Unfortunately, the convolution in above cannot directly solve as it contains some divergent integrals, so you should consider on this approach instead.
With the result of http://eqworld.ipmnet.ru/en/auxiliary/inttrans/LapInv7.pdf,
$\mathcal{L}^{-1}_{s\to t}\left\{\dfrac{\pi}{2}\dfrac{\log s}{s^2-1}\right\}$
$=\mathcal{L}^{-1}_{s\to t}\left\{\dfrac{\pi}{2}\dfrac{\log s}{s^2\left(1-\dfrac{1}{s^2}\right)}\right\}$
$=\mathcal{L}^{-1}_{s\to t}\left\{\dfrac{\pi}{2}\sum\limits_{n=0}^\infty\dfrac{\log s}{s^{2n+2}}\right\}$
$=\dfrac{\pi}{2}\sum\limits_{n=0}^\infty\sum\limits_{k=1}^{2n+1}\dfrac{t^{2n+1}}{(2n+1)!k}-\dfrac{\pi}{2}\sum\limits_{n=0}^\infty\dfrac{t^{2n+1}(\gamma+\log t)}{(2n+1)!}$
$=\dfrac{\pi t}{2}+\dfrac{\pi}{2}\sum\limits_{n=1}^\infty\sum\limits_{k=1}^n\dfrac{t^{2n+1}}{(2n+1)!2k}+\dfrac{\pi}{2}\sum\limits_{n=0}^\infty\sum\limits_{k=0}^n\dfrac{t^{2n+1}}{(2n+1)!(2k+1)}-\dfrac{\pi(\gamma+\log t)\sinh t}{2}$
$=\dfrac{\pi t}{2}+\sum\limits_{k=1}^\infty\sum\limits_{n=k}^\infty\dfrac{\pi t^{2n+1}}{4^{n+1}n!\left(\dfrac{3}{2}\right)_nk}+\sum\limits_{k=0}^\infty\sum\limits_{n=k}^\infty\dfrac{\pi t^{2n+1}}{4^{n+1}n!\left(\dfrac{3}{2}\right)_n\left(k+\dfrac{1}{2}\right)}-\dfrac{\pi(\gamma+\log t)\sinh t}{2}$ (according to http://mathworld.wolfram.com/PochhammerSymbol.html)
$=\dfrac{\pi t}{2}+\sum\limits_{k=0}^\infty\sum\limits_{n=0}^\infty\dfrac{\pi t^{2n+2k+3}}{4^{n+k+2}(n+k+1)!\left(\dfrac{3}{2}\right)_{n+k+1}(k+1)}+\sum\limits_{k=0}^\infty\sum\limits_{n=0}^\infty\dfrac{\pi t^{2n+2k+1}}{4^{n+k+1}(n+k)!\left(\dfrac{3}{2}\right)_{n+k}\left(k+\dfrac{1}{2}\right)}-\dfrac{\pi(\gamma+\log t)\sinh t}{2}$
$=\dfrac{\pi t}{2}+\sum\limits_{n=0}^\infty\sum\limits_{k=0}^\infty\dfrac{\pi t^{2n+2k+3}(1)_k}{2^{2n+2k+3}3(2)_{n+k}\left(\dfrac{5}{2}\right)_{n+k}(2)_k}+\sum\limits_{n=0}^\infty\sum\limits_{k=0}^\infty\dfrac{\pi t^{2n+2k+1}\left(\dfrac{1}{2}\right)_k}{2^{2n+2k+1}(1)_{n+k}\left(\dfrac{3}{2}\right)_{n+k}\left(\dfrac{3}{2}\right)_k}-\dfrac{\pi(\gamma+\log t)\sinh t}{2}$
Related techniques (I), (II). Using the fact about the Laplace transform $L$ that
$$ L(f*g)=L(f)L(g)=F(s)G(s)\implies (f*g)(t)=L^{-1}(F(s)G(s)) .$$
In our case, given $ H(s)=\frac{1}{(s+1)}\frac{s}{(s^2+4)}$
$$F(s)=\frac{1}{s+1}\implies f(t)=e^{-t},\quad G(s)=\frac{s}{s^2+4}\implies g(t)=\cos(2t).$$
Now, you use the convolution as
$$ h(t) = \int_{0}^{t} e^{-(t-\tau)}\cos(2\tau) d\tau . $$
Best Answer
All you need to know is that the ILT of $1/(s^2-9)$ is $(1/3) \sinh{(3 t)}$. The convolution integral...doesn't matter which is a function of $t'$ or $t-t'$. Thus, the ILT is
$$\frac{40.5}{3} \int_0^t dt' \sinh{(3 t')} $$
which I am sure you can handle.