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The purpose of this research is present an experimental and numerical study of the mechanical properties of the acrylonitrile butadiene styrene (ABS) in the additive manufacturing (AM) by fused filament fabrication (FFF). The characterization and mechanical models obtained are used to predict the elastic behavior of a prosthetic foot and the failure of a prosthetic knee manufactured with FFF.

Tension tests were carried out and the elastic modulus, yield stress and tensile strength were evaluated for different material directions. The material elastic constants were determined and the influence of infill density in the mechanical strength was evaluated. Yield surfaces and failure criteria were generated from the tests. Failures over prosthetic elements in tridimensional stresses were analyzed; the cases were evaluated via finite element method.

The experimental results show that the material is transversely isotropic. The elasticity modulus, yield stress and ultimate tensile strength vary linearly with the infill density. The stresses and the failure criteria were computed and compared with the experimental tests with good agreement.

This research can be applied to predict failures and improve reliability in FFF or fused deposition modeling (FDM) products for applications in high-performance industries such as aerospace, automotive and medical.

This research aims to promote its widespread adoption in the industrial and medical sectors by increasing reliability in products manufactured with AM based on the failure criterion.

Most of the models studied apply to plane stress situations and standardized specimens of printed material. However, the models applied in this study can be used for functional parts and three-dimensional stress, with accuracy in the range of that obtained by other researchers. The researchers also proposed a method for the mechanical study of fragile materials fabricated by processes of FFF and FDM.

Encapsulant materials for flip‐chip‐on‐board (FCOB) were developed to address issues that have been observed during assembly of consumer electronic products on a high volume manufacturing FCOB/SMT line. The viscosity, surface tension, and filler particle sizes of several encapsulants were studied in an attempt to correlate these properties to their recorded underfill times and to observe their flow properties under the gap. Materials characterization studies were performed to determine their glass transition temperatures (Tg), tensile elastic and loss moduli (E′ and E′′), coefficients of thermal expansion (CTE), and apparent strengths of adhesion (ASA). In addition, reliability tests were conducted, and several promising materials were identified. The ASA of the encapsulant to the die passivation and the printed circuit board (PCB) is critical to the robustness of the assembly. Studies were conducted to observe the ASA as a function of FCOB assembly conditioning prior to underfilling and the degradation of the ASA as a function of humidity exposure. The ASA of the FCOB encapsulants was highest when the assembly was “baked‐out” prior to underfilling. Conditioning the assemblies for 24 hours at 23°C/85 per cent RH, to simulate the “worse case” factory environment, reduced the ASA. The ASA was also reduced when the “baked‐out” assemblies were placed in the 85°C/85 per cent RH chamber after underfilling. Although the ASA was decreased when the boards were not “baked‐out”, the reliability performance was not affected during air to air temperature cycling (AATC). A new class of low stress encapsulant materials systems were developed to reduce the stress state of the backside of the die. Studies showed that for specific materials compositions, the stress was proportional to the glass transition temperature of the encapsulant. In addition, it was observed that the stress state was a function of humidity, temperature, and time. FCOB assemblies were built with several low stress encapsulants and placed in reliability testing and they performed as well as assemblies underfilled with the qualified encapsulant.

The purpose of this paper is to analyze, computationally, the kinematic response (including large‐scale rotation and deformation, buckling, plastic yielding, failure initiation, fracture and fragmentation) of a pick‐up truck to the detonation of a landmine (shallow‐buried in one of six different soils, i.e. either sand, clay‐laden sand or sandy gravel, each in either dry or water‐saturated conditions, and detonated underneath the vehicle) using ANSYS/Autodyn, a general‐purpose transient non‐linear dynamics analysis software.

The computational analysis, using ANSYS/Autodyn, a general‐purpose transient non‐linear dynamics analysis software, included the interactions of the gaseous detonation products and the sand ejecta with the vehicle and the transient non‐linear dynamics response of the vehicle.

The results obtained clearly show the differences in the blast loads resulting from the landmine detonation in dry and saturated sand, as well as the associated kinematic response of the vehicle. It was also found that the low frequency content of the blast loads which can match the whole‐vehicle eigen modes is quite small so that resonance plays a minor role in the kinematic/ballistic response of the vehicle. Furthermore, it was demonstrated that mine blast analytical loading functions which are often used in transient non‐linear dynamic analyses have limited value when used in the analyses of a complete vehicle.

