Properties of solid wood and laminated wood lumber manufactured by cold pressing and heat treatment

Physical, mechanical, and morphological properties of solid wood lumbers which were cold pressed in a press and then heat treated in a kiln. Two different kinds of domestic thinning small-diameter softwood (Ginko biloba L.) and hardwood (Tilia amurensis Rupr.) were used in this study. First 50 mm thick lumbers were cold pressed until 35 mm (30% of control lumber) using a stopper for 5 min. Then the cold pressed lumbers were heat treated in an electric kiln at 180 °C for 6, 12, 24, or 48 h. To increase the utilizability of woods, the LVLs were produced from 4 mm thick veneers prepared from the heat treated lumbers using a veneer saw. Each LVL sample consisted of 5 layers which were subsequently 48 h-, 24 h-, 12 h-, and 6 h-treated veneers and untreated veneer (from top layer to bottom layer). The shrinkage rates of softwood and hardwood were considerably decreased with increasing temperature. The mechanical properties of heat treated samples were better than those of unpressed control samples. The bending strength and modulus of elasticity of the LVLs manufactured from cold pressed and then heat treated lumbers were slightly lower than those of untreated woods. The colour values obtained from the heat treated wood samples showed a clear effect of the temperature on the colour changes.     

Studies on mechanical properties of wood fiber reinforced cross-linked starch composites made from enzymatically degraded allylglycidyl ether-modified starch

In a previous work we introduced a new family of thermoset composites of softwood fiber and allylglycidyl ether modified potato starch (AGE-starch with a degree of substitution of 1.3 and 2.3) prepared by hot pressing. To improve the processability of AGE-starch with a DS = 1.3 (LDS-3) and to increase hygromechanical properties, the LDS-3 matrix has now been partially degraded by α-amylase at 45 °C (pH 6) for 0.5, 6 and 18 h. The study shows that already a 30 min enzymatic hydrolysis has a marked effect on the modified starch molecular weight and its thermal properties. The new composites with enzyme hydrolyzed AGE-starch, generically named D-LDS-3, showed good fiber dispersion and excellent interface between the fiber and matrix as studied by SEM. Premixes of D-LDS-3 matrix and fiber showed improved processability. The water vapor absorption was evaluated at 43.2% and 82.2% RH and the stiffness and strength properties were measured. The water uptake was shown to be reduced. The strength of neat matrix D-LDS-3-6 at ambient 68% RH reached 63 MPa and Young’s modulus 3200 MPa and with 40 wt.% wood fiber reinforcement impressive 128 MPa and 4500 MPa, respectively.     

Cell-wall hardness and Young's modulus of melamine-modified spruce wood by nano-indentation

Samples of spruce wood were infiltrated with a melamine–formaldehyde resin. After curing of the resin, a melamine concentration of 24% (v/v) was measured in the secondary cell walls of melamine treated wood. Nano-indentation tests revealed an average Young's modulus of 16.1 GPa and a hardness of 0.24 GPa for untreated secondary cell walls. In the melamine treated cell walls, an increase in the Young's modulus of 33% to 21.4 GPa was observed. With 115%, i.e. 0.52 GPa, the increase in longitudinal hardness due to melamine–formaldehyde treatment was even more pronounced. This proves clearly that melamine treatment of wood improves mechanical properties of cell walls. Thus, treatment of wood with melamine–formaldehyde resin shows a considerable potential to improve mechanical properties, as desired for applications where large stresses normal to grain arise.     

Xylan polysaccharides fabricated into nanofibrous substrate for myocardial infarction

Myocardial infarction, a main cause of heart failure, leads to loss of cardiac tissue impairment of left ventricular function. Repair of diseased myocardium with in vitro engineered cardiac muscle patch/injectable biopolymers with cells may become a viable option for myocardial infarction. We attempted to solve these problems by in vitro study by selecting a plant based polysaccharides beech wood Xylan for the normal functioning of infarcted myocardium. The present study fabricated Xylan based nanofibrous scaffolds cross-linked with glutaraldehyde (Glu) vapors for 24 h, 48 h and 1% Glu blended fibers for the culture of neonatal rat cardiac cells for myocardial infarction. These nanofibers were characterized by SEM, FT-IR, tensile testing and cell culture studies for the normal expression of cardiac proteins. The observed results showed that the Xylan/polyvinyl alcohol (PVA) 24 h Glu vapor cross-linked nanofibers (427 nm) having mechanical strength of 2.43 MPa and Young modulus of 3.74 MPa are suitable for the culture of cardiac cells. Cardiac cells proliferation increased only by 11% in Xylan/PVA 24 h Glu cross-linked nanofibers compared to control tissue culture plate (TCP). The normal cardiac cell morphology was observed in 24 h cross-linked Xylan/PVA nanofibers but 48 h cross-linked fibers cell morphology was changed to flattened and elongated on the fibrous surfaces. Confocal analysis for cardiac expression proteins actinin, connexin 43 was observed normally in 24 h Glu cross-linked nanofibers compared to all other nanofibrous scaffolds. The fabricated Xylan/PVA nanofibrous scaffold may have good potential for the normal functioning of infarcted myocardium.     

