Loss Of Mechanical Strength Research Articles

New Eco-Cements Made with Marabou Weed Biomass Ash

Biomass ash is currently attracting the attention of science and industry as an inexhaustible eco-friendly alternative to pozzolans traditionally used in commercial cement manufacture (fly ash, silica fume, natural/calcined pozzolan). This paper explores a new line of research into Marabou weed ash (MA), an alternative to better-known conventional agro-industry waste materials (rice husk, bagasse cane, bamboo, forest waste, etc.) produced in Cuba from an invasive plant harvested as biomass for bioenergy production. The study entailed full characterization of MA using a variety of instrumental techniques, analysis of pozzolanic reactivity in the pozzolan/lime system, and, finally its influence on the physical and mechanical properties of binary pastes and mortars containing 10% and 20% MA replacement content. The results indicate that MA has a very low acid oxide content and a high loss on ignition (30%) and K2O content (6.9%), which produces medium–low pozzolanic activity. Despite an observed increase in the blended mortars’ total and capillary water absorption capacity and electrical resistivity and a loss in mechanical strength approximately equivalent to the replacement percentage, the 10% and 20% MA blended cements meet the regulatory chemical, physical, and mechanical requirements specified. Marabou weed ash is therefore a viable future supplementary cementitious material.

Utilization of marine waste enteromorpha prolifera powder to prepare sustainable lightweight cementitious materials

This study innovatively used enteromorpha prolifera powder (EPP) to prepare lightweight cementitious materials. The effect of EPP on the physical properties, mechanical strengths, and microstructure of mortar was tested and discussed. The results indicated that the density and thermal conductivity of mortar were significantly reduced after adding EPP, but the water absorption and porosity were increased accordingly, resulting in a significant loss of mechanical strength. Surprisingly, the density and thermal conductivity of mortar incorporated with 8 % EPP was only 855.00 kg/m3 and 0.28 W/m•K (reduced by 57 % and 83 % respectively compared with plain mortar), and the 28 d compressive strength was still as high as 1.90 MPa. The results of thermogravimetric analysis and X-ray diffraction showed that as the EPP content increases, the Ca(OH)2 content decreases, and the CaCO3 content increases. This was due to the increase in porosity causing CO2 in the environment to enter the interior of the matrix. This study not only proposed new material for preparing sustainable lightweight cement mortar but also found a new way to utilize large amounts of waste enteromorpha prolifera resources.

The Influence of the Comonomer Ratio and Reaction Temperature on the Mechanical, Thermal, and Morphological Properties of Lignin Oil-Sulfur Composites.

Although lignin is a plentiful biomass resource, it continually exists as an underutilized component of biomass material. Elemental sulfur is another abundant yet underutilized commodity produced as a by-product resulting from the refining of fossil fuels. The current study presents a strategy for preparing five durable composites via a simple one-pot synthesis involving the reaction of lignin oil and elemental sulfur. These lignin oil-sulfur composites LOSx@T (where x = wt. % sulfur, ranging from 80 to 90, and T represents the reaction temperature in °C) were prepared via the reaction of elemental sulfur and lignin oil (LO) with elemental sulfur. The resulting composites could be remelted and reshaped several times without the loss of mechanical strength. Mechanical, thermal, and morphological studies showed that LOSx@T possesses properties competitive with some mechanical properties of commercial building materials, exhibiting favorable compressive strengths (22.1-35.9 MPa) and flexural strengths (5.7-6.5 MPa) exceeding the values required for many construction applications of ordinary Portland cement (OPC) and brick formulations. While varying the amount of organic material did not result in a notable difference in mechanical strength, increasing the reaction temperature from 230 to 300 °C resulted in a significant increase in compressive strength. The results reported herein reveal potential applications of both lignin and waste sulfur during the ongoing effort toward developing recyclable and sustainable building materials.

