Question $2$

$($a$)$ An element of a balanced orthotropic graphite$/$epoxy lamina is under the state of stress shown in Figure Q$2.$ If the properties of the woven graphite fabric$/$epoxy material are $E_1=70$GPa,$v_{12}=0\mathrm{.}25,G_{12}=5$GPa. Determine all the stresses and strains along the fibre directions.

$(12$ marks$)$

$($b$)$ Explain stress transferability in composites.

$(6$ marks$)$

$($c$)$ If a carbon fibre$-$polyimide matrix composite with fibre volume fraction $V_f=50\%$ has the parameters $E_f=280$GPa and $E_m=276$MPa, then compute the elastic modulus of the composite in the fibre direction, $E_1,$ and transverse to the fibre direction, $E_2.$

$(7$ marks$)$