In this work, the process of impact that takes place in a partially filled tank is analyzed, performing a numerical simulation, in order to understand the response of the composite laminated ...structure. The commercial finite-element code LS-DYNA v.R7 has been used to simulate an Hydrodynamic RAM event created by a steel spherical projectile impacting a partially water-filled woven CFRP square tube using two different approaches (MM-ALE and SPH). The intralaminar and interlaminar damage have been taken into account implementing an user subroutine and by means of a cohesive interaction, respectively. Once the numerical model is validated using available experimental data, the effect of the filling level in the failure of the tank is analyzed in detail taking advantage of the information provided by the numerical model.
In this work it has been characterized the impact behaviour of quasibrittle fragments against a Hopkinson bar in a wide range of impact velocities (70-180 m/s). Hopkinson bar is designed to measure ...the impact forces thanks to a proper instrumentation. In this case, semiconductor strain gauges, which sensibility is higher than common strain gauges, are used. Two material are studied to widen the range of applicability of the experimental facility: PMMA and a woven composite material. Moreover, two high speed cameras (Photron SA-Z) have been used to obtain the displacement and strain field of the fragment impactor using 3D Digital Image Correlation (DIC). A special technique has been used to print the speckle in the fragment based on previous works. The developed experimental methodology has shown the different failure modes that may happen in the fracture process when the quasibrittle fragments acts as the impactor providing a better understanding of its physical behaviour.
•The main failure mechanism that appears in the composite fragments is laminate crushing.•A double cantilever beam opening process appears in all specimens impacted.•A simple analytical model is ...defined to predict the contact force, and the eroded mass.
This work analyses the impact against a rigid plate of carbon epoxy fragments. Experimental tests have been performed by means of a gas gun capable of launching rectangular pieces of composite laminates at a wide range of impact velocities (from 70 to 180 m/s). The impact process has been recorded using three high speed video cameras which allowed to analyse the phenomenon and to obtain the deceleration of the fragment and hence the force–time history and impulse induced on the plate. The failure process of the impacted fragments has been studied to identify the main absorption mechanisms and based on that a simple analytical model is proposed in order to predict the erosion and the impact force.
Background
Persistent alopecia (PA) after docetaxel has been recently described. The aim of our study is to establish the incidence and characteristics of PA following adjuvant docetaxel for breast ...cancer (BC) and to test the ability of scalp cooling in prevention.
Patients and methods
BC patients receiving adjuvant chemotherapy followed or not by endocrine therapy (and a control group receiving only endocrine therapy) were interviewed in a single institution at 1.5 to 5 years following primary diagnosis searching for PA. A confirmatory prevalence study was later performed in other two institutions. Finally, a prevention study using prophylactic scalp cooling (PSC) with ELASTO-GEL hypothermia caps in patients receiving adjuvant docetaxel was performed.
Results
In the initial prevalence study (492 patients), minor forms of PA (grade 1) were recorded with all chemotherapy regimens and aromatase inhibitors. Patients receiving docetaxel regimens at cumulative dose (CD) ≥ 400 mmg/m
2
presented a significantly higher prevalence of grades 1 PA (33–52%) and 2 PA (5–12%). Prevalence of grade 2 PA with docetaxel CD ≥ 400 mmg/m
2
was confirmed in two other institutions. Overall, grade 2 PA was seen in 10.06% (95% CI 7.36–13.61) of 358 patients with docetaxel regimens reaching CD ≥ 400 mmg/m
2
, but not in patients with lower docetaxel CD, other chemotherapy regimens, or endocrine therapy alone. In prevention trial, no grade 2 PA occurred among 116 patients receiving adjuvant docetaxel (≥ 400 mmg/m
2
) and PSC followed-up after a 96 months median time. PSC was well tolerated. No scalp relapses were seen among 30 patients (22% of all inclusions) having disease relapse.
Conclusion
Adjuvant treatment with docetaxel (CD ≥ 400 mmg/m
2
) is associated with a significant rate of grade 2 PA, leading to wearing a wig, in around 10% of patients. This toxicity was completely prevented with scalp cooling. Clinical Trial Reference: NCT00515762.
In this work, it is proposed a numerical methodology to model the behaviour of composite laminates when they act as impactors at high velocity. The numerical model uses an intralaminar criterion ...based in the Hashin model and a Progressive Damage model to describe the ply behaviour, whereas the interlaminar failure is taken into account by means of cohesive interactions. The validation of the model is performed attending the kinematics and erosion of the laminate during the impact process onto a rigid target as well as the force and impulse generated. Once validated, the model is used to analyse the influence of the fragment miss-alignment in the impact process.
