Evidence for the strength function of rays in living trees

The tensile strength of isolated wood rays of beech ( Fagus sylvatica L.) and its significance for the biomechanics of living trees

“…Indeed, Albrecht et al (1995), Zipse (1997) and Burgert et al (1999) showed that the radial tensile strength of wood is high in the curved parts of different tree species experiencing large lateral forces, and that these parts are associated with wood containing a large volume fraction of wood rays (Burgert et al 1999).…”

“…The available knowledge on wood properties under different moisture contents (Goulet 1960;Schniewind 1962) enables one to derive the strength of rays in wet conditions (wood moisture >30%) from their strength in dry conditions measured approximately. The radial tensile strength of wet beech wood determined by Goulet (1960) and Burgert et al (1999) was 11.7 MPa and 13.7 MPa, respectively. In both cases, this was roughly one half the strength of wood measured in dry conditions; a relation that can also be found in the longitudinal direction.…”

“…Mattheck and Kubler (1995) mention the possibility that the wood rays in living trees may, in addition, have a strengthening function. Due to the fact that the radial strength of deciduous trees is significantly higher than their tangential strength (Youngs 1957;Goulet 1960), it is assumed that as the wood rays are arranged in a radial direction they increase the radial strength of the wood (Beery et al 1983) and that in this way living trees adjust to radial stress, which often occurs in nature (Mattheck and Kubler 1995;Burgert et al 1999). The object of this research was to directly test the tensile strength of isolated wood rays and to examine the hypothesis that wood rays function mechanically in living trees, and thus achieve a better understanding of wood as a multifunctional "composite material".…”

Root to branch wood anatomical variation and its influence on hydraulic conductivity in five Brazilian Cerrado species

“…Burgert et al (1999) and Reiterer et al (2002) emphasize the biomechanical role of rays. Longui et al (2016) studied shear strength parallel to grain with distinct ray orientation on four Brazilian wood species (Balfourodendron riedelianum (Engl.)…”

Fracture characterisation of yew (Taxus baccata L.) and spruce (Picea abies [L.] Karst.) in the radial-tangential and tangential-radial crack propagation system by a micro wedge splitting test

“…This could be confirmed for yew specimens in this study (F crit RTs31.3 N, F crit TRs25.0 N). The radial reinforcement of wood tissue by means of wood rays (Burgert et al 1999) is one of several effects contributing to this anisotropy. Yew wood is characterised by a relatively high percentage of ray cells (;14%) compared to spruce (;5%) (Wagenfü hr 2000).…”