Load-bearing Conditions Research Articles

Highly Interfacial Active Gemini Surfactants as Simple and Versatile Emulsifiers for Stabilizing, Lubricating and Structuring Liquids.

To date, locking the shape of liquids into non-equilibrium states usually relies on jamming nanoparticle surfactants at an oil/water interface. Here we show that a synthetic water-soluble zwitterionic Gemini surfactant can serve as an alternative to nanoparticle surfactants for stabilizing, structuring and additionally lubricating liquids. By having a high binding energy comparable to amphiphilic nanoparticles at the paraffin oil/water interface, the surfactant can attain near-zero interfacial tensions and ultrahigh surface coverages after spontaneous adsorption. Owing to the strong association between neighboring surfactant molecules, closely packed monolayers with high mechanical elasticity can be generated at the oil/water interface, thus allowing the surfactant to produce not only ultra-stable emulsions but also structured liquids with various geometries by using extrusion printing and 3D printing techniques. By undergoing tribochemical reactions at its sulfonic terminus, the surfactant can endow the resultant emulsions with favorable lubricity even under high load-bearing conditions. Our study may provide new insights into creating complex liquid devices and new-generation lubricants capable of combining the characteristics of both liquid and solid lubricants.

Porous Ti3SiC2 ceramics with improved osteogenic functions via biomineralization as load-bearing bone implants

Ti3SiC2 ceramics exhibit excellent mechanical properties and good biocompatibility, rendering them promising bone substitutes for load-bearing conditions. However, the bone integration and osteogenic ability of Ti3SiC2 ceramics remain unclear. Herein, porous Ti3SiC2 ceramics were prepared and systematically investigated as bone scaffolds. The Ti3SiC2 scaffolds with a porosity of 62.9 % ± 2.5 % showed high compressive strength ∼68.12 ± 4.33 MPa. Silicon hydroxyl groups formed on the surface of Ti3SiC2 after soaking in simulated body fluid, which played a critical role in the apatite mineralization of the scaffolds. Biomineralization of Ti3SiC2 scaffolds was found when implanted subcutaneously in the rat dorsum for 2 weeks, demonstrating good osteogenesis ability. The apatite mineralization of the Ti3SiC2 scaffold facilitated the polarization of RAW264.7 cells from M1 to M2 phenotype, which also promoted the differentiation of MC3T3-E1 cells. The porous Ti3SiC2 scaffolds improved osteointegration and bone regeneration after implantation in rabbit femoral defects. Impressively, the number of the newly formed trabeculae in the Ti3SiC2 group was three times of the control group after implantation for 8 weeks, showing excellent bone defect repair. This work demonstrates that Ti3SiC2 implants with improved biological functions likely via in-situ biomineralization are promising candidates for bone regeneration.

Stress-Adaptive Stiffening Structures Inspired by Diatoms: A Parametric Solution for Lightweight Surfaces.

The intricate and highly complex morphologies of diatom frustules have long captured the attention of biomimetic researchers, initiating innovation in engineering solutions. This study investigates the potential of diatom-inspired surface stiffeners to determine whether the introduced innovative strategy is a viable alternative for addressing engineering challenges demanding enhanced stiffness. This interdisciplinary study focuses on the computer-aided generation of stress-adaptive lightweight structures aimed at optimizing bending stiffness. Through a comprehensive microscopical analysis, morphological characteristics of diatom frustules were identified and abstracted to be applied to a reference model using computer-aided methods and simulated to analyze their mechanical behavior under load-bearing conditions. Afterwards, the models are compared against a conventional engineering approach. The most promising biomimetic approach is successfully automated, extending its applicability to non-planar surfaces and diverse boundary conditions. It yields notable improvement in bending stiffness, which manifests in a decrease of displacement by approximately 93% in comparison to the reference model with an equivalent total mass. Nonetheless, for the specific load case considered, the engineering approach yields the least displacement. Although certain applications may favor conventional methods, the presented approach holds promise for scenarios subjected to varying stresses, necessitating lightweight and robust solutions.