Photochromic webbing structures for monitoring UV-induced mechanical strength degradation

Abstract Webbing structures are critical load-bearing components in a wide array of applications from structural restraint layers in inflatable space habitats to safety harness belts used by construction workers. In the field, webbings are subjected to ultraviolet (UV) irradiation from sunlight, leading to material degradation and a loss of mechanical strength. To date, health monitoring of webbings has relied on empirically correlating UV-induced strength loss with variations in their inherent color, which often yields inconsistent and imprecise results. To fill this gap, we propose a novel class of photochromic webbing structures that afford noninvasive monitoring of UV-induced degradation of their mechanical strength. The webbings’ sensing capabilities are achieved by integrating a class of photochromic yarns, fabricated through a pressurized coating process. Under continuous UV irradiation, the proposed photochromic webbings exhibit a substantial color change, demonstrating a sensing lifetime equivalent to several months in field conditions. We establish a strong correlation between the webbings’ photochromic response and their strength loss, supporting the feasibility of the proposed webbings in monitoring their mechanical integrity. To elucidate the sensing mechanism, we propose a physics-based mathematical model that describes the underlying photochemical reactions. Through an asymptotic analysis, we demonstrate that the model accurately predicts the webbing’s long-term photochromic responses under extended UV irradiation. The proposed photochromic webbing structures and the predictive mathematical model could enhance the safety and integrity of webbing-based engineering systems.

Octadecylamine modified gelatin-based biodegradable packaging film with good water repellency and improved moisture service reliability

Industrial gelatin is a good candidate for fabricating biodegradable packaging film, but the strong hydrophilicity of gelatin-based film lowers its moisture service reliability. Herein, we demonstrated a low surface energy water repellency surface design combined with covalent cross-linking for decreasing the water absorption and improving the moisture service reliability. Biodegradable octadecylamine (ODA) was chosen as the low surface energy providing material to fabricate the water repellency surface through a dehydration condensation reaction between the amine groups of ODA and gelatin chains via tetra-hydroxymethyl phosphonium chloride (THPC) in an aqueous phase. THPC also was employed as the cross-linking agent to form covalent bonding between the gelatin chains. The results determined that ODA modification and covalent cross-linking endowed the gelatin-based film with good water repellency and improved moisture service reliability. But high dose of ODA would result in phase separation and mechanical strength loss of the fabricated film. Additionally, ODA modification did not change the biodegradability of gelatin-based film, all the modified films were completely biodegradable in natural soil. Considering the sustainable modification process and abundant raw materials, the proposed strategy facilitates the effective utilization of low value industrial gelatin and provides a facile way for gelatin-based film as biodegradable packaging film.

A step to microplastic formation: Microcracking and associated surface transformations of recycled LDPE, LLDPE, HDPE, and PP plastics exposed to UV radiation

Plastics when exposed to UV radiation start to degrade via photooxidative aging including free radical formation, oxidation, chain scission and/or crosslinking reactions. These chemical changes can cause loss in mechanical strength, surface embrittlement, and eventually surface erosion. The eroded particles are microplastics (MPs), which have been identified as a potentially serious threat to the environment and its inhabitants. In general, photodegradation of virgin plastics has been studied extensively, but there is not much literature on the degradation of recycled plastics. The goal of the study was to investigate the changes caused by photodegradation in recycled plastics and assess the potential risks of MPs formation. And eventually, knowing the chemical and physical transformations occurring on the surface understand the mechanism behind surface microcracking, which is the first step of MPs formation. Pellets of five industrially recycled plastics (low-density polyethylene (rLDPE), linear low-density polyethylene (rLLDPE), high-density polyethylene (rHDPE), and two polypropylenes (rPP)) from different waste sources were analysed. UV irradiation was performed in an accelerated weathering chamber for milled (< 400 µm) plastic powder to ensure homogeneous changes throughout the sample. The properties were investigated by ATR-FTIR, HT-SEC, XPS and DSC. Formation of microcracks was studied on plastic pellets by SEM. The results showed that the degradation significantly differed between the recycled plastics, and the waste source was more important than the plastic type. rLDPE and one of the rPP samples showed a significant increase in carbonyl index as well as decrease in molar mass during the first 500 h of UV exposure. The other rPP and rHDPE samples showed first considerable signs of degradation only after 1000 h of UV exposure. Minor changes were observed for the rLLDPE sample during the whole test. The SEM revealed microcracking on the surface of all samples, which also had noticeable degradation identified by other methods. These recycled plastics can be considered the ones with the highest potential of MPs formation. From the chemical and physical transformations identified on the surface, the mechanism leading to microcracking, which is the first step in the formation of MPs, is proposed.

