Impact of defects during automated fibre placement on the compression behaviour of cured CFRP structures

Abstract

Process induced defects during automated fibre placement (AFP) can have an impact on the mechanical behaviour of cured fibre composite structures. The influence of recurring defects such as gaps and overlaps have been extensively studied whereas the impact of tow-twists and fuzzballs is not well known.
Hence, the findings of compression tests carried out on carbon fibre-reinforced polymer (CFRP) test specimens with intentionally placed tow-twists and fuzzballs are presented in this study. The defects are characterised based on geometric data acquired during layup. The fully cured defect specimens are further examined by computer tomography (CT), giving an unprecedented understanding of how the defects deform during curing and affect the neighbouring laminae.
In addition, representative 3D meso-scale finite-element simulations of laminates containing the aforementioned defects are conducted, using the geometric data acquired by the CT-scans. The simulation output is then compared to the behaviour observed in the experimental tests.
The results from the compression tests indicate an influence of the defects on the compression strength, compression stiffness and buckling behaviour of the laminate, depending on the characteristic defect size and defect position in the layup. A conclusion is drawn towards being able to accurately predict the mechanical impact of fuzzballs and tow-twists numerically, thus aiding in the decision-making of when to remove such defects during parts production in the AFP process.

Full text

SAMPE Europe Conference 2022 Hamburg - Germany
1
IMPACT OF AUTOMATED FIBRE PLACEMENT INDUCED
DEFECTS ON THE COMPRESSION BEHAVIOUR OF CFRP
STRUCTURES
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ABSTRACT
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1. INTRODUCTION
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SAMPE Europe Conference 2022 Hamburg - Germany
2
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Figure 1: Tow-twist (left) and fuzzball (right)
2. EXPERIMENTATION
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Table 1: Layup of the three test laminates used in experimentation
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SAMPE Europe Conference 2022 Hamburg - Germany
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2.1 Naming convention
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2.2 Data processing
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Figure 2: 3D rendering of a segmented fuzzball. Pores inside the fuzzball are marked in red.
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SAMPE Europe Conference 2022 Hamburg - Germany
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3. RESULTS
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Table 2: E-module from classical lamination theory and mean E-module from tests of the three test laminates
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Figure 3: Stress-strain diagram for P1-REF-4. Local strain fields are shown at four distinct points during testing.
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SAMPE Europe Conference 2022 Hamburg - Germany
5
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Figure 4: Broken test specimen after compression testing.
Figure 5: Simulation boundary conditions
3.1 Simulation
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$%M$%'%"/&/*C%( 13#%+( '*L%( ;&'( '%/( /3( 1&/56( /6%( 'M%5*1%"'( ?$%%( /%'/( &$%&,( *P%P(
W^(11 c W^(11
P(86%(M+J(/6*59"%''(*"(/6%('*1>+&/*3"(;&'(&$.*/$&$*+J('%/(/3(
h"#$ iGX[(k1
P(
86%(.3//31(+3&#*"<('>$?&5%(;&'(5+&1M%#(*"('M&5%(Nu%"5&'/$%vOP(86%(/3M(+3&#*"<('>$?&5%(
;&'($%'/$*5/%#(/3(3"+J(13C%(*"(:R#*$%5/*3"(/3(&553>"/(?3$(/6%(+*"%&$(<>*#&"5%(3?(/6%(/%'/(
'%/>M(&"#(&MM3*"/%#(&(531M$%''*C%(+3&#(N)*<>$%([OP(86%(+3&#(;&'(*"5$%&'%#(*"(*"5$%1%"/'(
3?(
^P[(9f
(>"/*+(?*.%$(?&*+>$%(;&'(#%/%5/%#(;*/6*"(/6%(+&1*"&/%P(
Table 3: Maximum strength values as measured in experiments and as expected from simulations for the three test laminates
(
K:M%$*1%"/&/*3"(
-*1>+&/*3"(
(
w=>?)89:
(
w@
(
wAA
(
wBAA
(
2G(
TX^P[ j GHPG(72&(
T[[PW j HTPG(72&(
]GWPT(72&(
x(
2H(
WXXPH j GTPT(72&(
WHGPH j HePG(72&(
[^`P[(72&(
T`[PH(72&(
2T(
WGGPT j GTPH(72&(
T][P` j GeP[(72&(
W]GP`(72&(
T[XPG(72&(
(
8&.+%(T(531M&$%'(/6%(%:M%$*1%"/&+(1&:*1>1('/$%"</6'(
t;<*)34%
(?$31(/6%($%?%$%"5%(/%'/'(
/3(/6%('/$%''%'(
tCC
,(&/(;6*56( ?*.$%(?&*+>$%(?*$'/( 355>$$%#( *"(/6%('*1>+&/*3"',( &"#(
tDCC
,(&/(
;6*56( *"/%$R?*.$%( ?&*+>$%,( *P%P( ?&*+>$%( 3?( /6%( 1&/$*:,( ?*$'/( 355>$$%#( *"( /6%( '*1>+&/*3"'P(
)>$/6%$13$%,(/6%('/$%''(
tE
(&/( ;6*56(/6%('M%5*1%"'('/&$/%#(/3(.>59+%(*'(&+'3(<*C%"P(f3/%(
/6&/(%'M%5*&++J(/6%( /%'/( +&1*"&/%(2G(*'( M$3"%( /3(9*"9*"<(;*/6(
t;<*)34% x tEiG[PG(72&
P(
E>59+*"<(;&'("3/( 3.'%$C%#(*"( /6%('*1>+&/*3"',( &'(/6%( '*1>+&/*3"'( ;%$%( '3+C%#( +*"%&$+J(
;*/6(&"(%:M+*5*/('3+C%$P((