Reliability of depleted cement–ground slab with waste granodiorite dust admixture on semi-saturated substrate

There are many types of pavements for roads. For technical roads, one of the most effective and economically advantageous pavement types is chemically stabilized soil pavement. When designing a pavement made of soil admixed with binders, it is necessary to meet the load-bearing conditions while considering the effects of environmental factors. The aims of this study were to optimize the strength parameters of pavement, minimize negative environmental effects, minimize the carbon footprint, and simultaneously dispose of mineral waste materials from the production of asphalt mixes for roads. After testing the strengths of samples admixed with cement or with reduced cement content and the addition of dust, questions arose as to how both materials affect the reliability of the pavement structure. Samples of soil doped with cement and dust were subjected to reliability analyses. Abaqus software with a three-dimensional subgrade model was used for a comparative analysis. The substrates under soil stabilization slabs were subjected to varying saturation states, which affected their vulnerability. In this study, the changes in the saturation characteristics of the subsoils associated with different types of climatic interactions were simulated. The Darcy–Buckingham law was used to describe the flow of liquids through the subsoil. Pavement reliability calculations were performed for a multidimensional space of random variables. The results served as an interesting starting point for recommendations to decrease the use of energy-intensive materials, increase the reuse of waste, and reduce the effects of the strengthening process on the environment.

DOES KINEMATICALLY ALIGNED TOTAL KNEE ARTHROPLASTY RESTORE NATIVE JOINT LAXITY BETTER THAN MECHANICAL ALIGNMENT? A CADAVERIC STUDY

Mechanical alignment (MA) in total knee arthroplasty (TKA), although considered the gold standard, reportedly has up to 25% of patients expressing post-operative dissatisfaction. Biomechanical outcomes following kinematic alignment (KA) in TKA, developed to restore native joint alignment, remain unclear. Without a clear consensus for the optimal alignment strategy during TKA, the purpose of this study was to conduct a paired biomechanical comparison of MA and KA in TKA by experimentally quantifying joint laxity and medial collateral ligament (MCL) strain.14 bilateral native fresh-frozen cadaveric lower limbs underwent medially-stabilised TKA (GMK Sphere, Medacta, Switzerland) using computed CT-based subject-specific guides, with KA and MA performed on left and right legs, respectively. Each specimen was subjected to sensor-controlled mediolateral laxity tests. A handheld force sensor (Mark-10, USA) was used to generate an abduction-adduction moment of 10Nm at the knee at fixed flexion angles (0°, 30°, 60°, 90°). A digital image correlation system was used to compute the strain on the superficial medial collateral ligament. A six-camera optical motion capture system (Vicon MX+, UK) was used to acquire kinematics using a pre-defined CT-based anatomical coordinate system. A linear mixed model and Tukey's posthoc test were performed to compare native, KA and MA conditions (p<0.05).Unlike MA, medial joint laxity in KA was similar to the native condition; however, no significant difference was found at any flexion angle (p>0.08). Likewise, KA was comparable with the native condition for lateral joint laxity, except at 30°, and no statistical difference was observed. Although joint laxity in MA seemed lower than the native condition, this difference was significant only for 30° flexion (p=0.01). Both KA and MA exhibited smaller MCL strain at 0° and 30°; however, all conditions were similar at 60° and 90°.Medial and lateral joint laxity seemed to have been restored better following KA than MA; however, KA did not outperform MA in MCL strain, especially after mid-flexion. Although this study provides only preliminary indications regarding the optimal alignment strategy to restore native kinematics following TKA, further research in postoperative joint biomechanics for load bearing conditions is warranted.

High Strength Titanium with Fibrous Grain for Advanced Bone Regeneration.

