Research On Manufacturing Process And Performance Of Flattened Bamboo Glulam For Structural Use

To explore a manufacturing process of flattened bamboo glulam for structure,and try to use it as a building material.Starting from the basic unit,this thesis analyzes the physical and mechanical properties of bamboo slabs with and without nicks as raw materials to explore the quality of bamboo slabs under different high-temperature softening processes;then,expand the flat bamboo with and without nicks Research on the physical and mechanical properties of laminated timber,explore the influence of different assembly methods on the quality of flattened bamboo laminated timber,and explore the influence of different lengthening methods on the mechanical properties of structural flattened bamboo laminated timber according to the form of finger joints;finally,The flattened bamboo glulam is used as a structural beam for bending performance testing to explore whether it meets the requirements of the building structure.The main conclusions are as follows:(1)When the bamboo wall thickness is constant,with the increase of the softening treatment temperature,the air-dry density,total dry density,air-dry volume shrinkage rate and total dry volume shrinkage rate of the bamboo slabs with and without nicks are all Shows a downward trend,and are smaller than the untreated material under the same size,so the overall dimensional stability is improving.When the softening process is constant,as the thickness increases,the airdry density,total dry density,air-dry volume shrinkage rate,and total dry volume shrinkage rate of the slabs with and without scoring will gradually decrease.When the softening process and wall thickness are the same,the air-dry volume shrinkage rate and the total dry volume shrinkage rate of the non-scored bamboo slab are lower than the corresponding scored bamboo slab.When the thickness of the bamboo wall is constant,the compressive strength of the horizontal stripes of the slabs with and without scoring will decrease with the increase of temperature.When the softening temperature is 175?,the horizontal stripes of the slabs with and without scoring will be reduced.The compressive strength has a maximum value of20.41 MPa and 19.37MPa;when the softening temperature is 185?,the horizontal compressive strength of the bamboo slabs with and without nicks will be reduced to the minimum,and they will decrease respectively compared with the untreated material.26.5% and 20.5%.When the thickness is different,the horizontal grain compressive strength of the 7mm flat panel at 175?and 185? is higher than that of the same type of panel with 8mm,but the opposite is true at180 ?.In terms of compressive strength along the grain,the thickness is constant.The compressive strength along the grain of the bamboo slab with and without nicks is inversely proportional to the softening temperature.At 185?,the bamboo slab with a score of 7mm in thickness reaches the minimum value of 34.58 MPa.;And the non-scored bamboo spreading plate has a minimum value of 32.41 MPa at a thickness of 8mm.When the softening process is constant,the thickness has basically no effect on the compressive strength of the slabs with or without nicks along the grain.When the thickness of the bamboo wall is constant,the softening temperature increases,and the horizontal tensile strength of the slabs with and without nicks decreases.In terms of tensile strength along the grain,with the increase of softening temperature,the two types of bamboo slabs are reduced accordingly,and the thickness of the bamboo has little effect on it.When the softening process and thickness are the same,the horizontal grain tensile strength and the alonggrain tensile strength of the non-marked bamboo spreading plate are stronger than the corresponding notched bamboo spreading plate.When the wall thickness is constant,the static bending strength and elastic modulus of the slabs with and without nicks are inversely proportional to the temperature.When the wall thickness is 8mm and the softening temperature is 175?,the static flexural strength of both has the maximum value,98.35 MPa and 109.24 MPa respectively.Regarding the modulus of elasticity,the maximum value of 7mm for the thickness of the scoring bamboo slab is 7494.07 MPa at175°C;the maximum value of 8588.81 MPa for the thickness of the non-scoring bamboo slab at175°C is 8mm.When the softening process is the same,the thickness has no significant effect on the static bending strength and elastic modulus of bamboo.