Composite Materials Research Progress

An Experimental and Analytical Study of Unidirectional Carbon Fiber… 157
Simulation Result and Discussion
Figure 24 shows the simulation results of neat and 1.5wt.% SiC nano-phased layered
composites along with the experimental tensile results. It can be observed that the numerical
simulation results agree well with the experimental results. This indicates that the numerical
model, the simulation method and the program are reliable. Simulated results and
experimental results also show that the strength of nanocomposite was about 7-10% higher
than that of the neat one. As already discussed in the previous chapter, it may have been
contributed from the improvement of matrix and interface properties.
Figure 24. Simulated Stress-strain curves of tensile test.
The failure strain of matrix is higher than that of fiber in unidirectional composites, the
fiber element with the lowest strength is first broken. Then, with increasing applied load, the
breakage of fiber elements occurs randomly. On the other hand, high shear stress are
generated in the matrix elements due to the fiber breakages, so that the matrix cracking and
interfacial debonding occur, leading to the final failure of composites. Figure 25 shows the
simulated failure process of composite from the above results. Figure 25a and 25b indicate
the initial fracture occurring at fiber at low stress level. Stress concentration in the matrix