Services of the

member countries of ASD, prior to its presentation to CEN.

This document shall be given the status of a national standard, either by publication of an identical

text or by endorsement, at the latest by December 2021, and conflicting national standards shall be

withdrawn at the latest by December 2021.

Attention is drawn to the possibility that some of the elements of this document may be the subject

of patent rights. CEN shall not be held responsible for identifying any or all such patent rights.

According to the CEN-CENELEC Internal Regulations, the national standards organizations of the

following countries are bound to implement this document: Austria, Belgium, Bulgaria, Croatia,

Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,

Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,

Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
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SIST EN 4866:2021
EN 4688:2021 (E)
1 Scope

This document provides a list of terms with their definitions illustrated by typical photographs, in order

to define a common vocabulary on the imperfections and damage that may occur during the

manufacture of organic matrix composite materials (which will be called “resin” in this document).

Some types of damage may also be encountered in use.

This document is restricted to their definitions and does not give any acceptance criteria. The word

“imperfection” will be preferred to the word “defect”, although the word “defect” might be usually used.

Defect acceptance criteria to be discussed between the user and customer and documented

appropriately between the two parties.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

• ISO Online browsing platform: available at https://www.iso.org/obp
• IEC Electropedia: available at https://www.electropedia.org/
3.1 General
3.1.1
damage

damage corresponds to degradation of the resin and/or the fibres caused by mechanical, thermal or

environmental stresses
3.1.2
defect
imperfection or damage which exceeds the part acceptance criterion
3.1.3
imperfection

particularity encountered in composite materials that may result from the manufacturing process

and/or the conditions of use

Note 1 to entry: Detection may be carried out visually or by using laboratory equipment.

3.1.4
indication

information given by non-destructive test means and which may correspond to an imperfection

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SIST EN 4866:2021
EN 4866:2021 (E)
3.2 Bonding imperfections
See also EN ISO 10365.
3.2.1
absence of adhesive
absence of adhesive with respect to the part definition
Note 1 to entry: See Figure B.1.
3.2.2
absence of contact

presence of the required adhesive on one or both faces of the assembly, but with no contact

Note 1 to entry: Encountered in case of poor matching.
Note 2 to entry: See Figure B.2.
3.2.3
adhesive joint colour heterogeneity

possible imperfections when using two-component adhesives of different colours, and caused by

incomplete mixing of the components (visible in particular in the adhesive bead)
3.2.4
adhesive rupture

total or partial separation of a bonding interface without rupture of neither the substrate nor the

adhesive

Note 1 to entry: As opposed to cohesive rupture (characterized by a rupture within the substrate or the

adhesive).
Note 2 to entry: See Figure B.3 and Figure B.4.
3.2.5
debonding

separation of two items as a result of adhesive or cohesive failure in the adhesive layer

3.2.6
excessive adhesive bead
localised adhesive surplus on the edge of a joint plane
3.2.7
insufficient adhesion

localised insufficient adhesion between two materials (substrate, adhesive, primer, etc.) characterised

by insufficient mechanical strength of the interface
3.2.8
junction imperfection
incorrect positioning of one part with respect to the other during bonding
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SIST EN 4866:2021
EN 4688:2021 (E)
3.2.9
lack of adhesive

local lack of adhesive (insufficient quantity or poor distribution) with respect to the part definition

Note 1 to entry: See Figure B.5.
3.3 Presence of foreign substance
3.3.1
foreign object

presence of any solid (non-metallic) particle, which is not part of raw material formulation

3.3.2
inclusion
metallic foreign object
Note 1 to entry: See Figure C.3 and Figure C.4.
3.3.3
pollution

presence of liquid or powder substance, which is not part of raw material formulation

Note 1 to entry: See Figure C.5 and Figure C.6.
3.4 Surface imperfections
3.4.1
fern

cluster of localised areas of insufficient resin on the surface, having the appearance of a fern leaf

Note 1 to entry: Fern is a special case of surface porosities.
Note 2 to entry: See Figure D.1 and Figure D.2.
3.4.2
flaking

local tearing-off of material (see 3.9.8) of millimetric dimensions from the surface layer of a composite

(flake detached or not) often localised on the edge of a part or of a hole
Note 1 to entry: See Figure D.3, Figure D.4 and Figure D.5.
3.4.3
wrinkle
fold of the fibres out of plane affecting one or more layers
Note 1 to entry: See Figure D.6, Figure D.7 and Figure D.8.
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SIST EN 4866:2021
EN 4866:2021 (E)
3.4.4
imprint

hollow mark on the surface of the part related to the production tooling (mould or environment

products)
Note 1 to entry: See Figure D.9.
3.4.5
indentation (dent/punching)
bump of material due to an impact on the part
Note 1 to entry: See Figure D.10.
3.4.6
line flash

line shaped accumulation of resin caused by an undulation close to the surface of the part

Note 1 to entry: See Figure D.11.
3.4.7
marbling
heterogeneity of the part’s colour or gloss
Note 1 to entry: See Figure D.12.
3.4.8
nick

cut opening onto the surface of the part, due to a mechanical action (tool), which could affect the fibres

