I was wondering if anybody ever tried Trex or a similar wood fiber/
polyetheline matrix matieral as a replacement for wood decking?

I've wondered that too.

I got tired of replacing my front porch every three years with salt-treated
pine because it would rot out in no time because of facing the hot evening sun,
and catching rain and all the elements.
I wen't with wood/fiber 8 years ago,a nd it's been absolutely great.