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MATERIALS 43
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Veneer Lumber (LVL), and Cross-Laminated Timber (CLT) offer for the unknown factors related to fatigue.
greater homogeneity and dimensional stability. To preserve wood as a renewable resource amid increasing
There is no clear consensus on whether engineered wood demand for green and sustainable products, it is essential
has a longer fatigue life than solid wood. to optimise wood-based structures and products. Therefore,

The type of adhesive and manufacturing process play a wood fatigue is an important research area that should be
significant role. Some studies indicate that engineered wood addressed by more researchers.
suffers less damage accumulation during fatigue, as evidenced
by a smaller reduction in the modulus of elasticity. Measurement Methods & Models
Wood-based composites are classified into two groups: Current timber design standards, such as EN 1995-2,
homogeneous and inhomogeneous. In homogeneous composites, incorporate fatigue through simplified methods based on
wood is present as small particles or even nanofibres, together constant amplitude loading and reduced allowable stresses.
with another component of the composite material. Examples This approach is conservative and not ideal for structural
of homogeneous wood composites include wood polymers optimisation. To better predict fatigue life, various experimental

and wood cements. methods and predictive models have been developed.
Inhomogeneous composite materials combine the positive Monitoring wood during fatigue tests involves tracking
properties of two or more materials in their primary form force, displacement, and other parameters like crack growth
of use. Examples include composites made of timber and and energy dissipation. Key non-destructive methods include:
concrete, wood reinforced with glass fibres, and composites Acoustic Emission (AE) is a prominent technique for detecting
made of wood and aluminium. crack formation and growth. AE sensors record high-frequency
A comprehensive review of their fatigue properties would sound waves released by micro-damage within the material.

require a separate study. Nevertheless, we mention some Studies show that the rate of acoustic events increases
examples of composite materials and their response to fatigue. significantly under cyclic loading compared to static loading,
Yeoh et al. investigated the behaviour of a composite providing an early warning of impending failure. It has potential
of timber and concrete. After two million load cycles, no for locating crack tips and estimating remaining fatigue life.
obvious loss of stiffness was observed in the rectangular Digital Image Correlation (DIC) is a non-contact, optical
notch-connected floor beams. method that measures full-field deformations by tracking
Davids et al. examined the response of used beams patterns on a sample's surface between consecutive images.
reinforced with glass fibres. Similarly, after two million cycles, It is highly effective for mapping strain distributions and
they did not observe a significant reduction in the static

strength of the Glulam timber beams. freepik.com
Yang et al. studied the response of a wood–polymer
composite to fatigue. As expected, wood–polymer composites
exhibit greater predictability than solid wood.
Few researchers are familiar with wood fatigue, as it
remains a highly specialised research area. The problem is that
allowable design stresses are based on static strength, even

though fatigue accounts for 90 percent of material failures.
As a result, structural elements are oversized to compensate