Note 1 to entry: See Figure D.13 and Figure D.14.
3.4.9
pill
cluster of fibre residues
Note 1 to entry: See Figure D.15.
3.4.10
projection
mark in relief (or surface topology imperfection) on the surface of the part
Note 1 to entry: See Figure D.16.
3.4.11
resin flash
thin layer of pure resin extending over the part surface
Note 1 to entry: See Figure D.17.
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SIST EN 4866:2021
EN 4688:2021 (E)
3.4.12
scratch
thin surface mark due to a mechanical action, affecting only the resin
Note 1 to entry: See Figure D.18.
3.4.13
surface porosities
localized points of insufficient resin on the surface

Note 1 to entry: The term “crater” can be used in case of an isolated cavity opening onto the surface, of dimension

greater than a few tenths of a millimetre.
Note 2 to entry: See Figure D.19 and Figure D.20.
3.5 Cavities
3.5.1
insufficient impregnation/dry area
lack of impregnation of the fibres by the resin
Note 1 to entry: See Figure E.1 and Figure E.2.
3.5.2
porosities
randomly distributed spherical gas cavities
Note 1 to entry: See Figure E.3, Figure E.4, Figure E.5 and Figure E.6.
3.5.3
voids
cavity with a tubular shape or whatever shape, e.g. bridging, piping

Note 1 to entry: Bridging is a condition where plies span an internal feature thus creating a void.

3.6 Fibres arrangement imperfection
3.6.1
bird eyes
local separation of two adjacent tows
Note 1 to entry: See Figure F.1.
3.6.2
gap/overlap

ply not positioned edge to edge with respect to the adjacent ply, which generates an overlap or gap of

material
Note 1 to entry: The gaps and overlaps may be in the part definition.
Note 2 to entry: See Figure F.2 and Figure F.3.
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SIST EN 4866:2021
EN 4866:2021 (E)
3.6.3
off-centring
modification of the angle between the warp and the weft
Note 1 to entry: See Figure F.4.
3.6.4
ply misorientation

deviation of the fibres’ direction in a ply (unidirectional or fabric) compared to the theoretical definition

3.6.5
resin accumulation

surplus of a resin volume without fibre which could locally affect the Fibre Volume Ratio (FVR) and

geometry of the part
Note 1 to entry: See Figure F.5, Figure F.6 and Figure F.7.
3.6.6
undulation
waviness deformation of the fibres in or out of the plane
Note 1 to entry: See Figure F.8 and Figure F.9.
3.7 Imperfection specific to sandwiches
3.7.1
accidental filling of honeycomb cells

filling of one or more honeycomb cells by skin resin, adhesive or densification resin

Note 1 to entry: See Figure G.1.
3.7.2
core crushing (honeycomb or foam)

damage to the core resulting in a local reduction in its thickness or shape, possibly leading to buckling

of the honeycomb or deformation of the foam
Note 1 to entry: See Figure G.2 and Figure G.3.
3.7.3
cut honeycomb
cut in the honeycomb during the implementation process, by a sharp object
Note 1 to entry: See Figure G.4.
3.7.4
deformed honeycomb cells

sideways movement of the cell walls to produce one or several line(s) of distorted cells

Note 1 to entry: See Figure G.5 and Figure G.6.
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SIST EN 4866:2021
EN 4688:2021 (E)
3.7.5
edge filling imperfection
insufficient resin filling on the edge of a sandwich panel
Note 1 to entry: See Figure G.7.
3.7.6
insufficient meniscus on honeycomb

the adhesive or resin does not produce an effective fillet on the honeycomb (fillet not formed or badly

formed)
Note 1 to entry: See Figure G.8 and Figure G.9.
3.7.7
lack of densification
partial or total absence of the densification filling
Note 1 to entry: See Figure G.10.
3.7.8
separation of the honeycomb nodal joints

separation of adjacent honeycomb cells, possibly due to insufficient adhesive or incorrect bonding of

the sheets forming the honeycomb
Note 1 to entry: See Figure G.11.
3.7.9
slope deformation (chamfer)

difference in slope angle with respect to the definition, by crushing of the core or slipping of the

honeycomb

Note 1 to entry: This imperfection occurs mainly during the polymerisation phase.

Note 2 to entry: See Figure G.12 and Figure G.13.
3.7.10
telegraphing
collapse of the composite skin into the honeycomb cells
Note 1 to entry: See Figure G.14, Figure G.15 and Figure G.16.
3.8 Stitching imperfections
3.8.1
incorrect stitching depth
stitching depth does not conform with the definition
3.8.2
loop
thread pulled out of the weaving plane
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SIST EN 4866:2021
EN 4866:2021 (E)
3.8.3
missing stitch

absence of stitch throughout the part thickness compared to the definition pattern

Note 1 to entry: See Figure H.1.
3.8.4
non-conforming spacing
spacing between the stitches does not conform with the definition pattern
3.8.5
non-conforming stitching angle
stitching angle does not conform with the definition
3.9 Damage
3.9.1
burn

sign of local thermal decomposition causing a colour variation, perhaps blackening, and which could

damage the material
Note 1 to entry: See Figure I.1.
3.9.2
crack

rupture in the part thickness, with broken fibres, not crossing through the entire part

Note 1 to entry: See Figure I.2.
3.9.3
cut ply
accidental cut of the reinforcement, caused by a mechanical action
Note 1 to entry: See Figure I.3.
3.9.4
decohesion
fibre/resin separation
Note 1 to entry: See Figure I.4 and Figure I.5.
3.9.5
delamination
rupture
...

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