Pure titanium is widely used in clinical implants, but its bioinert properties (poor strength and mediocre effect on bone healing) limit its use under load-bearing conditions. Modeling on the structure of collagen fibrils and specific nanocrystal plane arrangement of hydroxyapatite in the natural bone, a new type of titanium (Ti) with a highly aligned fibrous-grained (FG) microstructure is constructed. The improved attributes of FG Ti include high strength (≈950MPa), outstanding affinity to new bone growth, and tight bone-implant contact. The bone-mimicking fibrous grains induce an aligned surface topological structure conducive to forming close contact with osteoblasts and promotes the expression of osteogenic genes. Concurrently, the predominant Ti(0002) crystal plane of FG Ti induces the formation of hydrophilic anatase titanium oxide layers, which accelerate biomineralization. In conclusion, this bioinspired FG Ti not only proves to show mechanical and bone-regenerative improvements but it also provides a new strategy for the future design of metallic biomaterials.

A strategy that combines the adhesion and hydration of polydopamine to realize targeted water lubrication

Water has many natural advantages for using as an ecological lubricant in engineering. However, how to ensure the efficiency and stability of water lubricating film with low viscosity has been always the key point of practical applications. For this, a strategy is given to improve lubricating capacity of water under loads by combining the biomimetic adhesion and hydration lubrication of polydopamine (PDA). The PDA nanoparticles were polymerized and purified, and its aqueous suspensions were used to solve the difficult problem of lubrication failure when using water as lubricant. The morphology characteristics and lubrication performance of PDA nanoparticles were experimentally tested and analyzed. The results showed that PDA nanoparticles can form an adhesive-lubricating film on the copper balls and effectively reduce the tribological behaviors in rubbing processes. This strategy that combines the biomimetic adhesion and hydration lubrication of PDA provides a novel method to realize targeted hydrated film and excellent water lubrication under load bearing conditions.

A Systematic Review of the Geotechnical and Structural Behaviors of Fiber-Reinforced Polymer Composite Piles

Composite piles have emerged as a popular alternative to conventional piling materials for deep foundations and have gained significant traction as a specific type of pile due to their potential to mitigate durability issues often associated with standard piling materials. A new type of composite piles can improve structural behavior and extend service life. This research uses an inclusive review methodology to evaluate the geotechnical and structural behaviors of fiber-reinforced polymer (FRP) composite piles. Scopus was utilized to address the relevant keywords and state-of-the-art documents, and VSOviewer software was adopted to spot recurring patterns in the data using scientometric maps. Low-stiffness composite materials are a concern, according to the research work. Thus, researchers are working on confined concrete-filled FRP piles to improve the structural and geotechnical properties used in various load-bearing conditions. However, more research is required to comprehensively understand the behaviors of the studied types of composite piles. Indeed, there is a need for large-scale lab and field studies to determine how axial and lateral loads influence composite piles. This could help create guidelines for constructing the reviewed types of composite piles.

Load-bearing composite fracture-fixation devices with tailored fibre placement for toy-breed dogs

Fibre reinforced composites are attractive materials for hard tissue reconstructions, due to the high strength and low flexural modulus. However, lack of contourability in the operation theatre inhibits their clinical applications.The study presents a novel in situ contourable composite implant system for load-bearing conditions. The implant system consists of a thin bioresorbable shell with several cavities, much like bubble-wrap. The central cavity contains a semi-flexible glass fibre preform prepared using Tailored Fibre Placement method. The preform is either pre-impregnated with a light curable resin, or the resin is injected into the cavity during the surgical procedure, followed by light curing. The semi-flexible glass fibre preforms were also examined as separate devices, “miniplates”. Two types of miniplates were scrutinized, a simplified pilot design and a spatially refined, “optimized” design. The optimized miniplates were implemented as biostable and bioresorbable versions.The feasibility of the in situ contourable composite implant system was demonstrated. The potential of Tailored Fibre Placement for the semi-flexible glass fibre preforms and miniplates was confirmed in a series of biomechanical tests. However, structural optimization is required. Antebrachial fractures in toy-breeds of dogs are exemplar veterinary applications of the devices; further applications in veterinary and human patients are foreseen.

Progression of microstructural deterioration in load-bearing immobilization osteopenia.

