本文選題：夾層結(jié)構(gòu)　切入點：木質(zhì)面板　出處：《中南林業(yè)科技大學》2017年博士論文

【摘要】：蜂窩夾層木質(zhì)復合材由于等效密度低、制造的便利性、力學的復合效應、可設計性及平整度高等優(yōu)點在家具產(chǎn)品、室內(nèi)裝飾、包裝運輸?shù)让裼妙I(lǐng)域具有廣泛應用前景。研究該種復合結(jié)構(gòu)材在橫向承載下的力學特性,為產(chǎn)品優(yōu)化設計與工程應用提供理論基礎(chǔ),意義重大。本文以蜂窩夾層木質(zhì)復合材為研究對象,系統(tǒng)研究了橫向載荷作用下夾層梁的彎曲性能及夾層板的平壓性能,結(jié)論如下:(1)推導出了基于等效單層梁理論計算軟夾芯夾層梁最大彎曲正應力的公式。運用正交試驗法進行蜂窩夾層梁三點彎曲試驗,結(jié)果表明:蜂窩邊長對靜曲強度的影響極其顯著,表板類型、涂膠量對靜曲強度的影響不顯著;芯層厚度對“//”方向試件靜曲強度的影響顯著,而對“⊥”方向試件影響極其顯著�！啊汀狈较蛟嚰撵o曲強度值均高于“//”方向試件。在Winkle彈性地基梁理論的基礎(chǔ)上,考慮了表板彎曲正應力對局部凹陷的影響,推導出軟夾芯夾層梁三點彎曲試驗表面壓潰載荷的計算公式。系統(tǒng)分析了芯層剪切失效與表面壓潰二種彎曲破壞模式,并將理論模型與試驗數(shù)據(jù)進行對比分析,相對誤差約±20%以內(nèi)。(2)建立了基于二變量的夾層梁彎曲變形的分層一階剪切理論。該理論與三點彎曲試驗結(jié)果、傳統(tǒng)一階剪切理論的對比分析,結(jié)果表明:小彈性變形范圍內(nèi),分層一階剪切理論比傳統(tǒng)一階剪切理論預測的跨中撓度值保守。在同樣的受力條件下,“//”方向試件跨中撓度均大于“⊥”方向試件。分層一階剪切理論計算的芯層切應變與切應力值比傳統(tǒng)一階剪切理論低,但隨著芯層厚度的增加,二種理論的計算差異逐漸變小。將分層一階剪切理論計算的切應力在橫截面積分,其剪力值滿足于靜力平衡條件。(3)在分層一階剪切理論的基礎(chǔ)上,建立了二節(jié)點六自由度的有限元梁單元模型。數(shù)值分析結(jié)果表明:小彈性變形范圍內(nèi),有限元模型與分層一階剪切理論計算的跨中撓度十分接近,平均差異小于10%。當芯層厚度較小時,有限元模型計算的橫截面切應變與切應力接近于分層一階剪切理論;隨著芯層厚度的增加,其值逐漸靠近傳統(tǒng)一階剪切理論。(4)在傳統(tǒng)一階剪切理論的基礎(chǔ)上,修正了夾層梁橫截面切應力值和芯層剪切模量,建立了修正一階剪切理論。數(shù)值分析結(jié)果表明:當芯層厚度較小時,修正一階剪切理論與分層一階剪切理論計算的跨中撓度十分接近;當芯層厚度增加時,修正一階剪切理論的模型預測值逐漸介于分層一階剪切理論與傳統(tǒng)一階剪切理論之間;同時,剪切撓度、因彎矩引起的撓度隨之減小,但剪切撓度占總撓度的比重越來越大。另外,當芯層厚度增加時,修正一階剪切理論與傳統(tǒng)一階剪切理論計算的剪切撓度值趨于一致。(5)在三點彎曲試驗的基礎(chǔ)上,推導出考慮上表板彎曲正應力的表面壓痕位移計算公式。對比試驗數(shù)據(jù),考慮壓痕分層一階剪切理論與考慮壓痕修正一階剪切理論的跨中撓度預測精度好于傳統(tǒng)一階剪切理論。(6)運用正交試驗法進行蜂窩夾層板平壓性能試驗,結(jié)果表明:蜂窩邊長對芯層橫向彈性模量和平壓強度的影響極其顯著,涂膠量對芯層橫向彈性模量和平壓強度的影響較顯著,表板類型、芯層厚度對芯層橫向彈性模量和平壓強度的影響不顯著。在平壓強度試驗的基礎(chǔ)上,推導出基于Timoshenko薄板穩(wěn)定理論的夾層板受壓等效臨界屈曲應力的計算公式,并與試驗數(shù)據(jù)進行對比,相對誤差約±15%以內(nèi)。在芯層蜂窩材料選定的情況下,增加胞元壁厚和減小胞元的邊長能有效增強蜂窩夾層板的抗壓性能。
[Abstract]:Honeycomb sandwich wood composites due to the equivalent of low density, convenient manufacturing, composite effect of mechanical design, and the flatness of the advantages in furniture, interior decoration, and has wide application prospect in civil field of packaging and transportation. The study on the mechanical properties of the composite material in the structure under the lateral load, and provide a theoretical basis for. Product optimization design and engineering application of great significance. This paper honeycomb sandwich wood composites as the research object, the bending properties of sandwich beam under transverse loading and flat sandwich compression performance of the system, the research conclusions are as follows: (1) derived the soft sandwich beam of maximum bending stress calculation based on the theory of equivalent single beam the formula. Using the orthogonal testing method of honeycomb sandwich three-point bending test, the results show that the influence of the edge length of static bending strength is extremely significant, table board type, amount of glue on the static bending strength No significant influence; the core layer thickness on the "/ /" direction effect of static bending strength and a significant, on the "t" direction of specimen effect is extremely significant. "An" direction of specimen mor values were higher than the "/ /" direction of specimen. Based on Winkle elastic foundation beam theory, considering the the table plate bending stress influence on local depression, calculation formula of soft sandwich three-point bending test surface crushing load. The system analyzes the core shear failure and surface collapse two bending failure mode, and the theoretical model and the experimental data were analyzed, the relative error is about 20%.. (2) established a layered bending deformation of the beam dissection in two variables based on the first-order shear deformation theory. The theory and three point bending test results, analysis, comparing with the traditional first-order shearing theory shows that the small elastic deformation range, a hierarchical order shear