Mechanical Compression Tests Research Articles

Ultrasounds could be considered as a future tool for probing growing bone properties

Juvenile bone growth is well described (physiological and anatomical) but there are still lacks of knowledge on intrinsic material properties. Our group has already published, on different samples, several studies on the assessment of intrinsic material properties of juvenile bone compared to material properties of adult bone. The purpose of this study was finally to combine different experimental modalities available (ultrasonic measurement, micro-Computed Tomography analysis, mechanical compression tests and biochemical measurements) applied on small cubic bone samples in order to gain insight into the multiparametric evaluation of bone quality. Differences were found between juvenile and adult groups in term of architectural parameters (Porosity Separation), Tissue Mineral Density (TMD), diagonal stiffness coefficients (C33, C44, C55, C66) and ratio between immature and mature cross-links (CX). Diagonal stiffness coefficients are more representative of the microstructural and biochemical parameters of child bone than of adult bone. We also found that compression modulus E was highly correlated with several microstructure parameters and CX in children group while it was not at all correlated in the adult group. Similar results were found for the CX which was linked to several microstructure parameters (TMD and E) only in the juvenile group. To our knowledge, this is the first time that, on a same sample, ultrasonic measurements have been combined with the assessment of mechanical and biochemical properties. It appears that ultrasonic measurements can provide relevant indicators of child bone quality (microstructural and biochemical parameters) which is promising for clinical application since, B-mode ultrasound is the preferred first-line modality over other more constraining imaging modalities (radiation, parent–child accessibility and access to the patient's bed) for pediatric patients.

3D printing of silk microparticle reinforced polycaprolactone scaffolds for tissue engineering applications.

Polycaprolactone (PCL) scaffolds have been widely investigated for tissue engineering applications, however, they exhibit poor cell adhesion and mechanical properties. Subsequently, PCL composites have been produced to improve the material properties. This study utilises a natural material, Bombyx mori silk microparticles (SMP) prepared by milling silk fibre, to produce a composite to enhance the scaffolds properties. Silk is biocompatible and biodegradable with excellent mechanical properties. However, there are no studies using SMPs as a reinforcing agent in a 3D printed thermoplastic polymer scaffold. PCL/SMP (10, 20, 30wt%) composites were prepared by melt blending. Rheological analysis showed that SMP loading increased the shear thinning and storage modulus of the material. Scaffolds were fabricated using a screw-assisted extrusion-based additive manufacturing system. Scanning electron microscopy and X-ray microtomography was used to determine scaffold morphology. The scaffolds had high interconnectivity with regular printed fibres and pore morphologies within the designed parameters. Compressive mechanical testing showed that the addition of SMP significantly improved the compressive Young's modulus of the scaffolds. The scaffolds were more hydrophobic with the inclusion of SMP which was linked to a decrease in total protein adsorption. Cell behaviour was assessed using human adipose derived mesenchymal stem cells. A cytotoxic effect was observed at higher particle loading (30wt%) after 7days of culture. By day 21, 10wt% loading showed significantly higher cell metabolic activity and proliferation, high cell viability, and cell migration throughout the scaffold. Calcium mineral deposition was observed on the scaffolds during cell culture. Large calcium mineral deposits were observed at 30wt% and smaller calcium deposits were observed at 10wt%. This study demonstrates that SMPs incorporated into a PCL scaffold provided effective mechanical reinforcement, improved the rate of degradation, and increased cell proliferation, demonstrating potential suitability for bone tissue engineering applications.

Mechanical performance of a node reinforced body-centred cubic lattice structure manufactured via selective laser melting

In most previously constructed lattice inspired structures, atoms were not included. Thus, their mechanical behaviours might not well simulate the lattice structures. In the present work, a body-centred cubic (BCC) inspired structure with atoms as reinforced nodes and atomic bonds as connected struts, was additively manufactured using Ti-6Al-4V alloy via a selective laser melting. Results of mechanical compression test and finite element analysis revealed the higher yield strength, collapse strength and energy absorption capability of the BCC-inspired structure with reinforced nodes than the ones without reinforcement.

