Elongation Measurements Research Articles

TECHNOLOGICAL PROPERTIES OF Eucalyptus grandis USING DIGITAL IMAGE CORRELATION (DIC)

This study aimed to characterize some technological properties of Eucalyptus grandis wood and evaluate the use of Digital Image Correlation (DIC) to obtain the displacement and the behavior of the samples in deformation and its relationship with tension in tensile and compression tests parallel to the fibers. Samples were produced from 23-year-old wood to determine the basic density, shrinkage coefficient, anisotropy in contraction and swelling, and the mechanical strength to tensile and compression parallel to the fibers. To calculate the Modulus of Elasticity (E), the stress wave velocity was measured in the tensile samples. The measurement of sample elongation during the test was obtained by DIC and then calculating strain and E. The basic density was 0.497 g/cm³ and the anisotropy values of contraction (1.25) and swelling (1.27) indicated that it was a very dimensionally stable wood. The tensile strength (118.50 MPa) was higher than normally obtained for the species. The parallel compression average values (53.06 MPa) were similar to those in the literature. As for E, the average value obtained by DIC was 12,664.24 MPa; by the stress wave timer, it was 11,941.35 MPa. The evaluated wood is indicated for structural uses according to the C40 class (NBR 7190-1997). Finally, DIC was able to adequately provide displacement values that occurred during tests, enabling the modulus of elasticity calculation.Keywords: wood characterization, non-destructive method, physical and mechanical properties, strain.

Physical structure of the environment contributes to the development of diversity of microalgal assemblages

Aquatic macrophytes form a three dimensional complex structure in the littoral zones of lakes, with many physical, chemical and biological gradients and interactions. This special habitat harbours a unique microalgal assemblage called metaphyton, that differs both from the phytoplankton of the pelagial and from the benthic assemblages whose elements are tightly attached to the substrates. Since metaphytic assemblages significantly contribute to the diversity of lakes’ phytoplankton, it is crucial to understand and disentangle those mechanisms that ensure their development. Therefore, we focused on the question of how a single solid physical structure contribute to maintaining metaphytic assemblages. Using a laboratory experiment we studied the floristic and functional differences of microalgal assemblages in microcosms that simulated the conditions that an open water, a complex natural macrophyte stand (Utricularia vulgaris L.), or an artificial substrate (cotton wool) provide for them. We inoculated the systems with a species rich (> 326 species) microalgal assemblage collected from a eutrophic oxbow lake, and studied the diversity, trait and functional group composition of the assemblages in a 24 day long experimental period. We found that both natural and artificial substrates ensured higher species richness than the open water environment. Functional richness in the open water environment was lower than in the aquaria containing natural macrophyte stand but higher than in which cotton wool was placed. This means that the artificial physical structure enhanced functional redundancy of the resident functional groups. Elongation measures of microalgal assemblages showed the highest variation in the microcosms that simulated the open water environment. Our results suggest that assembly of metaphytic algal communities is not a random process, instead a deterministic one driven by the niche characteristics of the complex three dimensional structure created by the stands of aquatic macrophytes.

Spinal height for growth guidance treatment in early onset idiopathic scoliosis: analysis through final surgical treatment.