Immobilization osteopenia is a major healthcare problem in clinical and social medicine. However, the mechanisms underlying this bone pathology caused by immobilization under load-bearing conditions are not yet fully understood. This study aimed to evaluate sequential changes to the three-dimensional microstructure of bone in load-bearing immobilization osteopenia using a fixed-limb rat model. Eight-week-old specific-pathogen-free male Wistar rats were divided into an immobilized group and a control group (n = 60 each). Hind limbs in the immobilized group were fixed using orthopedic casts with fixation periods of 1, 2, 4, 8, and 12 weeks. Feeding and weight-bearing were freely permitted. Length of the right femur was measured after each fixation period and bone microstructure was analyzed by micro-computed tomography. The architectural parameters of cortical and cancellous bone were analyzed statistically. Femoral length was significantly shorter in the immobilized group than in the control group after 2 weeks. Total area and marrow area were significantly lower in the immobilized group than in the control group from 1 to 12 weeks. Cortical bone area, cortical thickness, and polar moment of inertia decreased significantly after 2 weeks. Some cancellous bone parameters showed osteoporotic changes at 2 weeks after immobilization and the gap with the control group widened as the fixation period extended (P < 0.05). The present results indicate that load-bearing immobilization triggers early deterioration of microstructure in both cortical and cancellous bone after 2 weeks.

Microstructure and tribological properties of sputtered MoSx-W composite films supported by porous alumina aperture array

Aluminum alloys are widely used in the aerospace and automotive industries due to their high strength and low density but also suffer from poor wear resistance. The employment of stable solid lubricants on aluminum alloys will be beneficial for their service life under load-bearing conditions. In this paper, MoSx-W composite coatings were deposited on porous anodic aluminum oxide (AAO)/Al substrates. The effects of tungsten content on the film structure and friction properties were systematically investigated. It is found that tungsten exists as metallic particles within the MoSx matrix, forming a system of hardness phase reinforced soft matrix. With the increase of W content, the film morphology transforms from nano-flower-like to ball-like, associated with an obvious enhancement of film density as well as hardness. The latter prolongs the service life of MoSx films from 10 min only in untreated specimen to 88.8 min in composite sample. Finally, the improvement of wear performance upon tungsten loading was discussed in detail.

Effect of temperature on the fracture energy of adhesive layers of engineered wood

Adhesive layers in engineered wood are critical for shear stress transfer, particularly under load-bearing conditions. Though there is some data on the shear strength of the adhesive layers, there is limited data on their fracture energy and how it varies with temperature. Understanding the fracture energy could reduce the inconsistencies caused by stress singularity and crack nucleation in a shear strength testing methodology. Therefore, in this article, a 4-pointing bending test framework was used to investigate the fracture energy of the adhesive layers at different temperatures. It is found that the fracture energy of the adhesive layer bonding the 0o/90o (cross-laminated) oriented timber plies is ∼30% lesser than that of the layer bonding 0o/0o (parallel) plies. More importantly, irrespective of the arrangement/orientation of the plies, a steady decline in fracture energy is seen with increase in temperature. For instance, by ∼130oC, the fracture energy of the adhesive layer has reduced by ∼53% in a cross-laminated state and ∼39% for those plies bonded in 0o/0o orientation. Finite element analysis was also conducted based on the cohesive elements and cohesive zone model for validation of the experimentally measured fracture energy.

Foot deformation analysis with different load-bearing conditions to enhance diabetic footwear designs.

In-depth analyses of foot surface measurements upon weight bearing are crucial to understand how the dorsal and plantar surfaces of the foot deform during motion to enhance the fit of footwear, which is particularly important for diabetic patients with stringent fit requirements to redistribute the plantar weight forces. This study analyzes diabetic foot deformations under 3 different weight bearing conditions (no weight bearing, half weight bearing, and 80% weight bearing) by using a novel foot scanning method that enables efficient scanning of the dorsal and plantar surfaces of the foot simultaneously. The feet of 48 patients with diabetes mellitus (DM) are scanned. With increased load on the feet, the width of the forefoot increases by 9.7%-10.4%, height of the midfoot decreases by 15.1%-18.2%, forefoot and midfoot rotate to the medial side by 16.9%-23.9% while the rearfoot rotates to the lateral side by 15.2% simultaneously, and the plantar of the foot increases contact with the floor by 11.4%-23.0%. Gender differences in foot shape are also found between males and females, males have a broader foot than females for the same foot length. Precise anthropometric information of foot changes and deformation therefore enables adequate foot protection, fit and comfort when designing footwear. This research contributes to shoe design considerations that focus on the deformation of the foot under different loads.