(2)Class A(bamboo yellow-bamboo green-bamboo yellow-bamboo yellow-bamboo greenbamboo yellow),B(bamboo yellow-bamboo yellow-bamboo green-bamboo green-bamboo yellow-bamboo yellow)and C category(Bamboo yellow-bamboo green-bamboo yellow-bamboo green-bamboo yellow-bamboo yellow)of the flattened bamboo laminated lumber,the basic density of the B-type flattened bamboo laminated lumber is the highest,while the A and C types The basic density of the flattened bamboo laminated timber is roughly the same and all are less than the B-type laminated timber.When the blank assembly method is fixed,the total average density of the scored and flattened bamboo laminated timber is greater than that of the non-scored plank.The moisture content of the two laminated lumbers with different forming methods is basically the same.In terms of water absorption,type B laminated lumber has the highest water absorption rate at 24 h and 48 h,while the water absorption rate of type A and C laminated lumber at 24 h and 48 h is basically close,and is significantly lower than that of type B laminated lumber.The dimensional stability of the laminated lumber made from the blank is the best.In addition,the water absorption rate of the scoring and flattened bamboo laminated timber is significantly lower than that of the non-scoring flattened bamboo laminated timber,and the average maximum difference can reach 13%.For a certain period of time,the water absorption thickness expansion rate of type A sheets is the smallest at 24 h and 48 h,while the thickness expansion rate of type B laminated lumber is the largest;but after 48 h,the water absorption thickness expansion rate of type B laminated lumber becomes the smallest,and type C layer The accumulation of materials is the largest.In addition,the water absorption thickness expansion rate of the scored and flattened bamboo laminated timber is lower than that of the non-scored flattened bamboo laminated timber,and the maximum difference can reach 20.6%.In summary,the scored and flattened bamboo layer of type B Laminated timber has the best dimensional stability.The board with scored flattened bamboo laminated timber under the A group billet has the highest compressive strength along the grain,the maximum can reach 51.09 MPa,and the B group billet method is the smallest,40.12 MPa,a reduction of 21.5%,the difference is obvious;no Scored laminated lumber is consistent with this behavior,with a difference of 16.3%.The compressive strength along the grain of the similar non-marked flattened bamboo laminated timber is higher than that of the notched flattened bamboo laminated timber,and the maximum difference of the type B group billet is 9.5%.The flattened bamboo laminated timber with and without nicks has the maximum alonggrain tensile strength in the A group billet,which are 70.63 MPa and 63.21 MPa respectively;while the B and C laminated timbers are similar and much smaller than the A type.The tensile strength along the grain of the same type of scoring flattened bamboo laminated timber is greater than that of the non-scoring flattened bamboo laminated timber.The flattened bamboo laminated lumber with and without nicks has the maximum static bending strength in the A group billet,which are 116.94 MPa and 119.63 MPa,respectively;the A and C types are similar,and the B type is quite different.In terms of modulus of elasticity,the flattened bamboo laminated timber with and without nicks has the highest value in the A-type billet,which are 10443.35 MPa and 14213.21 MPa respectively.The two types of laminated lumber have the largest bonding strength in the A-type billet assembly mode,the B-type is the second,and the C-type is the smallest.The bonding strength of flat bamboo laminated timber with and without nicks has no fixed rules,but they all meet the strength requirements of GB/T9846-2015 Type I plywood.(3)The manufacturing process of flattened bamboo laminated timber for structure.It mainly includes the processes of material preparation,flattened bamboo laminate manufacturing,specification shaping,lengthening assembly,lamination and bonding,curing and health preservation.The glulam made of two finger joints,namely,exposed teeth and concealed teeth,is extended and repressed to test its bending and tensile properties.The static flexural strengths of the flattened bamboo structural timber with and without nicks were 57.50 MPa and 68.07 MPa when exposed to finger joints,and 55.35 MPa and 67.36 MPa when exposed to finger joints.The elastic modulus of the bamboo structural material with and without nicks is 10289.28 MPa and 10890.17 MPa when finger-joined with open teeth,and9385.94 MPa and 9405.78 MPa when finger-joined with dark teeth.The modulus of elasticity is basically not affected,but its static flexural strength is greatly affected,and the strength loss rate is up to 55%.The non-scoring bamboo slab is recompressed into a bamboo glulam in the form of a finger joint and a B-type assembly blank.The square beam with the joint position at both ends during the test has a flexural ultimate load and flexural strength greater than that of the joint at the center position.Square beams,but they can meet the strength requirements for beams in the wood structure building standards.