Experimental Study of the Flexural and Compression Performance of an Innovative Pultruded Glass-Fiber-Reinforced Polymer-Wood Composite Profile

The plate of a pultruded fiber-reinforced polymer or fiber-reinforced plastic (FRP) profile produced via a pultrusion process is likely to undergo local buckling and cracking along the fiber direction under an external load. In this study, we constructed a pultruded glass-fiber-reinforced polymer-light wood composite (PGWC) profile to explore its mechanical performance. A rectangular cross-sectional PGWC profile was fabricated with a paulownia wood core, alkali-free glass fiber filaments, and unsaturated phthalate resin. Three-point bending and short column axial compression tests were conducted. Then, the stress calculation for the PGWC profile in the bending and axial compression tests was performed using the Timoshenko beam theory and the composite component analysis method to derive the flexural and axial compression rigidity of the profile during the elastic stress stage. The flexural capacity for this type of PGWC profile is 3.3-fold the sum of the flexural capacities of the wood core and the glass-fiber-reinforced polymer (GFRP) shell. The equivalent flexural rigidity is 1.5-fold the summed flexural rigidity of the wood core and GFRP shell. The maximum axial compressive bearing capacity for this type of PGWC profile can reach 1.79-fold the sum of those of the wood core and GFRP shell, and its elastic flexural rigidity is 1.2-fold the sum of their rigidities. These results indicate that in PGWC profiles, GFRP and wood materials have a positive combined effect. This study produced a pultruded composite material product with excellent mechanical performance for application in structures that require a large bearing capacity.     

Life Cycle Assessment of Novel Aircraft Interior Panels Made from Renewable or Recyclable Polymers with Natural Fiber Reinforcements and Non‐Halogenated Flame Retardants

A comprehensive life cycle assessment of panels for aircraft interiors was conducted, including both a conventional glass fiber‐reinforced panel and different novel sustainable panels. The conventional panel is made of a glass fiber‐reinforced thermoset composite with halogenated flame retardant, whereas the sustainable panels are made of renewable or recyclable polymers, natural fiber reinforcements, and nonhalogenated flame retardants. Four different sustainable panels were investigated: a geopolymer‐based panel; a linseed‐oil–based biopolymer panel; and two thermoplastic panels, one with polypropylene (PP) and another with polylactic acid (PLA). All of the sustainable panels were developed to fulfil fire resistance requirements and to be lighter than the conventional panels in order to reduce fuel consumption and air pollutant emissions from the aircraft. The environmental impacts associated with energy consumption and air emissions were assessed, as well as other environmental impacts resulting from the extraction and processing of materials, transportation of materials and waste, panel manufacturing, use, maintenance, and end of life (EoL). All the sustainable panels showed better environmental performance than the conventional panel. The overall impacts of the sustainable panels were offset by the environmental benefits in the use stage attributed to weight reduction. One square meter of the novel panels could save to 6,000 kilograms of carbon dioxide equivalents. The break‐even point (in months) at which the use of sustainable panels would yield an environmental benefit relative to the impacts arising in production and EoL was as follows: 1.2 for the geopolymer panel; 1.7 for the biopolymer panel; 10.4 for the PLA panel; and 54.5 for the PP panel.     

Mechanical loading of orthodontic miniscrews - significance and problems: an experimental study

Orthodontic miniscrews are exposed to three mechanical loading phases during clinical use: torsional loading upon insertion, flexural loading during anchorage function, and torsional loading upon removal. The aim of this study was to simulate clinical loading conditions for different types of orthodontic miniscrews in vitro to quantify the effects of combined torsional and bending stress. Various orthodontic miniscrew systems (Lomas, Dual-top, Aarhus anchorage, Tomas-pin and T.I.T.A.N.-pin) comprising 10 samples each were subjected to the following loading sequences in vitro: a torsional load corresponding to manual insertion with limited torque; and flexural loading at two different insertion depths. For all screw systems with torsional pre-loading (simulating insertion), subsequent flexural loading (simulating anchorage) yielded permanent deformations of approximately 0.15-0.25 mm, depending on the insertion depth. Since EDX analysis revealed comparable elemental compositions for the different screw systems, the differences in mechanical properties are attributed to screw design. Torsional loading during screw insertion may cause premature mechanical weakening and needs to be minimized. Unless fully inserted, screws show pronounced plastic deformation and hence fracture risk under subsequent flexural loading.     

