GPa For Elastic Modulus Research Articles

Synthesis mechanism and interface contribution towards the strengthening effect of in-situ Ti5Si3 reinforced Al matrix composites

As a titanium-silicon intermetallic compound, Ti5Si3 can offer great potentials as a reinforcement agent in metal matrix composites due to its exceptional mechanical and physical properties. In this study, Ti5Si3 particles are successfully in-situ synthesized in Al-Si-Ti system through the interdiffusion reaction between Ti-Si using a powder metallurgy approach. The composites interface structure is transformed from Al/Ti5Si3 non-coherent interface to Al/TiSi/Ti5Si3 coherent/semi-coherent interface with the formation of TiSi transition layer. It enhances the interface bonding between Ti5Si3 particles and Al matrix, mitigates the mechanical differences between the matrix and the reinforcements, thereby enhancing the coordinated deformation ability. Simultaneously, the generated gradient interface between Ti@Ti5Si3 core-shell structure particles and Al matrix suppresses the rapid propagation of cracks in brittle reinforcement. As a result, the mechanical performance of AMCs is improved to 96.1 GPa for elastic modulus and 327 MPa for strength while maintaining a fracture elongation of 6.5 %, which shows significantly enhancement compared with Al-5Si and Al-2.37Ti matrix. These findings establish a robust microstructural foundation for fully harnessing the strengthening effects of the reinforcements and provide a feasible technical route of utilizing the in-situ synthesized reinforcing particles for improving the mechanical performance of Al matrix composites.

Constructing quasi-vertical fiber bridging behaviors of aramid pulp at interlayer of laminated basalt fiber reinforced polymer composites to improve flexural performances

Basalt Fiber Reinforced Polymer (BFRP) composites have huge potential application respects for some civil fields due to enough strength/modulus to weight and low cost by replacing carbon fiber composites. Aiming at the issues in the Resin-Rich Region (RRR) and Interfacial Transition Region (ITR) of fiber reinforced polymer composites, the characteristic Aramid Pulp (AP) fibers with micro-fiber trunk and nano-fiber branches were manufactured into multiple non-woven ultra-thin interleaving at the interlayers of BFRP composites via compression molding to reinforce the flexural strengths and elastic moduli. AP fibers were introduced into RRR to form interleaving at the interlayer, the brittle epoxy adhesive layer was improved and enabled to avoid cracking under a low external load. Free fiber branches of AP were also embedded into BF layer to construct quasi-vertical fiber bridging behaviors in ITR, stronger mechanical interlocking was created to prevent crack propagation along the bonding interface of BF/epoxy. Three-point bending testing results showed the interleaving film with 4 g/m2 AP exhibited the best effect among various areal densities and yielded average 315.75 MPa in flexural strength and 21.38 GPa in elastic modulus, having a 63.4% increment and a 47.1% increment respectively compared with the bases. Overall, the simple and low-cost AP interleaving is confirmed as an effective method in improving interlayer structure and flexural performance of BFRP composites, which may be considered to manufacture high-performance laminated fiber reinforced polymer composites in civil aviation industry.

HYDROXYAPATITE/Si-DOPED TiN INTERLAYER COATINGS AS POTENTIAL CANDIDATES FOR SURFACE MODIFICATION OF MEDICAL-GRADE 316 LVM STAINLESS STEEL FOR BIOIMPLANT APPLICATIONS

