Composite articles with artificial defects and methods for making them

摘要

The present invention relates to a composite article comprising a plurality of layers, wherein at least one of the layers is a defective polymeric layer. The defective polymeric layer has at least one artificial defect, in the form of a volume of air confined by walls made of the defective polymeric layer, and by layers adjacent thereto. The invention further provides the use of the composite article for calibrating non-destructive equipment and a method for making such a composite article.