Finite element analysis of natural convection flows in a square cavity with non-uniformly heated wall(s)

A penalty finite element analysis with bi-quadratic rectangular elements is performed to investigate the influence of uniform and non-uniform heating of wall(s) on natural convection flows in a square cavity. In the present investigation, one vertical wall and the bottom wall are uniformly and non-uniformly heated while the other vertical wall is maintained at constant cold temperature and the top wall is well insulated. Parametric study for a wide range of Rayleigh number (Ra), 10³ ⩽ Ra ⩽ 10⁶ and Prandtl number (Pr), 0.2 ⩽ Pr ⩽ 100 shows consistent performance of the present numerical approach to obtain the solutions as stream functions and temperature profiles. Heat transfer rates at the heated walls are presented in terms of local Nusselt number.     

Full-field shear analyses of sandwich core materials using Digital Image Correlation (DIC)

Mechanical properties and global stability of foam core sandwich structures are highly controlled by the shear response of the core material. In this work, we have studied the shear deformations of three common structural core materials with the aid of full-field optical analysis. The chosen core materials are namely extruded PET foam (ρ = 105 kg/m³, G_xz = 21 MPa,) and cross-linked PVC foam (ρ = 60 kg/m³, G_xz = 22 MPa) which have comparable shear properties, as well as Balsa wood with the lowest density commercially available (ρ = 94 kg/m³, G_xz = 106 MPa) as a reference core material. Both global and local shear strains in the core materials are calculated and graphically visualized. In the elastic region, foam cores showed more uniform deformations than Balsa. Yielding and shear failure of the two foam core materials were quite different. The PVC foam experienced a high local deformation under the load introduction bars, from which sub-interface shear failure initiated. The PET foam, in contrast, showed no sign of stress concentrations, resulting in a homogenous evolution of shear deformations in the mid-core regions. A comparison between the direct foam shear test and sandwich specimen bending suggested that the former method might not be capable of capturing a full picture of the in-service core shear response.     

Improved mechanical properties of recycled linear low-density polyethylene composites filled with date palm wood powder

Recycled linear low-density polyethylene (RLLDPE) was blended with date palm wood powder to prepare composites in which the concentration of the filler ranged from 10 to 70 wt.%. The cross-linking of composites was performed in some selected cases. The Young’s modulus of the composites significantly increased as the filler content increased over the entire concentration range. A maximum value of 1989 MPa was observed for the composite filled with 70 wt.% filler, which was approximately 6.5 times higher than that observed for neat RLLDPE. The presence of filler increased the flexural strength from 11.4 MPa for unmodified RLLDPE to 17 MPa for the composite containing 70 wt.% filler. The Young’s modulus and stress at break measured at 50 °C decreased significantly compared with those values measured at 25 °C. The ratio between the stress at break at 25 °C versus 50 °C (σ₂₅/σ₅₀) was between 2.7 and 3.8, whereas the ratio of Young’s modulus of E₂₅/E₅₀ was between 1.6 and 2.6.     

Evaluation of hardness and surface quality of different wood species as function of heat treatment

The objective of this study was to evaluate the effect of heat treatment on surface roughness and hardness of four wood species, namely black alder (Alnus glutinosa L.), red oak (Quercus falcata Michx.), Southern pine (Pinus taeda L.) and yellow poplar (Liriodendron tulipifera). Samples were exposed to heat treatment schedules having two temperature and exposure levels of 120 °C and 190 °C for 3 and 6 h, respectively. Average hardness value of red oak samples exposed to a temperature of 190 °C for 6 h was 41.7% lower than that recorded before the heat treatment. Temperature of 190 °C produced 7.9% lower hardness values for black alder with the increased exposure time from 3 h to 6 h. No significant differences were found between same type of Southern pine and yellow poplar specimens before and after the heat treatment in terms of their hardness values. Among the four species considered in this study red oak having the most porous anatomical structure showed the roughest surface. An improvement in surface quality (R_a) with 7.46% with extending exposure time from 3 h to 6 h at the temperature level of 190 °C was noticed. However all four types of wood species kept in the oven at 190° for 6 h presented smoother surface quality. It was found that increased temperature from 120 °C to 190 °C for both exposure times showed significant differences from the surface quality of nontreated samples at 95% confidence level. The anatomical structure of samples was also observed by scanning electron microscope (SEM) and some damage of the cell wall was determined due to heat treatment. The findings of this study demonstrated that heat treatment resulted in adverse effect on hardness characteristics of the samples. It appears that strength losses can be limited through alternative modified heat treatment techniques. On the other hand, surface quality of the samples from all species was enhanced as a result of heat treatment. Therefore such heat treatment would be considered to improve surface quality of the sample for furniture applications where smooth surfaces are ideal adding potential value on wood material to be used more effectively in furniture manufacturing.     

