Compressive Failure Mechanism of Structural Bamboo Scrimber

Bamboo scrimber is one of the most popular engineering bamboo composites, owing to its excellent physical and mechanical properties. In order to investigate the influence of grain direction on the compression properties and failure mechanism of bamboo scrimber, the longitudinal, radial and tangential directions were selected. The results showed that the compressive load–displacement curves of bamboo scrimber in the longitudinal, tangential and radial directions contained elastic, yield and failure stages. The compressive strength and elastic modulus of the bamboo scrimber in the longitudinal direction were greater than those in the radial and tangential directions, and there were no significant differences between the radial and tangential specimens. The micro-fracture morphology shows that the parenchyma cells underwent brittle shear failure in all three directions, while the fiber failure of the longitudinal compressive specimens consisted of ductile fracture, and the tangential and radial compressive specimens exhibited brittle fracture. This is one of the reasons that the deformation of the specimens under longitudinal compression was greater than those under tangential and radial compression. The main failure mode of bamboo scrimber under longitudinal and radial compression was shear failure, and the main failure mode under tangential compression was interlayer separation failure. The reason for this difference was that during longitudinal and radial compression, the maximum strain occurred at the diagonal of the specimen, while during tangential compression, the maximum strain occurred at the bonding interface. This study can provide benefits for the rational design and safe application of bamboo scrimber in practical engineering.

Experimental study on bending behavior of glulam beams strengthened with bamboo scrimber

PurposeIn view of the defects of glued wood beams, a new composite member – reconstituted bamboo board reinforced glued wood beams is proposed to improve the bearing capacity of glued wood beams.Design/methodology/approachThe bending test studied the ordinary glulam beams and the reinforced glulam beams with different layer numbers and different layer thicknesses by comparing with six kinds of glulam beams strengthened with bamboo scrimber and one kind of ordinary glulam beams and used the method of third-point stepwise loading on the glulam beams strengthened with bamboo scrimber.FindingsThe bamboo scrimber improved the bending behavior of the ordinary glulam beams. The 10 mm bamboo scrimber layer can meet the requirements of the maximum ultimate bending capacity and minimize the defects. So 10 mm bamboo scrimber layer was the optimal thickness. During the loading process, the strain change of the normal section of the reconstituted bamboo board reinforced glued wood beam basically conforms to the plane section assumption.Originality/valueThe bending rigidities of the glulam beams strengthened with bamboo scrimber increased up to 28.25%, 8.53% and 76.67%, and the ultimate bending capacity increased from 83.44% to 99.34% with the increase of the bamboo scrimber plate layers (the replacement rate). The ultimate bending capacities and the bending rigidities of the glulam beams strengthened with bamboo scrimber increased to 52.32%∼60.18% and 90.07%∼99.34% with the changing of the bamboo scrimber thicknesses from 7.1 mm to 25 mm.

Influence of Four Ageing Methods on the Mechanical Properties of Bamboo Scrimber

In this study, the six-cycle accelerated ageing method (method I), the 6 h boiling-freezing-drying method (method II), the wet circulation method (method III), and the boiling-testing method (method IV), which are accelerated ageing testing methods, were used to study the ageing resistance of bamboo scrimber. Changes in the nail-holding power of the plane, the side, and the end face of untreated/treated bamboo scrimber were analyzed systematically, including other changes in mechanical properties, such as the horizontal shear strength, the modulus of rupture (MOR), and the modulus of elasticity (MOE) along the smooth grain, etc. The results show that all mechanical properties decreased after treatment with the four accelerated ageing testing methods: the nail-holding power decreased by 4%~42% on the plane, 8%~40% on the side, and 5%~66% on the end face. The horizontal shear strength decreased by 3.1%~16.7%, the MOR decreased by 15%~27.2%, and the MOE decreased by 2.6%~12.8%. The nail-holding power of the three sides and the MOR were the most affected properties after treatment. So, the nail-holding power and the MOR can be chosen as important indices to evaluate bamboo scrimber’s weather resistance. For the four accelerated ageing testing methods, the degree of influence on the nail-holding power was in this sequence: method I > method III > method IV > method II. However, after comprehensive consideration, the degree of influence on the mechanical properties was in this sequence: method I > method IV > method III > method II.