Determination of residual shear stresses in composites by a modified layer-removal method

摘要

The layer-removal method is often used for measurement of internal stresses in homogeneous polymeric materials. In order to extend the use of the method to laminated composites containing shear stresses, certain refinements are needed. These include (i) determination of twisting moments, (ii) use of varying material properties (elastic moduli) through the thickness of the composite plate, (iii) use of geometric non-linear analysis accounting for large deformations, and (iv) measurement not only of normal curvatures but also twisting curvatures and normal and shear strains. These refinements are necessary, because a non-symmetric laminate is created when layers are removed, which shows large (twisting) curvatures. The modified layer-removal method was theoretically validated on a typical compression-moulded continuous fibre laminate (polyetherimide/glass) and a typical injection-moulded short fibre-reinforced laminate (polycarbonate/glass). The modified method produced good results and the need to use the modified layer-removal analysis is clearly demonstrated. (C) 1998 Chapman & Hall. [References: 16]