Physicochemical properties and cytocompatibility assessment of non-degradable scaffolds for bone tissue engineering applications

Bone is a dynamic tissue with an amazing but yet limited capacity of self-healing. Bone is the second most transplanted tissue in the world and there is a huge need for bone grafts and substitutes which lead to a decrease in bone banks donors. In this study, we developed three-dimensional scaffolds based on Ti6Al4V, ZrO2 and PEEK targeting bone tissue engineering applications. Experimental mechanical compressive tests and finite element analyses were carried out to study the mechanical performance of the scaffolds. Overall, the scaffolds presented different hydrophilicity properties and a reduced elastic modulus when compared with the corresponding solid materials which can in some extension minimize the phenomenon of stress shielding. The ability as a scaffold material for bone tissue regeneration applications was evaluated in vitro by seeding human osteosarcoma (SaOS-2) cells onto the scaffolds. Then, the successful culture of SaOS-2 cells on developed scaffolds was monitored by assessment of cell's viability, proliferation and alkaline phosphatase (ALP) activity up to 14 days of culturing. The in vitro results revealed that Ti6Al4V, ZrO2 and PEEK scaffolds were cytocompatible allowing the successful culture of an osteoblastic cell line, suggesting their potential application in bone tissue engineering.Statement of Significance.The work presented is timely and relevant since it gathers both the mechanical and cellular study of non-degradable cellular structures with the potential to be used as bone scaffolds. This work allow to investigate three possible bone scaffolds solutions which exhibit a significantly reduced elastic modulus when compared with conventional solid materials. While it is generally accepted that the Ti6Al4V, ZrO2 and PEEK are candidates for such applications a further study of their features and their comparison is extremely important for a better understanding of their potential.

Durability of glass-fibre-reinforced polymer composites under seawater and sea-sand concrete coupled with harsh outdoor environments

This article presents an investigation on the durability of different glass-fibre-reinforced polymer composites when subjected to harsh outdoor conditions, including freeze/thaw cycles, ultraviolet radiation and moisture, as well as when used with seawater sea-sand concrete for construction applications. To achieve this, the effects of a number of parameters, including the environment of exposure, exposure time, profile cross-sectional configuration and orientation of fibres, on the mechanical properties of different glass-fibre-reinforced polymer composites were studied. To investigate the degradation of the mechanical properties, three-point bending, compression and tension tests were conducted on both reference and conditioned samples. Moreover, scanning electron microscopy analyses were performed to examine the contribution of microstructural deterioration to the damage mechanisms of the conditioned composites. Finally, the test results were used to develop empirical regression models to predict the level of retention of mechanical properties of different composites under different environmental conditions. The findings showed the maximum flexural, compressive and tensile strength reductions to be 35%, 48% and 37%, respectively, with regards to the pultruded profiles exposed for 3000 h to freeze/thaw cycles followed by 90 days of seawater sea-sand concrete immersion, while the flexural strength reductions recorded for the vacuum-infused samples subjected to 2000 h of freeze/thaw cycles followed by 90 days of seawater sea-sand concrete immersion were 28%, 72% and 56% for the unidirectional, woven and chopped strand mat laminates, respectively.

Selective Laser Melting of NiTi Shape Memory Alloy: Processability, Microstructure, and Superelasticity

Nowadays, thanks to the growing interest regarding the manufacturing of 3D complex parts with integrated functionalities, the additive manufacturing of NiTi shape memory alloy is a challenging technological issue. Particularly, 3D printing of NiTi components requires a strong interaction between technological and metallurgical approaches, due to the significant correlation among the process conditions, the microstructure, and the functional performances. The goals of the present work are to define the processability of NiTi powder for realizing fully dense samples using Selective Laser Melting process and the correlation between the microstructure and the superelastic response of specimens processed in different process conditions. It was found that highest relative density values can be obtained for a laser fluence in the range 63–160 J/mm3. The resulting microstructures exhibit variable degrees of orientations, according to the different cooling rates and melt pool size, specific for each condition. Finally, mechanical testing in compression indicated that the as-built alloy exhibits a limited superelastic behavior. A typical flag-like behavior, characterized by 6% of complete recoverable strain, was obtained through heat treatment at 500 °C. This suggests that the microstructure of as-built samples is highly efficient to promote superelasticity after annealing.

