As an Engineer, I can say it does look like composite structure from an aircraft, but could be from many things that use this type of structure e.g. do sailing yachts, shipping products etc use sandwich/honeycomb construction? If it is aircraft, I'm not convinced it is a NLG Door either due to the thickness depth of the honeycomb, and one side of it appears to be unpainted (grey/black). If it is from an aircraft I'd say it was more likely to be a Wing to Body or Belly fairing.