The contribution of pore size and porosity of 3D printed porous titanium scaffolds to osteogenesis

Porous titanium implants were popularly fabricated to promote bone formation. A desirable porous scaffold was recommended to be with porosity of >60% or/and pore size of >300 μm for better osteointegration. However, whether the pore size and porosity could be randomly selected within the recommended values? And what is the correlation between pore size and porosity for accelerating osteointegration? In this study, porous titanium with cubic cell structure was produced by selective laser melting. The designed porosities of scaffolds with 700-μm pore size were 40%, 70% and 90%; and the pore sizes of scaffolds with 70% porosity were 400, 700 and 900 μm. The in vitro osteogenic potential and in vivo bone formation were investigated. Results showed that porosity and pore size could be tuned by altering strut size, which was further directly responsible for mechanical properties. Besides, pore size and porosity synergistically contributed to osteogenic activity in vitro and new bone formation in vivo. In regard to pore sizes herein, the optimized one for better osteogenic response and bone forming ability was ~600–700 μm (p70). Too smaller or too larger pore size might more or less hinder cellular behaviors and bone regeneration, even if both pore size (300–900 μm) and porosity (70%) were within the recommended value range. At a constant pore size (~600–700 μm), p70 and p90 with higher porosity was more conductive to biological effects, compared with p40. As a result, pore-size variation revealed more significant influence on osteogenesis, compared with variation of porosity within recommended values. However, the applicable porosity within recommended values should be designed with the consideration of specific load-bearing conditions. This study helps to provide guidance for designing porous scaffolds with appropriate mechanical strengths and effective bone-forming ability, so as to develop better custom-made bone substitutes.

Cavovarus With a Twist: Midfoot Coronal and Axial Plane Rotational Deformity in Charcot-Marie-Tooth Disease

The cavovarus deformity of Charcot-Marie-Tooth (CMT) disease is often characterized by a paradoxical relationship of hindfoot varus and forefoot valgus. The configuration of the midfoot, which links these deformities, is poorly understood. Accurate assessment of 3-dimensional alignment under physiologic loadbearing conditions is possible using weightbearing computed tomography (WBCT). This is the first study to examine the rotational deformity in the midfoot of CMT patients and, thus, provide key insights to successful correction of CMT cavovarus foot. A total of 27 WBCT scans from 21 CMT patients were compared to control WBCTs from 20 healthy unmatched adults. CMT patients with a history of bony surgery, severe degenerative joint disease, or open physes in the foot were excluded. Scans were analyzed using 3-dimensional software. Anatomic alignment of the tarsal bones was calculated relative to the anterior-posterior axis of the tibial plafond in the axial plane, and weightbearing surface in the coronal plane. Maximal rotational deformity in CMT patients occurred at the transverse tarsal joints, averaging 61 degrees of external rotation (supination), compared to 34 degrees among controls (P < .01). The talonavicular joint was also the site of peak adduction deformity in the midfoot, with an average talonavicular coverage angle measuring 12 degrees compared with -11 degrees in controls (P < .01). This 3-dimensional WBCT analysis is the first to isolate and quantify the multiplanar rotational deformity in the midfoot of CMT patients. Compared with healthy unmatched control cases, CMT patients demonstrated increased axial plane adduction and coronal plane rotation at the talonavicular (TN) joint. These findings support performing soft tissue release at the TN joint to abduct and derotate the midfoot as a first step for targeted deformity correction. Level III, retrospective case-control study.

