Some properties of thin medium density fiberboard panels treated with sunflower waste oil vapor

The objective of this study was to investigate the effect of hot waste oil vapor on some of the physical and bending properties of commercially manufactured thin medium density fiberboard (tMDF) panels. The samples were treated with waste oil vapor at a temperature of 220 °C for 10 and 20 min time durations. Based on the findings in this work, the water absorption and thickness swelling of the samples were improved by the treated panels with hot vapor oil and heat. It appears that the samples had some discoloration as a result of treatment processes. It was also observed that modulus of rupture (MOR) and modulus of elasticity (MOE) of the samples were adversely influenced. However, it seems that the thermal conductivity of the samples enhanced by such treatments. Panel products treated with these processes could have some promising potential in various applications including outdoor use.     

Surface quality of thermally compressed Douglas fir veneer

The objective of this study is to evaluate surface quality of compressed Douglas fir (Pseudotsuga menziesii) veneer sheets in the form of its roughness. Veneer samples were compressed using pressure levels of 1.0 N/mm², 2.0 N/mm², and 2.5 N/mm² at two temperatures of 180 °C and 210 °C for 3 min. A fine stylus profilometer was used to evaluate surface roughness of the veneer samples. Three roughness parameters, namely average roughness (R_a), mean peak-to-valley height (R_z), and maximum roughness (R_max) values were determined. The results obtained in this study showed that the surface roughness parameters of the thermally compressed veneers decreased with increasing press temperature and pressure level. It appears that initial data found in this work would provide some benefit to more efficient use of adhesive to manufacture plywood and laminated veneer lumber (LVL) panels with enhanced properties.     

Maximization of fundamental frequency of axially compressed laminated curved panels with cutouts

Free vibration analyses of laminated curved panels with central circular cutouts and subjected to axial compressive forces are carried out by employing the Abaqus finite element program. The fundamental frequencies of these composite laminated curved panels with a given material system are then maximized with respect to fiber orientations by using the golden section method. Through parametric studies, the significant influences of the panel aspect ratio, the panel curvature, the cutout size and the compressive force on the maximum fundamental frequencies, the optimal fiber orientations and the associated fundamental vibration modes of these panels are demonstrated and discussed.     

Properties of laminated panels made from compressed oil palm trunk

This study evaluated physical and mechanical properties of laminated panels made from compressed oil palm trunk (OPT). The OPT were steamed at 130 °C before being compressed and laminated using polyvinyl acetate adhesive at 250 g/m² and 500 g/m² spread rates. The modulus of rupture and compression strength values of laminated panels made from compressed OPT was greater than those of laminated panels made from uncompressed OPT. Surface roughness, water absorption, and thickness swelling of laminated panels made from compressed OPT significantly improved. The findings in this study indicated that compressing of OPT would be considered as an alternative to produce value-added material with enhanced properties.     

Nonlinear equations of laminated panels with laminated stiffeners

The nonlinear equations for a stiffened laminated panel, which modeled by plate and beam elements, are derived by applying the variational principle on the potential energy. The equations include the equation for the panel sections between the stiffeners, the continuity requirements and the boundary conditions. These nonlinear equations by which the post-buckling behavior is characterized are exact in terms of Von Karman's kinematic relations.     

Effects of geometric imperfections on vibration of compressed shear deformable laminated composite curved panels

Summary The vibrational behavior of geometrically imperfect single and multilayered composite double-curved shallow panels subjected to a system of tangential compressive/tensile edge loads in the pre- and postbuckling ranges is investigated. The effects of transverse shear deformations, lamination, the character of in-plane boundary conditions, and of transverse normal stress are incorporated and their influence is emphasized.Numerical illustrations enabling one to compare the obtained results based on higher order and first order shell theories with their classical counterparts, based on the Love-Kirchhoff model are presented and conclusions related to their range of applicability are outlined.     