Hydroxyapatite (HAp) was deposited by plasma spraying technique with TiSiN adhesive interlayer on the medical-grade 316 LVM stainless steel. The surface topographies of HAp and HAp/TiSiN were evaluated using X-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The important mechanical properties of the films such as hardness ([Formula: see text]) and elastic modulus ([Formula: see text]) were determined by the nanoindentation test. Lastly, the adhesion and anti-scratch behaviors of the films were evaluated by Rockwell-C indentation and nanoscratch test, respectively. The elemental analysis showed the values of Ca/P (at.%/at.%) ratio to be 1.80 and 1.59 in HAp and HAp/TiSiN coatings, respectively. The mechanical properties of HAp film with TiSiN interlayer were greatly improved from 1.23[Formula: see text][Formula: see text][Formula: see text]0.26[Formula: see text]GPa to 10.6[Formula: see text][Formula: see text][Formula: see text]1.12[Formula: see text]GPa for hardness and from 18[Formula: see text][Formula: see text][Formula: see text]3[Formula: see text]GPa and 29.8[Formula: see text][Formula: see text] 5[Formula: see text]GPa for elastic modulus, respectively. The results of the Rockwell-C indentation test showed a significant reduction in HAp coating delamination with TiSiN interlayer which can be categorized with HF2 or HF3 Daimler–Benz quality ranking. What is more, the nanoscratch profile of HAp coating showed wider scratch with evidence of deformation at the edges which got significantly reduced with the TiSiN interlayer. The results are suggestive of improved mechanical properties, viz. hardness and elastic modulus, and improved adhesion strength of HAp coating with TiSiN interlayer.

Comparison of three different deconvolution methods for analyzing nanoindentation test data of hydrated cement paste

The micromechanical properties of hydrated cement paste were investigated by nanoindentation with a large data set (4000 indentation points) to reveal the influences of multiple factors on analysis results. Three different deconvolution analysis methods, i.e. the Gaussian mixture model (GMM) with the maximum likelihood evaluation (MLE) algorithm, the probability distribution function (PDF) and the cumulative distribution function (CDF) with least square estimate (LSE) algorithm, were employed to analyze the nanoindentation test data. It was found that the GMM with a diagonal-unshared matrix is the most appropriate for the deconvolution of nanoindentation data of hydrated cement paste for the MLE algorithm. The PDF and CDF methods are equally effective for the LSE algorithm, but the former is subjected to the influences of bin sizes and the optimal bin size is 1.5–2 GPa for elastic modulus and 0.075–0.1 GPa for hardness. The threshold number of indentation points necessary to obtain reliable micromechanical parameters and phase contents by all three deconvolution methods is approximately 800-1000, significantly higher than the values used in the literature. The phase content seems to show more variations than elastic modulus and hardness when the number of indentation point is insufficient. With sufficient number of indentation points, the three different deconvolution methods give consistent results regarding the properties and contents of six phases identified. The various phase contents calculated by deconvolution of nanoindentation test data are in reasonable agreement with that estimated by QXRD and SEM except for the pore phase.

Compression and flexural properties of plantation-grown Eucalyptus pellita in Borneo, Malaysia. Potential for structural timber end use

ABSTRACT Plantation-grown Eucalyptus pellita in Sabah, Malaysia, was analysed for compression and flexural properties to assess the potential for solid-timber and engineered wood product end uses. It is necessary to consider not only the volume of wood produced in a plantation but also the wood quality, particularly those aspects important for end-product performance. Tree volume is readily measured from height and diameter at breast height using appropriate form factors. This paper discusses the compression, strength and stiffness of E. pellita compared with tropical hardwood species, and variation within trees and at different ages (7–23 years). Small clearwood test samples obtained from radial positions within log heights were subjected to analysis of compression parallel to grain and three-point bending according to ISO 13061-4, 2014. Results indicate that plantation-grown E. pellita in the tropics has potential for structural-use applications. The average basic density across the trials was 658 kg m−3, while the bending strength for all trials was in the range of 11.7–15.5 GPa for modulus of elasticity and 96.3−120.1 MPa for modulus of rupture, and the compression strength parallel to grain ranged from 52.3 to 67.8 MPa. Mean mechanical strength increased from pith to bark and from the butt log to the top log. Because the wood-processing sector in Malaysia is transitioning from reliance on a harvest of mixed tropical hardwood towards plantation-grown species, these results indicate that plantation-grown E. pellita meets the structural requirements of strength and stiffness.

