Lightweight primary and secondary structures of aircraft, wind turbines and automobile are mostly made of polymer-matrix composites. The selection of fibre reinforced polymer (FRP) composites for the primary structure is performance-based assuming defect-free components, especially in the aerospace industry. However, for the usage of FRP composites for secondary structures, the effect of manufacturing induced defects can be tolerated for cost-effective manufacturing. Fibre waviness has a major influence on the mechanical performance of composites and its study is one of the major concerns. The present work deals with an overview of the earlier reported studies on the effect of fibre waviness, and its formation, on the elastic properties and mechanical response of the FRP composites. Accumulation and discussion of results of the existing literature over the past two decades are summarized together up to the current status in the field. Capabilities of different non-destructive techniques used for characterisation of fibre waviness defect are summarized.

An Overview of The Formation of Fibre Waviness and Its Effect on The Mechanical Performance of Fibre Reinforced Polymer Composites

https://pureadmin.qub.ac.uk/ws/files/184228727/Sebaey_et_al_preprint.pdf

A microscale integrated approach to measure and model fibre misalignment in fibre-reinforced composites

Among a variety of defects associated with composite technology, fibre wrinkles are known to be a major source of failure for fibre reinforced plastic and closely associated with the ever popular automated fibre placement technique. In the present work, with the aim to investigate their influence on the failure of carbon fibre reinforced plastics (CFRP), composite laminates containing fibre wrinkles of varying architectures have been designed and prepared utilizing gaps and overlaps based on the understanding of wrinkle formation mechanisms. The effects of these engineered wrinkles with different combination of gaps and overlaps on the mechanical performance of CFRP were systematically investigated. A maximum of 21% and 37% drop in the tensile and compressive strength were recorded for the most severe combination of gaps and overlaps. A simple analytical model was proposed to relate the wrinkle angle to the defect characteristic parameters and a good agreement with experimental results was obtained. Furthermore, numerical simulations were conducted to inform the failure mechanisms where different wrinkle models were generated using previously developed pre-processing tools. Good agreements with experimental observations were obtained in terms of ply waviness, strength and failure modes. These findings provide certain practical insights for controlling defects in composite manufacturing processes.

Satish S. Nimbal

Papers

Effect of Gap Induced Waviness on Compressive Strength of Laminated Composites