ABSTRACT.- FAC IAL PROTECTlON OF MOTORIZED TWO

FA C I A L PROTE C T l ON O F MOTOR I Z E D TWO- W H E E L E R R I DE RS .
NEW FEATURES O F A S P E C I F I CA T I ON FOR " FU L L FA CE" H E LM E T .
G . Wa l f i sc h , F . Chamouard , A . Fayon , C . Tarr i ere , Laborato i re d e
Phys i o l og i e et de B i omec an i q u e Peugeot S . A . / Ren a u l t , 1 32 rue d e s
s u i s s e s , Nanter re . FRANC E .
C . Got , F . Gu i l l on , A . Fate i , I RA C B A , Hop i t a 1 Rayrnond f.io 1 n c a re ,
1 ü4 �d Raymond P o i n c are , 9 2 380 Ga rche s . FRANC E .
J . Hurea u , Laborato i re d 1 An atom i e , Un i vers it e Rene De s c a rt e s , 4 7
r u e des Sa i nt s Pere s , 750 0 5 P a r i s .
ABSTRAC T . Recent a c c i dent i n ve s t i g at i on s ( 1 ) ( 2 ) h a ve shown t hat f ac 1 a i i mpacts
account for some 3 1 % of th e head i n j ur i e s s u s t a i ned by two-whe e l -mot o r i zed­
veh i c l e r i d e rs , and that t h e e x i s t i ng fu l l face he lme t s h a ve brought out no
s i gn i f i c ant redu c t i on in i n j u r i e s with the except i on of mi nor f a c i a l i n j ur i e s * .
I n f act , they i n d i c ate some 7 9 % of t h i s type of i n j u ry for non -wearers of
vi zors and 2 1 % of th es e s ame i n j u r i e s for we a re r s of t he se .
Howe ve r , i f th e i n j u r i e s that are more s e r i o u s than m i no r are con s i d e re d ,
the
bas i s of these s ame b i b l i og rap h i c a l source s , i t e merges that t he deg ree
on
of f ac i a l protect i on pro v i d ed by the f i tt i ng s that are standard e q u i pment on
most of the h e l mets a va i l ab l e on the market e nab l e s �o mean i ngf u l reduct i on i n .
the frequency of occurrence and t he seve r i ty of these i n j u r i es .
Thes e reason s , added to the absence of reg u l at i on s go vern i ng t h i s area ,
prompted to d e s i g n and produ c e , under a French Government contract , a proto­
type he l met in accordance w i th ECE regu l at i on 22-02 to whose f ac i a l part
( v i zor and j aw p a rt ) spec i f i c i n ve s t i g at i on s were d e voted .
The un i t composed of the v i zor , j a w protecto r , and s h o c k - a b sorbent ma­
"
ter i a l l ocated in the f ront part of the' i nt egra f' h e l met con s t i tutes the f ac i a l
protec t i on of t h e prototype .
A separate i n ve s t i g a t i on wa s d e voted to e ach of the features l i s ted
above . The comp l ete prototype h e l met was then t e sted wit h human s u b j e ct s ,
under the s a me cond i t i on s a s other commerc i a l l y a v a i l a b l e h e l me t s reputed to
be "s at i sf actory" .
I - PROTOTYPE V I ZO R . - Mathemat i c a l mode l l i ng - I n order to better p i n po i n t and g u i de t h e
cho i ce of the rrechanical and geomet r i c a l c h a racte r i s t i c s of a " s a t i s f actory1'
v i zor t h at wou l d be ad a�ta b l e to t he f u l l face prototype he l me t , t he s o - c a l l ed
"f i n i shed e l ement s " mathemat i c a l mode l l i ng was u sed .
( * ) The i n j ury seve r i ty s c a l e u sed was the A I S ( 3 ) . M i n o r f ac i a l i n j u r i es are
c l a s s i f i ed as 1 ( oc u l a r - , denta l - , and c ut aneous i n j ur i e s ) , moderate
i n j u r i e s are rated as 2, and ser i o u s i n j u r i e s are c l a sse d i n A I � 3 .
193
I n the present c a se , the pro b l em was the mode l l i ng of the beha v i ou r of
the v i zor of a he l met e xposed to i mpact . Dyn am i c mode l l i n g of an i mpact ( e ven
i n the absence of the occu r rerce of f racture ) a s s o c i ated w i t h non l i n e a r beh a ­
v iour of t h e mate r i a l i s d i f f i cu l t . In t h i s c a s e , the object i s n o t t o deter­
m i ne the re a l v a l ue s of t he d i s p l acement s and stresses in the e l ement s ;
rather , i t i s to a s c e rt a i n the areas of concent rat i on of stre s s and to compare
v a r i o u s d i fferent techn i c a l s o l u t i on s . lt i s then suff i c i ent to con s i d e r a
stat i c l o ad i n g of th8 v i zo r and to a s s ume t h e mater i a l 1 s be h a v � u r to be l i nea r
and e l a st i c .
The v i zo r i s d i v i ded i nto 226 t r i angu l ar e l ement s , def i n i t i on of the
mes hwork was automat i c , and the node po i nt s ( a pexes of the t r i ang l e s ) were
mEa s u red on the p l ane s u rfaces of the v i zor .
Fou r types of v i zo r were mode l l ed w i t h the parameters of t h i c k n e s s and
shapes bei n g made t o v a ry .
o r i g i n a l v i zo r
o r i g i n a l v i zo r
cu rved v i zo r
c u rved v i zo r
t h ickness
t h i ck n e s s
t h i c kness
t h i c kness
2 . 5 mm
4 mm
2 . 5 mm
4 mm
The cu rve g i ven to the v i zor was that of a c u rve w i thout the vert i c a l
sect i on s , a s h a p e whose effect was to t ransform t he o r i g i n a l f l at ve r s i on
i nto a 1 1 bu bb l e 11 -type h a v i ng two d i rect i on s of c u rvature : one a round a vert i ­
c a l a x i s due t o the s h ape of the h e l met ( i dent i c a l to t h at of the o r i g i n a l
v i zo r ) and one around a h o r i zonta l t r a n s verse a x i s .
F i g u re 1 shows v i ews of the two v i zors after they had been c u t i nto
f i n i s hed components .
