## 3 Full-Scale Testing
### Results
#### 3.4.2 Failure and Deformation Modes  
The failure mode observed in all specimens eventually involved ruptures initiating at the extremes of the minimum diameter, i.e., either points A or C in Figure 11b. As shown in Figure 14 for the PLA specimens, the point of failure was not necessarily at mid-height. In Figure 15, the deformations observed in the more ductile ABS specimens indicate the evolution of local buckling of the tube walls before a more catastrophic rupture of the material; these losses of stiffness are also evident in the load-end shortening curves shown in Figure 13. This behaviour is commensurate with the stable post-yield response shown in Figure 8c from compression testing of the ABS material specimens. \begin{table}
\begin{tabular}{l c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Specimen**} & \multirow{2}{*}{_a/b_} & \multirow{2}{*}{\(D_{\text{eq}}\)} & \multirow{2}{*}{\(D_{\text{eq}}/\text{{tr}}^{2}\)} & \multirow{2}{*}{\(\sigma_{\text{cr}}\)} & \multirow{2}{*}{\(\sigma_{\text{u,exp}}\)} & \multirow{2}{*}{\(\overline{\lambda}_{\ell}\)} & \multirow{2}{*}{\(\rho_{\text{exp}}\)} & \multirow{2}{*}{\(\rho_{\text{d}}\)} & \multirow{2}{*}{\(N_{\text{u,exp}}\)} & \multirow{2}{*}{\(N_{\text{Rd}}\)} & \multirow{2}{*}{\(N_{\text{u,exp}}/N_{\text{Rd}}\)} \\ \cline{3-11}  & & \multicolumn{3}{c}{**(mm)**} & & & & & & & (kN) & (kN) & \\ \hline EHS01-PLA1-100-50-3.0 & 2.0 & 201 & 1419 & 51.8 & 36.0 & 1.14 & 0.53 & 0.44 & 26.59 & 21.84 & 1.22 \\ EHS02-PLA1-90-60-2.0 & 1.5 & 135 & 1470 & 50.0 & 37.3 & 1.16 & 0.55 & 0.42 & 17.88 & 13.75 & 1.30 \\ EHS03-PLA1-90-60-2.0 & 1.5 & 135 & 1456 & 50.5 & 33.7 & 1.16 & 0.50 & 0.43 & 16.23 & 13.94 & 1.16 \\ EHS04-PLA1-90-60-2.0 & 1.5 & 135 & 1483 & 49.5 & 34.0 & 1.17 & 0.50 & 0.42 & 16.08 & 13.50 & 1.19 \\ EHS05-PLA1-100-50-3.0 & 2.0 & 200 & 1447 & 50.8 & 41.1 & 1.15 & 0.61 & 0.43 & 29.68 & 21.00 & 1.41 \\ EHS06-PLA1-100-50-1.5 & 2.0 & 200 & 3096 & 23.7 & 25.4 & 1.69 & 0.38 & 0.23 & 8.76 & 5.34 & 1.64 \\ EHS07-PLA1-105-35-2.0 & 3.0 & 315 & 3509 & 20.9 & 17.9 & 1.80 & 0.26 & 0.21 & 8.22 & 6.44 & 1.28 \\ EHS08-PLA1-105-35-1.5 & 3.0 & 315 & 5100 & 14.4 & 12.9 & 2.17 & 0.19 & 0.15 & 4.10 & 3.33 & 1.23 \\ \hline EHS09-PLA2-90-60-1.0 & 1.5 & 136 & 2440 & 31.0 & 28.3 & 1.50 & 0.41 & 0.28 & 7.50 & 5.12 & 1.46 \\ EHS10-PLA2-90-60-1.5 & 1.5 & 135 & 1710 & 44.2 & 42.3 & 1.26 & 0.61 & 0.37 & 15.77 & 9.68 & 1.63 \\ EHS11-PLA2-90-60-3.0 & 1.5 & 135 & 904 & 83.6 & 64.2 & 0.91 & 0.92 & 0.59 & 44.39 & 28.35 & 1.57 \\ EHS12-PLA2-100-50-1.0 & 2.0 & 200 & 3597 & 21.0 & 18.1 & 1.82 & 0.26 & 0.20 & 4.87 & 3.81 & 1.28 \\ EHS13-PLA2-100-50-2.0 & 2.0 & 200 & 1797 & 42.0 & 39.0 & 1.29 & 0.56 & 0.36 & 20.73 & 13.25 & 1.57 \\ EHS14-PLA2-100-50-2.5 & 2.0 & 200 & 1484 & 50.9 & 49.1 & 1.17 & 0.71 & 0.42 & 31.34 & 18.69 & 1.68 \\ EHS15-PLA2-105-35-1.0 & 3.0 & 315 & 5075 & 14.9 & 12.8 & 2.16 & 0.18 & 0.15 & 3.70 & 3.12 & 1.19 \\ EHS16-PLA2-105-35-2.5 & 3.0 & 315 & 2352 & 32.1 & 28.1 & 1.47 & 0.40 & 0.29 & 17.23 & 12.23 & 1.41 \\ EHS17-PLA2-105-35-3.0 & 3.0 & 315 & 1992 & 37.9 & 34.4 & 1.35 & 0.49 & 0.33 & 24.72 & 16.44 & 1.50 \\ \hline EHS18-ABS-100-50-1.0 & 2.0 & 196 & 4413 & 9.44 & 5.28 & 2.00 & 0.14 & 0.17 & 1.53 & 1.89 & 0.80 \\ EHS19-ABS-90-60-1.0 & 1.5 & 136 & 3202 & 13.01 & 12.18 & 1.71 & 0.32 & 0.23 & 3.30 & 2.29 & 1.43 \\ EHS20-ABS-90-60-1.5 & 1.5 & 135 & 2052 & 20.31 & 17.13 & 1.36 & 0.45 & 0.32 & 7.15 & 5.06 & 1.39 \\ EHS21-ABS-105-35-1.0 & 3.0 & 312 & 6434 & 6.48 & 2.13 & 2.42 & 0.06 & 0.13 & 0.65 & 1.49 & 0.43 \\ EHS22-ABS-105-35-2.5 & 3.0 & 315 & 3126 & 13.33 & 8.74 & 1.68 & 0.23 & 0.23 & 5.44 & 5.35 & 1.00 \\ EHS23-ABS-100-50-1.0 & 2.0 & 198 & 4846 & 8.60 & 6.79 & 2.10 & 0.18 & 0.16 & 1.80 & 1.61 & 1.11 \\ EHS24-ABS-100-50-2.0 & 2.0 & 198 & 2475 & 16.84 & 11.00 & 1.50 & 0.29 & 0.28 & 5.66 & 5.35 & 1.05 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Experimental results and design parameters for EHS in compression. Figure 13: Load–end shortening graphs for ABS EHS specimens in compression.