Comparative evaluation of the mechanical properties of Phyllostachys edulis and Guadua angustifolia applying digital image correlation

Abstract The sustainable and fast-growing natural material bamboo accommodates the potential for partially substituting energy-intensive materials in specific technical applications (e.g., in the building industry), thus playing a significant role in bringing about a turning point in reducing the disconcerting effects of global warming and climate change. Beyond the mechanical properties required for the intended applications and rapid growth, the plant exhibits a notable ability of CO 2 storage and eco-restoration. Bamboo is available in many different species in large parts of the world, growing under different climate conditions. With each species possessing its own unique characteristics, the Phyllostachys edulis (Moso) from the Asian region and the Guadua angustifolia (Guadua) from South America were contrasted as two of the best-known and most extensively researched species. The following investigations were conducted in accordance with normative standard ISO 22157 that has been previously established. Material responses are typically recorded using displacement sensors or strain gauges, which are spatially limited to the measurement zone. Because bamboo is a natural material with locally varying properties, this spatial limitation can lead to inaccuracies by failing to capture the actual material response during testing. Digital image correlation (DIC) is therefore employed, as it enables the observation of larger specimen areas and offers flexibility in subsequent data analysis. In addition, the area-based and visually interpretable evaluation makes it possible to assess whether loads are transferred uniformly or whether naturally occurring defects cause an uneven stress distribution, as discussed later in this paper. The method also serves to verify the intended load introduction into the bamboo culm and to identify, and thus exclude, local failure caused by improper loading. The mechanical test results confirmed the excellent mechanical properties of bamboo when loaded parallel to the fiber direction, as high strength values were observed particularly in compression and bending tests in this direction. While Guadua exhibited slightly higher compressive strength, Moso showed overall higher strengths in transverse tensile and bending tests. Generally, a marked reduction in strength was observed when comparing tensile tests perpendicular to the grain.