Lars Hammar

Evaluation of an automatic system for detection and positioning of small pore defects using digital radiography

A recently developed algorithm for positioning of small defects within metal bodies using digital radiography has been experimentally validated. The algorithm has been validated in the high contrast to noise limit. A calibration method has also been developed and validated. The average error in defect interspacings are found to be approximately 0.03mm with a maximum at 0.2 mm, this is at the same order as the errors predicted by simulations. The relative error in interspacings are all less than 2% which is comparable to simulated ideal case at 0.25%.

Cellulose nanofibril-reinforced composites using aqueous dispersed ethylene-acrylic acid copolymer

In order to explore the reinforcing capabilities of cellulose nanofibrils, composites containing high contents of cellulose nanofibrils were prepared through a combination of water-assisted mixing and compression moulding, the components being a cellulose nanofibril suspension and an aqueous dispersion of the polyolefin copolymer poly(ethylene-co-acrylic acid). The composite samples had dry cellulose nanofibril contents from 10 to 70 vol%. Computed tomography revealed well dispersed cellulose fibril/fibres in the polymer matrix. The highest content of 70 vol% cellulose nanofibrils increased the strength and stiffness of the composites by factors of 3.5 and 21, respectively, while maintaining an elongation at break of about 5%. The strength and strain-at-break of cellulose nanofibril composites were superior to the pulp composites at cellulose contents greater than 20 vol%. The stiffness of the composites reinforced with cellulose nanofibrils was not higher than for that of composites reinforced with cellulose pulp fibres.Graphical Abstract