The growth guidance (GG) method for treatment of early onset scoliosis has as its primary goal the restoration of apical spinal alignment, facilitating normal spinal growth to achieve a suitable adult thoracic height. To evaluate whether GG surgical treatment achieves comparable thoracic and spinal height to distraction-based treatment (DBT) in idiopathic early onset scoliosis (I-EOS) patients. We hypothesized that GG would prove superior to DBT at the time of definitive fusion surgery. All I-EOS patients who underwent GG at a single center were reviewed. T1-L1 and T1-S1 heights were measured using the traditional coronal method as well as the Halifax sagittal spinal length (SSL) technique. The same measurements were obtained from a comparable control group obtained from a multi-center pediatric early onset scoliosis database who underwent treatment with traditional growing rods (TGR) or magnetically controlled growing rods (MCGR). Of the I-EOS patients who underwent GG 2004-2019, 15 patients underwent final fusion after GG completion, with a mean 5.5years of GG treatment prior to fusion (range 2.0-11.4years). Mean age at GG implantation was 8.4years (range 2.0-11.7years); 7 were male and 8 female. GG patients experienced a mean coronal thoracic height increase of 6.2cm during treatment through final fusion, and a mean coronal spinal height increase of 8.8cm. At the time of final fusion, GG patients achieved greater significant mean increases than DBT patients by 2.9cm in coronal thoracic height (p = 0.0023), 4.5cm in coronal spinal height (p = 0.001), and 4.0cm in SSL spinal height (p = 0.01). No GG patient concluded treatment with a thoracic height less than 18cm in either coronal or sagittal plane. Not only did 100% of GG patients reach minimum thoracic height of 18cm at time of final fusion, but GG also proved to be superior to distraction-based constructs in a comparison cohort on 3 of 4 spinal elongation measures. 3.

An Investigation of Changes in the Rheological Properties of Toast Pan Bread Dough during the Various Processing Steps of Kneading in an Industrial Bakery

The dough formation during the kneading for the industrial production of toast pan bread was examined using a series of mechanical tests to assess possible transformations in its rheological properties. For this purpose, the Young’s modulus of elasticity and squeeze flow viscometry of the doughs taken from various processing stages of the kneading process were determined. The rheological properties of the dough were assessed using dynamic and creep tests. Young’s modulus data revealed the changes in the elasticity of the dough exhibited during the different steps of kneading, whereas dynamic and creep tests indicated that throughout kneading, the dough displayed the behavior of a weak solid. Elongational viscosity measurements showed that the dough exhibited pseudoplastic behavior throughout the kneading process. The doughs from the various processing steps exhibited differences in zero shear viscosity values. It is suggested that the changes occurred during the processing stages, related to the development of secondary bonding within the gluten matrix.

Prediction of the Bubble Growth Behavior by Means of the Time-, Temperature-, Pressure- and Blowing Agent Concentration-Dependent Transient Elongational Viscosity Function of Polymers.

Bubble growth processes are highly complex processes, which are not only dependent on the foaming process parameters (temperature, pressure and blowing agent concentration) but also on the type and structure of the polymer used. Since the elongational viscosity at the bubble wall during bubble growth also depends on these influencing factors, the so-called transient elongational viscosity plays a key role in describing the gas bubble growth behavior in polymer melts. The model-based description of the transient elongational viscosity function is difficult due to its dependence on time, Hencky strain and strain rate. Therefore, representative viscosities or shear viscosity models are usually used in the literature to predict the bubble growth behavior. In this work, the transient equibiaxial elongational viscosity function at the bubble wall during bubble growth is described holistically for the first time. This is achieved by extending the so-called molecular stress function (MSF) model by superposition principles (temperature, pressure and blowing agent concentration) and by using the elongational deformation behavior (Hencky strain and strain rate) at the bubble wall during the initial, and thus viscosity-driven, bubble growth process. Therefore, transient uniaxial elongational viscosity measurements are performed and the non-linear MSF model parameters of the two investigated polymers PS (linear polymer chains) and PLA (long-chain branched polymer chains) are determined. By applying the superposition principles and by changing the strain mode parameter to the equibiaxial case in the MSF model, the transient equibiaxial viscosity master curve is obtained and used to describe the bubble growth process. The results show that the extended MSF model can fully predict the transient equibiaxial elongational viscosity function at the bubble wall during bubble growth processes. The bubble growth behavior over time can then be realistically described using the defined transient equibiaxial elongational viscosity function at the bubble wall. This is not possible, for example, with a representative viscosity and therefore clearly demonstrates the influence and importance of knowing the transient deformation behavior that prevails at the bubble wall during bubble growth processes.