Cavovarus with A Twist: Coronal and Axial Plane Rotational Deformity in the Midfoot of Charcot- Marie-Tooth Patients

Category:Hindfoot; Midfoot/ForefootIntroduction/Purpose:The cavovarus deformity of Charcot-Marie-Tooth (CMT) disease typically presents with hindfoot varus and forefoot valgus. This seemingly paradoxical relationship is poorly understood. Better insight into this complex three- dimensional alignment under physiologic load-bearing conditions is possible using weight-bearing computed tomography (WBCT). This is the first study to examine the extreme rotational deformity in the midfoot of CMT patients, and thereby provides a key to the successful operative correction of the CMT cavovarus foot.Methods:We retrospectively reviewed the WBCTs of patients with CMT who presented to a single surgeon. Those with history of bony surgical correction, severe degenerative joint disease, or open physes in the foot, were excluded. Scans were analyzed using three-dimensional analysis software (Disior Bonelogic) to generate axes of select bones and their relationship relative to the tibial plafond anterior-posterior axis in the axial plane. The coronal alignment of the foot involved angular measurements of the calcaneus, talar dome, midfoot and forefoot relative to the ground. We reported quantitative alignment parameters and compared the measurements to WBCT of 20 controls.Results:17 WBCT scans from 15 CMT patients (average age 24 years) met criteria for inclusion. In the axial plane, external rotation of the distal tibia accounted for the varus heel position rather than subtalar malalignment. The greatest change in axial alignment occurred between the talar neck and navicular (26 degrees). The average talonavicular (TN) medial uncoverage angle was -15 degrees for CMT patients, indicating medial overcoverage, compared to +11 degrees for controls, (p<0.01). Coronal plane analysis revealed varus rotational deformity at the calcaneus (23 degrees), a peak of 61 degrees varus across the navicular and cuboid, then compensatory rotation of the cuneiforms and metatarsals to achieve a plantigrade forefoot (11 degrees varus). In comparison, controls averaged 9 degrees coronal valgus at the calcaneus and 34 degrees varus at the naviculo-cuboid level, (p<0.01). Figure 1 shows the WBCT scans of a representative CMT patient and control case.Conclusion:This three-dimensional WBCT analysis is the first to characterize and quantify the axial and coronal rotational deformity in CMT. Axial plane deformity had a center of rotational angulation at the talonavicular joint, associated with medial ’overcoverage’ of the talar head, likely from chronic tibialis posterior over-pull. The peak coronal deformity was localized at the navicular and cuboid, which measured nearly twice as much as controls. These observations suggest dorsiflexion osteotomy of the 1st metatarsal would fail to address the coronal rotation; releases through the talonavicular joint may be necessary to abduct and de-rotate the midfoot to achieve a plantigrade foot.

Mechanical characteristics of a new type of cable-supported photovoltaic module system

Cable-supported photovoltaic (PV) modules have been proposed to replace traditional beam-supported PV modules. The new system uses suspension cables to bear the loads of the PV modules and therefore has the characteristics of a long span, light weight, strong load capacity, and adaptability to complex terrains. It provides an excellent supplement to traditional structures in special sites such as sewage treatment plants, highways, farms, fishponds, and roofs with poor load-bearing conditions. However, most of the traditional cable-supported PV systems use only two cables to support the PV modules. The settlement of the support cables due to self-weight of PV modules always reduces their power generation efficiency. Therefore, it is necessary to make a reasonable design to flatten the structures. Recently, the authors (He et al., 2020) proposed a new cable-supported PV system using three cables and four triangle brackets to form an inverted arch to reduce the vertical displacement of the PV modules. In this study, the structural characteristics of the new PV system with a span of 30 m are numerically investigated in terms of mode shapes, modal frequency, and nonlinear structural stiffness through using the finite element method. The increase of torsion stiffness when the torsion displacement rises benefits the stability of the new PV system. The load bearing capacity of the PV system is discussed under self-weight, static wind load, snow load, and their combination. The influences of row spacing, tilt angle, initial cable force, and cable diameter on the structural characteristics are further studied. The results verify that the new system has a strong load capacity and potential for wide application.

