托盘用人造板弹性模量与强度的相关关系

目的缓解托盘用人造板抽样检测时资源浪费且费时费力的现状,推进实现常用板材的无损检测。方法采用纵向共振法对9层胶合板、单板层积材及一种工厂用新型层积材进行共振频率的检测并计算得到动弹性模量,分析动弹性模量与静弹性模量、静曲强度之间的相关性。结果胶合板、单板层积材的动弹性模量与静弹性模量、静曲强度之间分别在0.001水平上具有较强的线性相关性,新型层积材的动弹性模量、静曲强度、静弹性模量在0.001水平上也具有一定的线性相关性,较胶合板及单板层积材相关性稍差。结论 3种结构人造板弹性模量与静曲强度均存在一定的线性相关性,纵向共振法在新型层积板材上的可应用性较胶合板及单板层积材略差。     

应用超声声压透射系数谱反演薄板的弹性模量

基于超声波在层状介质中传播规律,建立理论声压透射系数Tp与材料弹性模量E的相关性.采用超声水浸技术测定微米厚薄板的双透射信号,通过信号分析获得实验声压透射系数Te,应用非线性最小二乘法反演薄板的弹性模量,并与声速法测量得到的弹性模量进行比较.结果表明:将反演的弹性模量代入到Tp中,发现在有效频带范围内Tp与Te吻合较好;反演获得的弹性模量值与声速法测定结果较接近,偏差介于1.4%和8.2%之间;实验证明了该方法可作为薄层材料弹性模量检测方法的一种补充.     

粉末冶金法制备PSZ/Mo复合材料的研究

本文采用粉末冶金法制备了不同成分的PSZ/Mo复合材料。并对其密度、弹性模量和热膨胀系数进行了测量和分析 ,用XRD进行了物相分析。实验结果表明 :纳米氧化锆的烧结性能比金属钼好 ;弹性模量估算选用简单混合法则进行计算时应进行修正 ;钼和氧化锆在烧结时不发生化学反应。通过热压PSZ/Mo功能梯度材料的断口扫描分析发现 :虽然金属钼和纳米氧化锆具有一定增韧作用 ,但材料断裂方式仍以脆性断裂为主     

SiCw/6061Al复合材料切屑热压回收工艺研究

利用简便的热压技术,对１８ｖｏｌ％ＳｉＣｗ／６０６１Ａｌ复合材料切屑进行了可回收性研究。结果表明,选择适当的热压参数（７０Ｃ／２００ＭＰａ）。回收复合材料拉伸强度法到原始复合材料的８５％,弹性模量与原始复合材料接近,切屑之间结合良好,已具备再利用的价值。     

粉末冶金法制备PSZ／Mo复合材料的研究

本文采用粉末冶金法制备了不同成分的PSZ/Mo复合材料。并对其密度、弹性模量和热膨胀系数进行了测量和分析，用XRD进行了物相分析。实验结果表明：纳米氧化锆的烧结性能比金属钼好；弹性模量估算选用简单混合法则进行计算时应进行修正；钼和氧化锆在烧结时不发生化学反应。通过热压PSZ/Mo功能梯度材料的断口扫描分析发现：虽然金属钼和纳米氧化锆具有一定增韧作用，但材料断裂方式仍以脆性断裂为主。     

以非结构用单板层积材为例的现代家具材料的创新与实践

针对非结构用单板层积材结构均匀、强度高、稳定性好等优良特性,在家具的造型设计和结构设计上进行有益的探索与实践,提出了适合其材性的家具造型与结构设计方法,为单板层积材家具的开发开辟了新的空间和方向。     

基于纳米压痕技术的碳纤维/环氧树脂复合材料各组分原位力学性能测试

基于纳米压痕技术对碳纤维/环氧树脂复合材料各组分的原位硬度、 弹性模量和蠕变性能进行了测试, 实验得到了基体、 纤维和微小厚度界面层的力学性能。结果表明, 从环氧树脂基体到碳纤维过渡过程中, 硬度和弹性模量有明显的梯度变化, 并且纤维和树脂基体的原位弹性模量平均值与其非原位性能有一定的变化, 实验得到纤维的原位弹性模量有所下降, 环氧树脂的弹性模量有所增加。试件制备过程中的机械研磨对其表面产生的残余应力和复合后两种材料的相互影响是组分材料原位性能变化的主要原因。各组分的蠕变性能呈现出明显的差异。     

不同热压方法对无胶烟秆碎料板力学性能的影响

分别采用普通热压和喷蒸热压2种热压方法制备了无胶烟秆碎料板,对它们的物理力学性能进行了对比研究与分析。结果发现,与普通热压法相比,喷蒸热压法制备的无胶烟秆碎料板的静曲强度、弹性模量与内结合强度明显提高,吸水厚度膨胀率显著减小,其原因可能是不同热压过程中烟秆碎料发生了化学变化。     

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％.     

