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.     

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.     

The influence of moisture content of raw material on the physical and mechanical properties,surface roughness,wettability, and formaldehyde emission of particleboard composite

The objectives of this research were to investigate surface characteristics, physical (thickness swelling) and mechanical (modulus of rupture, modulus of elasticity and internal bond strength) properties, and formaldehyde emission of particleboard composite, as affected by moisture content of wood. Three-layered particleboard panels manufactured from wood particles at five different moisture contents (20%, 40%, 60%, 80% and 95%). Roughness measurements, average roughness (R_a), mean peak-to-valley height (R_z), and maximum roughness (R_y), were taken from the sanded samples along and across the sandmarks using a fine stylus tracing technique. Contact angle measurements were obtained by using a goniometer connected with a digital camera and computer system. Statistical analysis showed significant differences in the surface roughness, contact angle, formaldehyde emission, physical and mechanical properties of the panels following moisture content. Based on the findings obtained from this study, an increase or decrease in the moisture content of wood beyond a certain limit, before chipping operations, negatively affected the wettability and smoothness of particles, and formaldehyde emission, physical and mechanical properties of particleboards.     

Hierarchical poly(p-phenylene benzobisoxazole)/graphene oxide reinforcement with multifunctional and biomimic middle layer

A new hierarchical reinforcement developed by coating biomimic polydopamine (PDA) on the surface of poly(p-phenylene benzobisoxazole) (PBO) fibers, which served as a platform for the graphene oxide (GO) grafting, using branched polyethyleneimine (b-PEI) as a bridging agent. The surface morphologies and chemical structures of PBO fibers were characterized for confirming the formation of covalent bond between GO and PBO fibers. The surface roughness (R_a) and wettability of the obtained fibers, denoted as PBO@PDA-PEI-GO, were obviously increased in comparison with those of untreated one. The reinforcement offered a 68.8% enhancement in the interfacial shear strength (IFSS) without degrading the base fiber. The PDA layer on the PBO fiber surface led to improved UV resistance. The hydrothermal aging resistance of PBO/epoxy composite was also greatly improved. This biomimic surface modification approach is facile to prepare, highly efficient to enhance interface, adaptable to all high-performance fibers, and meaningful in multifunctional applications.     

Effect of extrusion process melt temperature on polyurethane catheter surfaces

Determination of optimum process melt temperature of medical-grade polyurethane (PU) is an indispensable challenge witnessed during the catheter manufacturing process. This resin does not contain a uniform crystal structure but exists in an amorphous state. The lower shore hardness PU material, used in catheter manufacture, has just a “melt temperature range” instead of a definite melt temperature. This temperature plays a significant role in shaping the catheter surfaces, which directly interact with human tissues and cause health-care-associated issues. The objective of this work is to evaluate the effects of variations in the melt temperature during the extrusion process of medical catheters on their outer surfaces. Medical PU, Pellethane, was used for this study and 12 Fr (4.0?mm) catheters were manufactured with optimal validated parameters, excluding melt temperature. The manufactured catheters were examined under Optical Microscopy and Atomic Force Microscopy (AFM) for surface topography studies. Wettability studies were carried out using a Goniometer for evaluating the water contact angles. The effects of melt temperature on the surface roughness (R_a) and wettability of the catheter surfaces were analyzed through analysis of variance (ANOVA). The conclusion was that the process melt temperature variations have a significant effect on catheter R_a and its wettability characteristics.     

Functional shape memory composite nanofibers with graphene oxide filler

In the present study, we prepared a series of graphene oxide (GO) filled shape memory polyurethane (SMPU) nanofibers and systematically investigated the morphological, thermal and mechanical properties, surface wettability, and the shape memory effect (SME) followed by the proposed programming model. The results show that GO can be well dispersed within the SMPU matrix, and the introduction of GO significantly improves the mechanical strength, surface wettability, and thermal stability of the SMPU. Compared with pristine SMPU nanofibrous mats, the prepared SMPU/GO nanofibrous mats have better SME and lower thermal shrinkage. When the loading amount of GO increased to 4.0 wt%, the thermal shrinkage ratio (R_ts) of composite nanofibrous mats could be as low as 4.7 ± 0.3%, while the average fixation ratio (R_f) and recovery ratio (R_r) could be as high as 92.1% and 96.5%, respectively. The study indicates that GO is a desirable reinforcing filler for preparing shape memory nanofibers with improved properties.     

