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The fibre-reinforced epoxy composite materials, thanks to their high specific strength, have found many applications in the last decades, especially in the transportation field. However, even though this great advantage allows having a lightweight and strong structure, their application is limited by many critical aspects. Some of these depend on the fact that the composite materials are prone to a large range of defects and damages if subjected to some types of loads. Such defects and damages can be very critical for composites structures, because they may be invisible and cause a significant decrease of the residual strength. In these circumstances, if a structure is not designed under a damage tolerance philosophy it might fail under an unexpected load value, also because the presence of defects can promote the arising of unexpected instability phenomena, as for example buckling under compressive loads. For this reason, one of the most critical aspects to consider during a design process is the structural behaviour of a component under compression load. In fact, fibre and matrix failures and delaminations could reduce the residual strength of a structural component and decrease the buckling load limit. So, defects and damages which could be due either to a critical phenomenon that has previously affected the structure, such as a Low Velocity Impact (LVI), or due to voids and defects caused by manufacturing and production processes, have to be taken into account during the design process. In particular, among different defects and damages, which can affect a composite material, both delamination and fibre failures are the most dangerous. In order to assess the residual strength of damaged composite structures, compression tests are usually performed on such structures. For example, compressive tests are experimentally carried out on damaged structural components, which have been affected to an LVI in a previous phase. With the aim of studying and better understanding the structural behaviour of composites panel under compressive loads, some experimental tests and the respective numerical simulations, based on finite elements theory, have been performed and presented in the paper. The compressive test is numerically reproduced by using the finite element code Abaqus®, which, thanks to its implemented algorithms, has allowed considering different failure modes. Moreover, the progressive damage of fibre reinforced composites has been modelled by using Hashin's criteria which allowed considering two different laws for damage initiation and propagation. In particular, the paper deals with structural behaviour of both undamaged and damaged aircraft panels, with omega stiffeners, made of fibre-reinforced composite materials subjected to static compression tests. A comparison between the structural behaviours of both types of panels has been performed and presented in the paper. Moreover, with numerical model validation purpose, also a correlation between numerical and experimental results has been performed and shown in the paper.

In the present paper, the preload reduction over the time attributed to the relaxation phenomenon which involves hybrid (composite-metal) bolted joints has been experimentally and numerically investigated. Unlike conventional materials (steel, aluminium, etc.), composite ones, due to the presence of the polymeric matrix with viscoelastic properties, feel more considerably the relaxation phenomenon, which begins at room temperature (around 20 °C). As a result, the loss in the mechanical fastening is a very critical aspect to consider when composite components have to be bolted to other; further investigations are still mandatory to increase the effectiveness of such jointing techniques.The test article consists of two bolted plates made of mild steel and a composite laminate made by E720 770gms 3×1 T E-Glass roving 1200 Tex 35% RW, respectively. Under this purpose, the preload reduction in the bolt has been experimentally emphasized by developing a novel strain-gauged bolt. Moreover, the relaxation phenomenon has been numerically simulated by developing a complex Finite Element (FE) model.

The study proposed within this paper deals with an application of finite element techniques to the thermo-structural analysis of a dissimilar butt-welded joint. Residual stresses induced by the fusion arc-welding of steel joints in power generation plants are a concern to the industry. Nowadays, the application of finite element method appears to be a very efficient method for the prediction and the investigation of the weld-induced residual stresses, nevertheless the detailed modelling of all phenomena involved in such process is still challenging. The structural integrity assessment of welded structures strongly requires a deep investigation of weld-induced residual stresses in order to be compliant with safety requirement of power plant. The longitudinal and transversal residual stresses in dissimilar material butt joints of 8 mm thick for V-groove shape were studied. The developed thermo-mechanical FE model as well as the simulation procedures are detailed and results are discussed. As a result of such work, it has been found out that residual stresses in the two dissimilar plates are characterized by very different magnitudes and distribution.

The paper deals with the study of the structural behaviour of laminated composite plates under low velocity impacts. Three test cases, respectively with 6J, 10J and 13J impact energies have been experimentally carried out under ASTM D7136 (American Standard Test Method for Measuring the Damage Resistance of a Fiber –Reinforced Polymer Matrix Composite to a Drop-Weight Impact) requirements. Within this work, virtual simulations of such impact tests have been developed by using the finite element code Abaqus®. The numerical model, based on explicit finite element theory, allows predicting the onset and evolution of both inter-laminar and intra-laminar damages. The former have been considered by using special-purpose elements (cohesive elements); the latter thanks to Hashin criteria. For validation purpose, numerical results have been compared with the experimental ones. After the validation phase, a parametric analysis has been numerically performed; the size of the panel support fixture has been considered as main parameter.

