Page 391 - Engineered Interfaces in Fiber Reinforced Composites

312 Symbols and abbreviations

L embedded fiber length (= a,)
maximum embedded fiber length allowed to pull-out
critical fiber transfer length ( = &)
La apparent crystal diameter
m Weibull modulus
M microstructural efficiency factor
P applied force
maximum applied load
AP driving force for infiltration
residual shrinkage stress in the radial direction
40
4* radial stress due to Poisson contraction
R fracture toughness or specific work of fracture (with units of kJ/m2)
measured composite fracture toughness

interfacial debonding
post-debonding fraction
plastic shear of fiber
interfacial fracture toughness (or Gic)
fracture toughness for longitudinal splitting
plastic shear of matrix material
frictional fiber pull-out
stress redistribution
surface energy
transverse fracture toughness
predicted total fracture toughness
radius of capillary
roughness factor
half the plastic deformation zone
stitch density
glass transition temperature
Tg
AT temperature difference
ut total strain energy (= U, + U,, stored in the bonded and
debonded regions)
area under the load-displacement trace
displacement (uf in the fiber; u, in the matrix)
volume fraction of fiber
work of adhesion
maximum embedded fiber length for unstable debond process

a coefficient of thermal expansion (CTE)
CTE of composite
CTE of composite in the longitudinal direction
CTE of composite in the transverse direction
CTE of fiber
CTE of interlayer or coating