Physical and mechanical properties of cardboard panels made from used beverage carton with veneer overlay

This study evaluated some of the important properties of the cardboard substrate panels overlaid with beech veneer. The experimental cardboards from recycled food and beverage carton containers having approximately 75% paperboard, 20% low density polyethylene (LDPE), and 5% aluminum foil were overlaid using four types of adhesives; polyurethane, phenol–formaldehyde, urea–formaldehyde, and melamine–urea formaldehyde. The cardboard specimens overlaid with veneer using polyurethane adhesive had better mechanical properties and water resistance than those of the specimens made with other three types of adhesives. Based on the findings of this study, composite cardboards overlaid with veneers could be considered as an alternative raw material with accepted properties to be used in furniture applications such as counter tops, flooring, and kitchen cabinets.     

单板层积材-木粉/高密度聚乙烯共挤出复合材料抗低速冲击性能

通过共挤出技术制备具有核壳结构的共挤出复合材料,其中壳层为木粉/高密度聚乙烯（W/HDPE）,核层为杨木单板层积材（LVL）,测试了LVL-W/HDPE和LVL在50 J、75 J及100 J能量下的低速冲击性能,并进一步研究水煮-冰冻-干燥环境处理后两者的低速冲击性能。结果表明,与LVL相比,在50 J能量冲击过程中LVL-W/HDPE的吸收能量和损伤深度分别降低2.9%和15.9%;在75 J能量冲击过程中LVL-W/HDPE的吸收能量和损伤深度分别降低3.9%和9.2%;而在100 J能量冲击下,两者的抗冲击性能基本相同;经水煮-冰冻-干燥环境处理后,由于壳层WPC的保护作用,LVL-W/HDPE不仅保持了良好的抗冲击性能,还表现出了优异的耐环境性能。     

The efficiency of tannin as a formaldehyde scavenger chemical in medium density fiberboard

The aim of this study was to determine the effect of tannin content of urea formaldehyde (UF) resin on the panel properties of medium density fiberboard (MDF). Tannin extracted from the bark of white oak (Quercus alba) was added to UF resin at different ratios (based on the resin) to decrease the free formaldehyde content of MDF panels in this study. It was determined that free formaldehyde values of MDF panels decreased when the ratio of tannin content in UF resin increased. However, the modulus of rupture (MOR), modulus of elasticity (MOE), and internal bond strength (IB) of these panels were a little lower, and the thickness swelling (TS) (24 h) and water absorption (WA) (24 h) values were a little higher compared to the control MDF panels.     

Mechanical and electronic-structure properties of compressed CdSe tetrapod nanocrystals

The coupling of mechanical and optical properties in semiconductor nanostructures can potentially lead to new types of devices. This work describes our theoretical examination of the mechanical properties of CdSe tetrapods under directional forces, such as may be induced by AFM tips. In addition to studying the general behavior of the mechanical properties under modifications of geometry, nanocrystal-substrate interaction, and dimensional scaling, our calculations indicate that mechanical deformations do not lead to large changes in the band-edge state eigenenergies, and have only a weak effect on the oscillator strengths of the lowest energy transitions.     

Mechanical properties of thermally sprayed Fe based coatings

Abstract

An additional coating against wear or corrosion on component parts is required for many applications. These coatings protect the substrate material against external influences, thus increasing the economic lifetime of the component. Coating processes such as build-up welding and thermal spraying are well established and commonly used. The thermal spray process, in particular, permits deposition of metals, ceramics, or cermets materials to produce near net shape coatings on complex surface geometries. However, commonly used coating materials suffer from high raw material costs, thus decreasing the cost effectiveness of the coating process. Fe based materials are low priced and possess noteworthy mechanical properties; they thus provide the possibility of substituting the expensive Ni and Co based materials commonly used for thermal spray processes. In this work, 2 mm thick high velocity oxyfuel sprayed Fe based coatings in the as sprayed and thermally sprayed and hot isostatic pressed condition were investigated with respect to their mechanical and wear properties. Additionally, the fracture surface was investigated by scanning electron microscopy to characterise the fracture behaviour. It could be demonstrated that the substrate and the heat treatment have the greatest impact on the shear strength of thermally sprayed cold work tool steel. It is shown that the substrate materials as well as the heat treatment are promoting diffusion processes across the interface between the coating and the substrate. Hence, a material integrated bond is formed. The microstructures of the thermally sprayed coatings become more important regarding the mechanisms of failure of the four point bending tests. The material strength is influenced by quenching and tempering and the specimen deflection is influenced by diffusion reactions induced by hot isostatic pressing treatment. The thermally sprayed coatings in the as sprayed condition feature the highest wear resistance due to their hardness.     