Polymer-based composite hip prostheses

A composite hip prosthesis (CHP) made from poly(ether-imide) reinforced with carbon and glass fibres was manufactured and characterized. The main objective of the study was to evaluate the effect of fibre organization on the mechanical properties of the composite femoral implant and compare with the bone. A stacking sequence of drop-off plies of carbon/glass fibres reinforcing poly(ether-imide) (PEI) constitutes a symmetrical and balanced CHP. The hip was manufactured according to the finite element modelling (FEM) design and using the compression moulding and water-jet technologies. The measured stress-strain data according to tensile, flexural and torsional tests showed agreement with the numerical calculation. Young's modulus and the strength in tension are uniform along the stem axis (40 GPa and 600 MPa, respectively) while the elastic modulus in bending varies from 10 to 60 GPa in the tip-head direction. The composite stem showed a linear load-displacement relation up to 4500 N without breaking. Mechanical behaviour of the CHP is compared to that of a canine femur. Comparison with metal prostheses has also been undertaken. CHPs control stress-strain distributions, and hence the mechanical signals to bone, through a material-structure design.     

Deformation mechanisms in nanotwinned γ-TiAl by molecular dynamics simulation

ABSTRACT

In this work, the plastic deformation mechanisms and fracture toughness of nanotwinned γ-TiAl with different twin boundary (TB) spacing are investigated by using molecular dynamics simulation. The simulation results reveal that there are pronounced shifts in the mechanical behaviour of nanotwinned γ-TiAl when the TB spacing is 3.50, 4.20 and 4.90?nm. In addition, the variation of the dislocation density with strain at these three TB spacing illustrates that a smaller TB spacing induces a higher dislocation density. Different TB spacing has an influence on the dislocation behaviour. The dislocation pile-up, dislocation–dislocation, dislocation–twin and twin–twin reactions, hierarchical twins including their generation and density, step formation, dislocation emission from steps and TB migration are the main plastic deformation mechanisms. The results also show that TB migration, twinning formation and interaction of crack and TB dominate the deformation mechanism of nanotwinned γ-TiAl with crack. The generation of hierarchical twins, lower distance between crack surface plane and twin plane, dislocation–twin, twin–twin interaction and crack deflection increase the fracture toughness of nanotwinned γ-TiAl.     

Plane penetration of uterine muscle by intrauterine shields

A finite element approach is used to predict stress and deformation states of uterine muscle tissue under plane strain indentation by a flexible shield. Realistic, one-dimensional "punch" elements at the shield edges assure that muscle shear stresses remain bounded within experimentally measured values. For typical tissue, bearing pressure, deformation flow fields and edge slip stresses leading to tissue damage are calculated. Penetration depth to shield width ratios are up to 3.0. A piecewise linear, elastic approximation to the highly variable, nonlinear mechanical behavior of the tissue is used. Results are applied to the prediction of possible tissue damage by a flexible shield intrauterine contraceptive device, in place and in equilibrium with typical multiparous uteri.     

An experimental and computational analysis of primary cilia deflection under fluid flow

In this study we have developed a novel model of the deflection of primary cilia experiencing fluid flow accounting for phenomena not previously considered. Specifically, we developed a large rotation formulation that accounts for rotation at the base of the cilium, the initial shape of the cilium and fluid drag at high deflection angles. We utilised this model to analyse full 3D data-sets of primary cilia deflecting under fluid flow acquired with high-speed confocal microscopy. We found a wide variety of previously unreported bending shapes and behaviours. We also analysed post-flow relaxation patterns. Results from our combined experimental and theoretical approach suggest that the average flexural rigidity of primary cilia might be higher than previously reported (Schwartz et al. 1997, Am J Physiol. 272(1 Pt 2):F132–F138). In addition our findings indicate that the mechanics of primary cilia are richly varied and mechanisms may exist to alter their mechanical behaviour.     

Improved recognition of figures containing fluorescence microscope images in online journal articles using graphical models

MOTIVATION: There is extensive interest in automating the collection, organization and analysis of biological data. Data in the form of images in online literature present special challenges for such efforts. The first steps in understanding the contents of a figure are decomposing it into panels and determining the type of each panel. In biological literature, panel types include many kinds of images collected by different techniques, such as photographs of gels or images from microscopes. We have previously described the SLIF system (http://slif.cbi.cmu.edu) that identifies panels containing fluorescence microscope images among figures in online journal articles as a prelude to further analysis of the subcellular patterns in such images. This system contains a pretrained classifier that uses image features to assign a type (class) to each separate panel. However, the types of panels in a figure are often correlated, so that we can consider the class of a panel to be dependent not only on its own features but also on the types of the other panels in a figure. RESULTS: In this article, we introduce the use of a type of probabilistic graphical model, a factor graph, to represent the structured information about the images in a figure, and permit more robust and accurate inference about their types. We obtain significant improvement over results for considering panels separately. AVAILABILITY: The code and data used for the experiments described here are available from http://murphylab.web.cmu.edu/software.     