Reconstruction of bilateral ramus-condyle unit defect using custom titanium prosthesis with preservation of both condyles

BackgroundNovel technologies for management and reconstruction of complex bony defects regarding both function and facial appearance are interestingly used in maxillofacial surgery. In the current study, we demonstrated reconstruction of a bilateral ramus-condyle unit (RCU) defect while preserving both condyles by a novel designed titanium prosthesis using virtual surgical planning (VSP), computer-aided design and manufacturing (CAD/CAM), and Selective Laser Melting (SLM) technologies. Materials and methodsA 3D customized titanium prosthesis was designed for a 49 -year-old patient with bilateral mandibular aggressive central giant cell granuloma (CGCG) according to mandibular normal anatomy and structure while preserving bilateral intact condyles. Finite element study was performed to investigate the effects of new design strength and the stress shielding phenomenon. The design of macro-pores inside the body of prosthesis allowed it to act as a scaffold for bone tissue engineering under load bearing conditions. ResultsAnalysis of the strength and stress shielding phenomenon demonstrated favorable outcomes regarding the novel design. For instance, there was no stress shielding in any of the preserved condyles with regard to the size and distribution of stresses. Also, the stress distribution around the pores showed that these pores had no effect on the strength of the prosthesis. Thirty month follow-ups after reconstruction of bilateral RCU defect showed normal jaw function with a favorable facial appearance and mandibular contour. ConclusionWe design a novel patient-specific prosthesis with desirable biomechanical features for reconstruction of bilateral RCU defect after resection of the benign tumor with preservation of bilateral intact condyles.

Fire resistance of external light gauge steel framed walls clad with autoclaved aerated concrete panels

This paper presents an investigation into the fire resistance of external light gauge steel framed (LSF) walls clad with autoclaved aerated concrete (AAC) panels exposed to fire on the external side. Past research has been limited to the fire resistance of internal LSF walls clad with gypsum plasterboard on both sides. A series of experimental studies including thermal material property tests, a full-scale (3 m × 3 m) ambient capacity test of LSF wall and full-scale standard fire tests of non-load bearing and load bearing LSF walls were conducted to investigate the fire resistance of external LSF walls clad with AAC panels. Finally, a small-scale (1.2 m × 1.2 m) fire test of a wall made of AAC panels was also conducted to investigate the performance of joints between AAC panels. AAC panels with very low thermal conductivity performed exceptionally well by keeping the temperatures low for 160 min achieving a fire resistance level (FRL) of 204 min in load bearing conditions and 240 min in non-load bearing conditions. Hence, LSF walls clad with AAC panels can be used when higher FRLs are required. Experimental studies such as these on the whole system enable a good understanding of the overall fire performance of external wall systems in terms of structural adequacy and integrity instead of focusing only on the cladding.

CARBON NANOTUBES REINFORCED ZIRCONIA COMPOSITES FOR ARTFICIAL HIP JOINTS BEARING SURFACES

This research focuses on the properties and capabilities of carbon nanotubes (CNTs) as reinforcing agents in ceramic composite bearing components. The addition of CNT to pure ceramics can form composites with much better performance than conventional ceramics for various applications. The study was started from the pure ceramics in their use as a component of bearing total hip arthroplasty and the damage that occurred after implantation. The study covers factors that cause degradation of conventional ceramics introduction of properties and use of CNTs as new reinforcing agents for ceramic composite materials widely used sintering method and the heat and pressure parameters used during the sintering process to meet the standards for the manufacture of Total Hip Arthroplasty (THA) bearing component. The contact and buckling behaviors of the CNTs influence the composites friction properties. The presence of CNT until 20 wt% of CNT exhibited improve wear resistance with lower friction with the increase of weight percent. CNT reinforced ceramic coating might be capable to withstand high load-bearing conditions. Plastic deformation can be one of the critical processes in wear in the ceramics wear mechanism. Other processes are cracking and chemical reaction. The microstructures and porosity take an important role in indicating the ceramics wear properties and wear mechanisms.