Local buckling loads of sandwich panels made with laminated faces

The paper is devoted to assessing the optimal arrangements of hybrid laminated faces of sandwich panels in order to maximize local buckling loads corresponding to the wrinkling of compressed faces. The analysis is carried out by modelling compressed faces as thin unsymmetric laminates resting on elastic two-parameter foundations. The First-order Shear Deformation Theory, in conjunction with the Rayleigh-Ritz method, has been used to evaluate buckling loads of simply supported flat laminates subjected to in-plane biaxial compression and shear forces. A numerical investigation is intended to support evidence for the influence of laminate parameters (fibre orientation, geometrical dimensions) and foundation parameters (modulus of subgrade reaction and shear modulus); obtained results are reported and discussed in the paper.     

Mechanical and physical properties of wood-wool slabs

This paper deals with an analytical and experimental investigation of the mechanical and physical properties of wood-wool slabs. Analytically, the material is treated as a composite where the cement paste acts as the matrix and the wood-wool as randomly oriented long fibers. The mechanical properties of the composite are derived by the laws of mixture. The effect of the random orientation of the wood fibers is taken into consideration by the introduction of dimensionless factors which are derived on the assumption that the geometric centers of the wood fibers are uniformly distributed in space and that any fiber has an equal probability to being oriented at any angle to the direction of the applied stress. Explicit expressions are derived for the various elastic rigidities of the slabs as well as the ultimate strengths in bending, tension and compression. Wood-wood samples with varying wood content and wood-cement ratio are tested in flexure, direct tension, axial compression, torsion, water absorption, impact, permeability, combustibility, creep and shrinkage. The test results are shown to be in good agreement with theoretically predicted values.     

工业废碱渣高密度纤维板制备与阻燃性能

以工业废碱渣(主要组分为氢氧化铝(Al(OH₃)))、 硼酸锌(2ZnO·3B₂O₃·3.5H₂O)、 硼酸(H₃BO₃)等为阻燃剂, 制备出具有良好阻燃性能的阻燃高密度松木纤维板(HDF), 对其物理及力学性能、 阻燃性能、 残炭形貌等进行了分析表征。结果表明: 在满足物理及力学性能的条件下, 废碱渣Al(OH₃)与2ZnO·3B₂O₃·3.5H₂O和H₃BO₃之间具有良好的阻燃协效性, 提高了纤维板的成炭性, 残炭量达到22.2%, 降低了总释热量, 降低幅度为32%, 使其氧指数提高到36.4%, 垂直燃烧等级达到V-0级。      

Mechanical properties of thermally cycled nylon bonded Nd-Fe-B permanent magnets

The effect of thermal cycling on the stress-strain behavior of polyamide (nylon) and polyphenylene-sulfide (PPS) based injection molded Nd-Fe-B magnets was investigated after test specimens were cycled between –40 and 150°C for 50, 500, or 5000 repetitions. It was found that PPS based magnets exhibit higher ultimate strengths, higher modulus and lower toughness than nylon based magnets. Furthermore, formulations containing platelet morphology particles exhibited higher strengths and modulus than those containing spherical morphology particles, with increases in particle volume fraction leading to a decrease in strength. Differences in strength, modulus, and toughness were attributed to the degree of bonding between the matrix and the magnet powder in the various formulations, the degree of crosslinking, along with the effects of powder morphology. Additionally, it was found that while the stiffness of these materials increased with thermal cycling, their toughness decreased significantly, by as much as 99%. The extent of these effects was found to be dependent on the polymer matrix, powder morphology, and volume fraction of powder in the magnet. Finally, it was found that the PPS composites showed less relative change due to thermal cycling than the Nylon composites.     

Mechanical properties of Al2O3/Ni laminated composites

Al₂O₃/Ni laminated composites were prepared by aqueous tape casting and hot pressing with intent to study mechanical properties including the fracture strength and toughness. The residual stress was evaluated and proved. The relations of mechanical properties with the thermal residual stress, the ductility of metal layers and the layer thickness ratio were studied, respectively. It was found that the toughness and work of fracture of Al₂O₃/Ni laminar reached to 12.56 MPa m^1/2 and 12 450 J m^− 2, which are 3.6 and 478.8 times that of pure Al₂O₃.     