3D-cubic interconnected porous Mg-based scaffolds for bone repair

Abstract Mg-based porous materials, as potential bone tissue engineering scaffolds, are considered an attractive strategy for bone repair owing to favorable biodegradability, good biocompatibility and suitable mechanical properties. In this work, 3D-cubic interconnected porous Mg–xZn–0.3Ca (x = 0,3,6) scaffolds were prepared to obtain desirable pore structures with a mean porosity up to 73% and main pore size of 400–500 µm, which pore structures were close to the human cancellous bone. The structure–property relationships in the present scaffolds were analyzed by experiments and theoretical models of generalized method of cells (GMC). Mg–xZn–0.3Ca scaffolds exhibited good compression properties with a maximum above 5 MPa in yield strength and about 0.4 GPa in elastic modulus. This was attributed to not only the alloy strengthening but also the large minimum solid area. On the other hand, the scaffolds showed undesirable and relatively serious degradation behavior in Hank's solution, resulting from Zn addition in Mg-based scaffolds and the high surface area ratio in the pore structure. Therefore, surface modifications are worth studying for controlled degradation in the future. In conclusion, this research would explore a novel attempt to introduce 3D-cubic pore structure for Mg-based scaffolds, and provide new insights into the preparations of Mg-based scaffolds with good service performances for bone repair.

Maximum likelihood estimation for nanoindentation on sodium aluminosilicate hydrate gel of geopolymer under different silica modulus and curing conditions

As an important inorganic material, geopolymer has been widely used for ceramics and sustainable cement in concrete. Sodium aluminosilicate hydrate (N-A-S-H) gel known as the zeolite precursor gel has the most critical impact on the performance of geopolymer. The nano/micromechanical properties of N-A-S-H have been investigated in several studies, but the resutls are always inconsistent. A novel “compromise approach” using Maximum Likelihood Estimation (MLE) for deconvolution of nanoindentation data is introduced to fundamentally further understand this issue in this study. Correlation and difference of different statistical techniques are compared to clarify the rationality of this method. Multiple characterization techniques including microstructure observation at micro -and nano-scale, element analysis, and crystal identification are applied to reveal the mechanisms. The results indicate that the elastic modulus and hardness of the N-A-S-H gel in geopolymer under different silica modulus and curing conditions vary in a small range from 10.50 to 14.30 GPa and from 0.40 to 0.57 GPa, respectively. When applying statistical nanoindentation in geopolymer, two kinds of spurious phases, mixed phases and sub-phases are unavoidable. For the MLE method adopted, the errors generated from analytical technique were estimated to be only 0.68 and 0.13 GPa for elastic modulus and hardness, respectively.

Formulation optimization and characterization of bamboo/polyvinyl alcohol/clay nanocomposite by response surface methodology

An investigation of the effects of montmorillonite nanoclay and polyvinyl alcohol (PVA) treatments on the physical, mechanical, and thermal properties of bamboo reinforced nanocomposites was carried out. Response surface methodology (RSM) was used to develop models for predicting mechanical properties of the nanocomposite and optimized the modification phase change materials. The FTIR spectra of the nanocomposites indicated incorporation of the polymer and nanoclay in the structure and diffractograms from XRD also higher crystallinity of the prepared nanocomposite compared to raw bamboo. The SEM image revealed that of the lumens of the raw bamboo were filled by the polymer and nanoclay after formation of the nanocomposite. Improved mechanical properties were observed in the prepared nanocomposites compared to the raw bamboo with the modulus of elasticity (MOE) increased from 7.82 GPa to 17.32 GPa and modulus of rupture (MOR) increased from 68.67 MPa to 118.74 MPa. Optimal values were found to be 15.082 GPa for MOE and 96.879 MPa for MOR with R2 of 0.9999. Better thermal properties were observed in the developed nanocomposites compared to the raw bamboo as revealed by both the DSC and TGA results.

