Compression failure mechanism in small scale timber specimens

• Compression tests on small clear-wood specimens to better understand the kinkband initiation and propagation.
• Results show a clear correlation between compression modulus, strength, steady-state stress and silviculture method.
• Mature wood has higher compression mechanical properties than juvenile wood, irrespective of the silviculture method.
• The deformation data measured globally over the specimen can be used to describe the local plasticity/kinkband behavior.

Understanding the failure mechanism of wood loaded in compression parallel to the grain has been shown to be an important parameter in the design of timber beams strengthened with fibre-reinforced plastics (FRP). In this paper, a constitutive relationship for wood under uniaxial compression load parallel to the grain was determined experimentally. Several parameters, such as silviculture, moisture content and radial position in the log in relation to the pith from where the specimen was sawn, were considered. Small clear-wood specimens were used. The strain localisation in the failure region (kinkband) was monitored using the digital image correlation method. The results show that silviculture and moisture content are two very important parameters which influence the compression failure mechanism. Furthermore, there is a significant difference in behaviour between specimens from the juvenile region of the log and specimens from mature wood. Based on experimental results, two numerical models were built, considering either a global or a local constitutive relationship. It was demonstrated that both numerical models yield accurate results and that, depending on the experimental equipment available, a constitutive relationship could be extracted and used as input in these numerical models.