Compressive behaviour of large undamaged and damaged thick laminated panels

Both intact and impact-damaged laminated panels under in-plane compressive loading are investigated with a purpose-built anti-buckling support. The readings of back-to-back strain gauges of selected locations are used to deduce panel behaviour in addition to post-mortem observation. The compression failure of intact panels is found to be close to the potted end. The failure characteristics of impact-damaged panels are dependent slightly on composite systems although they all failed in compression in the impact-damaged region with a kink shear band passing through the mid-section. E-glass/polyester panels with a greater shear angle do not seem to involve global buckling like S-glass/phenolic panels with small shear angles. The fact that the region covered by a kink shear band from impact surface to the distal surface is considerably less than the delamination area suggests that the initiation of overall failure is due to the collective result of flexural stiffness reduction compounded by the local impact damage and the associated change of fibre curvature. As a result, the residual compressive strengths are reduced significantly. Further outward propagation of the existing delamination(s) along the mid-section during loading is visible only for E-glass/polyester panels but is not significant.     

Experimental determination of torsion and shear properties of sandwich panels and laminated composites by the plate twist test

A recently developed sandwich plate twist test is employed here for determination of the transverse shear modulus of the core and twist stiffness (D₆₆) of a sandwich panel consisting of a soft (H45 PVC foam) core and glass/vinylester face sheets. The shear modulus of the H45 PVC foam core extracted from the twist test was in good agreement with shear modulus obtained from ASTM plate shear testing of the foam core. D₆₆ values obtained from the sandwich twist test were in good agreement with predictions from classical laminated plate theory. In addition, the twist test was used to determine the in-plane shear modulus of glass/vinylester laminates isolated and as face sheets in sandwich panels with a stiff (plywood) core. The in-plane shear modulus of the face sheets, isolated and as part of a sandwich panel, was in good agreement with shear modulus determined using the Iosipescu shear test. The results point to the potential of the twist test to determine both in-plane and out-of-plane shear moduli of the constituents of a sandwich structure, as well as D₆₆.     

Free vibration analysis of axially compressed laminated composite beam-columns with multiple delaminations

In this work free vibration analysis is performed for multi-delaminated composite beam-columns subjected to axial compression load. In order to investigate the effects of multi-delaminations on the natural frequency and the elastic buckling load of multi-delaminated beam-columns, the general kinematic continuity conditions are derived from the assumption of constant slope and curvature at the multi-delamination tip. The characteristic equation of multi-delaminated beam-column is obtained by dividing the global multi-delaminated beam-columns into segments and by imposing recurrence relation from the continuity conditions on each sub-beam-column. The natural frequency and the elastic buckling load for multi-delaminated beam-columns are obtained in this work. The latter is based on the incremental load of axial compression, which is limited to the maximum elastic buckling load of the sound laminated beam-column. To verify the results of the present models, experimental results are obtained for isotropic single delaminated beam-columns. Comparisons are conducted between these experimental results and the present analysis. Good agreement is obtained from this comparison of results. It is found that the sizes, locations and numbers of multi-delaminations have significant effect on the natural frequency and the elastic buckling load, specifically the latter ones.     

苎麻纤维布和玻璃纤维布混杂铺层复合材料的力学性能

利用真空吸注成型(vacuum resin absorbable molding,VRAM)工艺制备苎麻纤维布与玻璃纤维布混杂铺层的环氧树脂基复合材料。测定复合材料的损耗因子、储能模量的温度谱和力学性能;利用单悬臂梁共振实验测量复合材料的共振频率和自由振动衰减曲线并计算出了阻尼因子。用有限元软件对其共振频率和自由振动衰减实验进行仿真分析。结果表明:通过苎麻纤维布/玻璃纤维布的混杂铺层,能够实现材料阻尼性能和力学性能的可控调节,充分发挥复合材料可设计性强的优势。其中RGR铺层的复合材料的损耗因子比纯玻璃纤维板提高了1.4倍,而拉伸强度比纯苎麻纤维板提高了3倍多;自由振动的有限元模拟曲线和实验曲线基本吻合,表明可以通过模拟软件实现复合材料的虚拟振动测试,从而为材料性能预测和设计提供方便。