Q1. A composite has fibers of diameter 150 μm with fracture strength of 1.0 GPa. The matrix yield strength is 100 MPa. The shear strength along the interface is 100 Mpa. Use a load transfer factor of 0.5 (linear build up) and calculate the following
a. critical aspect ratio.
b. composite strength when fiber length is 5 mm
c. critical and minimum volume fractions when fiber length is 5 nun.
d. Critical and minimum volume fractions when the fiber length is 750 pm.
Q2.
A composite is made of unidirectionally aligned carbon fibers in glass ceramic matrix.
Ef(long)=150 Gpa, Ef(trans)=30 GPa, Em=70 Gpa, vf(long)=0.2, vf(trans)=0.3 and Gfl2=18 Gpa.
a. Consider a volume fraction of 40% short fiber with aspect ratio of 100. Compute the longitudinal modulus assuming that the fibers are aligned.
b. Compute E(trans), G12, and compare with E(trans) by isostress model.
c. Compute vc(long) and vc(trans).
Use Halpin-Tsai Equations for part (a). And expressions for and r).