2.1.1. Dimensional Measurements

We employed a five-point sampling method to obtain 100 random samples of ramie stalks. The plant height was measured using a tape measure (with an accuracy of 1 mm), and the xylem outer diameter, xylem inner diameter, and phloem thickness of the ramie stalk were measured using a DL91150 Vernier caliper (with an accuracy of 0.01 mm). The results are the average values of the measurements.

The results of the measurements are shown in Table 1. The average values of the ramie plant height, xylem outer diameter, xylem inner diameter, and phloem thickness were 1969.38 mm, 12.56 mm, 7.98 mm, and 0.71 mm, respectively.


**Table 1.** Structural dimensions of the ramie.

2.1.2. Density and Moisture Content

The density of the phloem and xylem of a fresh ramie stalk was measured using a liquid immersion method [23] by immersing a certain mass of phloem and xylem in water and measuring the drainage volume to obtain the volume of each component of the ramie stalk and then calculating its density. The test was repeated ten times, and the average value was taken. The average densities of the phloem and xylem were 1618.95 kg/m3 and 751.50 kg/m3, respectively.

The moisture content of the ramie stalk was determined according to the "Method for determination of the moisture content of wood" [24] using a high-precision balance (with a weighing range of 220 g and an accuracy of 0.001 g) and a DGT-G220 blast drying oven. The moisture content of the ramie stalk was calculated to be approximately 79.72%.

#### 2.1.3. Elastic Modulus and Shear Modulus

Tensile testing is a common method for obtaining the elastic modulus. This method has been used to measure the elastic modulus of wood [25], corn straw [26], rice stalk [27], bamboo stalk [28], and reed stalk [29], providing the most concentrated measurement of the elastic modulus [30]. In this study, based on the standard "Method of sample logs sawing and test specimens selection for physical and mechanical tests of wood" [31] and the relevant literature [32], tensile tests of the phloem and xylem of the ramie stalks were performed using a microcomputer-controlled electronic universal material testing machine (produced by Shanghai Tuofeng Instruments Co., Ltd., Shanghai, China), model TFW-508, with a 500 N transducer, and the accuracies of the force transducer as well as the displacement transducer were within ±0.1%. The test parameters were set to a loading speed of 5 mm/min. The stopping condition was judged to be a drop in the force value of more than 80% of the peak force. The tensile test is shown in Figure 1. The elastic modulus was calculated based on the slope of the linear region of the stress–strain curve. The shear modulus was derived from the elastic modulus using a conversion formula.

**Figure 1.** Tensile test to determine the modulus of elasticity: (**a**) xylem tensile test; (**b**) phloem tensile test.

The results show that the average elastic modulus of the phloem and xylem were 1721.4 MPa and 630.3 MPa, respectively. The average shear modulus values of the phloem and xylem were calculated to be 614.8 MPa and 242.4 MPa, respectively, using Equation (1):

$$\begin{cases} \quad E = \frac{F\_1}{\delta A} \\ \quad \varepsilon = \lim\_{T\_1 \to 0} \frac{\Delta L}{L\_1} \\ \quad G = \frac{E}{2(1+v)} \end{cases} \tag{1}$$

where *E* represents the elastic modulus of ramie, MPa; *F*<sup>1</sup> represents the axial load on ramie, N; *A* represents the contact area, mm2; *ε* represents the strain value; Δ*L* represents the deformation of the ramie after tension, mm; *L* represents the length of the tensile area of the ramie specimen, mm; *G* represents the shear modulus, MPa; and *v* is the Poisson's ratio.