The ac c i dent d at a referred to above ( 1 ) ( 2 ) st ate t h at two types of
obstac l e are most l i ke l y to be struck by the v i zo r , i .e . the p l an a r and
ang l ed ones . The ma j o r i ty of the s e r i o u s i n j u r i e s were due to i mpacts aga i n st
ang l e s : th i s type of i mpact i s what was used for t he mathemat i c a l mod e l l i n g .
A 1 00 d a N re s u l t ant stat i c l oad was a p p l i e d to the v i zor on a med i an
hor i zon t a l p l an e and f o r two c a s e s of l o ad i ng s .
-0
Symmet r i c a l l o ad i ng
Latera 1
1 oad i ng
1 94
0::
0
N
>
Cl
UJ
>
0::
=>
'-'
0::
0
N
>
<.!)
z
--"
--"
UJ
Cl
0
:::e:
.....
«:
--"
�
<.!)
�
195
The force was ap p l i ed onto t h ree node po i n t s of the me shwork . The v i zor
wa l he l d i n p l ace on the he l met , and the he l met s upports and anc horage
sup ports were i nt roduced onto the mod e l .
The Young ' s mod u l e of the mate r i a l was t aken to be equal to 240 d a N/mm
�
- Re s u l t s of mode l l i n g - For each e l ement , the c a l cu l at i on prog ram
y i e lded the p r i n c i pal s t r e s se s , t he reac t i on s to su pport po i nt s and to f i xt u ­
re-embedment po i nt s ( fo rces , moment s ) , the d i s p l acements and rotat i on s o f th e
mes hwork n o de p o i nt s , e t c .
I n order to j udge t h e va r i ou s res ponses of the v i zors accord i n g to
the i r t h i c k n e s s es a n d s h a pe s , t h e ex ped i ent c r i te r i on chosen was the VON
M I S E S max i mum : the h i gh e r i t i s , the h i gher i s t he s t ate of the s t re s s e s i n
the e l ement s under cons i de r a t i o n . The fol l ow i n g t a b l e summa r i ze s the resu l t s
obt a i ned i n terms of t h e reduct i o n of the VON M I S ES ma x i mum c r i te r i on when
v i zor t h i c k n e s s was i n c re a s ed f rom 2 . 5 mm to 4 mm .
Tab l e 1 - Coeff i c i ent of reduc t i on of VON M I S E S i n the e l ement the most acted
u pon .
Cu r ved V i zo r
F l at v i zor
Coeff i c i en t of
red u c t i on · Of
the VON M I S E S
Symmet r i c a l l o ad i ng
1 . 98
2 . 39
Lat e r a l l oad i ng
1 . 78
1 . 89
- Concern i ng t h e i n f l uence of v i zor t h i c k n e s s - The preced i n g t a b l e
shows t hat t h e reduction of t he stresses i s more than proport i onate to the
red u c t i on of the t h i c k n e s se s .
4 mm
2 . 5 mm
�
1 .6
The i n c rease i n t h i ck n e s s t herefore appe a r s to be a s at i sf actory
parameter for i n c re a s i n g v i zo r re s i stance .
- Concer n i ng the i nf l uence of v i zor c u r v e - A con s i derab l e red u c t i on
i n s t re s s e s appears when t h e c u rvature i n c rease s .
The f i gures l i sted here shou l d , howeve r , not to be taken at t he i r f a c e
v a l u e i n order to j udge the effect o f the curvat u re . I n fact , when i mpact
occu rs , the phy s i c a l mag n i tude i n put i s not the force of the i mpact , a s i t
i s here i n the c a l c u l at i on ; rathe r , i t i s the energy of i mpact . I n c re a s i ng
the c u rves howe ver , l e a ds t o i n c re a s i n g the st i ff n e s s of the v i zor ; f o r a
g i ven energ y , the forces c a n be g reater .
An e x pe r i men t a l i n ve s t i g at i on u s i n g the d ev i c e shown hereaft e r was
perfo rmed for the purpose of showing that the force var i at ion at c o n s t a n t
energy w a s very s l i g h t when t he v i zor was c u r ved .
The v i zo r was he l d r i g i d l y between two su pport s . I t s cu rve rad i u s was
ad j u st a b l e , a s was the center d i stance of the a xe s of the s u pport s . Two
exper i me n t s were perfo rmed at several d i ff e re n t d rop he i g ht s .
1 96
g u id e w i re
l
1
Acce l erometer
Fa l 1 i ng mass
1 . Center d i stance of a xe s 1 90 mm ( d )
( rad i u s of c u rve R � 4 1 5 mm )
h
2 . Center d i stance of axes 1 90 mm ( d )
( rad i u s of c u rve R � 235 mm )
h
=
=
1 1 mm
20 mm
The f i n d i ng s are l i sted i n the t a b l e be l o w .
Tab l e 2 Ma x i mum acce l e rat i on
Drop h e i ght ( H )
0 . 50 m
1 . 00 m
1 . 50 m
h
=
1 1 mm
1 8 g / 80 d a N
3 0 g / 1 36 d a N
44 g/ 196 daN
max i mum Fo rce
h
=
20 mm
14 g/ 63 daN
34 g / 1 54 d a N
48 g / 2 1 8 d a N
The above f i nd i ng s show that , for t he k i nd of ex�e r i ment i n vo l ved and f o r
t h e type of mate r i a l tested , a c on s id erab l e reduct i on i n t h e v i zor 1 s c u r v a ­
ture rad i u s f a i l s t o b r i ng out any ma j o r i n c rease i n the l e ve l s o f forces
and stre s s e s , by f a i l i n g to l ower the fr acture thresh o l d , and w i t h the
oppo s i t e effect e ven seem i n g po s s i b l e .
I n add i t i on , an i n c re a s e i n the v i zor 1 s c u rvature i nduces the
f ol l ow i n g :
1 97
The mo v i n g of the head f a rther away f rom t he obstac l e , and t h ereby i n t he
event of i mpact a l l o w i n g t h e head to h a ve a l anger stop p i n g d i st ance ,
- I n c re a s ed f ac i a l r i g i d i t y of t h e he l met by t h u s e n a b l i n g the v i zo r to
better part i c 1 pate i n i mpact absorpt i on .
I n con c l u s i on , on the bas i s of the c o n s t r a i nt s of o pt i c a l q u a l i t y
( p r i smat i c effect ) , aerodyn am i c s and sty l e , we were l ed t o propose a pro­
nounceo c u rvature of the v i zo r , bot h around the vert i c a l a x i s and around a
h o r i zon t a l a x i s .
