Composite Materials Research Progress

An Experimental and Analytical Study of Unidirectional Carbon Fiber… 131
Monte Carlo simulation on the tensile failure process of unidirectional carbon prepreg
laminates.
Materials
T700SC 12000-50C carbon fiber used in this research is manufactured by Toray Carbon
Fibers America, Inc., USA. It is the highest strength, standard modulus fiber in the form of
continuous filament tows with outstanding processing characteristics for filament winding,
weaving and prepregging produced using the PAN (polyacrylonitrile) process.
The epoxy system used was CR46T. It’s a high temperature cure prepreg resin system.
To avoid degradation of its properties, the resin is kept under sub-zero temperatures in a
sealed atmosphere. This resin system is well suited for prepreg applications, and its properties
are shown in Table 1.
Table 1. Resin properties
Density 0.0457 lb/in 3
Gell (min) @ 350 0 F 6 – 10
GIC
0.733
lb/in
± 0.3
2
Tg DRY 2hr @ 375 0 F 437 0 F
Tg WET 2hr @ 375 0 F 295 0 F
Tensile strength @ RT 10 ksi
Tensile modulus @ RT 643 ksi
Poisson ratio 0.36
Elongation 1.7 %
The nanosized fillers for this present investigation were chosen as nano-sized silicon
carbide particles. These are highly complex material existing primarily in amorphous or
crystalline states. The amorphous SiC is mainly used in coating industries. In functional and
structural applications, crystalline SiC are extensively used due to their excellent thermomechanical
properties such as high hardness and stiffness, good corrosion and oxidation
resistance, high thermal conductivity and high chemical and thermal stability. [10-12]. Such
SiC is available in two different phases, namely alpha (α) and beta (β) phases. The formation
of these two structures depends on the molecular organization of the basic structural unit, a 2layer
planner unit of Si and C in tetrahedral coordination. β−SiC is formed when the planes of
Si and C are rearranged in a cubic symmetry with a lattice constant a = 0.4358 nm. On the
other hand, heating of β−SiC to high temperature causes the transformation of the cubic
symmetry to a mixture of hexagonal (6H) and rhombohedral (15R) polytypes known as α-
SiC. The corresponding lattice constant parameters of α-SiCs are: a = 0.3082 nm and c =