Influence of Single- and Double-Aging Treatments on the Mechanical and Corrosion Resistance of Alloy 625

Nickel–chromium–molybdenum Alloy 625 exhibits an excellent combination of mechanical properties and corrosion resistance. However, the high-temperature plastic deformation process and the heat treatment represent critical aspects for the loss in mechanical strength by grain coarsening. This detrimental behavior is worsened by the absence of phase transformation temperatures. However, the chemical composition permits slow precipitation-hardening response upon single aging. Therefore, when the soft- or solution-annealed condition is associated with insufficient mechanical properties, this potentiality can be exploited to improve the mechanical strength. Since the 𝛾″ precipitation can be accelerated by double-aging treatment, different time–temperature combinations of double aging at 732 °C and 621 °C are investigated. The simultaneous precipitation of intergranular carbides can dramatically affect the corrosion resistance. Such an undesired phenomenon occurs very quickly at 732 °C, but it is obtained only after very long exposure times at 621 °C. For this reason, a performance chart is developed to compare all the tested conditions. In particular, single aging at 621 °C for 72 h and 130 h are associated with an acceptable combination of mechanical and corrosion properties. Double aging permits a conspicuous acceleration of the aging response. For instance, with double aging at 732 °C 3 h and 621 °C 72 h, it is possible to obtain the same mechanical properties of single aging at 621 °C for 260 h. Such acceleration is accompanied by a more critical corrosion behavior, especially because of the primary step. However, even after its optimization, none of the tested conditions were acceptable.

Effect of temperature on high strain-rate damage evolving in CFRP studied by synchrotron-based MHz X-ray phase contrast imaging

The present study demonstrates experimental evidence of subsurface mesoscale damage initiation and evolution in angle-ply CFRP laminates under high strain-rate loading at low temperatures using synchrotron-based X-ray MHz radiography. A bespoke set of loading, temperature control and in-situ X-ray imaging systems were applied to simultaneously correlate high strain-rate mechanical response with observed subsurface damage in a time-resolved manner. The results demonstrate that independent of temperature, damage evolved following a specific sequence; firstly intra-ply shear cracking along the fibre direction, developing into multi-layer cracking with continued deformation, and finally culminating in inter-ply delamination and complete failure of the specimen. The timescale for this sequence, however, was observed to strongly depend upon temperature, with low temperatures resulting in more rapid damage evolution and loss of mechanical strength.

Use of a hydrotalcite isopropanol dispersion for deacidification and preservation of cellulose cultural heritage objects - Preliminary study

Preservation of cellulose cultural objects, particularly books, is a field of research with about 100 years of history. The most dangerous in terms of their lifespan is the use of acidic wood-based paper which represents a problem in both quality and durability. Acid hydrolysis of polymeric cellulose chains is a key factor responsible for loss of visual appearance quality and mechanical strength. Sulphate and aluminium ions together with generated formic, acetic, and other higher carboxylic acids accelerate the rate of degradation catalytically as well as autocatalytically. Alkaline species (alkali and alkali earth hydrogen carbonates, oxides, organocompounds, and amines) suppress the degradation processes. This paper refers to the utilisation of hydrotalcites (HT, MgxAl2(OH)2x+4CO3, x > 6) as deacidifying agents in a non-halogenated low toxic carrier – isopropanol. Preparation of an HT dispersion, its characterisation, and application to (acidic) test paper are described. Due to its ion exchange and neutralization capabilities, HT increased pH of test papers from about 4 to at least 6. Similarly to the action of HT as antacids, it is possible to suppose the neutralizing capability in deacidifying of aged-acid papers, even at pH lower than 7. A higher increase of pH was achieved only with extremely high loadings of HT; 16 g / m2 allowed to reach a surface pH value equal to 7.8. Both the optical properties and mechanical strength of treated samples were improved at loadings up to 3 g / m2.