theory than. Unified prediction order shear theory deflection value. In the conservative force under the same conditions, "/ /" direction of specimen deflection are greater than the "t" direction of specimen. The core layer calculation of layered first-order shearing theory of shear strain and shear stress values than conventional first-order shearing theory is low, but with the increase the thickness of core layer, calculate the difference between the two theories gradually become smaller. The calculation of layered first-order shear deformation theory of the shear stress in the cross section of the shear integral value satisfies in static equilibrium conditions. (3) based on a hierarchical order shear deformation theory, a finite element beam element model of six degree of freedom two nodes. The numerical results show that the small range of elastic deformation, finite element model and a hierarchical order shear theory calculation of deflection is very close, the average difference is less than 10%. when the core layer thickness is small, the cross section calculation of finite element model of shear strain and shear stress is close to A hierarchical order shear theory; with the increase of the thickness of core layer, its value is gradually close to the traditional first order shear theory. (4) based on the traditional first-order shearing theory, modified sandwich beam cross section of shear stress and shear modulus of core layer, a modified first order shear deformation theory and numerical analysis results. Show that: when the core layer thickness is small, modified first order shear deformation theory and layered first-order shear deformation theory calculated deflection is very close; when the core layer thickness increases, forecast the first-order shear deformation theory model gradually between layered unified first-order shear deformation theory and order shear theory; at the same time, shear deflection due to the deflection caused by the bending moment, shear deflection decreases, but the increasing proportion of the total deflection is larger. In addition, when the core layer thickness increases, the shear deflection correction calculation of the first-order shear deformation theory and the traditional first-order shearing theory value tends to be consistent. (5) in three point bending Based on the test of curved surface indentation displacement is derived, the table plate bending stress formula. Compared with experimental data, and considering the deflection prediction accuracy of indentation modified first-order shearing theory is better than the traditional first-order shear deformation theory considering indentation layered first-order shear deformation theory. (6) by using orthogonal test method the honeycomb sandwich plate flat compression test, the results show that the influence of the edge length of the transverse elastic modulus of compressive strength of core layer and the effect is extremely significant, amount of glue on the transverse elastic modulus and compressive strength of the core layer and significantly, table board type, core layer thickness on the transverse elastic modulus of the core layer of peace pressure strength is not significant based on the compressive strength test, stress calculation formula of the critical buckling pressure equivalent sandwich plate Timoshenko plate based on stability theory is derived, and compared with the experimental data, the relative error less than about 15%. In the selected core layer of honeycomb material under the condition of increased cell wall thickness and length reduction swelling element can effectively enhance the compression performance of honeycomb sandwich plates.

【學位授予單位】：中南林業(yè)科技大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：TB33

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