Method for making composite articles with artificial defects
The present invention concerns 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 said defective polymeric layer, and by layers adjacent thereto. The invention further provides the use of a composite article for calibrating equipment and a method for making such a composite article.
1. A method of making a composite article comprising a plurality of polymeric layers consisting of polymeric matrix and, optionally, fibers, said composite article having at least one artificial defect in the form of an air-filled void, the method comprising bonding polymeric layers to both sides of a partially cured sticky polymeric layer having an artificial defect in the form of an opening of a predetermined size and shape and having dimension of from 1 mm to 5 cm, thereby obtaining a composite article having at least one artificial defect in the form of an air-filled void confined by walls made by said polymeric layer containing the defect and by said polymeric layers adjacent thereto, the size and shape of said artificial defect in the composite article being of the predetermined size and shape of said opening.
2. A method according to claim 1 , wherein said bonding is carried out by heat pressing.
3. A method according to claim 1 , wherein said partially cured sticky polymeric layer having an artificial defect therein is made by:
(a) making at least one hole in a polymeric layer; and
partially curing said polymeric layer to obtain a sticky layer having a hole therein as said artificial defect.
4. A method according to claim 1 , wherein said partially cured sticky polymeric layer having an artificial defect therein is made by:
(a) partially curing a polymeric layer so as to obtain a sticky polymeric layer; and
(b) making a hole in said sticky polymeric layer.
5. A method according to claim 1 , wherein at least one of said polymeric layers bonded to either side of said polymeric layer having an artificial defect, is partially cured.
6. A method according to claim 1 , wherein said polymeric layers consist of polymeric matrix and fibers.
7. A method according to claim 1 , wherein at least one of said polymeric layers bonded to both sides of said polymeric layer having an artificial defect is a polymeric layer having no artificial defect therein.