- Ch o i c e of v i zo r mater i a l - For rea sons of h i g h cost , we s e l ected t h e
mate r i a l on the ba s i s of e x i st i ng v i zors that wou l d i nt e rface w i t h the proto­
type he 1 met .
The mater i a l c hosen was the one whose penet rat i o n res i stance proved to
be the h i ghest in dyn a m i c tests of the f ree f a l l of a 5-kg corne r .
( he 1 g h t of f ree-f a l l = 1 meter ) .
These t e s t s were perfo rmed i n accordance w i th t h e cond i t i on s def i ned i n
the proced u re set out for Fre n c h norm N . F . 72304 ( see F i g u re 2 ) , at d i f f e rent
tempe ratu res .
Two v i zo r s were te sted a s fo l l ows
- One made of acetobutyrate , w i t h two c u r v ature d i rect i on s and a
t h i c k n e s s of 2 . 5 mm ,
One made of po l yc a r bon ate , w i t h one cu rvature d i rect i o n and the
s ame t h i c kn e s s .
Two tests were perfo rmed for each test cond i t i on . The f o l l ow i n g t a b l e
s h ows the f i n d i n g s .
Ta b l e 3 Di stance
( c orne r ) ( mm )
Tempe rature
0° c
Nat u re of
mate r i a l
+
20° c
Acetobutyrate
+
20° c
Po l y c a r bonate
+
50° c
Acetobutyrate
0
0
+
50° c
Po l y c a rbon ate
10
10
- 20° c
Ac etobutyrate
0
0
- 20° c
Po l y c a r bonate
f ace /pun c h
0
0
11
10
1
11
Observat i on s
V i zor p i e rced
and broken
No crac k i ng of
v i zo r
Punctu r i ng o f f ace
with c r ac k i ng of
v i zo r a l ong 50 mm
No c r a c k i ng
V i zor p i erced and
broken
No crack i ng
1 98
.......
"°
"°
r IG
2
Rigid
Support
-:r--·
35 mm
-
1
1
1
.... � ..,,.
,
;ti
.
"" ,,,
'
\
//
'
\
1
1
I
I
\
V ! ZOR P E NETRAT ION TESTS
1
l
1
.- �
'
t
He i gh t o f Free Fa l l
( 1 mete r )
Fa l l i ng m a s s
FIG 3
-
TEST CON F I GURAT I ONS
EVALUAT I ON OF THE I MPROVED PROTECT I O N
AFFORDED BY T H E V I ZOR
An a l y s i s of t h e t a b l e c l e a r l y s hows t h at the po l y c a rbonate res i st s
penetrat i o n muc h better than t h e aceto butyrate .
I n f act , i n a l l t h e test s , and at whatever the tempe r atu re , the aceto­
buty rate v i zo r was con s i sten t l y broken and punctured by the corner wh i c h ,
after the test , was s t i l l i n contact w i t h the s u rrogate head .
Howe ve r , w i t h the p o l yc arbo n ate v i zo r , under the s ame i mpact cond i t i o n �
there w a s n o o c c u rrence o f v i zo r c r ac k i ng and t h e d i stance between t h e
corner and t h e head rema i ned a t between 1 0 and 1 2 mm .
I n conc l u s i on concern i n g t hese test s , t h e mater i a l s e l ected for the
proto type f u l l -f a c e he l met was po l y c a rbonate .
For t h e rea sons of cost noted , for equ i p p i n g t h e prototype he l met we
c h o s e t h e 2 . 5 mm t h i c k f l at po l y c a rbonate v i zo r w i t h one c u rvature d i rect i on
( i n re l at i on to the vert i c a l a x i s ) .
- Eva l u at i on of t h e i mproved protec t i on afforded ty t h e v i zor Th i s evalu at i on was performed by me a n s of dyn a m i c f ree -fall tests
( a s s hown in F i g u re 3 ) of a Part 5 7 2 d ummy he 2 d , whose f ac i a l part h ad been
mod i f i ed so as to i n corporate the s i mu l ated h uman face des i gned by Leu�g et
a l . ( 4 , 5 ) Th i s s i mu l at i on h a s the advant age of h a v i n g a honeyco�c structure
( see F i g u re 4 ) , of � h i c h t h e deformat i on co rre l ates with t h e seve r i ty of the
bone i n j u r i e s that wou l d h a ve been s u s t a i ned by the face of a human be i n g
struck under the s ame i mpact cond i t i on s .
Se vera l d i fferent drop h e i ghts were u s ed . The f i n d i ng s are set out i n
the fo l l ow i ng t a b l e , wh i c h a l s o l i st s the d at a obt a i ned w i t h a reputed l y
" s a t i s f actory " commerc i a l l y a v a i l a b l e h e l met , tested under the s e.me i mpact
cond i t i on s ( i de nt i f i ed as h e l met " G" i n the p r e sent repcrt ) .
Th i s h e l met h a s a p o l yc a r bonate v i zo r l i ke t h at of t h e protctype he l met .
The v i zo r ' s c u rve , i t s d i men s i on s , t h e s u rface area of i t s s u pport s on t h e
" G" he l met , a n d i t s m a s s a re c l o s e l y s i m i l a r to those o f t h e prototype
he l �et . V i zo r ' s t h i c k n e s s i s 2 mm .
Ta b l e 4 Drop he i g ht
(m)
Depth of i mp r i n t of the hcneycomb
structure of the s u b s t i tute face ( mm )
1 0 / Prototype he l met
1 .5
2
2.5
1 .5
4
7
20 / " G" he l met
9
9
13
1 .5
2
2.5
F i gure
5
i l l ust rates these f i n d i ng s
200
FIG 4
-
HUMAN FACE MODEL
Impact s peed
5,4
m/S
Impact s peed
7
FIG 5
-
m/S'
FAC I A L D E F C RMAT I ONS OF THE HUMAN FACE MOD E L
201
S i n c e , i n aad i t 1 o n , n e i ther of the two v i zo r s was c r a c ked , and a l so
s i n c e the f i xat i on components h o l d i ng t h e v i zor ontc the he l met und erwent n o
dete r i orat i on , there i s reason t o be l i eve that t h e f i nd i n g s a r e l a rge l y
att r i bu t a b l e t o the d i fference between the two v i zors , i .e . bas i c a l l y t he i r
t h i c k n e s se s .
