Enabling Interlaminar Fracture Testing of MULTIdirectional composite LAMinates for safe and efficient structures

This project aims at solving long-standing problems affecting the characterisation of interlaminar properties of high-performance fibre reinforced polymer matrix composites.

For these materials, interlaminar fracture, known as delamination, represents one of the most critical damage mechanisms.

Standard procedures to characterise interlaminar fracture toughness exist, but their scope is restricted to use with unidirectional specimens, in which delamination is propagated along the fibre direction.

On the other hand, real components and structures are made using multidirecitonal laminates, where delamination may appear at any interface and propagate in any direction; under such condition, interlaminar fracture toughness may be different from that obtained in standard tests. This results in uncertainties in structural design, and thus to oversized, inefficient structures.

Until now, problems caused by elastic couplings, residual thermal stresses and delamination migration have prevented an effective interlaminar characterisation for multidirectional laminates.

Recently, however, a new class of delamination specimens (Fully-Uncoupled Multi-Directional, FUMD) eliminating elastic couplings and reducing problems related to residual stresses has been proposed; also, new insight on the migration phenomenon has emerged. These developments open new possibilities.

This project will combine the experience of the participating organisations on delamination migration and that of the researcher on FUMD specimens to explore these possibilities and achieve, for the first time, an effective, problem-free, characterisation of interlaminar fracture in multidirectional laminates.

Possibly, this will contribute towards the creation of standard procedures, with an impact on the composite industry on a global scale.

Lightwight structural design practices will benefit from this, contributing toward a more efficient, safe, and environmentally friendly transportation sector.