桉木单板剩余物定向刨花板的制备

目的为了有效地解决定向刨花板的原料问题,利用桉木单板剩余物为原料制备定向刨花板。方法通过设计正交实验,分别探索热压温度、铺装角度、板坯厚度等因素对定向刨花板的干湿状内结合强度、静曲强度及弹性模量等各项性能的影响。结果在热压温度为130℃,铺装角度为90°,板坯厚度为10mm,表芯层厚度比为4∶2∶4,醛树脂胶黏剂的施加量为4%(以刨花干质量计)时所制备的材料性能最佳,内结合强度达0.61MPa,平行弹性模量高达5566.9MPa,平行静曲强度高达36.85 MPa。结论利用桉木单板剩余物为原料所制备的定向刨花板,力学性能均达到LY/T 1580—2010定向刨花板标准中OSB/3的要求,且力学性能优异,这为制备一种低成本、高性能的定向刨花板提供了理论依据。     

基于声-超声技术的木材弹性模量测定方法研究

提取声信号基频是声-超声方法测定木材弹性模量的关键。由于噪声和传感器谐振频率等因素的影响,直接应用快速傅里叶变换（FFT）方法提取信号基频计算弹性模量通常比标准的力学方法大20%左右。基于此,提出应用最大公约数算法提取信号基频,构建一种测量木材弹性模量的改进方法,并给出此算法的详细步骤。应用该方法和FFT方法分别对杨树木芯样本进行测试,弹性模量Eu和Ef的计算值范围分别为8.23~40.32Gpa和7.94~51.87Gpa,对比标准力学方法（弹性模量Es测量值为6.72~36.35Gpa）,误差下降了约10%。进一步分析Eu-Es和Ef-Es的相关性,相关系数分别为0.94和0.86,都呈显著相关。实测数据表明,应用本文方法计算所得的木材弹性模量与力学方法测试的数值更加吻合,相关性更好。     

用废纸与木片制备复合包装材料的热压工艺研究

热压温度与热压时间是热压工艺的主要参数,是影响废纸－木材复合材料物理力学性能的重要因素.为了获得较好的热压工艺条件,以杨木刨花为原料,废纸为补充原料,异氰酸酯改性的脲醛树脂为胶黏剂,生产了废纸－木材复合材料,并测试了热压温度与热压时间对废纸－木材复合材料物理力学性能的影响.试验结果表明：随着热压时间的延长,废纸－木材复合材料的物理力学性能相应地提高;在140～170 ℃的热压温度范围内,升高热压温度有助于提高废纸－木材复合材料的物理力学性能.废纸－木材复合材料较适宜的热压工艺条件为：热压时间为每mm板厚30 s,热压温度为170 ℃.     

低弹钛合金弹性模量的无损评价

以掠入射纵波法研究了超声波在Ti6Al4V合金和Ti27Nb8Zr时效样品中的传播速度,推算其弹性模量,并与拉伸法获得的弹性模量进行比较.结果发现:两种方法测得的数值较为接近,相差仅为3.6%,表明掠入射纵波法实现低弹钛合金弹性模量的无损评价是可行的,这为小尺寸稀有合金样品弹性指标的评价提供了极有价值的测试方法.应用该方法进一步考察了时效温度对Ti18Nb7Zr弹性模量的影响,结果表明:随着时效温度的升高,弹性模量E,切变模量G,体弹模量K分别增加11%,10%和6%,泊松比σ仅下降了1.2%.分析认为:弹性模量的变化与合金的组织由层片状的β+α向弥散分布的α相和β相的转变密切相关.     

Shear characterisation of uni-directional fibre reinforced thermoplastic melts by means of torsion

Intra-ply shear appears during the forming process of hot thermoplastic laminates with a uni-directional fibre reinforcement. This paper proposes a torsion bar test to characterise the longitudinal shear mechanism, which can be performed with a standard rheometer. Sensitivity analyses showed that most reliable shear property measurements can be obtained by using torsion bar specimens with a close to square cross section. The method is implemented in practise and critically evaluated. Storage and loss moduli were determined for carbon UD/PEEK specimens at high temperatures. Non-linear material behaviour was found for relatively small shear strains. The linear regime was focussed on subsequently, where the characteristics were found to be similar to that of a visco-elastic solid or weak gel, confirmed by a dominant storage modulus and a weak frequency dependency. Future work is recommended to be focussed on the large strain regime, for which this paper provides a found basis.     

