TY - THES

T1 - Micromechanical testing of wood samples: A new preparation route using femtosecond pulsed laser ablation

AU - Jakob, Severin

N1 - embargoed until null

PY - 2017

Y1 - 2017

N2 - Ultrashort pulsed laser ablation becomes more and more important for micromachining. Any type of material can be processed with little or no damage to the surrounding volume due to the ultrashort pulse duration. In contrast to the Focused Ion Beam workstation laser ablation provides 4-6 orders of magnitude higher ablation rates and avoids ion implantation. In this work a solid-state-laser with a wavelength of 515 nm and pulse duration of 435 femto¬seconds (fs) was used to prepare wood samples from spruce for mechanical testing at the micrometre level. After optimisation of the different laser parameters, tensile and compressive specimens were manufactured from microtomed cross and tangential sections. For comparison a different preparation route, using an ion milling system and a copper mask, was used. Additionally, two laser-processed samples were exposed to an electron beam prior testing to study a possible beam damage. The specimens originating from these different preparation conditions were tested on a fibre tensile testing module and monitored with a stereo light microscope. Advantages and limitations of the fs-laser preparation technique, as well as the deformation and fracture behaviour of the samples, are discussed. The results have shown that fs-laser processing is a fast and precise preparation technique, which enables the production of samples with sizes at the microscale. Mechanical evaluation of tested tensile samples yielded comparable results to literature. Compression samples showed typical behaviour of cellular materials.

AB - Ultrashort pulsed laser ablation becomes more and more important for micromachining. Any type of material can be processed with little or no damage to the surrounding volume due to the ultrashort pulse duration. In contrast to the Focused Ion Beam workstation laser ablation provides 4-6 orders of magnitude higher ablation rates and avoids ion implantation. In this work a solid-state-laser with a wavelength of 515 nm and pulse duration of 435 femto¬seconds (fs) was used to prepare wood samples from spruce for mechanical testing at the micrometre level. After optimisation of the different laser parameters, tensile and compressive specimens were manufactured from microtomed cross and tangential sections. For comparison a different preparation route, using an ion milling system and a copper mask, was used. Additionally, two laser-processed samples were exposed to an electron beam prior testing to study a possible beam damage. The specimens originating from these different preparation conditions were tested on a fibre tensile testing module and monitored with a stereo light microscope. Advantages and limitations of the fs-laser preparation technique, as well as the deformation and fracture behaviour of the samples, are discussed. The results have shown that fs-laser processing is a fast and precise preparation technique, which enables the production of samples with sizes at the microscale. Mechanical evaluation of tested tensile samples yielded comparable results to literature. Compression samples showed typical behaviour of cellular materials.

KW - laser ablation

KW - ultrashort

KW - femtosecond

KW - laserparameter

KW - wood

KW - spruce

KW - cellular material

KW - micromechanics

KW - tensile module

KW - sample preparation

KW - beam damage

KW - fibre debonding

KW - cell wall rupture

KW - Laserablation

KW - ultrakurz

KW - Femtosekunde

KW - Laserparameter

KW - Holz

KW - Fichte

KW - Zelluläres Material

KW - Zugfasermodul

KW - Mikromechanik

KW - Probenvorbereitung

KW - Elektronenstrahl

KW - Zellwand

M3 - Master's Thesis

ER -