Theme C: Ductile constituents
This theme aims to design composite constituents that will enable new mechanisms for ductility, whilst retaining high strength and stiffness. These will ultimately be integrated with novel architectures to produce high performance composites with a ductile response.
Example
One example of this is the work we have undertaken with Cellulose nanocrystals (CNCs). Despite their promise, mechanical properties of CNC/polymer composites, especially in terms of tensile strength and Young’s modulus, have often been limited.
Method
High loadings of water-soluble CNCs were well dispersed in poly vinyl alcohol (PVOH) to form coagulation spinning dopes for composite fibres. The resulting CNC/PVOH composite fibres showed significantly increased yield strength and Young’s modulus for all fibres, compared with PVOH fibres. The 40 wt.% of CNC/PVOH showed the highest Young’s modulus (29.6 ± 4.2 GPa) and tensile strength (0.85 ± 0.06 GPa) with a strain-to-failure of 5.6 ± 0.2 %.
Incorporation of CNC into the PVOH matrix increased the tensile strength and Young’s modulus, and the PVOH fibre become tougher and more resistant to deformation in the presence of CNC:
Final reports
High performance ductile fibres
Fibres with a 40 wt% loading of SWCNTs showed a tensile strength of ~1.4 GPa with a strain to failure of 12.7%. Cyclic tests demonstrated excellent ductility.
High Performance Ductile Fibres Report (PDF, 232kB)
Email: m.shaffer@bristol.ac.uk
Nacre-inspired interphase
A nanostructured coating was developed with ~ 90 wt% of well aligned inorganic platelets embedded in a polymer matrix. Fibres were successfully coated, showing reduced local stress concentrations at fiber breaks and increased extent of fibre slippage.
Nacre-inspired interphase Report (PDF, 245kB)
Email: m.shaffer@bristol.ac.uk
Aerogel modified matrices
Bi-continuous hybrid aerogel polymer matrices may provide a nano‑reinforcement which both reduces stress concentrations at broken primary fibres and gives a strain hardening response in shear.
High Performance Ductile Matrices Report (PDF, 119kB)
Email: m.shaffer@bristol.ac.uk
Carbon Nanotube Fibres and Sheets
High interfacial shear strength at strains of up to 13% for CNT fibres was successfully demonstrated, offering the potential to create high performance ductile composites.
Optimised Matrices
The properties of polybenzimidazole were investigated in fibre form and as a possible matrix.
Optimised Matrices Report (PDF, 287kB)
Email: ian.hamerton@bristol.ac.uk
Ductile Superlattice Nanoparticle Matrices
A metal-oxide superlattice was produced that showed a similar stiffness and strength as epoxy but significantly more plastic deformation.
Ductile Superlattice Nanoparticle Matrices Report (PDF, 191kB)
Email: m.shaffer@bristol.ac.uk