Damage progression and defect sensitivity: An experimental study of representative wrinkles in tension

This paper presents an experimental study on the effect of localised wrinkling defects on the strength of glass reinforced epoxy laminates. A method for generating wrinkles based on the ‘natural’ mechanism of formation was developed and used to make larger scale laminates, with the aim of being representative of industrial components. Wrinkle severity was characterised using optical microscopy and correlated to the results obtained from tensile testing, which showed that the most serious misalignment can cause a 40% strength knock-down. Two optical systems – Digital Image Correlation and Video Extensometry were used to visualise the strain distribution, which showed highly localised concentrations surrounding the wrinkle. The role of the strain distribution in causing the initiation and progression of damage is explored, and finally some implications for the design of composite components are considered.