Extending the application range of Z-pins in composites

Abstract

This dissertation expands the scope of Z-pins' application in composites by investigating their unconventional uses. The mechanical behaviour, electrical performances, and magnetic properties of Z-pinned laminates are examined, respectively.

In addition to exploring the well-established fracture toughness and in-plane properties of Z-pinned flat panels, the study experimentally investigates the through-thickness tensile strength of Z-pinned curved laminates under four-point bending. The effects of Z-pins at different volume fractions on the strength and failure mode are analysed, comparing the results to unpinned specimens. High fidelity finite element models of both unpinned and carbon-fiber Z-pinned specimens are developed in Abaqus/Explicit to provide insights into the experimental observations and different failure mechanisms introduced by Z-pins.

Moreover, the study investigates the electrical (and consequential thermal) behaviour of Z-pinned laminates under localised in-plane and through-thickness fault currents. The effects of Z-pin material and volume fraction on the current conducting path and temperature are discussed through experiments and micro structural observations.

Furthermore, traditional fibre-reinforced composites are magnetically inert, which limits their potential applications in certain fields. Therefore, the study explores the influence of carbon-fibre and ferromagnetic Z-pins on the global magnetic properties of composites. The effects of pin material, misalignment, and volume fraction on the in-plane and through-thickness magnetic properties are experimentally studied, with further insights provided by numerical modelling conducted in COMSOL.

In conclusion, this dissertation contributes to the wider understanding and utilisation of Z-pins in composites, potentially enabling the development of novel and practical applications.

Date of Award	20 Jun 2023
Original language	English
Awarding Institution	University of Bristol
Supervisor	Stephen R Hallett (Supervisor), Bing Zhang (Supervisor), Giuliano Allegri (Supervisor) & Sven Friedemann (Supervisor)