木塑复合材料力学性能的无损检测

采用纵向共振实验、弯曲振动实验等振动方法对木塑复合材料的力学性能进行了无损检测，并对检测结果进行了分析．研究表明，木塑复合材料的动态弹性模量可以通过无损检测方法测量．木塑复合材料的动态弹性模量随着木塑比的减小而降低；而对于同一木塑比的木塑复合材料，利用各种无损检测法测得的动态弹性模量值相差不大。木塑复合材料的动态弹性模量大于静态弹性模量MOE，且有一定的比值；应用这一比值关系可由动态弹性模量估算静态弹性模量．利用动态的无损检测法测得的弹性模量与静态的破损检测法测得的静曲强度MOR具有密切的相关性；其中，纵向共振实验测得的弹性模量Ep与MOR的相关系数最高；应用相关方程可由动态弹性模量估算静曲强度。     

高频热压杨木单板层积材纵向弹性模量和泊松比的测定与分析

基于四点弯曲法,对一种基于高频热压技术的厚型杨木单板层积材的纵向弹性模量和纵横向泊松比进行了试验测定。其中纵向弹性模量的测定,分别采用了挠度法和应变片法。实验结果表明,2种测量方法所得纵向弹性模量数值比较接近,但又存在一定的差异,并对其差异的影响因素进行了探讨。基于高频热压技术的杨木单板层积材纵向弹性模量的测定结果表明,其纵向弹性模量接近甚至超过杨木单板,为该材料引入重型产品包装箱领域甚至结构用材料,从而替代原木,提供了一定的参考价值。     

木塑结构板材的可靠性预测

通过纵波传播、纵向共振和弯曲振动三种方法对木塑结构板材的动态弹性模量(MOE)进行了无损检测.采用三点弯曲试验检测木塑结构板材的静态弹性模量和最大弯曲力(Fm).运用最大弯曲力和动态弹性模量之间的回归方程,预测相同木塑结构板材的最大弯曲力,并采用一次二阶矩法评价木塑结构板材基于预测和检测的最大弯曲力的可靠性指标.结果表明:动态弹性模量和最大弯曲力间存在较强的相关性;基于预测最大弯曲力的可靠度大于基于检测最大弯曲力的可靠度,其最大差值为0.66％.     

木塑结构板材的可靠性预测

通过纵波传播、 纵向共振和弯曲振动三种方法对木塑结构板材的动态弹性模量(MOE)进行了无损检测。采用三点弯曲试验检测木塑结构板材的静态弹性模量和最大弯曲力(F_m)。运用最大弯曲力和动态弹性模量之间的回归方程, 预测相同木塑结构板材的最大弯曲力, 并采用一次二阶矩法评价木塑结构板材基于预测和检测的最大弯曲力的可靠性指标。结果表明: 动态弹性模量和最大弯曲力间存在较强的相关性; 基于预测最大弯曲力的可靠度大于基于检测最大弯曲力的可靠度, 其最大差值为0.66%。     

防白蚁胶合板的制备及性能研究

目的实现包装人造板的防白蚁功能。方法采用联苯菊酯、溴氰菊酯和高效氯氰菊酯为防白蚁剂,制备具有防白蚁功能的三聚氰胺甲醛树脂胶(MF)速生杨胶合板。研究防白蚁剂对MF胶黏剂的初粘度和胶合强度,白蚁作用方式,胶合板的防白蚁性能和力学性能等的影响。结果所用的防白蚁剂在MF中分散性良好,无分层现象。防白蚁剂对胶合强度有不良影响,溴氰菊酯和高效氯氰菊酯对弹性模量、静曲强度产生不良影响,但其浓度对弹性模量、静曲强度无显著影响。结论当联苯菊酯占MF的质量分数为1.25%,或溴氰菊酯占MF的质量分数为5%,或高效溴氰菊酯占MF的质量分数为2.2%时,胶合板的防白蚁性能最佳,白蚁死亡率达到100%,而且其主要力学性能指标均达到国家标准要求。     

冲击回波法检测水工混凝土耐久性的试验研究

研究了冲击回波法用于混凝土棱柱体试件动弹性模量的测试情况,发现测试的波速为理论的一维P波波速,且获取混凝土动弹性模量的方法在本质上与传统的共振法是一致的。采用冲击回波法检测混凝土试件在冻融循环中波速的变化,与共振法测试的自振频率的变化进行对比研究,总结其内在规律,最终换算到相对动弹性模量的下降值来评价混凝土的抗冻性。初步的试验和理论分析的结果表明,利用冲击回波法进行水工混凝土抗冻性检测的方法切实可行,可用于水工混凝土的耐久性评估。     

