Our research activities focus on mechanics of fibrous and composite materials, wood mechanics, impact mechanics and fracture mechanics.
Wood fibre micromechanics
The research focus on experimental micromechanics of heterogeneous materials, in particular biocomposites based on fibres from wood. The aim is to strengthen the link between materials and mechanics of composites: primarily damage mechanisms and mechanical properties of polymer-matrix composites. This relies on experimental identification and quantification of damage development with non-destructive techniques, development of mechanism-based models aiming at predictive capabilities and microstructural design/tailoring.
Mechanics of fibre-based materials
Per Isaksson’s research interests deals mainly with problems concerning fracture and other complex physical deformation processes in materials on different scales. The approach strategies are theoretical, combinations of analytical and numerical studies, and always supported by vital experimental observations such as in the figure below. The various numerical methods utilized are high-performance multiscale computer models based on non-linear finite elements or particle models inspired from classical molecular dynamics and Newtonian mechanics. Naturally, software development is a part of the main activities and Per with colleagues have a strong tradition in design of efficient algorithms for solving the scientific problems studied
Figure 1. X-ray microtomography of a crack-tip region during a fracture test on a soft fiber material. Experiment performed at the well-known European Synchrotron Research Facility together with colleagues Drs. P. Dumont and S. Rolland du Roscoat at INP Grenoble.
Most important current projects: Modeling of rapid dynamic deformations in heterogeneous materials, Multiscale modeling of fracture in porous materials, Structural degeneration of cellulose fiber materials subjected to moisture and/or heat, Failure mechanisms in light-weight corrugated boards.
Time-dependent deformation behavior of Vasa oak
The strength in the Vasa has been reduced with up to 80%, while the stiffness is up to 50% lower compared to recent oak. This is due to chemical degradation and impregnation with polyethylene glycol (PEG), respectively. From positioning measurements we have also seen that the ship is also subjected to deformation over time, i.e. creep. Taken together, the reduction in mechanical properties and the creep deformation constitute a serious threat to the mechanical stability.
In this project we are investigating the time-depentent behavior of Vasa oak. The aim is to be able to predict how much additional support the ship needs in order to reduce the onging creep deformation to a minimum.This information can serve as valuable input information for a future computer model of the ship, where different support scenarios are evaluated.