Microstructural and textural evolution of double stage cold rolled non-grain oriented electrical steel

Non-grain oriented electrical steels (NGOES) are typically used in electric applications with rotating magnetic fields and thus essential for the production of electric motors. The increasing number of electric vehicles results in a growing demand for electrical steel sheets used in the stacked laminations of rotor and stator components. E-mobility applications require the best possible magnetic properties for optimum performance and efficiency, especially at high frequencies. In addition, increased mechanical strength is necessary to withstand the centrifugal forces resulting from high revolution speeds. Chemical composition, microstructure and crystallographic texture strongly influence the magnetic properties, whereas the mechanical properties are mainly affected by the chemical composition and grain size. Optimizing the texture is a possible method for improving the magnetic properties without significantly compromising the mechanical strength. In this work a special processing route for the production of 3.25% Si NGOES sample material has been studied, using laboratory cold rolling and annealing facilities. Compared to the classical processing route of single stage cold rolling and annealing, this alternative method involves two cold rolling steps with an intermediate annealing treatment between the first and second rolling sequence and a final annealing treatment after the second rolling step. The samples were produced with different intermediate thicknesses, changing the amount of cold rolling deformation of each sample variation. The degree of deformation affects the recrystallization and grain growth behavior and thus the resulting microstructure and texture. The microstructural and textural evolution was investigated in the hot rolled, intermediate annealed and final annealed state using electron backscatter diffraction (EBSD). Finished samples were additionally examined using magnetic testing and tensile testing. The results indicate a correlation between the intermediate thickness and the final grain size of the steel samples. Furthermore, the highly grain size dependent mechanical strength and magnetic losses are influenced. EBSD-data were used to interpret the texture and to calculate a parameter describing the magnetic quality of the texture. The results show a strong improvement of magnetically favorable texture components along with increasing intermediate thickness, enabling significantly better polarization values in rolling direction and transversal direction. However, anisotropy of the magnetic properties increases as well due to the textural changes.

Microwave assisted self-repairable vitrimeric coating for anti-corrosive applications

Vitrimeric coatings are revolutionary and most widely emerging materials for metal corrosion inhibition. As harsh environmental conditions damages polymer-derived protective films and results into micro cracks and corroded metal surfaces. In this work, an active microwave responsive vitrimeric epoxy coating embedded with weathering resistant properties is introduced along with systematic comparative study for the effect of ortho and para position of amine in hardening agent. The developed microwave radiation responsive coating system felicitates self-healing due to disulfide exchange mechanism and corrosion inhibition properties in marine environments. Compared to conventional coatings, prepared graphene oxide (GO) incorporated vitrimeric network showed more promising protection against corrosion in offshore applications with 95.4 % protection efficiency and hydrophobicity with 96-degree contact angle. This study covers the self-healing properties, thermal mechanical study, hydrophobicity measurement, and thorough corrosion examination of synthesized material coated on 304 grade SS substrate. The coating reports excellent self-healing efficiency, reliable mechanical strength (storage modulus-129GPa and loss modulus-83GPa), fast stress relaxation and low activation energy (63KJ/mol) for dynamic disulfide exchange reaction, furthermore low corrosion rate of 1.20 × 10−3mm/y was observed for the coating. Thus, demonstrates its importance for self-healable anti-corrosive application for the marine environment.

