Characterization of Laminated Bamboo Lumber Using Digital Image Correlation in Mechanical Testing

Abstract

The purpose is to investigate the use of bamboo as an outstanding material in terms of sustainability in various technical fields,
such as civil engineering. Therefore, the Phyllostachys edulis (Carrière) J. Houz. (Moso) culms are further processed into
laminated bamboo lumber (LBL) to bring the material closer to technical applications according to European standards. The
testing program was divided into three parts. First, LBL was examined in its initial condition. Computed tomography (CT)
was applied to detect pores and other defects. In particular, the visualization of potential bonding defects between the individual
laminate layers of bamboo was of key importance, as this type of defect is expected to have a major impact on the mechanical
properties of LBL. Afterwards, the bamboo specimens underwent mechanical testing, including compressive and shear testing.
The results were promising for the intended technical applications. The engineered bamboo product LBL exhibited strengths
comparable to those of wooden products already used in the targeted areas. Material reactions were recorded during the tests
using appropriate measuring devices. In particular, the digital image correlation (DIC) was applied to record deformations and
strains on the surface of bamboo specimens. This measuring technology enabled a subsequent visualization of the influence of
the applied loads, highly loaded areas, and resulting crack progression. During compressive testing, it was observed, that the
failure of the specimens often began at the nodal area of the bamboo culm, still clearly visible in the engineered bamboo product.
The moisture content of specimens was determined using the oven-dry method, as moisture has a proven influence on material
properties. After completing the mechanical characterization, the third phase of the study began, including analytical tests of
damaged specimens. The focus was on examining the damaged areas and fracture surfaces to identify the operating damage
mechanisms. The research indicates that LBL shows promise as a sustainable alternative to commonly used building materials.