SAMPE Europe Conference 2022 Hamburg - Germany
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3.2 Test laminate P1
86%( /%'/( $%'>+/'( 3?( /6%( 'M%5*1%"'( ?$31( /%'/( +&1*"&/%( 2G( &$%( '63;"( *"( )*<>$%( ]P( 86%(
'M%5*1%"'( 3?( /%'/( +&1*"&/%( 2G( '63;%#( /6%( <$%&/%'/( /%"#%"5J( /3( 9*"9*"<P( -M%5*1%"'(
?%&/>$*"<(?>LL.&++'(<%"%$&++J('63;(&(#%5$%&'%(*"(/3+%$&.+%(531M$%''*3"('/$%''(
t;<*
P(-1&++(
?>LL.&++'(6%$%.J(/%"#(/3(6&C%(&(<$%&/%$(*1M&5/(3"(/6%(531M$%''*3"('/$%"</6P(-M%5*1%"'(
;*/6(?>LL.&++'(?>$/6%$('63;(&(53$$%+&/*3"(.%/;%%"(/6%(M3'*/*3"(3?(/6%(?>LL.&++(;*/6*"(/6%(
+&J>M( &"#( /6%( '/*??"%''(
r
P( Q6%"( ?>LL.&++'(&$%( *"/$3#>5%#( *"(+3;%$( M+*%',( /6%J(/%"#( /3(
#%5$%&'%('/*??"%'',(;6%$%&'(?>LL.&++'(M+&5%#(6*<6%$(>M(*"(/6%('/&59('63;(&"(*"5$%&'%(*"(
'/*??"%''P(
(
Figure 6: Deviation of
𝜎!"#
and
𝐸
relative to P1-REF for test laminate P1.
-M%5*1%"'(;*/6( /;*'/%#(/3;'(<%"%$&++J('63;(&"(*"5$%&'%(*"(.3/6(531M$%''*3"('/*??"%''(
&"#( '/$%"</6( ;6%"( 3$*%"/&/%#( M&$&++%+( /3( /6%( #*$%5/*3"( 3?( 531M$%''*3"P( 2%$M%"#*5>+&$(
+3&#*"<('63;'(3"+J(C%$J('1&++(#%5$%&'%(*"('/$%"</6(&"#('/*??"%''P((
83;R/;*'/'(;%$%("3/('*1>+&/%#P(I%"%$&++J,(/6%(*"?+>%"5%(#%?%5/'(6&C%(3"(/6%(1%56&"*5&+(
M$3M%$/*%'(3?(/6%(531M3'*/%(+&1*"&/%(*'(531M&$&.+J( '1&++( &"#(13'/+J($%'*#%(*"'*#%(/6%(
C&$*&/*3"(3?(/6%($%?%$%"5%('M%5*1%"'P((
3.3 Test laminate P2
)>LL.&++'(&+'3('63;(&"(*1M&5/(3"(/6%(1%56&"*5&+(.%6&C*3>$(3?(/%'/(+&1*"&/%(2H,(?%&/>$*"<(
&"(*"5$%&'%(*"('/$%"</6(?3$(/6%(+&$<%(?>LL.&++(*"/$3#>5%#(*"(+&J%$(X(N)*<>$%(XOP(86*'(1&J(
.%( *"/%$M$%/%#( '>56( &'( /6&/( ?>LL.&++'( *"( 1*##+%( +&J%$'( '/$%"</6%"( /6%( 531M&5/*3"(
.%6&C*3>$,(*P%P( /6%( ?>LL.&++(1&/%$*&+(1&J('>MM$%''(9*"9*"<(.J(/6*59%"*"<(/6%(531M3'*/%P(

