*2.1. Fabrication*

Flax fiber plain weave fabrics (50% weft yarns per 50% warp yarns: [0◦/90◦] purchased from Linyi City, Shandong Province, China) and epoxy resin (LY1564/Aradur22962, Huntsman, from Shanghai, China) were selected to fabricate laminated composites by VARI. The diameters of the tows of the fabrics varied from about 0.6 mm to 1.5 mm. The nominal area density of the fabric and the fabric weight fraction were measured to be approximately 230 g/m<sup>2</sup> and 48%, respectively. The quasi-static tension tests of the pure matrix were performed and the stress-strain curves were provided in Figure S1. The viscosity of the resin was 450 mPa·<sup>s</sup> and the glass transition temperature was 140◦C. The operating time of the resin was about 120 min, within which the fabrication should be finished outside the heating oven. The curing cycle was 80 ◦C for 2 h and 120 ◦C for 3 h.

VARI is a type of low-cost molding technology for manufacturing large-scale composite structures. The process in this study includes the following four steps:


**Figure 1.** (**a**) Schematic of woven fiber and other supplementary materials; (**b**) composite sheet; (**c**) detailed image of the sheet.

In the present study, the fabricated composite sheet consisted of 20 layers, with a total thickness of 11.0 mm. The measured density of the composite sheet was 1.18 g/cm3. Cylindrical specimens with measuring 9 mm in diameter and 5 mm in length were adopted for both quasi-static and dynamic compression experiments. For consistency with the fiber orientation of the trusses of the lattice structure in Section 4.3, the same direction with a fiber orientation of 45◦ was used for the specimens of quasi-static and SHPB compression experiments (Figure 2).

**Figure 2.** Cutting direction (**a**) and size (**b**) of the material test specimen.