In this work a numerical model was developed to predict the behavior of thin woven laminates under high velocity impacts. The material model, implemented in a user subroutine to be used with a ...commercial FE code, takes into account different failure mechanisms. The inter-lamina failure prediction is achieved by means of the use of cohesive elements. Finally, in order to validate the model, experimental tests were accomplished in a wide range of velocities from 100 to 400m/s. Residual velocity of the projectile and damaged area of the laminates are compared with the numerical results. Once the model is validated, a further investigation has been made in order to analyze the influence of projectile slenderness on the laminate response.
Abstract
Aims
To define a stepwise application of left bundle branch pacing (LBBP) criteria that will simplify implantation and guarantee electrical resynchronization. Left bundle branch pacing has ...emerged as an alternative to biventricular pacing. However, a systematic stepwise criterion to ensure electrical resynchronization is lacking.
Methods and results
A cohort of 24 patients from the LEVEL-AT trial (NCT04054895) who received LBBP and had electrocardiographic imaging (ECGI) at 45 days post-implant were included. The usefulness of ECG- and electrogram-based criteria to predict accurate electrical resynchronization with LBBP were analyzed. A two-step approach was developed. The gold standard used to confirm resynchronization was the change in ventricular activation pattern and shortening in left ventricular activation time, assessed by ECGI. Twenty-two (91.6%) patients showed electrical resynchronization on ECGI. All patients fulfilled pre-screwing requisites: lead in septal position in left-oblique projection and W paced morphology in V1. In the first step, presence of either right bundle branch conduction delay pattern (qR or rSR in V1) or left bundle branch capture Plus (QRS ≤120 ms) resulted in 95% sensitivity and 100% specificity to predict LBBP resynchronization, with an accuracy of 95.8%. In the second step, the presence of selective capture (100% specificity, only 41% sensitivity) or a spike-R <80 ms in non-selective capture (100% specificity, sensitivity 46%) ensured 100% accuracy to predict resynchronization with LBBP.
Conclusion
Stepwise application of ECG and electrogram criteria may provide an accurate assessment of electrical resynchronization with LBBP (Graphical abstract).
Graphical Abstract
Graphical abstract
Electrocardiographic- and electrogram-based stepwise approach for electrical resynchronization with left bundle branch pacing. QRS should be measured from the start of fast deflection in left bundle branch capture Plus (QRS ≤120 ms).
In recent years, vulnerability against high-velocity impact loads has become an increasingly critical issue in the design of composite aerospace structures. The effects of Hydrodynamic Ram (HRAM), a ...phenomenon that occurs when a high-energy object penetrates a fluid-filled container, are of particular concern in the design of wing fuel tanks for aircraft because it has been identified as one of the important factors in aircraft vulnerability. The projectile transfers its momentum and kinetic energy through the fluid to the surrounding structure, increasing the risk of catastrophic failure. In the present paper, the commercial finite-element code ABAQUS/Explicit has been used to simulate an HRAM event due to the impact of a steel spherical projectile into a water-filled woven CFRP square tube. In order to simulate the fluid–structure interaction, the Coupled Eulerian Lagrangian (CEL) approach is used. Experimental tests which indicate the pressure at different points of the fluid, strains of the walls and cavity evolution for different impact velocities are compared with the numerical results in order to assess the validity and accuracy of CEL technique in reproducing such a complex phenomenon. Also, several numerical impacts at different initial projectile velocities are performed to study its influence in the HRAM phenomenon.
In this work an analytical model has been developed in order to predict the residual velocity of a cylindrical steel projectile, after impacting into a woven carbon/epoxy thin laminate. The model is ...based in an energy balance, in which the kinetic projectile energy is absorbed by the laminate through three different mechanisms: linear momentum transfer, fiber failure and laminate crushing. This last mechanism needs the quantification of the through-thickness compressive strength, which has been evaluated by means of quasi-static punch tests. Finally, high velocity impact tests have been accomplished in a wide range of velocities, to validate the model.
In this work, a study has been made of the effect of the adhesive layer thickness on the efficiency of alumina/aluminium armours. Full-scale tests were made shooting armour piercing projectile ...against panels thick enough to arrest the projectile and also close to the ballistic limit. The adhesive layer, of different thickness, was of the toughened epoxy resin. The fire tests revealed the influence of thickness on the response of the lightweight protection. Numerical simulations were performed to analyse the experimental results. The anaysis showed an optimum adhesive layer thickness for the best performance of the lightweight protection considered.
PDF