Elastic properties of powders during compaction. Part 2: elastic anisotropy

Isotropy in the elastic properties of powders undergoing uniaxial compaction in a cylindrical die was evaluated from in situ measurements of elastic wave speed. Shear and bulk longitudinal wave speeds were measured in both the axial (pressing) and radial directions. For the five different metal powders studied, wave speeds were generally higher in the axial direction. As such, the powder body was best described as a transversely isotropic material; complete isotropy was approached only when the powder was close to the loose packed state, or completely solid. Transversely isotropic elastic moduli analogous to the common isotropic ‘engineering’ moduli (Young’s modulus, Poisson’s ratio, etc.) were calculated by combining elastic wave speed measurements with the Saint-Venant approximation. Pseudo-isotropic elastic moduli (calculated from axial wave speed measurements and assuming elastic isotropy) were found to be only qualitatively similar to transversely isotropic elastic moduli for the axial plane.     

反相气相色谱法表征PU和PF树脂的表面性质

为了研究胶粘剂的表面性质对木材胶接强度的影响,采用反相气相色谱技术(IGC)测定了聚氨酯树脂(PU)和酚醛树脂(PF)的色散表面自由能γd、表面酸碱常数Ka和Kb,PU和PF的色散表面自由能分别是39.22 mJ/m2和34.38mJ/m2(50℃),PU和PF的酸、碱常数分别是0.1、0.92和0.15、0.57;测试了用PU和PF热压三层杨木胶合板的湿剪切强度分别是1.74 MPa和1.18 MPa。结果表明,PU的色散表面自由能大于PF,PU和PF表面均呈路易斯碱性特征,但PU碱性更强,对多数表面酸性占优势的木材胶接强度更大。     

The modeling and determination of dynamic elastic modulus of magnesium based metal matrix composites

The aim of the present study was to determine elastic modulus of the magnesium-based composites containing different volume fraction of SiC particulates using an innovative free-free beam type impact based technique. This technique is based on classical vibration theory, by which the geometry and material properties of the metal matrix composites are related to resonant frequency of the test specimen. With the fundamental resonant frequency obtained from the experiment and density determined by the Archimedes' principle, the elastic modulus values were determined. In addition, a finite element model is proposed for different SiC weight percentage samples for the determination of dynamic elastic modulus using the first natural frequency corresponding to the flexural mode. The elastic modulus values obtained using finite element method were found to be in close agreement with the values obtained from the impact based experiments and in better agreement when compared to theoretical methods such as Halpin-Tsai method. Both the theoretical approaches, in common, exhibit the increasing trend of elastic modulus value with an increase in weight percentage of SiC particulates.     

A nanoindentation study on Al3Ni interface of Ni reinforced aluminum-silicon composite

Aluminum-silicon (AlSi) composite reinforced with 20 wt% Ni particulates was produced by hot pressing and characterized using nanoindentation. Energy dispersive spectrometry and X-ray diffraction analyses showed that Al₃Ni intermetallic was formed in the interface between Ni particulates and AlSi matrix. Chemical composition, hardness, and elastic modulus were studied along the interface from inner (near Ni) to outer (near AlSi) regions. A uniform composition was found throughout the interface, having 805.6 HV hardness and elastic modulus of 185.4 GPa. Interface properties have a crucial influence on the composite performance and their assessment is of paramount importance on composite properties estimation using predictive models.     

Effect of fiber coating on the longitudinal damping capacity of fiber-reinforced metal matrix composites

A novel model for calculating the damping capacity of continuous fiber-reinforced metal matrix composites (FMMCs) is proposed based on the viewpoint of energy loss. Finite element method (FEM) has been employed to investigate the effect of fiber coating on the longitudinal damping capacity of a composite by varying the thickness and the material properties of the coating. The results show that the damping of a composite containing the elastic coating increases with a decrease in the elastic modulus of the coating, while for the case of plastic coating, the weak coating or the high elastic modulus coating may help in improving the overall damping of composite.     

Experimental analysis of the through-thickness compression properties of z-pinned sandwich composites

This paper presents an experimental investigation into the flat-wise compression properties, strengthening mechanisms and failure modes of sandwich composite materials reinforced with orthogonal z-pins. The compression modulus of the sandwich composite increases rapidly with the volume content of z-pins due to their high longitudinal stiffness, however acoustic emission monitoring and X-ray computed tomography reveal that some z-pins are damaged during elastic loading. The compression stress to induce core crushing is increased greatly by z-pinning (up to nearly 700%), although a large percentage of the z-pins fail close to the elastic stress limit by longitudinal splitting and/or kinking. The total absorbed compressive strain energy of the sandwich composite is also improved greatly by z-pinning (more than 600%) due to the z-pins resisting core crushing, even though they are severely damaged. The results and observations presented in this paper have implications on the mechanical modelling of sandwich materials reinforced with brittle z-pins.