Thesis Topic

Characterisation and mechanical modelling of hardwood species for use in construction

Abstract

France's forest resources are mainly hardwoods, but the construction sector uses mainly softwoods, which are less abundant, and therefore imports a large proportion of its construction timber. This shortfall is partly due to the fact that the hardwood industry, unlike the softwood industry, has not yet removed its regulatory barriers. Sawn timber used in construction must first be graded to ensure its mechanical properties. There are two possible grading methods: visual grading, which is the most widely used but disadvantages hardwoods due to their many defects, and machine grading. Methods based on laser measurements of fibre orientation on the surface have already proved their worth in oak, as they can be used to develop models for predicting the mechanical properties of sawn timber. The aim of this work is therefore to evaluate the potential of this method and to improve it for other hardwood species. The first task of this work will be to carry out a non-destructive characterisation campaign on approximately 2,500 sawn hardwood timbers that have not been widely used in construction. LaBoMap is equipped with an industrial scanner to measure the orientation of two-dimensional fibres on all 4 sides of the timber. The data provided by the scanner will be used to build models of mechanical behaviour and to validate the potential of this method for the hardwoods under consideration. Knowledge of fibre orientation is particularly important for hardwoods and one of the objectives will be to quantify this effect and make comparisons between species. Knowledge of fibre orientation in 3D is one of the ways to improve grading methods. This line of work is the most ambitious, as it involves trying to obtain the orientation of the fibres in the volume in a non-destructive way. LaBoMap has developed a non-destructive method for measuring the orientation of fibres in a volume of wood by combining surface measurement and ring detection; this method will therefore be applied to the hardwoods in the project. Around the knots, many studies propose modelling based on the analogy of fluid flow. The aim will be to check the relevance of these equations for hardwoods with larger knots and, if necessary, to propose adaptations or developments.

Doctoral advisors

• Guillaume POT - Director,
• Joffrey VIGUIER,
• Bertrand MARCON.

Partners

• ADEME
• FCBA
• CTBF Guyane
• Fibois IDF
• Efectis
• Linkcity IDF (Bouygues)

Project

PhD in the frame of the Feuillu CHOC project

Funding

• ADEME

Distinctions and awards

• Second prize for poster GDR Wood Sciences 2023
• First prize for poster GDR Wood Sciences 2024

Personal interests

Modélisation

Start

1st of December 2023

Expected end

30th of November 2026