Magnetic wood-based biomorphic Sr3Co2Fe24O41 Z-type hexaferrite ecoceramics made from cork templates

Ecoceramics (environmentally conscious ceramics) are biomimetic/biomorphic ceramics, which use a naturally occurring and sustainable material as a template for their unique morphology and structure. Usually woods (or lignocellulosics) are used, due to the inherent cellular nature of their microstructures. The wood is pyrolised and the resulting carbon skeleton impregnated with a fluid, and this is then heated to combust the carbon template and convert the fluid precursor into a ceramic, while maintaining the structure of the original natural template. For the first time, ecoceramics have been made from cork, a totally sustainable wood that is harvested without harming the tree. Also for the first time, ecoceramics have been made of soft magnetic Z-type hexaferrites, in this case the room temperature multiferroic strontium Z ferrite Sr₃Co₂Fe₂₄O₄₁ (SrZ). Cork powder was pyrolised at 1000 °C, infiltrated with an aqueous sol–gel SrZ precursor, and then heated at 1200 °C/2 h to produce the ecoceramic. The cellular structure of the cork was maintained, with a small reduction in the hexagonal cell dimension to 10 μm diameter, but the cell walls remained 1–2 μm thick, of a similar magnitude to the hexaferrite grain size. Both magnetic and XRD data agreed that there was a small portion of the SrW phase present in these ecoceramics as well, and the magnetic loop showed a magnetically soft ecoceramic with M_s = 59.5 A m² kg⁻¹ (at 3 T), and a low H_c of 16 kA m⁻¹.     

Influence of cell wall microstructure on the energy absorption capability of aluminium foam

The microstructure of aluminium foam produced by decomposing TiH₂ in the stabilized melt can be modified by heat treatment to improve the mechanical properties of the cell wall. Different microstructures were developed through solutionizing and quenching followed by thermal ageing treatment. Uniaxial compression tests were performed on foam specimens to understand as to how the microstructure of the cell wall influences the energy absorption capability of the foam. It is found that the solutionized sample has the best energy absorption capability (29.3 MPa) when compared to the as-foamed (13.2 MPa) and aged samples (15.9 MPa). The crack progression studies carried through interrupted compression tests confirm the detrimental influence of the cast dendritic structure and the lamellar Al₂Cu precipitate formed during aging. The results suggest that the extent of thermal aging in aluminium foam depends on the precipitation behaviour in the aluminium matrix.     

Preparation and characterization of genipin-crosslinked rat acellular spinal cord scaffolds

The feasibility of rat acellular spinal cord scaffolds for tissue engineering applications was investigated. Fresh rat spinal cords were decellularized and crosslinked with genipin (GP) to improve their structural stability and mechanical properties. The GP-crosslinked spinal cord scaffolds possessed a porous structure with an average pore diameter of 31.1 μm and a porosity of 81.5%. The resultant scaffolds exhibited a water uptake ratio of 229%, and moderate in vitro degradation rates of less than 5% in phosphate-buffered saline (PBS) and slightly more than 20% in trypsin-containing buffer, within 14 days. The ultimate tensile strength and elastic modulus of GP-crosslinked spinal cord scaffolds were determined to be 0.193 ± 0.064 MPa and 1.541 ± 0.082 MPa, respectively. Compared with glutaraldehyde (GA)-crosslinked acellular spinal cord scaffolds, GP-crosslinked scaffolds demonstrated similar microstructure and mechanical properties but superior biocompatibility as indicated by cytotoxicity evaluation and rat mesenchymal stem cell (MSC) adhesion behavior. Cells were able to penetrate throughout the crosslinked scaffold due to the presence of an interconnected porous structure. The low cytotoxicity of GP facilitated cell proliferation and extracellular matrix (ECM) secretion in vitro on the crosslinked scaffolds over 7 days. Thus, these GP-crosslinked spinal cord scaffolds show great promise for tissue engineering applications.     