Using crack propagation fracture toughness to characterize the durability of wood and wood composites

We measured fracture resistance curves (or R curves) for laminated veneer lumber (LVL) made with Douglas-fir veneer and polyvinyl acetate resin and for solid wood Douglas-fir. The LVL and solid wood R curves were the same for initiation of fracture, but the LVL toughness rose much higher than solid wood. Because a rising R curve is caused by fiber bridging effects, these differences show that the LVL resin has a large effect on the fiber bridging process. We exploited this resin effect to develop a test method for characterizing the ability of a resin to provide wood composites that are durable to moisture exposure. The test method exposed LVL specimens to vacuum pressure soaking and drying (VPSD) cycles and then monitored the rising portion of the LVL R curves as a function of treatment cycles. Douglas-fir/polyvinyl acetate LVL lost about 30% of its toughness after 16 cycles. In characterizing toughness changes, it was important to focus on the magnitude and rate of the toughness increase attributed to fiber bridging. We suggest that these properties are much preferred over other fracture or mechanical properties of wood that might be used when characterizing durability.     

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.     

Sidewall roughness characterization and comparison between silicon and SU-8 microcomponents

Surface characterization of microcomponents provides key information to help understand and predict the performance of microdevices. For example, in a microgear transmission, the surface roughness has a strong effect on the friction, running life and power consumption. In a static fluid microdevice, the liquid distribution is influenced by the surface tension and capillary force, which are primarily determined by the surface roughness. In a flowing microchannel case, surface roughness results in unsteady secondary flows. In this paper, a study is presented to characterize the surface roughness of silicon and SU-8 microcomponents. The silicon components studied are fabricated using an ICP plasma etching system manufactured by Surface Technology Systems. The sidewall roughness of the component is measured using atomic force microscopy. Repeated measurements have been conducted at different sidewall depths of the microstructure. The AFM images of the measurements are present. The measurement results show that the sidewall is smoother at the lower level than that at the upper level in a Si microstructure, and the average roughness R_a obtained throughout the depth is 151.11 nm. The UltraThick SU-8 Process (UTSP) provides another way to fabricate microstructures as thick as 1 mm with a very vertical sidewall. The roughness contour of the sidewall shows that the surface topography is similar throughout the depth. The average roughness R_a is 46.46 nm. Other surface parameters, such as R_q, R_p − p, R_pk and R_sk, are also obtained and analysed. The implication of the smooth surface roughness of SU-8 structures to their applications is discussed in terms of transmission efficiency, the changes in friction to flowing liquid in a microchannel and the changes in the surface tension and capillary effect.     

Experimental Study on Hybrid Cryogenic and Plasma-Enhanced Turning of 17-4PH Stainless Steel

This article presents machinability of 17-4PH stainless steel using a hybrid technique composed of plasma-enhanced turning and cryogenic turning. First of all, using some primary experimental tests and nonlinear regression, a mathematical model was developed for surface temperature of uncut chip as a function of plasma current and cutting parameters. Then, the influence of cutting speed (V_c), feed (f), and surface temperature of uncut chip (T_sm) was studied on surface roughness (R_a), cutting force (F_z), and tool flank wear (V_B). The results show that hybrid turning (HYT) is able to lower the main cutting force and tool flank wear in comparison with conventional turning. In addition, surface roughness was improved except for high level of surface temperature of uncut chip. However, hardness measurement of machined workpiece showed that HYT does not change the hardness of machined surface.     

Modification of bifunctional epoxy resin using CO2 fixation process and nanoclay

A bifunctional epoxy resin was modified by using a CO₂ fixation solution process in the presence of tetra n-butyl ammonium bromide (TBAB) as catalyst and the modified treated resin was treated by cloisite 30B as nano additive. The Unmodified epoxy resin (UME), CO₂ fixated modified epoxy resin (CFME), and CFME/clay nano composite (CFMEN), were cured by diethylenetriamine (DETA). A cycloaliphatic compound as a reactive diluent was used to control the viscosity of high viscose CFME. The exfoliation of organoclay in UME and CFME was investigated by X-ray diffraction and activation energy was computed using the advanced integral isoconversional method. The activation energy dependency demonstrated that the mechanism of UME curing did not change in the presence of nanoclay. In contrast, the CO₂ fixation results showed a significant change in the activation energy dependency. The Thermal stability parameters include the initial degradation temperature (IDT), the temperature at the maximum rate of weight loss (T_max), and the decomposition activation energy (E_d) were determined by thermal gravimetry analysis. Dynamic mechanical thermal analysis measurements showed that the presence of organoclay in CFME increases the T_g of nano composite in contrast to UME. The fracture roughness of UME, CFME and CFNE were determined by scanning electron microscope. The exfoliated UME/1%clay nanocomposite was confirmed by TEM image.     

