Compressive properties of Hemp (Cannabis sativa L.) stalks

Compressive behaviour of hemp (Cannabis Sativ L.) stems is important for the design of hemp handling and processing machines. Experiments were carried out to measure the compressive properties of stems from two hemp varieties: Alyssa (grown for fibre only) and Petera (grown for both fibre and seed), produced in Manitoba, Canada. The physical properties of the hemp specimens were measured. For each variety, an air-dried hemp stem was divided into three height sections along the stem: upper, middle and lower. For each section, the hemp stem was further cut into 25.4 mm long specimens. Individual specimens were compressed in the axial and lateral directions using a universal testing machine. The load-displacement curves were recorded, and compressive properties were derived from the load-displacement curves. The outer diameter of the hollow hemp specimens varied from 6 to 17 mm; the linear density varied from 10 to 37 g m−1. Diameter and linear density were greater for Petera than Alyssa, and at the lower height section than the higher section for both varieties. The compression tests showed that the maximum compressive load varied from 58 to 1425 N, and the energy requirement varied from 23 to 1809 mJ, depending on the variety, height section and diameter of stem, and compression direction. In general, the maximum compressive load and the energy requirement were greater in the lower section and for larger diameters; higher loads and energy were observed for Petera than for Alyssa and for the axial compression direction than for the lateral direction.