A water drop-shaped slingshot in plants: geometry and mechanics in the explosive seed dispersal of Orixa japonica (Rutaceae)

Background and AimsIn angiosperms, many species disperse their seeds autonomously by rapid movement of the pericarp. The fruits of these species often have long rod- or long plate-shaped pericarps, which are suitable for ejecting seeds during fruit dehiscence by bending or coiling. However, here we show that fruit with a completely different shape can also rely on pericarp movement to disperse seeds explosively, as in Orixa japonica.MethodsFruit morphology was observed by hard tissue sectioning, scanning electron microscopy and micro-computed tomography, and the seed dispersal process was analysed using a high-speed camera. Comparisons were made of the geometric characteristics of pericarps before and after fruit dehiscence, and the mechanical process of pericarp movement was simulated with the aid of the finite element model.Key ResultsDuring fruit dehydration, the water drop-shaped endocarp of O. japonica with sandwich structure produced two-way bending deformation and cracking, and its width increased more than three-fold before opening. Meanwhile the same shaped exocarp with uniform structure could only produce small passive deformation under relatively large external forces. The endocarp forced the exocarp to open by hygroscopic movement before seed launching, and the exocarp provided the acceleration for seed launching through a reaction force.ConclusionsTwo layers of water drop-shaped pericarp in O. japonica form a structure similar to a slingshot, which launches the seed at high speed during fruit dehiscence. The results suggest that plants with explosive seed dispersal appear to have a wide variety of fruit morphology, and through a combination of different external shapes and internal structures, they are able to move rapidly using many sophisticated mechanisms.     

Flexural properties of repaired heat‐polymerising acrylic resin after wetting with monomer and acetone

doi:10.1111/j.1741‐2358.2009.00321.x
Flexural properties of repaired heat‐polymerising acrylic resin after wetting with monomer and acetone Objectives: Repair strength can be improved by treating fractured surfaces of a denture. Background: This study investigated flexural properties of heat‐polymerised acrylic resin specimens repaired with auto‐polymerising and visible light curing (VLC) resins after the repair surfaces were wetted with monomers or acetone. Materials and Methods: Fifty‐four specimens (65 × 10 × 2.5 mm) were prepared and 48 of them were sectioned to simulate denture fracture. Butt‐joint designed repair surfaces were wetted with heat‐, auto‐polymerising monomers and acetone for 180 s and repaired with auto‐polymerising and VLC resins. After repairs, specimens were subjected to three‐point bending test and flexural strength, strain, fracture load, modulus of elasticity and deflection values were recorded. Data were analysed with Student t and LSD tests (p ≤ 0.05). Results: Overall flexural strength, strain, fracture load and deflection values of specimens repaired with VLC resin were significantly higher than the specimens repaired with auto‐polymerising resin for all types of wetting agent (p < 0.05). Within the wetting agents, heat‐ and auto‐polymerising monomers produced the best mechanical properties, while wetting with acetone did not provide superior effect over both monomers. Conclusion: In clinical use, wetting the repair surfaces may result in stronger repairs. The use of bonding agent in VLC resin repairs in combination with wetting agent results in improved flexural properties.     

Pole-vaulting: identification of the pole local bending rigidities by an updating technique

The development of composite material poles since 1960 has played a prominent part in performance improvement in pole-vaulting. Previous studies devoted to pole-vaulting models were based on constant mechanical characteristics. It is thus necessary to identify the local bending rigidities of the pole to build realistic pole-vaulting models. Updating methods developed for dynamic structure studies allow us to describe local mechanical characteristics. These methods are based on the comparison between experimental results and those determined numerically by finite element models. This study presents an adaptation of these methods to determine the local bending rigidities of the pole. The updating technique is validated by a deflection test of a homogeneous beam. Then, a study of the model sensitivity is carried out to investigate the procedure robustness. Finally, the updating method is applied to an old design pole and to a recent one. The results obtained vary greatly from one pole to the other; they highlight the evolutions in pole design.     