废旧利乐包 / 木屑复合板热压优化工艺研究

为提高废旧利乐包的再利用效率,扩大其在包装领域的应用范围,研究了废旧利乐包/木屑复合板制备的热压优化工艺。采用正交试验法,以施胶量、热压温度、热压时间、利乐包与木屑质量比为影响因素,分别以静曲强度、弹性模量和2 h吸水厚度膨胀率为检测指标,得到了此种复合板热压优化工艺参数。结果表明板材热压优化工艺参数为:施胶量14%,热压温度150℃,热压时间420 s,利乐包与木屑质比比4∶6,在此条件下,板材最大静曲强度为23.1 MPa,最大弹性模量为2917 MPa,2 h吸水厚度膨胀率最小,为6.1%。     

"利乐包"塑木托盘的有限元分析

采用塑木挤出成型技术,将打碎的"利乐包"挤压成型,选择其板材加工成托盘。根据林派检测报告相关数据:弹性模量、静曲强度以及塑木材料弯曲强度,基于ANSYS有限元分析软件,对托盘板材在静态承重与叉车叉起时的力学性能和承载性能进行分析。结果表明:1.1 t的承载下,板材不会开裂,满足实际使用要求。     

迷彩刨花板的研制及力学性能分析

目的研究不同色彩处理方式对大片刨花表面相对自由基浓度的影响,及不同迷彩组合色对板材力学性能的影响。方法通过对大片刨花进行煮沸染色,采用电子自旋共振波谱仪对各类处理方式刨花检测其相对自由基浓度,然后根据不同迷彩色方案进行压制板材,采用万能力学电子实验仪检测其力学性能,分析不同迷彩刨花板的相对自由基浓度与力学性能的关系。结果刨花的不同处理方式(煮沸与否、染色与否、染料种类、染料浓度等)对其相对自由基浓度影响方差分析F值为119.4;5类不同色刨花板的力学性能MOR方差值为9.38;丛林迷彩板材力学强度最高,弹性模量为5883.47 MPa,结合强度为0.68 MPa,静曲强度为52.37 MPa。结论各迷彩色酸性染料染色处理对刨花表面的相对自由基浓度有显著影响,有益于板材的胶合性能;4种常见迷彩配色方案中,板材的力学性能也有所提升,尤其是丛林迷彩板材具备较优的力学性能。     

硅烷偶联剂对高密度聚乙烯薄膜/杨木胶合板性能的影响

采用硅烷偶联剂乙烯基三甲氧基硅烷(A-171)对杨木单板进行预处理,然后与高密度聚乙烯(HDPE)薄膜复合制备胶合板。研究了A-171对板材物理力学性能的影响,利用红外光谱、X射线光电子能谱及扫描电镜探讨了界面增容的机理。结果表明,经过A-171处理后,板材的胶合强度和耐水性都有所改善,当偶联剂用量为2%时处理效果最好,胶合强度达到1.8MPa,比未处理材的胶合强度增加128%,木破率也由10%提高到99%。胶合板的24h吸水率(WA)和吸水厚度膨胀率(TS)分别降低了28%和42%。通过X射线光电子能谱、红外光谱和扫描电镜分析可知,A-171成功在杨木单板表面发生了接枝反应,有效地改善了单板与HDPE的界面相容性。     

Development a new method for pilot scale production of high grade oil palm plywood: Effect of resin content on the mechanical properties,bonding quality and formaldehyde emission of palm plywood

