Improving the Energy Absorption Capability of 3D Woven Composites for Aerospace and Automotive Structures

Abstract

There is a need for increasing sustainability and a reduction in the emissions of transportation structures. Composites are increasingly being applied in structures as a means of addressing this issue due to their high specific properties. 3D woven composites are perfectly poised to better address this issue by virtue of their high damage tolerance and delamination resistance. These properties, along with their manufacturing advantages, give the potential to provide increased energy absorption during crash scenarios. The wider application of 3D woven technology is hindered by the high initial investment costs associated with equipment and a lack of understanding of how weave parameters affect mechanical properties and energy absorption.
The main objective of this study is to investigate the relationship between weave parameters and energy absorption in 3D woven layer-to-layer composites. An additional study is presented where the matrix is modified with CaCO3 nano fillers, to further improve energy absorption. The axial crushing response of these carbon-epoxy composites, fabricated with changes to the fabric pick density, binder float and with a nano CaCO3 modified matrix is reported here.
It has been demonstrated that significant changes to the specific energy absorption (SEA) can be achieved through relatively minor changes to the weave parameters and/or by matrix modification in a defined iteration of a 3D woven composite. Quasi-static SEA increases towards the extremes of fabric pick densities (very low and very high pick densities). The highest quasi-static SEA (104J/g) in a 3D woven composite reported to date has been achieved in this research in low pick density specimens. Dynamic SEA is also greatly improved at high pick densities (93J/g). Increasing binder float significantly improves damage tolerance at the expense of SEA. This shows that the properties of 3D woven composites can be tailored by changing the in-plane weave parameters. Adding CaCO3 nanofiller to the matrix of high pick density specimens boosts quasi-static SEA up to 97J/g (9% increase), but severely degrades the dynamic SEA (18% decrease). SEA was also found to be generally superior in 3D woven composites compared to 2D, and shows no correlation to axial fibre content, unlike in 2D composites.
It can be concluded that sizable improvements to SEA can be achieved in a 3D woven structural component without adding significant cost, time or complexity to the 11 manufacturing process. Furthermore, these changes can be applied locally in a structure which expands the potential of this material for functional gradation and multifunctionality.

Date of Award	May 2020
Original language	English
Sponsors	Vice Chancellor's Research scholarship
Supervisor	Alistair McIlhagger (Supervisor), Eileen Harkin-Jones (Supervisor) & Edward Archer (Supervisor)