The Question

A composite laminate has been constructed from six identical layers of a plain $(\backslash (0/90\backslash )$ woven$)$ aramid fabric with epoxy resin. Each layer, or lamina, has a fibre volume fraction $(\backslash ($ V$\_\{$f$\}\backslash ))$ of $0\mathrm{.}57,$ and a resin volume fraction $\backslash (\backslash$left$($V$\_\{$m$\}\backslash$right$)\backslash )$ of $0\mathrm{.}43.$ Each lamina constitutes $\backslash (1/6^\{\backslash$text $\{$th $\}\}\backslash )$ of the volume$/$thickness of the entire laminate.

Use the rule of mixtures formula, with efficiency factor, to determine the tensile strength $(\backslash (\backslash$sigma$\_\{$x$,1\}\backslash ))$ of the entire laminate in the zero degree direction. The tensile strengths of the fibre $(\backslash (\backslash$sigma$\_\{$f$\}\backslash ))$ and resin $(\backslash (\backslash$sigma$\_\{$m$\}\backslash ))$ are $2538$ MPa and $60$ MPa $,$ respectively. Give your answer to the nearest MPa $.$

Following manufacture, it was found that the laminate has insufficient tensile strength for its desired application. It has been suggested that the two outermost laminas should be replaced with a uni$-$directional aramid fabric, with the fibres running parallel to the direction of applied load. This fabric will result in a fibre volume fraction $\backslash (20\backslash \%\backslash )$ greater than that of the plain aramid fabric. Each uni$-$directional lamina will also constitute $\backslash (18\backslash \%\backslash )$ of the total laminate volume$/$thickness$.$

Use this information to determine by how much the tensile strength of the second laminate exceeds that of the first laminate. Give your answer in megapascals, correct to one decimal place.