This is the first time that the kinematic response of a pick‐up truck to the detonation of a shallow‐buried landmine (using a full‐scale/complete model) has been analyzed computationally.

This study aims to achieve a “pseudo-ductile” behaviour in the response of hybrid fibre reinforced composites under uniaxial traction by solving properly formulated optimization problems.

The composite material model is based on the combination of different types of fibres (with different failure strains or strengths) embedded in a polymer matrix. The composite failure under tensile load is predicted by analytical models. An optimization problem formulation is proposed and a Genetic Algorithm is used. Multi-objective optimization problems balancing failure strength and ductility criteria are solved providing optimal mixtures of fibres whose properties may come either from a pre-defined list of materials, currently available in the market, or simply assuming their continuum variation within predefined bounds, in an attempt to attain unprecedented performance levels.

Optimal solutions of hybrid fibre reinforced composites exhibiting pseudo-ductile behaviour are presented. It is found that a fibre made from a material exhibiting relatively low stiffness combined with high strength is preferred for hybridization. Furthermore, the ratio of the average failure/critical strains between the low and high elongation fibres to be hybridized must be equal or greater than two.

Typically, a ductile failure is an inherent property of metals, that is, their typical response curve after the linear (elastic) region exhibits a yielding plateau still followed by an increase in stress till collapse. In stark contrast, composite materials exhibit (under some loading conditions) brittle failure that may limit their widespread usage. Therefore, a “pseudo-ductility” in composites is valued and targeted through optimization which is the main original contribution here.

This paper gives a bibliographical review of the finite element methods (FEMs) applied to the analysis of ceramics and glass materials. The bibliography at the end of the paper contains references to papers, conference proceedings and theses/dissertations on the subject that were published between 1977‐1998. The following topics are included: ceramics – material and mechanical properties in general, ceramic coatings and joining problems, ceramic composites, ferrites, piezoceramics, ceramic tools and machining, material processing simulations, fracture mechanics and damage, applications of ceramic/composites in engineering; glass – material and mechanical properties in general, glass fiber composites, material processing simulations, fracture mechanics and damage, and applications of glasses in engineering.

The ability of light‐weight all fiber‐reinforced polymer‐matrix composite armor and hybrid composite‐based armor hard‐faced with ceramic tiles to withstand the impact of a non‐Armor‐ Piercing (non‐AP) and AP projectiles is investigated using a transient non‐linear dynamics computational analysis. The results obtained confirm experimental findings that the all‐composite armor, while being able to successfully defeat non‐AP threats, provides very little protection against AP projectiles. In the case of the hybrid armor, it is found that, at a fixed overall areal density of the armor, there is an optimal ratio of the ceramic‐to‐composite areal densities which is associated with a maximum ballistic armor performance against AP threats. The results obtained are rationalized using an analysis based on the shock/blast wave reflection and transmission behavior at the hard‐face/air, hard‐face/backing and backing/air interfaces, projectiles’ wear and erosion and the intrinsic properties of the constituent materials of the armor and the projectiles.

The purpose of this study is to explore the dependence of material properties and failure criteria for fused deposition modeling (FDM) polycarbonate on raster orientation.

Tension, hardness and density measurements were conducted on a range of specimens at raster angles between 0 and 90° at 15° intervals. Specimens were manufactured so the raster angle was constant throughout each specimen (no rotation between adjacent layers). The yield strength, tensile strength, per cent elongation, elastic modulus, hardness and density of the material were measured as a function of raster angle. The orientation dependence of the properties was then analyzed and used to motivate a failure mechanism map for the material.

The properties of the material were found to be highly orientation-dependent. The variations in mechanical properties were explained to first order using a failure mechanism map similar to those generated for fiber-reinforced composites.

In addition to providing valuable experimental data for FDM polycarbonate, the study proposes micro-mechanisms of failure that appear to explain and capture the angular variation of strength with raster orientation. The fact that analysis methods which have been used for composites appear to apply to FDM materials suggests rich areas for future exploration.

The purpose of this paper is to address the issue of perceptions of suitability of different materials for a repair. The use of highly cementitious materials in the repair of historic masonry is causing great concern due to their incompatibility with adjacent stone and the associated accelerated deterioration which results from their use. The relatively recent development of so‐called “restoration mortars” based on a “mix and go” application, combined with the enhanced weathering of stone in a changing climate, may be contributing to the use of “plastic” repair materials on stone across Scotland.

Following a literature review, case studies of repairs are presented to highlight the advantages and disadvantages of using such materials, and comparisons are made with the alternative options.