Lithiophilic Li-Si alloy-solid electrolyte interface enabled by high-concentration dual salt-reinforced quasi-solid-state electrolyte

Solid polymer electrolytes (SPEs) are urgently required to achieve practical solid-state lithium metal batteries (LMBs) and lithium-ion batteries (LIBs). Herein, we proposed a mechanism for modulating interfacial conduction and anode interfaces in high-concentration SPEs by LiDFBOP. Optimized electrolyte exhibits superior ionic conductivity and remarkable interface compatibility with salt-rich clusters: (1) polymer-plastic crystal electrolyte (P-PCE, TPU-SN matrix) dissociates ion pairs to facilitate Li+ transport in the electrolyte and regulates Li+ diffusion in the SEI. The crosslinking structure of the matrix compensates for the loss of mechanical strength at high-salt concentrations; (2) dual-anion TFSI–n-DFBOP–m in the Li+ solvation sheath facilitates facile Li+ desolvation and formation of salt-rich clusters and is conducive to the formation of Li conductive segments of TPU-SN matrix; (3) theoretical calculations indicate that the decomposition products of LiDFBOP form SEI with lower binding energy with LiF in the SN system, thereby enhancing the interfacial electrochemical redox kinetics of SPE and creating a solid interface SEI layer rich in LiF. As a result, the optimized electrolyte exhibits an excellent ionic conductivity of 9.31 × 10−4 S cm−1 at 30 °C and a broadened electrochemical stability up to 4.73 V. The designed electrolyte effectively prevents the formation of Li dendrites in Li symmetric cells for over 6500 h at 0.1 mA cm−2. The specific Li-Si alloy-solid state half-cell capacity shows 711.6 mAh g−1 after 60 cycles at 0.3 A g−1. Excellent rate performance and cycling stability are achieved for these solid-state batteries with Li-Si alloy anodes and NCM 811 cathodes. NCM 811|| Prelithiated silicon-based anode solid-state cell delivers a discharge capacity of 195.55 mAh g−1 and a capacity retention of 97.8% after 120 cycles. NCM 811||Li solid-state cell also delivers capacity retention of 84.2% after 450 cycles.

Optimizing sulfate and acid resistance in rubberized engineered cementitious composite with graphene oxide-pretreated crumb rubber: A response surface methodology approach

Crumb rubber (CR) pretreatment methods effectively mitigate mechanical strength loss in cementitious composites. Yet, their impact on composite durability remains underinvestigated. This study examines the effect of CR pretreatment with graphene oxide (GO) on the durability of rubberized engineered cementitious composite (RECC), employing response surface methodology (RSM) for predictive model development and optimization. Water absorption, sulfate and acid resistance, compressive strength, and the porosity using mercury intrusion porosimetry were evaluated across 16 RSM-generated mixes using five GO concentrations (GOC) (0–1 mg/mL) and three pretreated CR (PCR) replacement levels (1–5%) as input variables. Results reveal increased resistance to water absorption, expansion, weight, and strength loss in sulfate and acid media with higher GOC levels across all PCR groups. Developed response predictive models demonstrate high R2 values (53–97%). Optimization resulted in 0.73 mg/mL and 2.5% for GOC and PCR, respectively.

A novel combined healing system for sustainable asphalt concrete based on loading-microwave dual responsive capsules

The cracked asphalt concrete with calcium alginate/Fe3O4 capsules can get partial strength recovery under cyclic loading or microwave irradiation. This paper introduced a novel combined healing system for sustainable asphalt concrete based on loading-microwave dual responsive capsules in different service condition. In this paper, the capsules were synthesized and their morphological structure, mechanical performance and thermal resistance were characterized respectively. The rejuvenator release ratio of the capsules and the healing level of asphalt concrete were evaluated after cyclic loading and microwave irradiation. Meanwhile, the rheological characteristic of extracted asphalt binder was explored after cyclic loading and microwave irradiation treatment. Besides, the surface temperature of asphalt concrete after microwave irradiation was observed. The results revealed that the mechanical strength and mass loss of prepared capsules were 11.8 N and 3.8% at 200 °C respectively. The capsules experiencing higher cycles of loading events released more rejuvenator during microwave irradiation period. The combined healing level of asphalt concrete with capsules could reach 91.7% after 64000 cycles of loading and 30s of microwave irradiation. Meanwhile, the released rejuvenator softened asphalt binder and improved its flow ability. The novel combined healing system provides a new way of pavement maintenance strategy under the background of low carbon maintenance.