SAMPE Europe Conference 2022 Hamburg - Germany
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86*'( ?*"#*"<( 5&"( &+'3( .%( ?3>"#( *"( /6%( 3>/+*%$( 2GR)RAXRA( *"( /6%( $%'>+/'( 3?(/6%( ?*$'/( /%'/(
+&1*"&/%( 2GP( 86%( '1&++%$( ?>LL.&++'( *"( /6%( /%'/( +&1*"&/%( H( 63;%C%$( 3"+J( '63;( &( $&/6%$(
'1&++(#%C*&/*3"(*"('/$%"</6(531M&$%#(/3(/6%($%?%$%"5%('M%5*1%"'P(86%('/*??"%''(&<&*"(*'(
*"?+>%"5%#(/6%(13'/(/6$3><6(/6%(+&J%$*"<(M3'*/*3"(;*/6*"(/6%(531M3'*/%P(
Z%<&$#*"<(/3;R/;*'/',(/%'/( +&1*"&/%(2H('63;'( +*//+%(%??%5/(3"( /6%(531M$%''*3"('/*??"%''(
%:5%M/( ?3$( /6%( RW[_( 3$*%"/%#( /3;R/;*'/( *"( +&J%$( HP( I%"%$&++J,( /3;R/;*'/'( *"( &(
j
W[_(
3$*%"/&/*3"('%%1(/3('/$%"</6%"(/6%(+&1*"&/%,(;6*56(*'(*"(53"/$&#*5/*3"(/3(/6%(?*"#*"<'(*"(
/%'/(+&1*"&/%(2GP(
(
Figure 7: Deviation of
𝜎!"#
and
𝐸
relative to P2-REF for test laminate P2.
3.4 Test laminate P3
86%( %??%5/'( 3?( ?>LL.&++'( 3"( /6%( /%'/( +&1*"&/%( 2T( &$%( '31%;6&/( >"5+%&$( &"#( *"( M&$/(
53"/$&#*5/(?*"#*"<'( 3?( 2G( &"#( 2HP( 86%( +&$<%$( ?>LL.&++'( *"#*5&/%( &( #%M%"#%"5J( 3?( /6%(
531M$%''*3"('/$%"</6(/3(/6%(M+J(+&J%$,(*"(;6*56(/6%(?>LL.&++(;&'(M+&5%#P(86%('M%5*1%"'(
;*/6(&('1&++(?>LL.&++(*"(+&J%$(X(63;%C%$('63;(&"(>"%:M%5/%#(.%6&C*3>$,(&'(/6%J('63;(&(
<$%&/(*"5$%&'%( .3/6(*"( '/$%"</6(&"#( '/*??"%''P(863><6( /6%(#%?%5/( *'(M+&5%#( .%/;%%"(/6%(
/6$%%(&#\&5%"/(^_R+&J%$'( 3?( /6%(531M3'*/%,('3( &$%(/6%(?>LL.&++'( *"( 'M%5*1%"'(2TR)RAeRA,(
;6*56(63;%C%$(3"+J('63;(&('+*<6/(*"5$%&'%(*"('/$%"</6(&"#('/*??"%''P((
86%(/3;R/;*'/'( 3?(/%'/( +&1*"&/%( 2T(53"/$&#*5/( ?*"#*"<'(3?( /6%(3/6%$( /;3( /%'/( +&1*"&/%'P(
I%"%$&++J,(&++('M%5*1%"'(;*/6(*"6%$%"/(#%?%5/'(/%"#(/3(.3/6('/*??%"(&"#('/$%"</6%"(/6%(/%'/(
+&1*"&/%P(86%(*"5$%&'%(*"('/*??"%''(1&J(.%(#%M%"#%"/(3"(/6%(+&J%$(*"(;6*56(/6%(/3;R/;*'/(