Performance of cementitious matrices incorporating concrete floor polishing sludge waste

The objective of this work is to analyze of reusing concrete floor polishing waste (CFPW) as an additional material to cementitious compounds, reducing at the same time both the consumption of Portland cement and the environmental problems. Mortars and pastes were produced with CFPW additions (4%mass up to 12%mass) and were characterized in terms of mechanical properties, chemical composition, and thermal analysis. The results of the thermal analysis showed that the moisture carbonation increased as the CFPW %mass increased. The results of the mechanical compression tests showed that the addition of CFPW increases the compressive strength of mortars. The conclusion is that adding CFPW to cementitious compound is feasible in order to reduce the consumption of Portland cement and preserve the environment.

FT-IR study of early stages of alkali activated materials based on pyroclastic deposits (Mt. Etna, Sicily, Italy) using two different alkaline solutions

The huge availability of volcanic deposits in Mt. Etna volcano and the wide use of volcanic materials as aggregates in local architecture encouraged us to apply them in alkaline environment to produce geopolymeric binders to restore historical buildings of Mt. Etna area. Two clusters of samples for each volcanic precursor (volcanic ash and ghiara paleo-soil) were produced, using 10 and 20% wt. of metakaolin and two different alkaline solutions based on sodium and potassium respectively. A comparative study was made in relation to activators used, focusing on evaluation of polycondensation step (in ATR); chemical and structural characterization (FT-IR); TGA analysis, qualitative XRD analysis and mechanical compressive test after 7 and 21 curing days. ATR results confirmed the occurrence of geopolymerization for all samples; FT-IR analysis showed a higher content of carbonates in potassium-samples, decreasing at increasing of metakaolin content. A low weight lost was recorded in consolidated samples, as well as a partial dissolution of volcanic phases. Higher mechanical compressive strengths for K-samples, reaching 89 MPa as highest value after 21 days, differently to sodium-samples (51 MPa) were recorded, reflecting the porosity of the different specimens.

Ultra-High Molecular Weight Polyethylene/Titanium-Hybrid Implant for Bone-Defect Replacement.

A hybrid implant with a structure mimicking that of natural bone was developed. Titanium alloy Ti–6Al–4V prepared with three-dimensional (3D)-printing technology was used to simulate the cortical-bone layer. The mismatch in the mechanical properties of bone and titanium alloy was solved by creating special perforations in the titanium’s surface. Porous ultra-high molecular weight polyethylene (UHMWPE) with high osteogenous properties was used to simulate the cancellous-bone tissue. A method for creating a porous UHMWPE structure inside the titanium reinforcement is proposed. The porous UHMWPE was studied with scanning electron microscope (SEM) to confirm that the pores that formed were open, interconnected, and between 50 and 850 μm in size. Mechanical-compression tests done on the obtained UHMWPE/titanium-hybrid-implant samples showed that their mechanical properties simulated those of natural bone.

Preparation and physicochemical characterisation of polyurethane foams prepared using hydroxybutylated condensed tannins as a polyol source

Renewable, bio-based and functional polyols are increasingly being sought as precursors for polyurethanes. A hydroxybutylated Pinus radiata bark tannin (HBBT) was prepared via a mild-base solvent-free synthesis and used as a polyol source in rigid polyurethane foams prepared in conjunction with commercial sorbitol or sucrose-based polyols. The resulting foams were physically and chemically characterised using FTIR spectroscopy, SEM, mechanical compression testing and thermogravimetric analysis. Addition of HBBT had minimal impact on the foam density, however the cellular structure became increasingly deformed at higher substitution levels. The specific modulus and strength increased with HBBT addition, by up to 50% at higher HBBT loadings. Thermal stability was improved through HBBT addition, increasing the degradation onset temperature, reducing mass loss at high temperature and providing higher char residuals. These findings indicate the potential to use HBBT in polyurethane foams for the building and construction industries, offering both improved mechanical properties and increased thermal resistance.

