Advances in engineered bamboo processing: Material conversion and structure

With bamboo's rapid renewability, short rotation period, versatility, and good mechanical properties, engineered bamboo composites have undergone significant evolution. This paper examines the recent changes in bamboo product manufacturing, starting with a wholistic classification of culm breakdown to the plethora of different constituent elements: full culm, flattened bamboo, bamboo bundles, splits/strips, mats/curtains, and strands. Highly cracked flattened strips used in bamboo scrimber are 4-5 times greater in specific surface area than crack-free strips, requiring an estimated 6-10 times higher resin consumption than laminated bamboo. Based on their structure, bamboo composites can be classified into three categories: 1) lamination of minimally modified culms, 2) laminated mat structures with controlled or semi-random placement of constituent elements and 3) random mat structures composed of thin bamboo strands. The formation structures have been transitioning from random placement of large, thick strips to controlled layup with secondary elements of stitched strip curtains, helping minimize edge-to-edge strip overlaps and improve bonding efficiency with less mat compaction. Density-structure-strength property relationships are also compared between various engineered bamboo and common engineered wood products. Other technical advancements include crack-free flattened bamboo and hybrid bamboo-wood products.