Experimental Research On Static And Dynamic Mechanical Properties Of Parallel Strand Bamboo At Different Temperature

Parallel Strand Bamboo(PSB)is a kind of unidirectional fiber composite engineering bamboo based on the gluing of loosened bamboo bundles.It has outstanding strength and weather resistance,and has further prospects in modern bamboo structures and bamboo-wood composite structures.At present,the research of parallel strand bamboo mainly focuses on the static mechanical properties at room temperature,and the bamboo structure building will inevitably be subjected to vibration,shock and other loads in addition to the static load during its service life.In addition,the mechanical properties of the adhesive in parallel strand bamboo are sensitive to temperature,especially high temperature.Therefore,mastering the mechanical properties of parallel strand bamboo at high temperature and under dynamic load is of great significance to ensure the safety of bamboo structures,but the current research in this area is basically blank.In this paper,two kinds of parallel strand bamboos with densities of 1100kg/m3(D1)and 1300kg/m3(D2)were selected,and the stress direction,strain rate and temperature were used as experimental parameters to carry out the static mechanical properties and dynamic performance at different temperatures.The mechanical properties test was carried out,and the test results were analyzed.The main research results obtained are as follows:(1)The static mechanical performance tests of 32 groups of specimens at 4 temperature levels were completed,including prismatic and cylindrical compression tests,tensile tests,shear tests and bending tests.The results show that compared with other engineered bamboos and engineered woods,the tensile and compressive strengths along the grain of the parallel strand bamboo are outstanding,and the test data have good repeatability;the compressive failure of the parallel strand bamboo has certain ductility characteristics.However,its tensile,flexural and shear failure brittle characteristics are remarkable;the direction of force has a significant effect on the static compressive strength of the parallel strand bamboo,but has little effect on the shear strength.(2)The impact test of 96 groups of parallel strand bamboo specimens at different temperatures and strain rates was completed by using the self-made constant temperature equipment and the split hopkinson pressure bar(SHPB)experimental device.The test found that:the two kinds of parallel strand bamboo test blocks showed significant strain rate effect,the larger the test strain rate value,the larger the compressive strength value,the results show that the DIF and the strain rate are basically linear;and after the material reaches the critical stress-strain value at the boundary point between the linear growth and nonlinear growth stages,the energy absorption density per unit volume of the material increases with the increase of the strain rate.(3)The SHPB test results of the parallel strand bamboo at different temperature levels show that the impact properties of the parallel strand bamboo have obvious temperature effects.At the same strain rate,the higher the test temperature,the more significant the reduction in the strength of the parallel strand bamboo,and the greater the corresponding DIF value.The surface heating has a significant effect on the mechanical properties of the parallel strand bamboo.At different temperature levels,the strain rate effect of parallel strand bamboo was different,and the increase of temperature increased the strain rate effect of recombination.(4)The density and the direction of the force also have a certain influence on the dynamic impact mechanical properties of the parallel strand bamboo.Generally speaking,the strain rate effect and temperature effect of D2 bamboo with high apparent density are smaller than those of D1 bamboo with low apparent density;under the action of impact load,the compressive strength of the parallel strand bamboo along the grain direction is higher than that in the horizontal grain direction,and the strain rate effect and temperature effect in the grain direction are also smaller than those in the cross-grain direction.