Th i s me a n s that w i t h the v i zor u sed , 0 . 5 mm of i nc re a s ed t h i c k n e s s ( i
25 %) e n a b l ed a 50 % reduct i on i n the depth of the c r u s h of the s u b s t i tute
f a c e . Th i s i s an i nterest i n g f i n d i ng , and it co rroborates those y i e l ded by
t h e mathemat i c a l mode l l i ng .
-�
I I - I MP ROVEMENT O F MAX I L LAR · P ROT ECT I ON As stated e a r l i e r , on t h e bas i s of t h e ac c i dent data a l ready men t i oned ,
t h e f u l l f ace he l mets do not make i t po s s i b l e to prevent ma x i l l o - f a c i a l
f r actures ( A I S
2) .
�
We consequen t l y endea voured to f i t the ma x i l l a ry parts of the prototype
" i nteg r a l 11 he l rr:et w i t h a s hoc k - a b sorbent mater i a l t h a t \'Ja s compat i b l e w i t h
t h e fracture tc l e r ance of t h i s body a re a , wi thout red u c i ng i t s comfcrt and
w i thout detract i n g from t he correct n e s s of i t s f i t onto the head .
Under these cond i t i o n s , t h e space a v a i l a b l e i n t h e prototype h e l met was
about 2 5 mm .
W i th t h i s s pace occupancy req u i rement , t h e object , then w a s to absorb a
ma x i mum amount of energy w i t h a s h o c k - a b sorbent mater i a l that wo u l d make i t
poss i b l e to . rema i n be l ow the j awbone s 1 f r a c � u re t o l erance . Eva l u a t i on .... a s
performed on the bas i s of e x i st i ng b i b l i ograph i c a l d a t a ( 6 ) . W h e n t he forces
were t r a n s m i tted to the two j awbones in t h e antero poster i o r d i rect i o n , a
force somewhere between 200 and 300 d a N seems to be esta b l i shed at t he t o l e ­
rab l e thresho l d .
I n add i t i on , anth ropomet r i c a l me a s u remen t s s h owed u s t h at the pres umed
maxi l l ary s u pport s u rface area cn the he l met i s 40 cm2 .
I n the l i ght of these data , and a l s o bec a u s e of the objec t i ve i n vo l ved ,
.,.,.e se l ected s h o c k - absorbent mate r i a l s whose p a rt i c u 1 a r f eature was t h a t they
were c r u s h a b l e under an a p prec i a b l y ste ady p re s s u re of from 5 to 7 . 5 d a N /cm2 .
Fou r mate r i a l s were s e l ected :
- " E L F i s o l at i on " w i t h a den s i ty c l o se to 5 0 g / l and 60 g / l : t h i s a
r i g i d , c r u s h a b l e p o l yu rethane foam .
- " Styrofoam" , a po l yester foam w i t h a den s i ty of about 30 g / l .
- " Ro h a c e l 1 3 1 " , a copo l yme r i c po l ymethacry l i c .
- I n add i t i on to t h e above , we u s ed expanded po l ystyrene f o am h a v i ng a
den s i ty of about 30 g / l for pu rposes of compa r i son , mak i n g t h i s c h o i ce bec a u ­
se t h i s mater i a l i s a very common l y empl oyed s u bstance , i s easy to i n s t a l l i n
a he l met , i s a l s o i nexpen s i ve .
202
- Test cond i t i on s - 1 he te s t i ng method c hosen i n vo l verl t h e free-f a l l of
a s u b s t i tute h e ad we i g h i n g 4 . 7 Kg , e n c a sed i n t h e prototype he l met and f a l ­
l i ng onto a f l at , r i g i d an v i l , a s i l l u s trated by f i g u re 6 , at a l e v e l of t h e
j awbone p a r t o f the he l met .
Impact ve l oc ity for a l l these tests was 5 . 5 m / s . Ta b l e 5 l i st s t h e
p r i n c i pa l mea s u rement f i nd i n g s .
The acce l e rat i o n s were me a s u red at t h e center of grav i ty of t h e s u r ro­
gate head , and force was me a s u red on the a n v i l .
l t s h ou l d here be noted t h a t t h e forces t r a n s m i tted t o t h e j awbones are
nec e s s a r i l y l ower than those me a s u red on the a n v i l bec a u s e of the i n ert i a of
the he l met in the beg i n n i n g of the i mpact .
Two tests were perfo rmed w i t h e a c h mater i a l . F i g u re 7 i l l u strates t h e
pr i n c i pa l f i nd i ng s .
A l l the tests were perfo rmed w i t h h e l n�t c h i n s t r a p s u n attac hed , so a s
to p i n po i n t more a c c u r ate l y the effects of the prototype s h o c k - absorbe n t
features i n st a l l ed i n t h e m a x i l l a ry p a r t o f t h e prototype i nteg ra l -de s i g n
h e l met i n p l ac e of t h e " comfort " foam padd i ng .
- Findings -
Ta b l e 5 l i st s t h e p r i n c i pa l me a s u remen t s .
- Te s t N ° . 1 re l ates to the " G" h e l met , wh i c h , i t w i l l be reca l l ed , i s
a commerc i a l l y a v a i l a b l e fu l l -f a c e he l met reputed to be " s a t i s f actory " .
- Te s � N ° . 2 and 3 re l ate to a prototype - de s i g n h e l met whose ma x i l l a ry
part wa s , l i ke t h at of h e l met " G" , f i tted w i t h " c omfo rt " f oam padd i n g on l y .
The s e t h ree tests served a s references for a s ses s i ng t h e i mpro vement i n
maxi l l ary protect ion prov i d ed by t h e s h ock- abso rbent feature s e l ected .
Un der t h e c on d i t i o n s of t h e tests performed , i f we u s e the red u c t i on i n
ma x i mum acce l e rat i o n s ( o r i n �ax i mu m forces t ransmi tted to t h e maxi l l a r i e s )
to j udge the s h o c k - a bsorbent c h aracte r i st i c s of t h e mate r i a l s emp l oyed ,
comp a r i son between the f i n d i n g s of t h e reference tests ( te s t s 2 and 3 of
t a b l e 5 ) and those of the other tests - s pec i f i c a l l y of tests 9 and 1 0- p o i n t
t o a n attenuat i o n o f i mpact w i t h t h e prototype h e l met wh i c h ranges between
60 % and 70 % .
l t w i l l be f u rther noted that , a s compared w i t h t h e " G" h e l met ( te s t 1 ),
the prototype h e l met that was f i tted w i t h 2 5 mm of " E L F i s o l at i o n " 5 0 g / l
( tests 9 and 1 0 ) e n a b l ed a n e a r l y 90 % reduct i on i n max i mu m a c c e l erat i o n s
t o be a c h i e ved .