Novel β-Ti35Zr28Nb alloy scaffolds manufactured using selective laser melting for bone implant applications

Titanium (Ti) based tissue engineering scaffolds can be used to repair damaged bone. However, successful orthopedic applications of these scaffolds rely on their ability to mimic the mechanical properties of trabecular bone. Selective laser melting (SLM) was used to manufacture scaffolds of a new β-Ti35Zr28Nb alloy for biomedical applications. Porosity values of the scaffolds were 83% for the FCCZ structure (face centered cubic unit cell with longitudinal struts) and 50% for the FBCCZ structure (face and body centered cubic unit cell with longitudinal struts). The scaffolds had an elastic modulus of ∼1 GPa and a plateau strength of 8–58 MPa, which fall within the values of trabecular bone (0.2–5 GPa for elastic modulus and 4–70 MPa for compressive strength). The SLM-manufactured β-Ti35Zr28Nb alloy showed good corrosion properties. MTS assay revealed that both the FCCZ and FBCCZ scaffolds had a cell viability similar to the control. SEM observation indicated that the osteoblast-like cells adhered, spread and grew healthily on the surface of both scaffolds after culture for 7, 14 and 28 d, demonstrating good biocompatibility. Overall, the SLM-manufactured Ti35Zr28Nb scaffolds possess promising potential as hard-tissue implant materials due to their appropriate mechanical properties, good corrosion behavior and biocompatibility. Statement of SignificanceNovel β Ti35Zr28Nb alloy scaffolds with FCCZ and FBCCZ structures were successfully fabricated by selective laser melting (SLM) for biomedical applications. The scaffolds showed values of elastic modulus of ∼1 GPa and plateau strength of 8–58 MPa, which fall within the ranges of the mechanical properties of trabecular bone. The SLM-manufactured β Ti35Zr28Nb alloy showed good corrosion properties. Both SLM-manufactured FCCZ and FBCCZ scaffolds exhibited good biocompatibility, with osteoblast-like cells attaching, growing, and spreading in a healthy way on their surfaces after culturing for different periods up to 28 d.

How the surface wettability and modulus of elasticity of the Amazonian paricá nanofibrils films are affected by the chemical changes of the natural fibers

The use of natural resources for the production of nanostructured cellulosic films of high quality could reduce pollution and raw material costs for cellulose industry. This work provides innovative information about the use of Amazonian species not explored in studies involving the production of nanostructured films, as well as the evaluation of important characteristics that may be decisive for the destination of the product. The aim of this study was to modify Schizolobium parahyba var. amazonicum (parica) waste fibers through alkaline (NaOH) and bleaching (NaClO2) treatments for cellulose nanofibrils (CNFs) production and evaluate the characteristics of the nanofibrils and the surface as well as the mechanical resistance of the films obtained. The alkaline treatment was carried out with sodium hydroxide (5% NaOH solution (w/v); 2 h), while the bleaching was performed using sodium chlorite and glacial acetic acid (1.5 g NaClO2; 10 drops of glacial acetic acid; 1 h). The treatments were performed in sequence, producing nanofibrils after alkaline treatment and after bleaching. Lignin content did not change with the alkaline treatment, but it significantly decreased with bleaching (from 26.1 to 6.8%). Hemicelluloses content decreased with the sequence of treatments. FTIR results showed that the mechanical defibrillation caused disruption of the fiber bonds. The temperature of thermal degradation observed in DTG analysis increased from the natural fibers (243 °C) to alkaline + bleached fibers (255 °C). The defibrillation process led to higher thermal stability of the alkaline + bleached nanofibrils in comparison to fibers. Moreover, films were prepared from the obtained CNFs and evaluated by the mechanical properties and surface contact angle. The mechanical properties showed values of 6.93 ± 0.18 GPa for modulus of elasticity (MOE) for the films produced from material which was submitted to the bleaching treatment. The results highlighted a more hydrophobic surface of the film produced with the CNFs generated from the bleached fibers. The results of mechanical properties showed the superiority of the films produced from the alkaline + bleached fibers.

Sub-1 nm Nanowire Based Superlattice Showing High Strength and Low Modulus.