AIMS: Patients with colorectal cancer harbouring KRAS mutations do not respond to antiepidermal growth factor receptor (anti-EGFR) therapy. Community screening for KRAS mutation selects patients for treatment. When a KRAS mutation is identified by direct sequencing, mutant and wild type alleles are seen on the sequencing electropherograms. KRAS mutant allele-specific imbalance (MASI) occurs when the mutant allele peak is higher than the wild type one. The aims of this study were to verify the rate and tissue distribution of KRAS MASI as well as its clinical relevance. METHODS: A total of 437 sequencing electropherograms showing KRAS exon 2 mutation was reviewed and in 30 cases next generation sequencing (NGS) was also carried out. Five primary tumours were extensively laser capture microdissected to investigated KRAS MASI tissue spatial distribution. KRAS MASI influence on the overall survival was evaluated in 58 patients. In vitro response to anti-EGFR therapy in relation to different G13D KRAS MASI status was also evaluated. RESULTS: On the overall, KRAS MASI occurred in 58/436 cases (12.8%), being more frequently associated with G13D mutation (p=0.05) and having a heterogeneous tissue distribution. KRAS MASI detection by Sanger Sequencing and NGS showed 94% (28/30) concordance. The longer overall survival of KRAS MASI negative patients did not reach statistical significance (p=0.08). In cell line model G13D KRAS MASI conferred resistance to cetuximab treatment. CONCLUSIONS: KRAS MASI is a significant event in colorectal cancer, specifically associated with G13D mutation, and featuring a heterogeneous spatial distribution, that may have a role to predict the response to EGFR inhibitors. The foreseen implementation of NGS in community KRAS testing may help to define KRAS MASI prognostic and predictive significance.

Colorectal cancer (CRC) is one of the most frequent and deadly malignancies worldwide. Despite the progresses made in diagnosis and treatment, the identification of tumor markers is still a strong clinical need, because current treatments are efficacious only in a subgroup of patients. UbcH10 represents a potential candidate biomarker, whose expression levels could be employed to predict response or resistance to chemotherapy or targeted agents. UbcH10 mRNA and protein expression levels have been evaluated in a large group of CRC patients and correlated with clinico-pathological characteristics, including KRAS mutations. Moreover, the endogenous levels of UbcH10 and its role on cell growth have been evaluated in CRC cells. Finally, to investigate the impact of UbcH10 protein expression on the response to irinotecan, its active metabolite SN-38 and cetuximab treatment, UbcH10 silencing experiments were carried-out on two colon carcinoma cell lines, Caco-2, and DLD1. Overexpression of UbcH10 mRNA and protein was observed in the vast majority of patients analyzed. UbcH10 suppression decreased CRC cell growth rate (at least in part through deregulation of Cyclin B and ERK1) and sensitized them to pharmacological treatments with irinotecan, SN-38 and cetuximab (at least in part through a down-regulation of AKT). Taken together, these findings indicate that UbcH10 expression regulates CRC growth and could play an important role in the personalization of the therapy of CRC patients. © 2015 Wiley Periodicals, Inc.

This paper concerns the numerical and experimental characterization of the static and fatigue strength of an aluminum structure of rolling stock's seats. A series of static and fatigue test on full scale structure has been carried out using a biaxial test machine specifically designed, built and located in the laboratory of A-Technology industry to investigate the static and fatigue strength. The experimental results have been compared with numerical ones showing a very good correlation. The present paper gives an overview of such experimental and finite element method investigations specifying the type of loading used in fatigue tests and in FEM analysis and the main results obtained.

Epoxy matrix composites reinforced with woven natural fiber were studied. Composites having fiber volume fraction greater than 55% were prepared by hand lay-up technique. For reinforcement, three different natural fibers were used, jute, flax and silk. The tensile and flexural properties were investigated and the influence of the orientation of fibers on the stiffness were analyzed. It was observed that the tensile and flexural strength of silk composites is almost equal to that of flax composite and 1.98 times that of jute composite. Moreover the stiffness of the silk composites isn't influenced by orientation of fibers. Morphological examinations were carried out using scanning electron microscopy (SEM). All specimens were coated with a thin layer gold alloy prior to SEM observations. A high voltage of 20 kV was used for making the micrographs. The SEM investigation was used to study the fracture surface of the tensile specimens of the composites samples. The results of this study indicate that using silk fiber as reinforcement could successfully develop a composite material in terms of high strength and stiffness to produce a bio-composites for light applications compared to conventional composites.