These f i n d i ng s are e s pec i a l l y s i g n i f i ant bec a u se t h e s h ock absorbers
d i d not a l ways " perform" under opt i mu m cond i t i o n s : some of them e i t h e r
part i a l l y o r tota l l y b u r s t d u r i ng the tests . I n these c a se s , an enve l o p p i ng
s k i n wou l d h a ve improved the energy - a b sorpt i on c a pac i t y .
I t shou l d a l so be noted t h a t t h e e xpanded po l y s ty rene , den s i ty
( test 1 2 ) , a l t h ough i t was i n t r i n s i c a l l y l e s s effec t i ve t h a n the
,.,_,.
30 g / l
203
N
0
+::>
FIG 6
-
JAW BONE TEST CON F I GURA T I ONS
e
_.
FIG 7
-
Test 8
Test 2
1 cm
Test 1 2
Test 1 O
Test 5
:
=
50 q
MA I N ACCE L E RA T I ON C U RVES JAW BONE IMPACTS
( See t a b l e 5 )
Test 1 1
Test 6
Test 1
S ca l e
" E L F i so l at i on " ( tests 9 and 1 0 ) y i e l ded h i g h l y s at i sf actory re s u l t s . S i n c e
t h i s i s a mater i a l wh i c h i s e a s i l y i n s t a l l ed i n a he l met , wh i c h req u i re s n o
e n ve l op p i n g s k i n , and wh i c h , i n add i t i o n , i s i n expen s i ve , we dec i ded to u s e i t
for padd i n g t he maxi l l ary part of the prototype f u l l - f a c e he l met .
Remark : We a l so endeavou red to e v a l uate t he p o s s i b i l i ty of shoc k ­
absorpt i on by me a n s of the c h i n s t r a p i n i n stances when t h i s i s snug l y f i tted
be l o w t he l ower maxi l l a ry . For t h i s purpos e , and u s i ng the s ame test proced ure ,
we performed two add i t i on a l t e s t s ( 1 3 and 1 4 ) w i t h prototype f u l l - f ac e he l mets
whose m a x i l l a ry part was u p h o l ste red o n l y with 11 comf o r t 1 1 foam padd i n g . The
f i nd i ng s are summa r i zed i n the t a b l e be l ow and are compared w i t h those of t e s t s
2 a n d 3 i n Ta b l e 5 .
Ta b l e 6 Test
No .
M a x i mum
re s u l t i ng
acce l e rat ion
(g )
Max i mu m
l o ad
(daN)
2
223
1 068
3
204
967
13
1 40
873
14
1 34
706
Observat i o n s
Ch i n st r a p u n attached
Ch i n s t r a p attached
A l l other t h i n g s be i n g e q u a l , it c an be noted t h at w i t h the he l met u s ed
under these test i ng cond i t i on s t he c h i n s t r a p e n a b l ed n e a r l y a 3 5 % red u c t i on i n
i mpact v i o l ence ( i f we con s i der t h e red u c t i on i n the max i mum resu l t i ng acce l e ­
rat i o n ) .
Th i s i s a s i gn i f i c ant f i n d i ng , and i t shows t h a t t he c h i n st r a p of a
g i ven he l met c a n be an e l ement i n t he i mprovement of f ac i a l protec t i o n . The
parameters to be c on s i dered are : the mate r i a l of wh i c h i t i s made , t he l oc a ­
t i on of t h e po i n t s of i t s attachment onto the he l met and i t s o r i e n t at i on i n
re l at i o n t o i mpact d i rect i on .
I I I - EVALUA T I ON O F THE MAX I L LO- FAC I A L P ROTEC T I ON PROV I DE D B Y THE PROTOT Y P E
F U L L - FACE H E LMETS Eva l u at i on of the ma x i l l o -f a c i a l protect i on p ro v i ded by t he prototype
'integ r a l " he l met was effected v i a compa r i son s betwee n , o n the one hand , t h e
f ac i a l i n j u r i e s observed on human c ad a vers * f i tted w i t h reputed l y " s a t i s f acto­
ry11 f u l l -f a c e he l mets [ 11 8 1 1 he l met in ( 2 ) ] and , or the other h and , the absence
of f ac i a l i n j u r i e s to human c ad a vers f i tted with t he prototype f u l l -face he l met
the i mpact v i o l en c e s of the t e s t s perfo rmed w i th the commerc i a l l y a v a i l a b l e
" s at i sf actory " he l met [ he l met 11 B 11 J were l e s s than o r equ a l to those of the
tests perfo rmed w i t h the prototype he l met .
( * ) The se c a d a ve r s were those of i nd i v i d u a l s who had spec i f i c a l l y beq ueat hed
t he i r bod i e s to Sc i e n c e .
2 05
Note : t h e 11 8 11 he l met was f i tted w i t h t h e so- c a l l ed " c omf ort " foam i n
i t s maxiTTäry part on l y .
- Method o l ogy - Te st i ng cond i t i on s - The human c ad a vers - those of
recen t l y deceased i nd i v i d u als , u n embalmed , prepa red and i n st rumented i n
accordance w i t h procedures a l ready d e s c r i bed i n the s c i e n t i f i c l i te ra t u re
( 7 ) ( 8 ) ( 9 ) - were he l d i n p l ace h o r i zonta l l y , w i t h t he i r heads i n the pro l on ­
g at i o n o f t h e t h o r a x , a s s h o wn i n Fi g u re 8 ; t hey d ropped i n f ree-f a l l s onto a
f l a t , r i g i d dyn amomet r i c p l atform that was not co vered w i t h s h o c k - absorbent
ma t e r i a l .
The d rop he i g h t s and the pr i n c i pa l anthropomet r i c d a t a concern i n g these
s u bj ec t s are set out in Tab l e 7 . Tab l e 8 l i s t s the v a l ue s ac h i e ved by the
v a r i o u s phy s i c a l parameters me a s u red a s we l l a s the de s c r i pt i o n s of the fac i a l
i n j u r i e s obse rved : F i gure 9 i l l u s t rated these .