Twist-to-Bend Ratios and Cross-Sectional Shapes of Petioles and Stems

Two structural properties, resistance to twisting (torsionalrigidity or torsional stiffness, GJ) and resistance to bending(flexural rigidity or flexural stiffness, El), were measuredon a variety of herbaceous stems and petioles. Specimens withnon-circular cross-sections had higher values of the ratio ofEl to GJ that is, such specimens were relatively more flexiblein twisting than in bending. But both kinds had higher ratiosthan those that characterize simple, isotropic materials, andthus both structural and material factors contribute to achievinga high twist-to-bend ratio. The composite property expressedas the dimensionless variable EI/GJ appears to be a functionallyrelevant parameter in many biological situations. Key words: Stems, petioles, flexural rigidity, torsional rigidity, biomechanics     

Highly Stretchable,Sparse, Metallized Nanofiber Webs as Thin,Transferrable Transparent Conductors

The need for transparent conductors (TCs) that are capable of withstanding high mechanical deformation in comparison to the brittle indium tin oxide (ITO) films is paramount for roll‐to‐roll production of flexible and stretchable displays, signage systems, lighting devices and solar panels with stringent weatherability requirements. This paper reports a highly stretchable TC comprising of a web of core‐shell nanofibers, which mimics the fibrous structure of natural systems such as veins of a leaf or nerve systems. The TC web demonstrates high transparency, low sheet resistance, and unprecedented stretchability and stability over repeated stretching. The nanofiber TC web can be transferred to different substrates, which is manifested by the transfer onto an organic solar cell, demonstrating a photovoltaic performance comparable to that of a device with an ITO electrode. This work presents a technological platform, scalable for the manufacturing of large area transparent conductors for flexible and stretchable displays, electronics and solar cells on unconventional substrates such as rubber, fabric and paper.     

Biomimetic Composite Structural T-joints

Biological structural fixed joints exhibit unique attributes,including highly optimized fiber paths which minimize stress concentrations.In addition,since the joints consist of continuous,uncut fiber architectures,the joints enable the organism to transport information and chemicals from one part of the body to the other.To the contrary,sections of man-made composite material structures are often joined using bolted or bonded joints,which involve low strength and high stress concentrations.These methods are also expensive to achieve.Additional functions such as fluid transport,electrical signal delivery,and thermal conductivity across the joints typically require parasitic tubes,wires,and attachment clips.By using the biomimetic methods,we seek to overcome the limitations which are present in the conventional methods. In the present work,biomimetic co-cured composite sandwich T-joints were constructed using unidirectional glass fiber,epoxy resin,and structural foam.The joints were fabricated using the wet lay-up vacuum bag resin infusion method.Foam sandwich T-joints with multiple continuous fiber architectures and sandwich foam thickness were prepared.The designs were tested in quasi-static bending using a mechanical load frame.The significantweight savings using the biomimetic approaches is discussed,as well as a comparison of failure modes versus architecture is described.     

Possibility of using waste tire composites reinforced with rice straw as construction materials

Agricultural lignocellulosic fiber (rice straw)-waste tire particle composite boards were manufactured for use as insulation boards in construction, using the same method as that used in the wood-based panel industry. The manufacturing parameters were: a specific gravity of 0.8 and a rice straw content (10/90, 20/80 and 30/70 by wt.% of rice straw/waste tire particle). A commercial polyurethane adhesive for rubber was used as the composite binder. The water proof, water absorption and thickness swelling properties of the composite boards were better than those of wood particleboard. Furthermore, the flexibility and flexural properties of the composite boards were superior to those of other wood-based panel products. The composite boards also demonstrated good acoustical insulation, electrical insulation, anti-caustic and anti-rot properties. These boards can be used to prevent impact damage, are easily modifiable and are inexpensive. They are able to be used as a substitute for insulation boards and other flexural materials in construction.     

An artificial muscle actuator for biomimetic underwater propulsors

In this paper, we introduce the analytical framework of the modeling dynamic characteristics of a soft artificial muscle actuator for aquatic propulsor applications. The artificial muscle used for this underwater application is an ionic polymer-metal composite (IPMC) which can generate bending motion in aquatic environments. The inputs of the model are the voltages applied to multiple IPMCs, and the output can be either the shape of the actuators or the thrust force generated from the interaction between dynamic actuator motions and surrounding water. In order to determine the relationship between the input voltages and the bending moments, the simplified RC model is used, and the mechanical beam theory is used for the bending motion of IPMC actuators. Also, the hydrodynamic forces exerted on an actuator as it moves relative to the surrounding medium or water are added to the equations of motion to study the effect of actuator bending on the thrust force generation. The proposed method can be used for modeling the general bending type artificial muscle actuator in a single or segmented form operating in the water. The segmented design has more flexibility in controlling the shape of the actuator when compared with the single form, especially in generating undulatory waves. Considering an inherent nature of large deformations in the IPMC actuator, a large deflection beam model has been developed and integrated with the electrical RC model and hydrodynamic forces to develop the state space model of the actuator system. The model was validated against existing experimental data.     