The main objectives of this research were to investigate the formaldehyde emission, some mechanical properties and bonding quality of oil palm trunk (OPT) plywood treated with low molecular weight phenol–formaldehyde (LmwPF), as affected by resin concentration. The mechanical properties are affected by different of amount resin solid contents used. The OPT veneer were treated at either 40%, 32%, 23% or 15% of resin concentration and 12 mm thickness of 3-ply plywood panel were manufactured for each group. In this study the formaldehyde emission, modulus of rupture (MOR), modulus of elasticity (MOE) and bonding quality (shear strength) of OPT plywood were determined. The results revealed that the resin-treatment method was tend to significantly improved the mechanical properties of the OPT plywood panel in which increased solid absorption gives better mechanical properties. Apparently, high mechanical properties were obtained for panel manufacturer from veneer treated with 32% and 40% resin content. The resin-treated OPT plywood provided superior mechanical strength with improvements at least 202% MOE and 159% MOR compared to commercial OPT plywood. Whereas, mechanical properties of the resin-treated OPT plywood were drastically decrease with increasing the water substitution. Formaldehyde emission content of OPT panels decreased upon reduction of resin content into treatment process and were significant at resin concentration. The resin-treated OPT panels at 32% solid content provided a reasonable amount of free formaldehyde (0.359 mg/L) which attained F⁷⁷ according to Japanese Agriculture Standard (JAS). The shear strength of resin-treated OPT plywood panel with 32% and 40% resin content achieved minimum requirements according to the standard European Norms EN 314-1 and EN 314-2 for the interior and exterior application.     

Properties of medium density fibreboard (MDF) from kenaf (Hibiscus cannabinus L.) core as function of refining conditions

The objective of this study was to evaluate physical and mechanical properties of medium density fibreboard (MDF) panels made from kenaf core as function of fibre geometry and refining conditions. Raw material was prepared by using pressure levels of 3, 5 and 7 bar at two heating times, namely 3 and 5 min. The length and width of the fibres were determined employing image analyser. Experimental samples with a target density of 700 kg m⁻³ were produced with 12% of urea formaldehyde as a binder. Physical properties such as swelling in thickness (TS) and water absorption (WA) of the panels in addition to their mechanical properties including modulus of rupture (MOR), modulus of elasticity (MOE) and internal bonding (IB) were evaluated based on MS 1787:2005. Based on the test results, low digestion pressure produced longer fibre length and panels made from these fibres had higher TS with MOR and MOE than those of the others panels. However, the IB properties of samples were low. Panels made from shorter fibre resulted in contradict properties found above. The ideal properties of the samples were found for the panels made having fibre length of 0.81 mm and aspect ratio of 23.4. Such sample had 14.6%, 63.2%, 30.3 MPa, 3619 MPa and 0.66 MPa for TS, WA, MOR, MOE and IB, respectively.     

A new method of making particleboard with a formaldehyde-free soy-based adhesive

A soy-based formaldehyde-free adhesive consisting of soy flour (SF) and a curing agent (CA) has been successfully used for the production of plywood. However, this adhesive cannot be easily sprayed onto wood particles for making particleboard because of its high viscosity. The following new method of using this adhesive was developed and investigated. SF was first mixed with water to form dilute soy slurry that could be easily coated onto wood particles. The soy-coated wood particles were dried to certain moisture content and then further coated with an aqueous curing agent. Effects of particleboard density, adhesive usages for both core and face particles, the solids content of the soy slurry, hot-press time, hot-press temperature, the storage time of the wet soy-coated wood particles, and the SF/CA weight ratio on the internal bond strength (IB), the modulus of rupture (MOR), and the modulus of elasticity (MOE) of particleboard were investigated.     

Effects of raw materials and process parameters on the physical and mechanical properties of flat pressed WPC panels

For the production of WPC, the flat pressing technology can be considered as an alternative to common techniques, particularly when manufacturing large-dimensioned panels. The aim of the present study was to identify and analyze the main influencing parameters on sheets made of wood flour (WF) imbedded in a polypropylene matrix. Test panels were made to measure the effects of panel density, polymer melt flow rate (MFR), WF content, coupling agent, WF size and press temperature on water absorption (WA), thickness swelling (TS), internal bond strength, MOE and MOR. Density, WF content and MFR were identified as main influencing parameters. The increase of density typically leads to an improvement of properties. Lower WF contents cause reduced WA and TS, while the MOE seems to have a maximum at a WF level of 50-70%, depending on raw material used. As an explanation for improving properties when using a high-MFR polymer, a better distribution on the wood surface is hypothesized.     