Polymers possess special dimension-dependent processing flexibility which is always absent in inorganic materials. Traditional inorganic nanowires own similar dimensions to polymers, but usually lack near-molecular diameters and the related properties. Here we report that inorganic nanowires with sub1 nm diameter and microscale length can be electrospinningly processed into superstructures including smooth fibers and large-area mat by tuning the viscosity and surface tension of the colloidal nanowires solution. These superstructures have shown both flexible texture and excellent mechanical properties (712.5 MPa for tensile strength, 10.3 GPa for elastic modulus) while retaining properties arising from inorganic components.

Synthesis, spinning, and properties of very high molecular weight poly(acrylonitrile-co-methyl acrylate) for high performance precursors for carbon fiber

In this paper, synthesis of very high molecular weight (VHMW) polyacrylonitrile-co-methyl acrylate (PAN-co-MA) polymers with weight average molecular weights of at least 1.7 million g/mole were repeatedly achieved on a laboratory scale using emulsion polymerization. The development of a hybrid dry-jet gel solution spinning technique for the VHMW PAN-co-MA enabled continuous spinning of 100 filament count tows, 100s of meters in length. Single filaments were analyzed and tested for tensile performance. Experimentally, the hybrid spinning method coupled with VHMW polymers produced precursor fibers with excellent tensile properties, averaging 954 MPa in strength and 15.9 GPa in elastic modulus (N = 296), with small filament diameters (5 μm). Results indicate a strong correlation between decreasing filament diameter, facilitated by high molecular weight polymer, and exponentially increasing tensile properties, using a hybrid dry-jet gel spinning process.

Microstructure and mechanical properties of high-pressure sintered Al2O3/SiC nanocomposites

Abstract Al 2 O 3 /SiC nanocomposites were synthesized by high-pressure sintering using α-Al 2 O 3 and β-SiC nanopowders as the raw materials. Microstructure and mechanical properties of the sintered samples were investigated using X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Atomic Force Microscope (AFM) et al. The results indicate that high-pressure sintering is an effective sintering technique, which can densify Al 2 O 3 /SiC nanocomposites at high pressure (4.5 GPa) and relatively low temperature (1000–1230 °C). Rapid grain growth of Al 2 O 3 is mainly restrained by the separation effect of nanosized SiC grains. Grain boundary, grain boundary-intragranular and nano-nano structured Al 2 O 3 /SiC nanocomposites can be achieved by controlling the sintering temperature and β-SiC content. The highly densified Al 2 O 3 /SiC nanocomposite (AS 5 -1170) exhibits excellent mechanical properties as 429.9 GPa in elastic modulus and 30.7 GPa in nano-hardness.

Bi-phase ceramic composite using an interpenetrating network

A secondary phase has been reinforced into a porous alumina (Al2O3) matrix using an interpenetrating network (IPN) method to enhance the mechanical properties of the porous matrix. To increase the addition effect of the secondary phase into the Al2O3 matrix, two types of SiO2 precursor were used: tetraethylorthosilicate (TEOS) of the silicate type and polydimethylsiloxane (PDMS) of the siloxane type. The PDMS does not undergo a sol–gel reaction, whereas the TEOS is converted into glass-phase SiO2 by a sol–gel reaction. This means that the siloxane type has a higher conversion ratio of precursor into the glass phase of SiO2 than does the silicate type. The mechanical properties of the composites prepared using TEOS and PDMS without sodium methoxide (NaOMe) have been improved, showing 12.9±5.9 and 9.9±6.4MPa in fracture strength, respectively, and 17.2±4.6 and 15.5±6.9GPa in elastic modulus, respectively, while the mechanical properties of the porous Al2O3 matrix were 6.0±1.2MPa and 8.0±4.0GPa in fracture strength and elastic modulus, respectively. However, the mechanical properties of the composite prepared using PDMS with NaOMe were higher than those of the composite prepared using TEOS with NaOMe, showing 25.3±7.3MPa and 26.3±5.5GPa in fracture strength and elastic modulus, respectively. The increase in mechanical properties was caused by the enhancement of glassification owing to the high conversion ratio of the SiO2 precursor, in the absence of a sol–gel reaction. Consequently, bi-phase composites with reasonable properties have been successfully prepared through the IPN method using inorganic precursors.