Polydopamine regulated hydroxyapatite microspheres grown in the three-dimensional honeycomb-like mollusk shell-derived organic template for osteogenesis

Layered osteochondral composite scaffolds are considered as a promising strategy for the treatment of osteochondral defects. However, the insufficient osseous support and integration of the subchondral bone layer frequently result in the failure of osteochondral repair. Therefore, it is essentially important to explore new subchondral bone constructs tailored to support bone integration and healing. In this study, a novel three-dimensional porous biomimetic construct (HA/pDA-OTMS) was successfully developed by polydopamine (pDA) regulating hydroxyapatite (HA) microspheres grown in the honeycomb-like mollusk shell-derived organic template (OTMS). The biomimetic OTMS had good mechanical properties, high toughness, biodegradability and excellent biocompatibility. Moreover, the long-range ordered cavity structure of OTMS allowed the smallest material to create the largest and most stable geometric space, endowing it high HA loading capacity. The modification of pDA on OTMS surface effectively promoted the mineral nucleation of HA in the micro-nano cavities of OTMS. The compression mechanical tests showed that the combination of inorganic HA and organic pDA-OTMS greatly improved the mechanical properties of the construct. Additionally, the HA/pDA-OTMS composite provided adequate 3-D support for osteoblast cell attachment, proliferation and differentiation, as well as significantly up-regulated the expression of osteogenesis-related genes. These results demonstrated that as-prepared HA/pDA-OTMS constructs with combined mechanical strength and excellent osteogenic activity show great application prospects in subchondral bone regeneration.

Liquid-Crystal-Elastomer-Based Dissipative Structures by Digital Light Processing 3D Printing.

Digital Light Processing (DLP) 3D printing enables the creation of hierarchical complex structures with specific micro- and macroscopic architectures that are impossible to achieve through traditional manufacturing methods. Here, this hierarchy is extended to the mesoscopic length scale for optimized devices that dissipate mechanical energy. A photocurable, thus DLP-printable main-chain liquid crystal elastomer (LCE) resin is reported and used to print a variety of complex, high-resolution energy-dissipative devices. Using compressive mechanical testing, the stress-strain responses of 3D-printed LCE lattice structures are shown to have 12 times greater rate-dependence and up to 27 times greater strain-energy dissipation compared to those printed from a commercially available photocurable elastomer resin. The reported behaviors of these structures provide further insight into the much-overlooked energy-dissipation properties of LCEs and can inspire the development of high-energy-absorbing device applications.

Compressive Strength Prediction of Quad-Diametral Lattice Structures

Additive manufacturing is rapidly developing technology in all areas of industry. It is reducing the delivering time of each prototype from the manufacturer to the final user. This paper deals with mechanical properties of lattice structures. They are produced by additive technologies from the plastic material. Lattice structures are special space-filling unit cells, which can fill gaps in parts. They have good ratio between overall weight and strength. Nowadays are these structures commonly used, but their mechanical properties are not well described. This makes the design process difficult. Mechanical compressive test and virtual evaluation by the finite element method was performed. It was done for three different Quad-Diametral structures (Quad-Diametral, Quad-Diametral-Line and Quad-Diametral-Cross). Results from both testing approaches (real measurement and finite element method) are deeply described in this paper. It was shown, that the Quad-Diametral-Cross lattice cell has higher mechanical properties comparing to others. Increasing of the stiffness was 121% only with weight higher by 43%. The plastic material Ultimaker PLA (polyactic acid) was used as reference material in this research.

The design of Ti6Al4V Primitive surface structure with symmetrical gradient of pore size in biomimetic bone scaffold

The living environment of bone cells is a complex curved one. And based on the modeling method of triply periodic minimal surfaces (TPMS) can be used to design a variety of complex surface structures, so it has been more and more widely studied and applied. In this paper, the main research object is the Primitive structure of TPMS. As an artificial bone scaffold structure, it must possess good mechanical properties, permeability, and is conducive to cell adhesion and proliferation. In this study, several groups of Ti6Al4V Primitive models are designed and fabricated by selective laser melting (SLM). The mechanical properties of scaffold are evaluated by mechanical compression test. The morphology of the scaffold model is characterized. The permeability of the scaffold was predicted and evaluated by computational fluid dynamics (CFD) analyses. Finally, the evaluation of the effects of Ti6A14V scaffold on cell growth is conducted by cytotoxicity test. The results show that the mechanical properties and permeability of the designed Primitive surface scaffold are pretty good as bone tissue replacement. Among them, the Psy scaffold with pore size and porosity varying along the axisymmetric gradient has significant research and application potential in the field of artificial bone scaffold.