- An a l y s i s of f ac i a l i n j u r i e s ( see Ta b l e 8 ) - W i t h the 11 8 11 he l met , at
a d ro p h e i g h t of 1 .83 mete r s , the hu man s u bj ect s u s t a i ned a nose f r acture . At
2 . 5 mete rs and 3 mete r s , t he f ac i a l f r actu re s �ere mu l t i p l e and very se vere
( see f i g u re 9 ) [ Lefort I , I I and I I I , d e pend i n g on c a s e s . J
Howe ve r , w i t h the prototype he l met , the f a c e s of t he two s u b j e c t s
tested rema i n ed i ntact a l t h o u g h i mpacted under t h e most severe i mpact cond i ­
t i o n s of a l l those tested ( d rop he i g h t 3 meters ) .
Th i s i s a h i g h l y i n t e res t i ng f i nd i ng and a l t h ough o bt a i ned on the bas i s
of on l y two test s , i t i s s i gn i f i c ant of the i mprovement brought about i n f ac i a l
protec t i o n .
- Me a s u rements f i n d i n g s - These me a s u rements f i nd i ng s are not the bas i c
purpose of t h i s report . Howe ve r , c e rt a i n po i nt s deserve t o be n oted , s pec i f i ­
c a l l y a s concerns the head ' s ac c e l erat i on s . I n f0ct , the l e ve l s a c h i e ved i n
tests 9 4 and 9 5 ( see Ta b l e 8 ) and t hose ac h i eved i n tests 309 and 3 1 0 , a l l of
wh i c h were perfo rmed at a 3-meter d ro p h e i g ht , are qu ite c l o s e , whereas the
f ac i a l i n j u r i es a re , respect i ve l y , very severe in t he f i rst two test s , and
none x i stent in t he ot her two .
I n t h e l i ght of t h i s s ma l l n u mber of test s , the tempt at i on i s to
c o n c l ude t h at there i s no c o r re l at i on between t he res u l t i n g a c c e l erat i o n s at
the head ' s center of g r a v i ty and the seve r i ty of f ac i a l i n j u r i e s . Actu a l l y , i t
i s t he c r u s h i ng forces a pp l i ed t o the f ac e i t s e l f that b r i ng s about the
corre s pon d i ng i n j u r i e s . I n the two pa i r s of tests compared above ( i .e . 94/95
versus 309/ 3 1 0 ) , we know on l y t h a t t h e sum of the forces a p p l i ed to the h e ad
i s rou g h l y the s ame , but we h a ve no me asu red i n d i c at i on of t he d i st r i but i on o f
t h e f o r c e s o f contact between the forehead a n d the actu a l face . I n a l l l i ke l i ­
hood , for tests 309 and 3 1 0 , t h e l o wer maxi l l ary p a rt of the face was s u b j e c ­
ted to f o r c e s sooner a n d more v i o l ent l y .
- Pro b l ems l i n ked to the def i n i n g of f ac i a l protect i o n c r i ter i a The preceding rema rks conf i rm t h at the me a s u rements of the head ' s
acce l e rat i on , i n the c a s e of a d i st r i buted f ro n t o - f ac i a l i mpact do n ot make i t
a l way s p o s s i b l e t o g auge the seve r i ty of po s s i b l e f ac i a l i n j u r i e s and hence the
degree of protec t i on p ro v i ded by fu l l -face h e l met s . I n add i t i o n , more l oc a l i ­
zed f ac i a l i mpacts ( ag a i n s t ang l e s , for e xamp l e ) wou l d tend to l e ad to t h e
206
. �... . ...
-
/
-
-
-
,
,
-
-
-
-
/
-
I
-
-
-
-
,
/
D namome t r i c
l a t form .
R i g i d s u r: o r t
F I G 8 - P R I NC I P L E O F CADAV E R TESTS
207
LCl
0\
+-'
U1
<Li
1-
'\
....... �,._,.
.
,r'
r
.J
---
0\
a:>
+-'
U1
<Li
1-
-
...,..,--..,.....
.,., � .... „
.... .
_J
c::r:
u
c::r:
u...
.......
(./')
1(./')
UJ
1-
0:::
UJ
>
c::r:
0
<:(
u
0\
<.!J
.......
u...
208
s ame cor1 c lu s i 011 s . Tt i s hence reason a b l e t o be l i eve , i n t he pers pect i ve of a l l
fac i a l - pro cect i on i n vest i g a t i on s , t h at i t w i l l be n e c e s s ary to f i t t he r i g i d
surfaces of the anth ropomorph i c d u mmy heads w i t h the proper mod e l i z at i on of the
human f ace , of the k i n d de s i gned by Leu n g et a l . ( 4 , 5 ) the c on st i tut i on of
wh i c h was n oted .
- An a l ys i s of bra i n i n j u r i e s - The oa:: u rrence Jf bra i n i n j u r i e s was
f requent l y obse r ved without the le ve l s ac h i e ved by the p hy s i c a l paramete r s
me a s u red ( acce l e rat i o n a n d force ) or t h e se ver ity o f f ac i a l i n j u r i e s mak i n g i t
po s s i b l e a p r i o r i t o e v a l uate t he i r sever i t y . On t h e other hand , an a l y s i s of
the h i g h - speed f i l ms reve a l ed k i nemat i c s of the head i n re l at i on to the t hora x ,
and amp l i tudes o f these var 1 o u s movement s , d e pend i n g o n the test s , that cou l d
be re l ated to the occ1..r ren c e of bra i n i n j u r i e s .
The compa r i son between tests 309 and 3 1 0 , wh i c h were performed w i t h the
s ame type of he l met and under the s ame i mpact cond i t i on s , i s f rom t h i s stand­
pc i nt s i g n i f i cant . I n fact , for test 309 , a n a l y s i s of the f i l m revea l ed on l y a
very s l i g ht tract i on on the neck ; a s l i g ht e xt ra v a s at i o n of the i n j ect i on
l i q u i d was found i n the m i c roscop i c exam i n at i on of the bra i n ( A I S 2 o r 3 ) .
