Fibre waviness defects in composite structures

Lead Research Organisation: University of Bristol
Department Name: Aerospace Engineering

Abstract

Composites are now widely used in a wide range of applications. In the wind turbine and aerospace sectors recent innovations, including larger and more sophisticated structures, have driven the need for better understanding of failure of composite structures. Use of lower-cost process routes requires a need for better understanding of the inevitable defects in such composite structures. Failure of well-controlled flat composite panels is now generally well understood. However real manufactured components contain a range of stress concentrators, some associated with relatively controlled features such as joints, ply drops, sandwich panel closures and holes, some more uncertain associated with defects including fibre waviness, resin-rich areas and gaps at sandwich core breaks. The aim of the project is to understand and model how such defects affect the strength of the structure.The project has three main strands: (i) characterising realistic defects in industrial components and in controlled laboratory specimens, (ii) identifying mechanisms of compressive failure under fatigue loading and developing predictive models for failure at waviness defects, validated with experiments, (iii) modelling of defect formation during processing. Case studies suggested by industrial partners Dowty and Vestas of a propeller and a wind turbine blade will be used. The models will be incorporated into software tools, in collaboration with Simulayt Ltd, for use in design.

Publications

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Description Defects in composite structures can have a significant impact on strength. Fibre waviness defects where the fibres deviate from their intended direction are a particularly serious form of defect and this project has developed an understanding of the impacts of these defects. In addition new ways of experimentally investigating these defects have been developed.
Exploitation Route The findings have been taken forward in further projects and have been disseminated through publications and conferences. The study of defects in composites, especially waviness defects has greatly expanded since this project was funded and the importance of these defects are now very widely understood.
Sectors Aerospace, Defence and Marine,Manufacturing, including Industrial Biotechology,Transport

 
Description The findings have been used by manufacturers of composite components and structures to identify necessary quality standards. The improved understanding of the impacts of fibre waviness have been extended by additional work on the origins of these defects in a further PhD project, and the papers from this project are well cited.
First Year Of Impact 2015
Sector Aerospace, Defence and Marine,Manufacturing, including Industrial Biotechology
Impact Types Economic