Full-field strain measurements for validation of meso-FE analysis of textile composites

Meso-scale (unit cell of an impregnated textile reinforcement) finite element (FE) modelling of textile composites is a powerful tool for homogenisation of mechanical properties, study of stress–strain fields inside the unit cell, determination of damage initiation conditions and sites and simulation of damage development and associated deterioration of the homogenised mechanical properties of the composite. Validation of meso-FE modelling requires registration of details of the deformed state on the scale of individual yarns inside the textile, registered using full-field strain measurements on the surface of the sample. The paper presents examples of such a validation of meso-FE models of woven (carbon/epoxy and glass/polypropylene) and braided (carbon/epoxy) composites. Digital image correlation and digital phase shifting grating shearography are used for full-field strain registration. The resolution of the strain field during elastic deformation is improved and damage onset is identified using time-dependent linear regression of the registered field.