On the contrary , for test 3 1 0 , an a l y s i s of the f i l m reve a l ed a c o n s i d e ­
rab l e e l ongat i on of the n e c k accompan i ed by a forward rotat i o n a l movement o f
t h e head . I n t h i s c a s e , the bra i n i n j u r i e s observed were mu l t i p l e and q u i t e
severe ( i n j u r i e s t o t h e bra i n - s tem a n d bra i n l o be s , i n -dept h ) . S i m i l a r l y ,
con s i d e r a b l e e l ongat i on s of the neck ( w i t hout the occu rrence of i n j ury at t h i s
l e ve l ) were obse rved i n the f i l ms for s u bj ects 88 through 9 5 , who f requent l y
s u s t a i ned bra i n i n j u r i e s ( see t a b l e 8 ) . A l l the movements of t he h e ad i n re l a ­
t i on to t�e t h o r a x and the a s soc i ated br a i n i n j u r i e s s uggest mec h a n i sms of a
type i mp l y i ng i n vo l vement o f the bra i n m a s s at the l e ve l of fo ramen mag n u m .
Compl ementary i n ve s t i g at i on s performed w i t h human s u b j e c t s tested under
the s ame cond i t i o n s as those des c r i bed above , but w i t h obser vat i on of the
nonoccurrence of e l ongat i o n of the neck , s ho u l d mak 2 it po s s i b l e to underst and
more thoroug h l y the effects of the head 1 s k i nemat i c s i n re l at i on to the t h o r a x
i n the tot a l p i c t u re of encepha l i c i n j u r i e s .
SUMMARY AND CONC L U S I ONS
At the conc l u s i on of t h i s i n ve st i g a t i on , a prototype f u l l - f ace he l met
was d e s i gned wh i l e i n c l ud i n g c r i t e r i a of cost and product i o n .
The var i ou s features t h at c o n s t i tute ma x i l l o - f ac i a l protect i o n ( v i zor
and ma x i l l ary part ) were i n ve s t i g ated v i a a pre l i m i n a ry a p proach by c a l c u l at i o�
They were des i g n ed and s e l e cted cn the bas i s of b i omechan i c a l d at a , and were
then tested dynami c a l l y .
Ove ra l l v a l i d at i on of the prototype i n tey r a l he l met was s u bsequen t l y
c a r r i ed out by me a n s o f tests performed o n h uman s u bj e ct s .
The overa l l f i nd i n g s have been set out ; they show the i mprovements
prov i ded by the � rototype he l met and the techn o l og i c a l so l u t i o n s c h osen .
The matter of the a p p l i c at i on of these f i nd i n g s to ma x i l l o - f ac i a l
protect i on was a l s o i n ve s t i gated , and i t reve a l s the v a l ue of u s i n g a proper
209
s i mu l at i on of t h e dyn a m i c beh av i o u r of t h e human f ace f o r a s se s s i n g the degree
of prote c t i on aff orded by h e l rr.e t s .
The u s e of s u c h s i mu l at i on of the f ace a l so emerges as worthwh i l e i f we
con s i de r the ma x i l l o- f ac i a l protec t ion of motor veh i c l e occu pant s .
AC KNOW L E DGEME�TS
Th i s i n ve s t i g at i o n was c a r r i ed out w i th i n the s c o pe of a research
contract between t h e Fren c h Adm i n i strat i o n and �en a u l t Tec h n i q u e s Nou ve l l e s
App l i q uees ( RTNA ) v i a the i n termed i a ry of t h e Tran s po rt at i on Re search I n s t i tuta
Op i n i on s and conc l u s i on s are those of the author s .
R E F ERENCES
( 1 ) H . Va l l ee et a l . , Laboratory of Phys i o l ogy and B i omec han i c s of
Peugeot S . A . / Ren a u 1 t , 1 3 2 rue des Su i s se s , 92000 Nanterre ( France ) , " Study of
1 1 7 moto r i zed two-whee l e r s i n vo l ved in co l l i s i on s , wea r i n g he l me t s accord i ng to
t he N . F . S 7 2 . 302 regu l at i on " , un publ i s hed , French Department of Tran sportat i o�
contract N° . 80 00 032 00 224 75 0 1 .
( 2 ) J . Sacreste , A . Fayon , Laboratory of Phy s i o l ogy and B i omec h a n i c s of
Peugeot S . A . / Re n a u l t , 1 3 2 rue des Su i s ses , 92000 Nanterre , France , " Ca sq u e 2
raue s . Def i n i t i on comp l ement a i re d u c a h i e r des c h arge s 11 , unpu b l i s hed , French
Department of Tra n s portat i on , contract N° . 8002 1 , report N° 2 .
( 3 ) 11 The abre v i ated i n j u ry s c a l e " , 1 980 re v i s i on , Ame r i c a n Assoc i at i on
for Automot i ve Medec i n e , Morton Grove , I I I . 6005 3 , USA .
( 4 ) Y . C . Leung , G . Wa l f i s c h , A . Fayon et a l . , Laboratory of Phys i o l ogy
and B i omec h an i c s of Peugeot S . A . / Re n a u l t , 1 32 , rue des Su i s ses , ·92000 Nante rre ,
France , " Hurr.an f a c e s i mu l at i on for du mmy head " , report s u bm i tted to the Fren c h
Soc i ety of Automot i ve Eng i n eers ( S . I . A . ) and pu b l i s hed i n " I ngen i eu r s de
l ' Automo b i l e " , N° 3 , 1 9 79 , PP . 2 1 0- 2 1 4 .
( 5 ) C . Tarr i e re , Y . C . Leu n g , A . Fayon et a l . , Laboratory of Phy s i o l ogy
and B i omec h a n i c s of Peugeot S . A . / Ren a u l t , 1 32 , rue des Su i s ses , 92000 Nanterre ,
france " F i e l d f ac i a l i n j u r i e s and study of t he i r s i mu l at i on w i th dummy " , 25th
· st a p p Car Crash Con feren c e , Sept . 8 1 , San D i ego , USA . SAE paper 8 1 1 0 1 3 .
( 6 ) D . C . Sc hn e i d e r , A . M . N a h u m , " I mpact Stud i e s of Fac i a l bones and
Sku l l 11 , 1 6t h St a p p Car Crash Con f e rence , Detro i t , Nov . 1 9 72 . USA , ed i ted by the
S.A.E.
