Modelling of deformation behavior of polymeric woven fabric prepreg-based composite materials in flexure and short beam interlaminar shear testing

The mechanisms of deformation behavior of woven fabric prepreg-based carbon-fiber composites with different reinforcement lay-up schemes are studied. The FEM stress-strain analysis is carried out for specimens in flexure and short beam interlaminar shear testing environments. Both methods are based on a three-point bend model. Theoretical grounds underlying the mechanisms governing the deformation of laminates in bending tests are studied. Tests were performed on specimens having different thickness and with different ratios of the distance between supports to the specimen thickness. The effects of the monolayer properties specified in the model, such as the modulus of elasticity in the z-direction and the interlaminar shear modulus, on the effective characteristics of the material are investigated. The problems of correct experimental determination of the interlaminar shear modulus related to the large thickness of specimens, the difficulty of manufacturing and the peculiarities of measurement and identification of the obtained values of deformation in shear are considered. Flexural modules versus actual monolayer thickness and unsupported lengths versus specimen thickness and width are plotted. The necessity of registration of shear deformation in three-point bend testing for proper design of experiments and execution of calculations is shown. The accuracy and adequacy of the structural and bending characteristics are verified against the testing modes. The results confirm the relevance and validity of any given factor in modeling the stress-strain state of tested specimens.