The case studies presented highlight the use of a number of different stone repair materials, sometimes in combination with stone replacement, representing functional and philosophical approaches to masonry repair. However, the research has also highlighted the increasing use of plastic repairs for large‐scale repair including façade rendering, which fail to incorporate these systematic and informed approaches, and can ultimately lead to failure of repairs.

An evaluation of the current standing of the materials, methods and the extent of this type of repair, is vital for the substantiation of further research, and to enhance the empirical knowledge of in‐use performance, longevity and failure. The increasing emergence of restoration mortars, and their manufacture and supply on an international scale, highlights the global impact and relevance of this research.

The main objective of this work is to assess the current capabilities of different commercial finite element (FE) codes in simulating the progressive damage of composite structures under quasi-static loading condition in post-buckling regime.

Progressive failure analysis (PFA) methodologies, available in the investigated FE codes, were applied to a simple test case extracted from literature consisting in a holed composite plate loaded in compression.

Results of the simulations are significantly affected by the characteristic parameters needed to feed the degradation models implemented in each code. Such parameters, which often do not have a physical meaning, have to be necessarily set upon fitting activity with an experimental database at coupon level. Concerning the test case, all the codes were found able to capture the buckling load and the failure load with a good accuracy.

This paper would to give an insight into the PFA capabilities of different FE codes, providing the guidelines for setting the degradation model parameters which are of major interest.

The purpose of this paper is to evaluate the risks of building defects associated with rapid advancement of “green” construction technologies. It identifies the methods adopted by the sector for the determination of pre-construction defects that are framed within the context of, traditional; scientific; and professional design approaches. These are critically evaluated and utilised in attempts to mitigate defects arising from diffusing low carbon construction innovations.

The paper takes the form of an evaluative literature review. Polemic in orientation, the paper critically compares two periods of time associated with rapid advancement of innovation. The first, the post-Second World War housing boom is synonymous with a legacy of substandard buildings that in many cases rapidly deteriorated, requiring refurbishment or demolition shortly after construction. The second, is today’s “green” technology “shift” with its inherent uncertainty and increased risk of latent building defects and potential failure to deliver meaningful long-term performance. Central to this is an exploration of the drivers for innovation, and subsequent response, precautionary measures initiated, and the limitations of institutionalised systems to identify and mitigate defects. Similarities and differences between these historical periods frame a discussion around the theoretical approaches to defects and how these may be limited in contemporary low carbon construction. A conceptual framework is presented with the aim of enhancing the understanding for obviation of defects.

Sufficient commonality exists between the periods to initiate a heightened vigilance in the identification, evaluation and ideally the obviation of defects. Design evaluation is not expressly or sufficiently defect focused. It appears that limited real change in the ability to identify defects has occurred since the post-war period and the ability to predict the performance of innovative systems and materials is therefore questionable. Attempts to appraise defects are still embedded in the three principle approaches: traditional; scientific; and professional design. Each of these systems have positive characteristics and address defect mitigation within constrains imposed by their very nature. However, they all fail to address the full spectrum of conditions and design and constructional complexities that lead to defects. The positive characteristics of each system need to be recognised and brought together in an holistic system that offers tangible advantages. Additionally, independent design professionals insufficiently emphasise the importance of defect identification and holistic evaluation of problems in design failure are influenced by their professional training and education. A silo-based mentality with fragmentation of professional responsibility debases the efficacy of defect identification, and failure to work in a meaningful, collaborative cross professional manner hinders the defect eradication process.

Whilst forming a meaningful contribution to stimulate debate, further investigation is required to tangibly establish integrated approaches to identify and obviate defects.

The structured discussion and conclusions highlight areas of concern for industry practitioners, policy makers, regulators, industry researchers and academic researchers alike in addressing and realising a low carbon construction future. The lessons learned are not limited to a UK context and they have relevance internationally, particularly where rapid and significant growth is coupled with a need for carbon reduction and sustainable development such as the emerging economies in China, Brazil and India.

The carbon cost associated with addressing the consequences of emerging defects over time significantly jeopardises attempts to meet legally binding sustainability targets. This is a relatively new dimension and compounds the traditional economic and societal impacts of building failure. Clearly, blindly accepting this as “the cost of innovation without development” cannot be countenanced.

Much research has been undertaken to evaluate post-construction defects. The protocols and inherent complexities associated with the determination of pre-construction defects have to date been largely neglected. This work attempts to rectify this situation.