Alumalite® has a corrugated plastic core and sandwiched between to aluminum sheets.  This board is amazingly lighweight yet is 50 times stronger than just an aluminum sheet.  It is sun, water, and temperature resistant, and has a "Class A" flame spread rating.   This board comes in 6mm and 10mm thicknesses and is ideally suited for outdoor and indoor applications where lightwieght and strength are needed.  Standard color is white, but also comes in 11 other special order colors.