RESIDUAL-STRESS EVALUATION IN COMPOSITES USING A MODIFIED LAYER REMOVAL METHOD

The layer removal method is often used for measurement of internal str esses in homogeneous polymeric materials. In order to extend the use o f this method to laminated composites certain refinements are needed. These include: (i) use of varying material properties (elastic moduli) through the thickness of the composite plate; (ii) use of geometric n on-linear analysis to account for large deformations; and (iii) measur ement not only of curvatures but also of strains. These refinements ar e necessary because a non-symmetric laminate is created when layers ar e removed, which shows large curvatures. The modified layer removal me thod was theoretically validated on a typical compression-moulded cont inuous-fibre laminate (PEI/glass) and a typical injection-moulded shor t-fibre-reinforced laminate (PC/glass). The modified method produced g ood results and the need to use the modified layer removal analysis is clearly demonstrated. (C) 1997 Elsevier Science Ltd.