Laminate Thickness and Vf

Fibre Volume Volume Fraction and Laminate Thickness

How much fibre…?

How much reinforcement? Weight fraction Used in manufacture. May refer to fibre or resin - !"# manufacturers will s$ecify a glass content of %e.&.' () wt*+ a $re$re& su$$lier mi&ht &i,e a resin content of  wt*.

Volume fraction Used in desi&n to calculate com$osite $ro$erties.  /lmost always refers to fibre content.

0ei&ht fraction ↔ ,olume fraction con,ersion For the s$ecial case of a two-com$onent com$osite %e& fibre and matri3'4 V f  =

W f Wf

W f  =

1  ρf

1  ρ f 

+ %2 − W f

' 1 ρ m

 ρ fV f   ρfVf + ρ m %2 − V f '  

Volume fraction - weight fraction conversion (epoxy resin matrix) 2   n   o    i    t 5.7   c   a   r    f 5.6   e   m   u 5.    l   o   v   e   r 5.(    b    i    f

&lass H8 carbon aramid

5 5

5.(

5.

5.6

fibre weight fraction

5.7

2

Ma3imum fibre ,olume fraction Theoretically9 a unidirectional fibre com$osite could ha,e V f  : ;5*. non-crim$ wo,en fabric 5. - 5.))   random %cho$$ed strand mat'

5.6

5.2) - 5.()

How much fibre? @ommercial reinforcements are characterised by their areal weight (Aw  ). This is sim$ly the wei&ht %usually &i,en in &' of 2 m ( of the reinforcement. /w de$ends on many factors - fibre density9 tow or bundle siAe9 wea,e style9 etc.  /w may ran&e from )5 &1m ( or less %for li&htwei&ht surfacin& tissues'9 u$ to more than (555 &1m ( for some hea,ywei&ht non-crim$ fabrics.

Laminate thickness Two laminates9 both containin& ) $lies of reinforcement4 fibre matri3

hi&h matri3 content

low matri3 content

low fibre content

hi&h fibre content

B thick laminate

B thin laminate

Laminate thickness Fibre ,olume fraction is thus in,ersely $ro$ortional to laminate thickness.