Polyester nonwoven that contains microspheres. Generally used as a thin core (to create bulk) or print blocker (liner) in fibre reinforced laminates, manufactured in Hand Lay-Up or Spray-Up processes. Core mats should always be fully impregnated with resin. The microspheres in core mats prevent excessive resin up-take. The most important reasons to use core mats are:
Weight Saving: Used as a core material in the center of a laminate. It can replace much heavier solid glass layers. Impregnated coremat has a density of 620 kg/m3, while impregnated CSM (chopped strand mat) has a density of 1,500 kg/m3. This is a weight saving of 60%.
Resin and Glass Saving: 1 mm of coremat contains 0.6 kg/m2 while 1 mm of CSM contains 1 kg/m2. Although coremat usually replaces glass layers, it should always be used between glass layers.
Cut Cost of Production: One layer of coremat builds up thickness rapidly. Available from 1 mm to 10 mm thickness. While multiple layers of glass fiber are required to achieve these greater thicknesses, single layer of appropriate thickness coremat is sufficient.
Excellent Print Blocker: Gives outmost surface finish as it can be used to block “print-through” of glass reinforcements. Coremat is most often applied against the “skin coat” to create a superior surface finish on hull sides in boat industry.