Compression properties at different loading directions of as-extruded Mg–9RY–4Zn (RY: Y-rich misch metal) alloy with long period stacking ordered phase

The compression properties at different loading directions of as-extruded Mg–9RY–4Zn alloy with long period stacking ordered (LPSO) phase were investigated. The compressive yield strength (σ_0.2), ultimate compressive strength (σ) and elongation to failure (ε) are 272 MPa, 520 MPa and 19% at ED, 172 MPa, 412 MPa and 17% at TD, and 150 MPa, 370 MPa and 16% at 45° orientation, respectively. The excellent compression properties result from the 14H LPSO strips and random oriented DRX grains with 14H LPSO lamellae. Meanwhile, the as-extruded Mg–9RY–4Zn alloy exhibits obvious mechanical anisotropy. The strength at ED is much higher than that at 45° orientation. Specific to the present alloy, besides the weak basal texture, it is considered that the LPSO long strips with characteristic orientation play an important role in influencing the mechanical anisotropy.     

Effects of Si addition on microstructure and mechanical properties of Mg–8Gd–4Y–Nd–Zr alloy

Effects of Si addition (1.0 wt.%) on microstructure and mechanical properties of Mg–8Gd–4Y–Nd–Zr alloy have been investigated using scanning electron microscopy (SEM) equipped with energy dispersive spectrum (EDS), X-ray diffraction (XRD), hardness measurements and tensile testing. The results indicated that the addition of Si led to the formation of Mg₂Si and (RE + Si)-rich particles, which enhanced the Young’s modulus of the alloy by 7 GPa while decreased the yield strength and ultimate strength by 10 MPa and 31 MPa, respectively. The tensile properties of the Mg–8Gd–4Y–Nd–Zr–Si alloy are as follows: Young’s modulus E = 51 GPa, yield strength σ_0.2 = 347 MPa, ultimate strength σ_b = 392 MPa and elongation δ = 2.7%. The increase in Young’s modulus was attributed to the formation of particles with high Young’s modulus, while the decrease in strength was ascribed to the decrease in volume fraction of metastable β′ precipitates caused by the consumption of rare earth atoms due to the formation of the rare earth containing particles.     

Energy-efficient milling method for woody biomass

Size reduction is essential to utilize biomass in many applications. Production of fine particles from biomass chips is usually performed using milling machines that consume large amount of energy. Steam explosion (SE) is a promising method for reducing the size of biomass using less energy consumption because it utilizes thermal energy. In this study, we focused on the possibility of the SE method to produce fine particles with a size below 1 mm from wood chips. Sakura (Prunus spp., hardwood) and Japanese cedar (Cryptomeria japonica, softwood) chips with a size of 5–10 mm were used in this study. The effects of SE conditions – such as temperature and residence time – and of the biomass type on the biomass size reduction were investigated in detail. The energy consumption of SE was also calculated and compared with that of the conventional mill. We found that SE is an energy-efficient method for biomass milling.     

Development of multi-walled carbon nanotubes reinforced monetite bionanocomposite cements for orthopedic applications

In this study, we present results of our research on biodegradable monetite (DCPA, CaHPO₄) cement with surface-modified multi-walled carbon nanotubes (mMWCNTs) as potential bone defect repair material. The cement pastes showed desirable handling properties and possessed a suitable setting time for use in surgical setting. The incorporation of mMWCNTs shortened the setting time of DCPA and increased the compressive strength of DCPA cement from 11.09 ± 1.85 MPa to 21.56 ± 2.47 MPa. The cytocompatibility of the materials was investigated in vitro using the preosteoblast cell line MC3T3-E1. An increase of cell numbers was observed on both DCPA and DCPA-mMWCNTs. Scanning electron microscopy (SEM) results also revealed an obvious cell growth on the surface of the cements. Based on these results, DCPA-mMWCNTs composite cements can be considered as potential bone defect repair materials.     

Tensile properties of hot rolled Mg–3Sn–1Ca alloy sheets at elevated temperatures

Mechanical behavior of hot rolled Mg–3Sn–1Ca (TX31) magnesium alloy sheets were studied in the temperature range 25–350 °C. The microstructure of the alloy consisted of the eutectic structure of α-Mg + Mg₂Sn and a dispersion of needle-like CaMgSn. The highest room-temperature ductility of 18% was obtained by hot rolling of the cast slabs at 440 °C, followed by annealing at 420 °C. The high temperature tensile deformation of the material was characterized by a decrease in work hardening exponent (n) and an increase in strain rate sensitivity index (m). These variations resulted in respective drops of proof stress and tensile strength from 126.5 MPa and 220 MPa at room temperature to 23.5 MPa and 29 MPa at 350 °C. This was in contrast to the ductility of the alloy which increased from 18% at room temperature to 56% at 350 °C. The observed variations in strength and ductility were ascribed to the activity of non-basal slip systems and dynamic recovery at high temperatures. The TX31 alloy showed lower strength than AZ31 magnesium alloy at low temperatures, while it exhibited superior strength at temperatures higher than 200 °C, mainly due to the presence of thermally stable CaMgSn particles.     