A comparison of pectoral fin ray morphology and its impact on fin ray flexural stiffness in labriform swimmers

The organization of tissues in appendages often affects their mechanical properties and function. In the fish family Labridae, swimming behavior is associated with pectoral fin flexural stiffness and morphology, where fins range on a continuum from stiff to relatively flexible fins. Across this diversity, pectoral fin flexural stiffness decreases exponentially along the length of any given fin ray, and ray stiffness decreases along the chord of the fin from the leading to trailing edge. In this study, we examine the morphological properties of fin rays, including the effective modulus in bending (E), second moment of area (I), segmentation, and branching patterns, and their impact on fin ray stiffness. We quantify intrinsic pectoral fin ray stiffness in similarly sized fins of two closely related species that employ fins of divergent mechanics, the flapping Gomphosus varius and the rowing Halichoeres bivittatus. While segmentation patterns and E were similar between species, measurements of I and the number of fin ray branch nodes were greater in G. varius than in H. bivittatus. A multiple regression model found that of these variables, I was always significantly correlated with fin ray flexural stiffness and that variation in I always explained the majority of the variation in flexural stiffness. Thus, while most of the morphological variables quantified in this study correlate with fin ray flexural stiffness, second moment of area is the greatest factor contributing to variation in flexural stiffness. Further, interspecific variation in fin ray branching pattern could be used as a means of tuning the effective stiffness of the fin webbing to differences in swimming behavior and hydrodynamics. The comparison of these results to other systems begins to unveil fundamental morphological features of biological beams and yields insight into the role of mechanical properties in fin deformation for aquatic locomotion.     

Actuating Mechanism and Design of a Cylindrical Traveling Wave Ultrasonic Motor Using Cantilever Type Composite Transducer

Background

Ultrasonic motors (USM) are based on the concept of driving the rotor by a mechanical vibration excited on the stator via piezoelectric effect. USM exhibit merits such as simple structure, quick response, quiet operation, self-locking when power off, nonelectromagnetic radiation and higher position accuracy.

Principal Findings

A cylindrical type traveling wave ultrasonic motor using cantilever type composite transducer was proposed in this paper. There are two cantilevers on the outside surface of cylinder, four longitudinal PZT ceramics are set between the cantilevers, and four bending PZT ceramics are set on each outside surface of cantilevers. Two degenerate flexural vibration modes spatially and temporally orthogonal to each other in the cylinder are excited by the composite transducer. In this new design, a single transducer can excite a flexural traveling wave in the cylinder. Thus, elliptical motions are achieved on the teeth. The actuating mechanism of proposed motor was analyzed. The stator was designed with FEM. The two vibration modes of stator were degenerated. Transient analysis was developed to gain the vibration characteristic of stator, and results indicate the motion trajectories of nodes on the teeth are nearly ellipses.

Conclusions

The study results verify the feasibility of the proposed design. The wave excited in the cylinder isn''t an ideal traveling wave, and the vibration amplitudes are inconsistent. The distortion of traveling wave is generated by the deformation of bending vibration mode of cylinder, which is caused by the coupling effect between the cylinder and transducer. Analysis results also prove that the objective motions of nodes on the teeth are three-dimensional vibrations. But, the vibration in axial direction is minute compared with the vibrations in circumferential and radial direction. The results of this paper can guide the development of this new type of motor.     

A highly informative SNP linkage panel for human genetic studies

We have developed a highly informative set of single-nucleotide polymorphism (SNP) assays designed for linkage mapping of the human genome. These assays were developed on a robust multiplexed assay system to provide a combination of very high accuracy and data completeness with high throughput for linkage studies. The linkage panel is comprised of approximately 4,700 SNPs with 0.39 average minor allele frequency and 624-kb average spacing. Based on almost 2 million genotypes, data quality was shown to be extremely high, with a 99.94% call rate, >99.99% reproducibility and 99.995% genotypes consistent with mendelian inheritance. We constructed a genetic map with an average 1.5-cM resolution using series of 28 CEPH pedigrees. The relative information content of this panel was higher than those of commonly used STR marker panels. The potent combination of this SNP linkage panel with the multiplexed assay system provides a previously unattainable level of performance for linkage studies.