Yentl Swolfs

Cluster analysis of acoustic emission signals for 2D and 3D woven carbon fiber/epoxy composites:

Understanding the failure mechanisms in textile composites based on acoustic emission signals is a challenging task. In the present work, unsupervised cluster analysis is performed on the acoustic emission data registered during tensile tests on two-dimensional and three-dimensional woven carbon fiber/epoxy composites. The analysis is based on the k-means+ + algorithm and principal component analysis. Peak amplitude and frequency features – peak frequency for two-dimensional woven composites and frequency centroid for three-dimensional woven composites – were found to be dominant in cluster analysis. Cluster bounds were identified for both reinforcement types. These bounds do not differ for both reinforcement types and can be used as a starting point for acoustic emission analysis of other carbon fiber/epoxy composites. The statistics of high-frequency acoustic emission events are compared with the estimates obtained from a fiber bundle model based on Weibull fiber strength statistics. The number of acoustic emission events agrees well with the number of groups of carbon fibers that fail simultaneously. This finding may provide a new way to explain why the Weibull distribution predicts much more fiber breaks than measured by acoustic emission.

Recent advances in fibre-hybrid composites: materials selection, opportunities and applications

ABSTRACT Fibre-hybrid composites are composed of two or more fibre types in a matrix. Such composites offer more design freedom than non-hybrid composites. The aim is often to alleviate the drawbacks of one of the fibre types while keeping the benefits of the other. The hybridisation can also lead to synergetic effects or to properties that neither of the constituents possess. Even though fibre-hybrid composites are attractive, they also pose more challenges in terms of materials selection than conventional, single fibre type composites. This review analyses the mechanisms for synergetic effects provides guidance on the fibre and matrix selection and describes recent opportunities and trends. It finishes by describing the current applications, and by contrasting how the industrial use is different from the academic research.