IMPACT RESISTANCE OF COMPOSITE MATERIALS

Abstract

Defects introduced through high velocity and low velocity impacts on composite materials such as those encountered in the aerospace industry, quite often appear innocuous at the surface. Indeed it is often termed barely visible impact damage (BVID). However the damage sub surface can be very significant. This dissertation aims to better understand the relationship between impact damage and residual in-plane compressive properties in woven S-glass composite structures. It is also intended to uncover the significance and the more dominant damage characteristics in terms of the damage length, width and depth on the post impact compressive loading capabilities of impact damaged composites.A combination of 2D and 3D S-glass fabrics were resin infused and oven cured to fabricate sample of dimensions 55mm X 89mm which were then impacted using an Instron CEAST Model 9350 drop weight impacting system at energies of 3 Joules, 6 Joules,9 Joules and 12 Joules. The severity of the impact damage was measured using both scanning/contrast imaging and X-ray tomographic techniques. The effect of individual damage properties on the maximum compressive loading capabilities of the samples tested were then analysed by correlating the data obtained through techniques outlined above to the data produced by the Instron 5989 Universal Testing System during compression testing.The study revealed the two 3D fabrics to be more resistant to impact when compared to the 2D fabric due to the availability of unique energy dissipating mechanisms introduced by the presence of reinforcement along the Z plane (Z tows). Furthermore, the study revealed that this higher tolerance resulted in lower damage volume in the 3D fabric composites and therefore the same exhibited higher compressive loading capabilities. Correlation of damage data obtained through scanning and contrast imaging, manual measurements and through tomographic analysis to the compression data revealed the damage depth and width to have the most significant impact on the maximum compressive loading capability of the tested composites.

Date of Award	1 Aug 2012
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Philip Withers (Supervisor) & Paul Hogg (Supervisor)