Nanomechanical properties of dental resin-composites

ObjectiveTo determine by nanoindentation the hardness and elastic modulus of resin-composites, including a series with systematically varied filler loading, plus other representative materials that fall into the categories of flowable, bulk-fill and conventional nano-hybrid types. MethodsTen dental resin-composites: three flowable, three bulk-fill and four conventional were investigated using nanoindentation. Disc specimens (15mm×2mm) were prepared from each material using a metallic mold. Specimens were irradiated in the mold at top and bottom surfaces in multiple overlapping points (40s each) with light curing unit at 650mW/cm2. Specimens were then mounted in 3cm diameter phenolic ring forms and embedded in a self-curing polystyrene resin. After grinding and polishing, specimens were stored in distilled water at 37°C for 7 days. Specimens were investigated using an Agilent Technologies XP nanoindenter equipped with a Berkovich diamond tip (100nm radius). Each specimen was loaded at one loading rate and three different unloading rates (at room temperature) with thirty indentations, per unloading rate. The maximum load applied by the nanoindenter to examine the specimens was 10mN. ResultsDependent on the type of the resin-composite material, the mean values ranged from 0.73GPa to 1.60GPa for nanohardness and from 14.44GPa to 24.07GPa for elastic modulus. There was a significant positive non-linear correlation between elastic modulus and nanohardness (r2=0.88). Nonlinear regression revealed a significant positive correlation (r2=0.62) between elastic moduli and filler loading and a non-significant correlation (r2=0.50) between nanohardness and filler loading of the studied materials. Varying the unloading rates showed no consistent effect on the elastic modulus and nanohardness of the studied materials. SignificanceFor a specific resin matrix, both elastic moduli and nanohardness correlated positively with filler loading. For the resin-composites investigated, the group-average elastic moduli and nanohardnesses for bulk-fill and flowable materials were lower than those for conventional nano-hybrid composites.

Synthesis, microstructure and mechanical properties of reaction-infiltrated TiB 2–SiC–Si composites

TiB 2–C preforms formed with different compositions and processing parameters were reactively infiltrated by Si melts at 1450 °C to fabricate TiB 2–SiC–Si composites. Phase constituent and microstructure of these composites were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The resulting composites are generally composed of TiB 2 and reaction-formed β-SiC major phases, together with a quantity of residual Si. Unreacted carbon is detected in the samples with a starting composition of 2TiB 2 + 1C formed at higher pressure and in all of the ones at the composition of 1TiB 2 + 1C. The distribution of these phases is fairly homogeneous in microstructure. TiB 2–SiC–Si composites show good mechanical properties, with representative values of 19.9 GPa in hardness, 395 GPa in elastic modulus, 3.5 MPa m 1/2 in fracture toughness and 604 MPa in bending strength. The primary toughening and strengthening mechanism is attributed to the crack deflection of TiB 2 particles.

Technological Characterization of Cupressus spp. Wood

The objectives of the present study were to determine anatomical characteristics, mechanical properties and natural durability to two fungi types [Gloeophyllum trabeum (Persoon ex Fries) Murrill and Trametes versicolor (Linnaeus ex Fries)Pilat] for cypress wood (Cupressus spp.). The wood has straight grain, brown to white color, medium texture, and moderate luster. It also showed medium to low density, low shrinkage, and moderate dimensional stability. Lignin content was relatively high, whereas extractive content was low. Cupressus spp. showed static bending properties of 4.1 GPa for modulus of elasticity; 91.0 MPa for modulus of rupture; 1.8 MPa for internal bond; and 6357 and 4039 N for end and side Janka hardness, respectively. All mechanical properties, in air-dry condition, were similar to those described to cypresses and some Amazonian hardwood species. Cypress wood was ranked as highly resistant to the brown-rot fungus Gloeophyllum trabeum and to the white-rot fungus Trametes versicolor, making it suitable for interior and exterior uses and high humidity environment.

