Experimental Analyses Of Two-scale Deformation And Damage In Thermoplastic Laminates Using DSCM

The thermoplastic composite laminates AS4/PEEK are now widely used in the aerospace industry. Compared with thermoset composites, the toughness of thermoplastic matrix is transparently increased, which results in the very remarkable plastic deformations of the composite laminates. Therefore it is the foundation of design and application of AS4/PEEK composites to analyze accurately their nonlinear interlaminar deformations and damages. In this paper,deformations of AS4/PEEK composites in two-scale are measured by means of digital speckle correlation method(DSCM),which is the one of advanced optical test technologies and also mecro-damage is studied.In this paper, related procedure is developed on the base of theories of DSCM and it is applied in the measurements of different scale deformations. This method proves to be reasonable.AS4/PEEK composite cross ply laminates [0/90]3S under three-point bending loading is tested.The multi-scale deformations on the free edge surface are studied by means of digital speckle correlation method using an OLYMPUS industrial microscope. In laminar scale, the interlaminare displacements are measured using DSCM for AS4/PEEK cross ply laminates. In sub-laminar scale, the tested area includes a limited number of fibers (about more than 50μm) for different laminas of above laminate; the local mesoscopic fields of interlaminar displacements and strains near the areas of fiber-matrix interface are obtained by DSCM.Moreover, the entire damage process of AS4/PEEK [0/90]3s is observed under the three-point bending experiments by industrial microscope. The causes of transverse matrix cracking, fiber failure, interfacial debonding and delamination et al. are analyzed. Finally, the evolution of damage is explored in micro-scale.