Erosion mechanisms of aluminium nitride ceramics at different impact angles

In this paper, erosion wear behaviour of aluminium nitride (AlN) ceramics is studied. The influence of particle hardness and shape on erosion of the AlN surface is examined. The effect of varying the impingement angle on the weight loss and the roughness parameters of AlN ceramics testing sample is also determined. Therefore, erosive wear behaviour of AlN ceramics was investigated using SiC and SiO₂ particles as erodents, at following impact angles: 30°, 45°, 60°, 75° and 90°. Scanning electron microscopy (SEM) was used to analyze the eroded surfaces in order to determine erosion mechanisms. The roughness parameters (R_a, R_z and R_max), before and after erosion with SiO₂ and SiC particles at 30° and 90° angles of impingement, respectively, were determined using a profilometer. It was found that the impact angle is influencing the erosion wear of the AlN ceramics and maximum erosion takes place at impact angle of 90°. The results indicate that hard, angular SiC particles cause more damage than softer, more rounded SiO₂ particles.     

Effect of CO2 fixation reaction on the thermal and dynamic mechanical properties of tetrafunctional epoxy resin

A tetrafunctional epoxy resin was modified using CO₂ fixation process in the presence of tetra-n-butyl ammonium bromide as catalyst. The unmodified tetrafunctional epoxy resin (UMTE) and CO₂ fixated modified tetrafunctional epoxy resin (CFMTE) were cured by diethylenetriamine. A bifunctional glycidyl ether compound was used as a reactive diluent to control the viscosity of CFMTE. The activation energy of curing reaction was computed using the advanced integral isoconversional method. The activation energy, which depends on the conversion, was considerably changed due to the CO₂ fixation process. The thermal stability parameters including the initial degradation temperature, the temperature at the maximum rate of weight loss (T _max), and the decomposition activation energy (E _d) were determined by thermal gravimetry. Dynamic mechanical thermal analysis measurements showed that the CO₂ fixation decreases the T _g of the epoxy resin. The surface morphology of UMTE and CFMTE were determined by scanning electron microscope. It is concluded that CO₂ fixation reaction improves the properties of tetrafunctional epoxy resin.     

Enhancing the adhesive wear performance of polyetherimide composites through nano-particle treatment of the carbon fabric

Rare earth compound Ytterbium fluoride (YbF₃) in nano-size (40–80 nm) was employed for surface treatment of carbon fabric (CF) to improve its wettability with polyetherimide matrix. Composites were developed based on untreated and surface-treated CF with three doses, 0.1, 0.3, and 0.5 wt%, of YbF₃ in ethyl alcohol suspension. The composites were analyzed for interlaminar shear strength (ILSS). Improvement in ILSS was observed for treated fabric reinforced composites and it was maximum (61%) for 0.3 wt% dose of YbF₃. The adhesive wear performance of composites was evaluated by sliding a pin of composite against mild steel disc under varying loads (200–600 N). The treated fabric composites exhibited lower coefficient of friction (μ) and higher wear resistance (W _R). ILSS and W _R showed good linear correlation. Both properties were highest for 0.3% YbF₃ dosing. Increased roughness of fiber surface and adhesion of nano-particles on the fiber surface was observed in scanning electron microscopic (SEM) studies. SEM studies of worn surfaces of composites were performed to understand wear mechanisms. Atomic force microscopic studies indicated substantial increase in roughness value of CF.     

Air plasma treatment of copper sheets using Diffuse Coplanar Surface Barrier Discharge

The treatment of copper sheets by atmospheric-pressure air plasma generated using the Diffuse Coplanar Surface Barrier Discharge was studied. The surface free energy measurements indicated a significant increase of the wettability after several seconds of plasma exposure. The atomic force microscopy technique revealed a relatively small increase of the surface roughness due to the plasma treatment. The observed increase of wettability, the influence of air humidity on treatment efficiency and the hydrophobic recovery of the plasma treated surfaces were studied by the x-ray photoelectron spectroscopy. A generation of surface -NO_x groups in humid air plasma was observed.     

Effect of temperature and substrate surface texture on wettability and morphology of IMCs between Sn–0.7Cu solder alloy and copper substrate

In the present work, the effect of soldering temperature (270 and 298?°C) and substrate surface texture (0.02 and 1.12?μm) on wetting characteristics and morphology of intermetallic compounds (IMCs) between Sn–0.7Cu lead-free solder on copper substrates was investigated. It was found that increase in temperature and substrate surface roughness improved the wettability of solder alloy. However, the effect of surface roughness on wettability was significant as compared to that of temperature. The spreading of solder alloy was uniform on smooth substrate, whereas spreading of the alloy on rough substrate resulted in an oval shape. The morphology of IMCs transformed from long needle shaped to short and thick protrusions of IMCs with increase in surface roughness of the substrate. Needle shaped and thick protruded intermetallics formed at the solder/Cu interface were identified as Cu₆Sn₅ compounds. The formation of Cu₃Sn IMC was observed only for the spreading of solder alloy at 298?°C which contributed to improvement in the wettability of solder alloy on both smooth and rough substrate surfaces.     