SAMPE Europe Conference 2022 Hamburg - Germany
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355>$$%#P(86*'(5&"(&+'3(.%(3.'%$C%#(*"(/6%($%'>+/'(3?(/%'/(+&1*"&/%(2GP(03;%C%$("3(5+%&$(
53$$%+&/*3"(;&'(?3>"#(?3$(/6%('/$%"</6(.%6&C*3>$(3?(/6%(/3;R/;*'/'(*"(/%'/(+&1*"&/%(2TP((
(
Figure 8: Deviation of
𝜎!"#
and
𝐸
relative to P3-REF for test laminate P3.
4. CONCLUSIONS
86%(&5S>*$%#(#&/&.&'%(3?(/6%(#%?%5/'(*'(>"*S>%,(&'(/6%(#%?%5/(<%31%/$J(3?(%&56(#%?%5/(;&'(
5&M/>$%#(.3/6(.%?3$%(&"#( &?/%$( &>/35+&C%(5>$*"<P(86*'(&++3;'( ?3$(&(#%/&*+%#(*"'*<6/( *"/3(
63;(#%?%5/'("3/(3"+J( $%&5/(/3(/6%(&>/35+&C%(M$%''>$%( 5J5+%,( .>/(&+'3(&??%5/('>$$3>"#*"<(
+&J%$'(;*/6*"(/6%(531M3'*/%(+&J>MP()>$/6%$13$%,(/6%$13<$&M6*5(*1&<%'($%53$#%#(#>$*"<(
+&J>M( &++3;( ?3$( &"( %:/%"'*C%( #&/&.&'%( /3( .%( .>*+#( >M( &"#( >'%#( ?3$( /$&*"*"<( 1&56*"%(
+%&$"*"<(.&'%#( 5+&''*?*%$'P( 86%($%'>+/'( ?$31(%:M%$*1%"/&/*3"( '>MM+%1%"/(/6%( #&/&.&'%,(
&++3;*"<(/3(M$%#*5/(/6%(1%56&"*5&+(*1M&5/(3?(#%?%5/'(3"+*"%(#>$*"<(/6%(+&J>M(M$35%''P(
86%(?*"*/%(%+%1%"/('*1>+&/*3"'(63;%C%$(#*#("3/(M$%#*5/(/6%(.%6&C*3>$(3?(/6%('M%5*1%"'(
#>$*"<(%:M%$*1%"/&/*3"P(86*'(*'(1&*"+J(#>%(/3(/6%(13#%+("3/(/&9*"<(.>59+*"<(*"/3(&553>"/P(
!+'3,( *11*"%"/( #%+&1*"&/*3"',( ;6*56( ;%$%( 5+%&$+J( &>#*.+%( #>$*"<( /%'/*"<,( ;%$%("3/(
&MM&$%"/(*"(/6%('*1>+&/*3"'P(86*'(.%6&C*3>$(1*<6/(.%(*"53$M3$&/%#(*"(?>/>$%('*1>+&/*3"'(
.J( *1M+%1%"/*"<( 536%'*C%( %+%1%"/'( *"( .%/;%%"( /6%( %+%1%"/'( 3?( &#\&5%"/( M+*%'P(
!##*/*3"&++J,(?>/>$%('*1>+&/*3"($>"'('63>+#(>'%(&"(*1M+*5*/('3+C%$(/3(&553>"/(?3$(.>59+*"<P((
KC&+>&/*3"( 3?( '*1>+&/*3"'( ;*/6( *"6%$%"/( ?>LL.&++'( *1M+*5&/%( &( $%#>5/*3"( 3?( /6%( 3C%$&++(
531M3'*/%('/$%"</6(#>%(/3(#%?%5/'P(86*'(*'(1&*"+J(#>%(/3(/6%( *"#>5%#( 3>/R3?RM+&"%( ?*.$%(
;&C*"%''( 5&>'%#( .J( /6%( ?>LL.&++',( ;6*56( *'( %:*'/%"/( *"( &++( +&J%$'( &.3C%( /6%( #%?%5/P(
f&/>$&++J,(*?(/6%(#%?%5/(*'(M+&5%#(*"(+3;%$(M+*%',(/6%(%??%5/(3?(/6%(#%?%5/(*'(/6>'(M$%#*5/%#(/3(

SAMPE Europe Conference 2022 Hamburg - Germany
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.%( 13$%( '%C%$%P( 03;%C%$,( %:M%$*1%"/&/*3"( '63;%#( /6&/( #%?%5/'( 1*<6/( %C%"( 6&C%( &(
M3'*/*C%( %??%5/( 3"( /6%( 531M$%''*3"( '/$%"</6( 3?( /6%( 531M3'*/%,( &'( /6%J( 1*<6/( 6*"#%$(
.>59+*"<($%'M3"'%(3?(/6%(531M3'*/%(M+&/%P(
86%( &>/63$'( ;3>+#( +*9%( /3( 6*<6+*<6/( /6&/( %:M%$*1%"/&/*3"( *"( /6*'( '/>#J( 53"/$&#*5/'(
?*"#*"<'(3?(4$3?/(%/(&+P(UGHV(&"#(3?(0&$*9(%/(&+P(U[V,(;6*56(.3/6(?3>"#(/6&/(/3;R/;*'/'(6&C%(
&("%<&/*C%(*1M&5/(3"(/6%(531M$%''*3"('/$%"</6(3?(531M3'*/%(M+&/%'P(86*'('/>#J('><<%'/'(
/6&/( *?( &( 531M3'*/%( M+&/%( *'( M$3"%( /3( .>59+*"<,(/6*59"%''R&+/%$*"<( #%?%5/'( '>56( &'( /3;R
/;*'/'(1*<6/(6*"#%$(.>59+*"<($%'M3"'%(&"#(/6>'(&5/>&++J(5&"(6&C%(&(M3'*/*C%,(&+.%*/(C%$J(
'1&++,(%??%5/(3"(/6%(531M$%''*C%('/*??"%''(&"#('/$%"</6(3?(&(531M3'*/%('/$>5/>$%P
(
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