Erosive Wear of Structured Carbon-Fibre-Reinforced Textile Polymer Composites under Sands Blasting

Textile polymer composite is made of structured fibre matrix using textile technologies in fabrication, and gains benefits from strong mechanical properties with extra light weight. However, erosion behaviours and associated wear mechanisms of the composites may be influenced by the fibre structures due to heterogeneous composition and complex architectural topologies. Understanding the erosive mechanisms of the structured composites can be important, not only for preventing surface damage and loss of mechanical strength but also for improving design and fabrication of the composites. This paper presents an experimental study of erosive wear under sand blasting on 3D woven carbon-fibre-reinforced textile composites with epoxy. The architectural topology methods of the composites include non-crimped bidirectional, tufted bidirectional, 3D layer-to-layer and 3D orthogonal textile methods. The erosion tests were conducted on four impact angles (20°, 30°, 45° and 90°) under one impact velocity at 40 m/s. The study results show that the erosive mechanism of the textile composites is different from that of the neat substrate material. The observations from this study also reveal the different erosive behaviours between the composites with different fibre structures. It concludes that architectural structures can influence the erosion of a textile composite but will not result in significant differences in the wear resistance of the composites (&lt;20%).

Comparative evaluation of two cetylpyridinium chloride-based mouthwashes on the mechanical properties and strength loss of elastomeric chains used in dentistry: An vitro study

ObjectivesEvaluate the strength degradation of polymeric ligature chains after their immersion in cetylpyridinium chloride-based mouthwashes. Methods240 elastomeric samples from four different manufacturers (Rocky Mountain®, Ormco®, Morelli® and Dentaurum®) in two types of configurations (with and without intermodular links) and divided in 3 groups (distilled water, Vitis CPC Protect® and PERIO·AID® 0.05%) at 5 follow-up periods (0–24 h, 7–14 -21 days) were immersed twice a day for 60 s, following the manufacturers' protocols. A universal traction machine was used to perform the measurements and a post hoc multiple comparisons were based on the Bonferroni test and extended to a 3-way ANOVA test (α = 0.05). ResultsThere was a drop in strength up to 35.9% at 24 h. After a week, the short chains (52%) degraded less than the long ones (57.3%) with significant differences (p < 0.001) and the same pattern was observed until 21 days (p < 0.001). At 24 h, the degradation of the chains exposed in distilled water was 25.8%, in VITIS CPC Protect® 28.6% and in PERIO· AID® 0.05%, 27% with significant differences (p < 0.001). At 21 days, the VITIS CPC Protect® group obtained a much greater loss of strength, being this drop statistically significant (p < 0.001). The chains from Ormco® and RMO® experienced the least loss of force when immersed in the control group or PERIO AID® 0 0.05% (48% and 51%), while Dentaurum's in VITIS CPC Protect® lost more than 75%. ConclusionsThe orthodontic elastomeric chains suffer a sharp drop in strength during the first days of treatment. When comparing the mouthwashes, there were statistically significant differences in terms of strength degradation. Clinical significanceBased on the results, some types of chains, such as the ones without intermodular links from Ormco® showed better properties throughout the study. When immersed in PERIO·AID®0.05%, all showed significantly better results over time. Thus, PERIO·AID®0.05% can be recommended as a complementary oral hygiene element in dental treatments when elastomeric chains are used.