Synchrotron X-ray micro-computed tomography imaging of 3D re-entrant micro lattice during in situ micro compression experimental process

3D re-entrant mechanical metamaterials were designed and fabricated with PμLSE (Projection Micro Litho Stereo Exposure) 3D printing technique, synchrotron X-Ray tomography 3D imaging and in situ mechanical experiments were performed for characterizing additive manufacturing (AM) process induced internal defects, corresponding relations between defects and mechanical behaviors of harvested 3D re-entrant lattice samples were explored through experiments and simulations comparisons. Firstly, in situ micro compression mechanical test device was designed and constructed for in situ synchrotron X-Ray 3D tomography mechanical experiments; Afterwards, interrupted in situ compression tests were performed for investigating the effects of manufacturing process induced defects on the deformation behaviors of 3D re-entrant lattice metamaterials, and finite element (FE) modeling was performed and compared with experimental results for understanding the mechanical behaviors of as-fabricated 3D re-entrant lattice metamaterials.

Tensile, compression, and flexural characteristics of acrylonitrile–butadiene–styrene at low strain rates: Experimental and numerical investigation

Acrylonitrile–butadiene–styrene (ABS) is a very significant and widely used amorphous thermoplastic which, on account of its importance in industry, multiplied billions of dollars are spent yearly in the United States alone, not to talk of the rest of the world. It is primarily utilized in industry and domestic situations due to its high damage resistance properties. This fact makes it a required exercise for serious and thorough research in this area to go ahead. In this article, the tension, compression, and bending response behavior of ABS material under various strain rate levels tests were investigated. Its characterization under tensile, compression, and other mechanical testing is thus quite important, to elicit ways of enhancing properties that would make the material or structures made from it, better in service. In the current phase, tension, compression, shear, and flexural samples were tested, because it is of interest to know how the longitudinal and shear loading damages propagate through the specimen length and thickness, and how the microstructure is affected from point to point, both laterally and depth-wise. The issues of energy transfer and dissipation are significant in terms of the effectiveness of this material as a damage retarder. Mat_187 nonlinear material model in Ls-Dyna was utilized to numerically evaluate the behavior of ABS under tension, compression, and three-point bending. The experimental results compared favorably to the numerical results.

Mechanical Gypsum Wall System Performance

This paper has the aim to evaluate the mechanical performance of gypsum walls. It was carried out a laboratory experimental characterization of the gypsum materials properties and different waterproofing contents, which determine their mechanical behaviour, by flexural and compressive strength tests, tensile adhesion and surface hardness. The wall system performance was also evaluated in terms of its water-tightness.The results showed that the samples with lower water repellent additive content present higher compressive strength values and the gypsum walls tested achieved the minimum level of performance (Level M).

Characterization and multiscale modeling of novel calcium phosphate composites containing hydroxyapatite whiskers and gelatin microspheres