( 7 ) C . Got , A . Pate l , I n s t i tute of Orthopaed i c Re searc he s , Raymond
Po i n c are Hos p i t a l , Ga rc h e s , France , A . Fayon , G . Wa l f i s c h , c . T a r r i ere ,
Laboratory of Phy s i o l ogy and B i omechan i c s of Peugeot S . A . / Ren au l t , 1 3 2 rue des
Su i s se s , 92000 Nanterre , Franc e , " Re s u l t s of Expe r i ment a l He ads Impacts on
c ad a vers - The v a r i ou s Data Obt a i ned and The i r Re l at i ons to Same Me a s u red
Phys i c a l Paramete r s " , 22nd St app Car Crash Conferen ce , Ann Arbor , M i c h i g an , USA
e d i ted by t h e S . A . E .
210
( 8 ) C . T a r r i ere , G . Wa l f i s c h , A . Fayon , Laboratory of Phys i o l ogy and
B i omec h an i c s of Peugeot S . A . / Ren a u l t , 1 3 2 rue des Su i s ses , 92000 Na nte rre ,
France , C . Got , A . Pate l , I n s t i tute of Orth opaed i c Re searches , Raymond Po i n c are
Hos p i t a l , Garche s , France , " Acce l e rat i on , Jerk , and Neck F l e x i on Ang l e - The i r
Respec t i ve I n f l uences on the Occu rrence of Bra i n I n j u r i e s " , AGARD Conference ,
Ap r i l 8 2 , Co l ogne , Germany .
( 9 ) G . Wa l f i sc h , A . Fayon , C . Ta r r i ere , Laboratory of Phys i o l ogy and
B i omec h a n i c s of Peugeot S . A . / Ren a u l t , 1 3 2 rue des Su i s ses , 92000 Nanterre ,
France , C . Got , A . Pate l , I n st i tute of Orth opaed i c Re searches , Raymond Po i n c are
Hos p i t a l , Garche s , France , " Human Head To l erance to Impact - I n f l uence of t h e
Jerk ( Rate o f On set o f L i ne a r Ac ce l e rat i o n ) on t h e Occ u rrence o f Bra i n i n j u ­
r i e s " , 6th Internat i o n a l I RCOB I Conference , Sept . 8 1 , Sa l on - d e - Provence , France .
211
5 -
Table
Findlngs for Loc a l l 1ed Impacts ())to the M.l xi l lary Parts of the Prototype " Fu l l Face"
Absorbent Haterl a l s .
F i n d i n9s of measurements
Testlng cond i t ions
....!!.!!..:.
Type of
helmet used
Test
Test
ft>.
88
I
> 2000
prototype
"Comfort" foam
223
1068
�rototype
"Comfort" foam
204
967
4
prototype
5
Copolymer polymethacry l ic
ref. 3 1
136
761
prototype
Copolymer polymethacry l i c
ref. 3 1
105
629
Burst ing of mat e r i a l into
several fragments
6
prototype
R i g i d , deformable polyure­
thane foam, density
45 g / l
126
733
Mater i a l part 1 a l l y burst
and reduced to polOder
7
prototypc
1 0,6
603
Mate rial part i a l ly burst
and reduced to polOder
8
prototype
R 1 g 1 d , deforma b l e polyure­
thane foarn, densi ty · 60 g / l
101
607
9
prototype
75
43 1
Mate r i a l part i a l l y burst
and reduced to polOder
10
prototype
R i g i d , deformable polyure­
thane foam, dens i t y
50 g / l
65
Bursting o f mater i a l
11
prototype
12
Polyester foam, denslty
30 g/l
397
84
466
Bursting o f mate rial
prototype
fxpanded polystyrene foam,
dens l ty
30 g / l
74
463
Burst1ng o f mate ri al
Fronto-Fac l a l
He i me t type
ß
95
1 .83
•
3
3
310
prototype
-
Fronto - F a c l a l
Mdss {k<J)
55.2
18
15
17.5
D.7
56
19.6
14
5 . 28
55.3
1 7 .8
14.6
4 . 56
4.37
3.53
4 . 42
3.4
16.5
14
56
18 .9
15
53.5
18.6
14.6
a l one
neck
3.9
2 . CJ
J.21
4
3 . 60
5.1
Impacts of the l\nnan Subjects ' Heads . He a surement
Measurement F l n d l n9s
Ac c e leratlon ( g )
Ma • imum
3 ms
Bursting of mate r i a l
He.ia�·ärr-
Wldth
55.5
3
3
Bursting of mate rial 1nto
several fragments
Testlng Cond 1 t l o n s , Anlhropomorphlc Data Concern ing the Heads
Length
55
2.5
R
prototype
C l rcumference
2.5
B
309
F i nd i ng s
. Record of
lnjuries
lnjurt es
N_
)_
�a_
1111pa ct Force
,tiU,�lnjurles
other lnju r i e s
1040
Fracture of nose bone
Brai nstem 1 n J u r i e s
540
1080
Corpus c a l l osum l n j ury
125
1 1 85
156b
l'\J l t 1 p l e fractures. s o - cal lec1
lefort 1 , Lefort I I , Lefort I I I
169
136
1500
800
Bralnstem lnjury
185
125
1 1 50
ftJse fracture • f rac ture of uppcr
maxi 1 l a ry
- - ···---··-
;29
95
150
95
90
1 16
94
9S
309
11111Ja cts of Heads of f\Jinan Subjects
----
B
'14
69
R i g i d , deformab l e po lyure­
thane foam, density
50 g/l
Drop height
(meters)
8
<)()
68
R i g i d , deformable polyure­
thane foam, density
60 g / 1
Oimens 1ons (cm)
89
Test
ft J .
Observations
620
•
Tabl� 0
Maxi mum force
(daH)
O r i g i n a l "comfort" foam
padding
2
3
Tdble
Resultant maxi­
mum acceleratlon {g)
Materi a l s i tuated in
max i l l ary part of helmet
"G"
Heimet W ith Var1oos Shock·
HIC
565
1'\11 t l ple fract.ures , so-cal ll'd
lefort 1 , Lefort I I
Clf
Fract11re of mand 1 b l e
ma x i l l ar
940
Ho
l nJ ury
+
d i s l oc d t i on
ß r d l nstem inJury •
contu s 1 on
VPry � l 1 9ht
vcnlri c 1 e
I O J U ry
cort i ca l
to 4th
B r a l n stcm 1 n 1 1 1 r 1 e � + many l n ­
740
310
Ho lnJury
160
1600
I SS
r l�
e�
s �
e cerebral hemi spheres
th. c...
u�
J· �
in....c.
�
�
�
�
_ .:
_
�
212