Research on the mechanical properties and constitutive models of bamboo-based composite structural materials

Bamboo-Based Composite Structural Materials (BBCS) has potential applications in low-density assembled buildings due to its advantages of lightweight, high strength, weatherability, renewability, and carbon negative. However, there are few studies on BBCS as a structural material. In this paper, BBCS with optimized formulation was used to carry out uniaxial tensile and compression tests on 345 specimens with 6 different extrusion thicknesses, to study the uniaxial tensile strength and compression strength, modulus of elasticity and its change rule with extrusion thickness along the parallel and perpendicular extrusion directions, to investigate the characteristics of the interfacial coupling of BBCS in the microscopic state, and to explore the advantages of BBCS over other bamboo wood structural materials by comparing the strength, deformation ductility and energy dissipation coefficients. Combined with the experimental results, the damage evolution mechanism of BBCS under uniaxial tension and compression was discussed. Based on the equivalent strain hypothesis and weibull distribution statistical theory, the damage variables were defined in sections, and the damage constitutive model of BBCS under uniaxial tension and compression was established. The results show that the tensile and compressive stress-strain curves of BBCS with different thicknesses exhibit nonlinear characteristics, the extrusion thickness has a significant effect on the tensile and compressive strengths.The bamboo fibers are evenly dispersed in the HDPE matrix, the material is well bonded at the interface. BBCS exhibits superior performance in strength, ductility, and energy dissipation, with a deformation ductility coefficient of 5.609 and an energy dissipation coefficient of 0.781, rendering it suitable for application as a structural load-bearing material in buildings. The damage constitutive model considering the effect of the extrusion thickness matches well with the experimental results, which provides a theoretical basis for the analysis of the structural system of BBCS. • Mechanical properties of Bamboo-Based Composite Structural Material (BBCS) versus extruded thickness were investigated. • The BBCS uniaxial tensile constitutive model is established. • The constitutive model of BBCS uniaxial compression is established.