Effect of particle geometry on the properties of binderless particleboard manufactured from oil palm trunk

Experimental binderless composite panels were manufactured using fine particles and strands of oil palm (Elaeis guineensis) trunks. Modulus of rupture (MOR), internal bond strength (IB), dimensional stability, and surface roughness of the panels made with a target density of 0.80 g/cm³ were evaluated. Strand type samples had MOR and IB values of 24.95 and 0.95 MPa, respectively. Corresponding values for the fine particle type samples were 4.04 and 0.49 MPa. Panels made from strands met MOR requirement stated in Japanese Industrial Standard (JIS). Enhanced bonding between strands observed by micrographs taken using scanning electron microscopy (SEM) also supported the findings. However, the samples having fine particles had lower MOR values than minimum requirement listed in JIS. Strand type panels had 41.6% thickness swelling which is only 4.6% lower than that of the panels made from fine particles. It appears that dimensional stability of both types of panels exhibited insufficient results according to JIS. Surface roughness quality of the samples made from fine particles had average surface roughness values comparable to those of panels made in past studies. Based on initial results of this work, raw material from oil palm trunks can have some potential to be used to manufacture binderless panels without using any adhesives. This study revealed that mechanical and physical properties of such experimental panels were influenced by the particle geometry. It would be important to consider possible addition of chemical or wax in the particles to improve their dimensional stability in further studies.     

Nondestructive test and prediction of MOE of FRP reinforced fast-growing poplar glulam

The modulus of elasticity (MOE) of fiber-reinforced plastic (FRP) reinforced fast-growing poplar glulam was investigated and predicted in this study. Firstly, MOE of FRP reinforced glulam with different FRP lengths were measured by longitudinal vibration and static bending tests and the effect of FRP length on MOE was investigated. Secondly, MOE of FRP globally reinforced (GR) poplar glulam and non-reinforced (NR) poplar glulam was predicted by improved transformed section method based on dynamic MOE of poplar laminas. At last, the deflection curve equation of FRP locally reinforced (LR) poplar glulam was obtained by singularity function method. Then MOE was predicted based on deflection curve equation of LR glulam. The results indicated that the reinforced effect of FRP on MOE of reinforced glulam increased as the FRP length increased. The predicted MOE had a good agreement with measured static MOE of glulam, and the accuracy of MOE prediction of LR glulam decreased as the FRP length decreased.     

Some technological properties of wood–styrofoam composite panels

Synthetic resins are widely used in wood based composites manufacturing. Besides their many advantages, most of them contain formaldehyde and a chemical agents that cause environmental problems. Styrofoam known as expanded polystyrene, is used all over the world for various purposes including thermal insulation, packing, coffee cups, fabrication of car parts etc. This study investigated the evaluation possibilities of styrofoam wastes in plywood production as a bonding material. Pine (Pinus pinea) and poplar (Populus deltoides I-77/51) veneers were used to produce wood–styrofoam composite (WSC) and traditional plywood. Urea-formaldehyde adhesive was used as bonding material for traditional plywood panels. Two different types of styrofoam having high density (25 kg/m³) and low density (10 kg/m³) were used as binder in the manufacturing of WSC panels. Bonding and bending strength, modulus of elasticity, density and thermal conductivity of plywood and WSC panels were investigated. Experimental results showed that mechanical properties of panels manufactured with low density styrofoam type were higher than those of panels manufactured with high density styrofoam type. The lowest thermal conductivity among the all panels was found for poplar panels manufactured with high density styrofoam.     

明胶鸟弹撞击复合材料蜂窝夹芯板试验

开展明胶鸟弹撞击复合材料蜂窝夹芯板试验,研究夹芯结构在软体高速冲击下的损伤形式,分析相关因素对结构动态响应结果的影响。通过CT扫描对复合材料蜂窝夹芯板内部进行检测可知,面板出现分层、基体开裂、纤维断裂、凹陷、向胞内屈曲等损伤形式,蜂窝芯出现芯材压溃、与面板脱粘的损伤形式;分析复合材料蜂窝夹芯板后面板的动态变形过程及撞击中心处位移-时间数据可知,复合材料蜂窝夹芯板在撞击过程中出现由全局弯曲变形主导和局部变形主导的两种变形模式;通过对比不同工况下的复合材料蜂窝夹芯板损伤程度可知,复合材料蜂窝夹芯板损伤程度随鸟弹撞击速度的增加而增大;蜂窝芯高度为10 mm的复合材料蜂窝夹芯板较蜂窝芯高度为5 mm的复合材料蜂窝夹芯板的损伤程度大;初始动能较大的球形鸟弹较圆柱形鸟弹对复合材料蜂窝夹芯板造成的冲击损伤程度更大。