SABIC project: The invention of strong, energy-absorbing foams: issues of scale and morphology
- Cell expansion and cell wall failure during solid-state nanofoaming
Polymer nanocellular foams or nanofoams are a relatively new class of polymer foams with a cell size in the order of 10 to 100 nm. As their cell size approximates to the mean free path of gas molecules, their thermal conductivity can be lower than air (< 0.025 Wm-1K). This phenomenon is known as the Knudsen effect. To fulfil this potential, however, a defect-free microstructure with a low cell size (< 100 nm) and high porosity (> 0.8) is required. This seems to be a challenge for the state-of-the art solid-state foaming process, the dominant route to produce polymer nanofoams, during which a mechanical blowing agent (e.g. CO2) is employed to nucleate and grow cells in a polymer matrix (e.g. PMMA) .
The aim of this study is to understand the interplay of the polymer-gas solid’s constitutive behaviour and key processing parameters on cell expansion and cell wall failure during the solid-state nanofoaming process.
- Molecular modeling and simulation of nanofoam properties
We develop molecular models and perform molecular dynamics simulations to investigate polymers' nanofoam properties. We explore the effects of cell wall thickness, molecular weight, temperature, and degree of side-branching on the thermomechanical response of nanofoams. The goal of this study is to provide molecular-level insight into the design and realisation of optimised polymer nanofoams.
- Design of hybrid foam materials for superior indentation and impact resistance
Hybrid materials typically comprise two or more materials and span from foams and lattices, to fibre reinforced composites. From the naturally occurring bone, wood or bird’s wings, to man-made aerogel and metal or polymer foams, hybrid material are ubiquitous in nature. Design of hybrid materials involves careful selection of material and topology to generate a structurally efficient, low-density material enabling gaps to be filled in material space. The primary goal of this research is the design of such a material and in particular, a hybrid material containing polymer foam. The desired properties of such a material should include superior energy absorption capabilities giving improvement of the indentation and impact resistance of the foam. These new materials will find applications in a myriad of industries; automotive, aerospace, and marine as well as sporting and military applications. Specific applications may include helmets, and panels in cars, boats as well as aircraft components which are susceptible to impact.