Chemical/mechanical polishing of diamond films assisted by molten mixture of LiNO3 and KNO3

Chemical/mechanical polishing can be used to polish the rough surface of diamond films prepared by chemical vapor deposition (CVD). In this paper, a mixture of oxidizing agents (LiNO₃ + KNO₃) has been introduced to improve the material removal rate and the surface roughness in chemical/mechanical polishing because of its lower melting point. It had been shown that by using this mixture the surface roughness R_a (arithmetic average roughness) could be reduced from 8-17 to 0.4 μm in 3 h of polishing, and the material removal rate can reach 1.7-2.3 mg/cm²/h at the temperature of 623 K. Pure aluminium is compared with cast iron as the contact disk material in the polishing. Although the material removal rate of aluminiumdisk is lower than that of cast iron, it can eliminate the carbon contamination from the contact disk to the surface of diamond films, and facilitate the analysis of the status of diamond in the chemical/mechanical polishing. The surface character and material removal rate of diamond films under different polishing pressure and rotating speed have also been studied. Graphite and amorphous carbon were detected on the surface of polished diamond films by Raman spectroscopy. It has been found that the oxidization and graphitization combined with mechanical cracking account for the high material removal rate in chemical/mechanical polishing of diamond films.     

Morphometrical evaluation of surface roughness during the initial fatigue stage in an austenitic steel

The microscopic behaviour of surface deformation in the precracked fatigue stage of AISI 310 stainless steel was examined. The fatigue experiments were conducted in a special servohydraulic miniature testing machine (BAERBEL) inside a scanning electron microscope. The object of the present study was the quantitative determination of material damage caused by fatigue straining. The roughness values, R_a, were determined by using both a stereo-photogrammetrical method and a contact stylus instrument. Both morphometrical methods allowed the deformation of fatigued surfaces to be quantified. It has proved possible to indicate the existence of a propagating crack by determining the maximum of the function of the roughness value, R_a, versus loading.     

Experimental Investigation and Optimization of Process Parameters of Al/SiC MMCs Finished by Abrasive Flow Machining

In the era of nontraditional finishing processes, it is of upmost importance that these processes can be applied to composite materials as these have replaced traditional materials in many applications. Abrasive Flow Machining (AFM) is an advanced finishing process. Composite materials have replaced traditional materials as their properties such as light weight, high strength, and good economy are of great benefit. In the literature, work has been reported on AFM of materials such as aluminum, brass, and EN8. In the present work, composite materials with a high percentage of SiC (e.g., 20–60% SiC in Al/SiC composites) were machined using abrasive flow finishing. The Taguchi method was applied to find the effect of input parameters on material removal rate (MRR), change in surface roughness (ΔR_a), and surface topography, and L27 array was designed for experimentation. It was observed that extrusion pressure is the most significant factor in regard to MRR and ΔR_a. Optimization of response parameters (MRR and ΔR_a) was determined using the Taguchi method. Microstructure analysis was also done for workpiece materials using SEM and XRD.     

Examination of the electropolishing behaviour of 73 brass in a 70% H3PO4 solution using a rotating disc electrode

The electropolishing behaviour of 73 brass in a 70% H₃PO₄ solution was studied using a rotating disc electrode (RDE). Based on the results of an anodic polarisation test, a transition peak from kinetic-controlled to diffusion-controlled dissolution was detected when a blue Cu²⁺-rich layer was developed on the RDE. The blue Cu²⁺-rich layer impedes the anodic dissolution rate of the brass-RDE and is essential for levelling during electropolishing. Potentiostatic polishing at different locations on the limiting-current plateau was studied. By polishing at the transition-peak potential, grain boundaries were preferentially etched. In contrast, a well-polished surface with a nanosized surface roughness (R_a) was achieved after electropolishing in the middle of the limiting-current plateau. By polishing at the end of the limiting-current plateau at a relatively low rotational speed, nipple-like and flow-streak features were observed. The formation of these features is attributed to the evolution of oxygen bubbles on the RDE surface. Mechanisms for the formation of the above-mentioned features were proposed.