Influence of drying on the mechanical behaviour of flax fibres and their unidirectional composites

The microstructure of flax fibres can be considered as a laminate with layers reinforced by cellulose fibrils. During a single fibre tensile test the S2 layer is subjected to shear. At room temperature, natural fibres contain water absorbed in the cell-walls. This paper examines the influence of this water at two scales: on the tensile behaviour of the flax fibres and on unidirectional plies of flax reinforced epoxy. Drying (24 h at 105 °C) is shown to reduce both failure stress and failure strain significantly. Analysis of normal stresses at the accomodation threshold provides an estimation of the shear strength of secondary cell walls as 45 MPa for fibres containing 6.4% by weight of water and only 9 MPa for dried fibres. Results from tensile tests on unidirectional flax/epoxy composites, reinforced by as-received and dried fibres, confirm the influence of drying on strength properties.     

Effect of impact force on Ti–10Mo alloy powder compaction by high velocity compaction technique

Ti–10Mo alloy powder were compressed by high velocity compaction (HVC) in a cylinderical form of height/diameter (h/d) in die 0.56 (sample A) and 0.8 (sample B). Compactions were conducted to determine the effect of impact force per unit area of powder filled in die for densification and mechanical properties of Ti–10Mo samples. The micro structural characterization of samples were performed by scanning electron microscope (SEM). The mechanical properties of the compressed samples such as Vickers hardness, bending strength, and tensile strength were measured. Experimental results showed that the density and mechanical properties of sample A and sample B increased gradually with an increase in impact force and decreased with an increase in height/diameter ratio. The relative green density for sample A reached up to 90.86% at impact force per unit area 1615 N mm⁻². For sample B, it reached 79.71% at impact force per unit area 1131 N mm⁻². The sintered sample A exhibited a maximum relative density of 99.14%, Vickers hardness of 387 HV, bending strength of 2090.72 MPa, and tensile strength of 749.82 MPa. Sample B revealed a maximum relative sintered density of 97.73%, Vickers hardness of 376 HV, bending strength 1259.94 MPa and tensile strength 450.25 MPa. The spring back of the samples decreased with an increase in impact force.     

A ferrite stainless steel Cr27Mo6Al3Cu with oxidation resistance

A new ferrite steel Cr27Mo6Al3Cu with high Mo and low Al is developed, exhibiting excellent oxidation resistance, corrosion resistance, and mechanical property. Alloy rods with a diameter of 10 mm were prepared by copper mold suction-casting method and then solution-treated at 1373 K for 2 h. The experimental results show that this alloy maintains a stable monolithic BCC microstructure. After oxidization at 1373 K for 100 h, a dense and thin oxide layer is generated on the surface of the alloy with the weight gain per unit area G⁺ being about 0.4863 g/m². Its corrosion-resistant property in 3.5 wt.% NaCl at 298 K is characterized with the corrosion potential E_corr being about −0.091 V, pitting corrosion potential E_b reaching up to 0.867 V. Its mechanical properties are yield tensile strength σ_0.2 = 523 MPa, ultimate tensile strength σ_b = 637 MPa respectively.     

Optimum manufacturing parameters for compressed lumber from oil palm (Elaeis guineensis) trunks: Respond surface approach

The objective of this investigation was to evaluate optimum manufacturing parameters to produce compressed lumber from oil palm (Elaeis guineensis) trunks. Experimental samples were made using steaming time, pressure, pressure time and temperature ranging from 2 to 4 h, from 5 to 12 MPa, from 20 min to 60 min and from 100 °C to 200 °C, respectively. Compression and recovery ratios of the specimens were determined employing Response Surface Methodology (RSM) approach within the scope of Central Composite Design (CCD) computer program. Experimental and calculated values were compared to each other. Based on the results of the work, the specimens steamed for 2 h before they were compressed using a pressure of 11.16 MPa at a temperature of 200 °C for 60 min resulted in optimum conditions. Measured and calculated compression and recovery ratios of the samples showed 0.70 and 0.83 correlation coefficient values, respectively.