Comparison between gas flame welding and shielded gas welding in case of aluminium alloys

Although the assembly by welding of aluminum alloys is a common assembly process, it is done in quite difficult conditions, being forced to take into account a number of shortcomings, such as: high thermal conductivity which translates into losses of high heat in the welding area; formation of aluminum oxide films that melt at high temperatures, well above the melting temperature of the alloy; large expansion coefficients that result in the appearance of large deformations, the appearance of cracks in the joint at high temperatures due to loss of mechanical strength of the alloy, but also the appearance of pores, inclusions of aluminum oxide and corrosion in various aggressive environments. Despite all these shortcomings that occur in welding, aluminum alloys can be joined indestructibly by welding. The present paper aims, is to make a comparative study, based on experimental data, of two welding assembly processes, one with gas flame and another with shielded inert gas environments-WIG, for aluminum alloys of group 6000. The base material will be presented, the preparation of the basic material for welding through the two mentioned welding procedures and the steps taken to make the welded joints. The comparative study will include the parameters of welding regimes, non-destructive defectoscopy methods with which certain discontinuities can be identified and the destructive mechanical tests. The experimental results will be able to lead to pertinent conclusions on the possibilities of aluminum alloys welding assembly, using those two welding processes mentioned above, the results being easily generalized in the industrial fields.

Feasibility of Non-Remanufactured Waste Bottle Glass as Supplementary Cementitious Material

Theoretically, glass can be recycled entirely, but there are several requirements for remanufacturing. For the first time, this work studied industrial bottle waste glass (WG), which cannot be used to remanufacture new glass as a cement replacement for concrete applications. Wet and dry milling treatments were performed to reduce the particle size of WG and remove fibre and plastic contaminants. The different waste glasses treated were characterised by chemical, physical, and morphological analysis. Afterwards, mortar-level studies followed, using raw WG and wet-milled WG (AGWG) as a 10% Portland cement replacement. Mechanical and several durability indicators were assessed. WG and AGWG incorporation improved mortar performance against water capillary absorption, chloride ingress, and alkali–silica reaction. The unfavourable effect, namely, mechanical strength loss on glass-modified mortars, was mainly due to fibre contaminants observed by SEM on WG and AGWG samples. Even though wet milling reduced the amount and length of the fibre contaminants, it still did not guarantee adequate mechanical strength for the mortar. Thus, additional or alternative treatments, such as thermal treatments, must be explored.

Allograft sterilization and processing: impact on biomechanical strength

The allograft used for anterior cruciate ligament reconstruction (ACLR) must posses good biomechanical properties and it should have similar properties to the original tendon. During reconstruction the allograft must undergo proper sterilization and several sterilization methods have been used in the clinical practice. There are varations in the sterilization process and it has significant impact on the allograft tissue performance during ACL reconstruction. It is advisable to refrain from utilising grafts that have been exposed to radiation doses exceeding 15 kGy, as well as grafts that have undergone more than eight freeze-thaw cycles. Gamma radiation has disadvantages when compared to electron beam radiation in term of loss of mechanical strength.

Mechanical Strength and Surface Analysis of a Composite Made from Recycled Carbon Fibre Obtained via the Pyrolysis Process for Reuse in the Manufacture of New Composites.

This work aims to obtain recycled carbon fibre and develop an application for this new material. The carbon fibres were obtained by recycling aerospace prepreg waste via the pyrolysis process. The recycled fibres were combined with an Araldite LH5052/Aradur LY5053 epoxy resin/hardener system using manual lay-up and vacuum bagging processes. For comparison, the same resin/hardener system was used to produce a composite using commercial carbon fibre. The recycled and commercial composites were subjected to flexural, tensile and Mode I testing. Fracture aspects were analysed via scanning electron microscopy (SEM). The pyrolysis process did not affect the fibre surface as no degradation was observed. The fracture aspect showed a mixture of failure in the recycled composite laminate and interlaminar/translaminar failure near the surface of the commercial composite caused by flexural stress. Flexural and tensile tests showed a loss of mechanical strength due to the recycling process, but the tensile values were twice as high. The sand ladder platform was the project chosen for the development of a product made with recycled carbon fibres. The product was manufactured using the same manufacturing process as the specimens and tested with a 1243 kg car. The method chosen to design, manufacture and test the prototype sand ladder platform made of recycled carbon fibre was appropriate and gave satisfactory results in terms of high mechanical strength to bending and ease of use.