In this study, novel calcium phosphate cement (CPC) composites were prepared by simultaneous incorporation of porogenic crosslinked gelatin microspheres (GMs) and reinforcing hydroxyapatite whiskers (HAWs) into the CPC matrix and the effects of the mentioned additives on the compositional characteristics, phase evolution, setting time, microstructure and mechanical properties of the CPC matrix, were thoroughly investigated. Simulation techniques and multiscale modeling were also employed to predict and compare mechanical properties of the composite formulations with those of real mechanical tests. For this purpose, composite CPCs of varying compositions were prepared by concurrent addition of GMs (5, 10 wt %) and HAWs (5–30 wt %) to the typical apatitic CPC composed of equimolar mixture of tetracalcium phosphate (TTCP) and dicalcium phosphate anhydrous (DCPA). Morphological observations by SEM confirmed proper dispersion of the additive materials in the CPC matrix. The results of the compositional evaluation of the composites by FTIR and XRD also revealed that the additives preferably didn’t exhibit a considerable inhibitive effect on the HA conversion during the composite CPC setting process. Porosity measurements approved that GMs could act as porogenic materials which introduced an increased total porosity of up to ∼69% to the structure of composites. The CPC sample and the composite cements also exhibited considerable specific surface area of 12.99 and 4.32–8.20 m 2 /g, respectively. Moreover, the results of compressive mechanical testing showed that the CPC control and the composites had a compressive strength of 28.1, 9.5–29.4 MPa and Young modulus of 3860 and 515–2630 MPa, respectively. However, in terms of mechanical and microstructural features, the composites containing 10 wt % of HAWs exhibited the most preferable characteristics. The mechanical results of the multiscale modeling method were also in the same range of those obtained by experimental compressive tests. Such finding was more notable for the composites with lower content of HAWs (5 and 10 wt %), when the predicted mechanical values for such samples were more than 80% accurate. In-vitro cellular tests also showed that the additives (GMs and HAWs) improved biological response of the composites, with 10 wt % of GMs and HAWs as the optimal amount. Nevertheless, depending on the bone graft requirements and the needed compromise between porosity and mechanical properties; the optimum composite can be chosen. • Successful synthesis of Gelatin Microspheres (GMs) and Hydroxyapatite whiskers (HAWs). • Incorporation of GMs and HAWs into the calcium phosphate cement (CPCs). • Designing novel composite CPC formulations with different amounts of GMs and HAWs. • Thorough characterization of CPC composites to determine optimum formulations. • Observation of reinforcing and porogenic roles by HAWs and GMs, respectively.

Effect of the Filling Pattern on the Compression Strength of 3D Printed Objects Using Acrylonitrile Butadiene Styrene (ABS)

The present study exhibits the behavior of ABS polymer (acrylonitrile butadiene styrene) subjected to mechanical compression tests considering two filling patterns, rectangular and hexagonal; these patterns have been selected due to the geometric arrangement of their internal structure improves the mechanical properties of 3D printed parts, in addition to the increase in tensile strength. The specimens were developed by molten deposition modeling (FDM) under the ASTM D695 standard in 2015, so five samples of each pattern were made; they have an 80% filler material. This is due to the demanding mechanical requirement in engineering applications. The results obtained show that the rectangular fill pattern at 0° and 90° registered the highest compressive strength obtaining as a result an average compression strength of 4 179.92 N, likewise a percentage of deformation of 5.96% and a maximum compressive strength of 33.147 MPa. Because of the evidenced data, the rectangular pattern is useful for engineering and industrial applications, including substituting car parts, machinery or household appliances.

Experimental and Numerical Assessment of Fibre Bridging Toughening Effects on the Compressive Behaviour of Delaminated Composite Plates.

Increasing the Mode I inter-laminar fracture toughness of composite laminates can contribute to slowing down delamination growth phenomena, which can be considered one of the most critical damage mechanisms in composite structures. Actually, the Mode I interlaminar fracture toughness (GIc) in fibre-reinforced composite materials has been found to considerably increase with the crack length when the fibre bridging phenomenon takes place. Hence, in this paper, the fibre bridging phenomenon has been considered as a natural toughening mechanism able to replace embedded metallic or composite reinforcements, currently used to increase tolerance to inter-laminar damage. An experimental/numerical study on the influence of delamination growth on the compressive behaviour of fibre-reinforced composites characterised by high sensitivity to the fibre bridging phenomenon has been performed. Coupons, made of material systems characterised by a variable toughness related to a high sensitivity to the fibre bridging phenomenon and containing artificial through-the-width delaminations, were subjected to a compressive mechanical test and compared to coupons made of standard material system with constant toughness. Out-of-plane displacements and strains were monitored during the compression test by means of strain gauges and digital image correlation to assess the influence of fibre bridging on delamination buckling, delamination growth and on the global buckling of the specimens, including buckling shape changes. Experimental data were combined with a numerical study, performed by means of a virtual crack closure technique based procedure, named SMart Time XB – Fibre Bridging (SMXB-FB), able to mimic the crack bridging effect on the toughness properties of the material system. The combination of numerical results and experimental data has allowed the deformations and the buckling shape changes to be correlated to the onset and evolution of damage and, hence, contributes to improving the knowledge on the interaction of the failure mechanisms in the investigated composite specimens.