Study of the surface hardness and modulus of elasticity of conventional and microwave-cured acrylic resins

The aim of this study was to evaluate the following acrylic resins: Clássico, QC-20 and Lucitone, recommended specifically for thermal polymerization, and Acron MC and VIPI-WAVE, made for polymerization by microwave energy. The resins were evaluated regarding their surface nanohardness and modulus of elasticity, while varying the polymerization time recommended by the manufacturer. They were also compared as to the presence of water absorbed by the samples. The technique used was nanoindentation, using the Nano Indenter XP, MTS. According to an intra-group analysis, when using the polymerization time recommended by the manufacturer, a variation of 0.14 to 0.23 GPa for nanohardness and 2.61 to 3.73 GPa for modulus of elasticity was observed for the thermally polymerized resins. The variation for the resins made for polymerization by microwave energy was 0.15 to 0.22 GPa for nanohardness and 2.94 to 3.73 GPa for modulus of elasticity. The conclusion was that the Classico resin presented higher nanohardness and higher modulus of elasticity values when compared to those of the same group, while Acron MC presented the highest values for the same characteristics when compared to those of the same group. The water absorption evaluation showed that all the thermal polymerization resins, except for Lucitone, presented significant nanohardness differences when submitted to dehydration or rehydration, while only Acron MC presented no significant differences when submitted to a double polymerization time. Regarding the modulus of elasticity, it was observed that all the tested materials and products, except for Lucitone, showed a significant increase in modulus of elasticity when submitted to a lack of hydration.

Inheritance and Genetic Gain in Wood Stiffness in Radiata Pine Assessed Acoustically in Young Standing Trees

AbstractWood stiffness, measured in terms of its modulus of elasticity (MoE) is an important characteristic of radiata pine for structural products. To select high stiffness radiata pine for breeding purpose, rapid, inexpensive methods for measuring wood stiffness are desirable. In this study, we explored acoustic instruments to measure stiffness of young standing trees in radiata pine and examined inheritance and genetic gain for stiffness in an Australian national breeding program. Time of flight of sound waves was recorded in standing trees in two progeny trials, one in eastern Victoria (Flynn) aged 8 years and the other in South Australia (Kromelite) aged 7 years. Average time of flight at Kromelite was higher than at Flynn, (519 μs/metre compared to 463 μs/metre) which corresponds to 3.7 GPa and 4.7 GPa for MoE, respectively. Heritability for time of flight was higher at Flynn (h2= 0.67 ± 0.10) than at Kromelite (h2= 0.30 ± 0.14). Selection of the best 10% for time of flight based on pooled data would result in 21% genetic gain in wood stiffness.

Fresh-wood bending: linking the mechanical and growth properties of a Norway spruce stem

To provide data and methods for analyzing stem mechanics, we investigated bending, density and growth characteristics of 207 specimens of fresh wood from different heights and radial positions of the stem of one mature Norway spruce (Picea abies L. Karst.) tree. From the shape of each stress-strain curve, which was calculated from bending tests that accounted for shear deformation, we determined the modulus of elasticity (MOE), the modulus of rupture (MOR), the completeness of the material, an idealized stress-strain curve and the work involved in bending. In general, all mechanical properties increased with distance from the pith, with values in the ranges of 5.7-18 GPa for MOE, 23-90 MPa for MOR and 370-630 and 430-1100 kg m(-3) for dry and fresh wood densities, respectively. The first three properties generally decreased with stem height, whereas fresh wood density increased. Multiple regression equations were calculated, relating MOR, MOE and dry wood density to growth properties. We applied these equations to the growth of the entire stem and considered the annual rings as superimposed cylindrical shells, resulting in stem-section values of MOE, MOR and dry and fresh densities as a function of stem height and cambial age. The standing tree exhibits an inner stem structure that is well designed for bending, especially at a mature stage.