Green synthesis of CdS/flaxseed mucilage nanocomposite films using gamma irradiation for packaging applications

Abstract The most common ways to produce nanoparticles are through chemical and physical processes, which can be expensive and environmentally hazardous. Using plant extracts (green synthesis) as reducing and capping agents is a simple, cost-effective, and environmentally friendly method of lowering the usage of dangerous chemicals in the synthesis of metal nanoparticles. This study covers the environmentally friendly synthesis of cadmium sulphide nanoparticles (CdS NPs) using a blend of flaxseed extracts (FM), polyvinyl alcohol (PVA), and chitosan (Cs). The composites are then exposed to gamma irradiation at doses of 20 kGy and 40 kGy. UV–VIS absorption spectroscopy, SEM, HRTEM, EDX, and FTIR were used to analyse the produced nanocomposite films. UV–Vis absorption spectra showed considerable surface Plasmon resonance (SPR) bands at 396–440 nm, indicating that CdS NPs had been successfully synthesized. A progressive red shift in wavelength was noted, along with the broadening of the absorption band as the irradiation dose increased. Transmission electron microscopy pictures revealed that the generated CdS nanostructures were dispersed as spherical nanoparticles with remarkable structural homogeneity. Tensile strength and elongation measurements of the films revealed that the inclusion of CdS NPs improved their mechanical properties. The addition of CdS NPs to the current blends limits biodegradation in soil. Thermal gravimetric analysis findings showed that CdS NPs included in FM/PVA films had improved thermal stability. The antimicrobial activities of the tested films were performed against Staphylococcus aureus, Escherichia coli, and Candida albicans. The results revealed that all of the films exhibited more antibacterial activity against S. aureus than the two others, with the highest activity observed in nanocomposites with a high concentration of CdS.

QUALITY BY DESIGN SUPPORTED CONSTRUCTION OF ORAL FAST-DISSOLVING FILMS FOR TELMISARTAN: RECONNOITERING THE QUALITY ATTRIBUTES

Objective: The angiotensin II receptor antagonist telmisartan (TMS) is often used to treat hypertension. The BCS class II antihypertensive drug TMS has a low solubility, poorly absorbed when taken orally. The goal of this study was to formulate an oral fast-dissolving film (OFDF) of TMS. In recent years, the concept of a rapidly dissolving dosage form as an innovative delivery system has gained popularity. By decreasing dosing frequency, maximize therapeutic effectiveness, bioavailability, and stability. It will also prevent the drugs from being metabolized in the first place. This technique allows for faster drug absorption from the gastrointestinal tract (GIT), which might result in a more rapid onset of action. Methods: An experimental design known as Box-Behnken was employed to optimize a OFDF. Mango kernel (100-300 mg), maltodextrin (200-350 mg), and propylene glycol (PG) (15-30%) were chosen as independent variables with the highest preference. Included measurements of T5 tensile strength, disintegration time, folding endurance, elongation, and drug release efficiency as dependent variables. Results: The physical properties of the films were found to be satisfactory, and Fourier transform infrared (FTIR) analysis failed to detect any drug-polymer interaction. F4 was found to have the greatest bioadhesive strength of 49.82 gm and the longest ex-vivo mucoadhesion duration of 189 min. A higher concentration of mango kernel in the formulation resulted in a greater rate of drug release. More than 60% of the drug was discharged within 10 min. Conclusion: The oral mucosa of a rat was used for ex-vivo for irritation studies. Based on the pharmacokinetic plasma parameters, which is made into quick-dissolving films that are taken by mouth, is much better absorbed than aqueous suspensions. Studies of the enhanced formulation's stability showed that F4 may be stored for up to three months without deterioration.

Measurements of Tensile Strength and Elongation of 3D Printed Polylactide Solids Produced with Different Temperatures of Extruder Using Coordinate Measuring Technique and Finite Element Method

Measurements of Tensile Strength and Elongation of 3D Printed Polylactide Solids Produced with Different Temperatures of Extruder Using Coordinate Measuring Technique and Finite Element Method

Uniform elongation measurements on creep specimens by a novel 3D-scanning system

ABSTRACT The ductility of a material represents a very important value for both the classification and application of high-temperature alloys in real components. Commonly, different values have been defined and can be used to characterise the ductility of the material. Within this work, a 3D-scanning system has been developed which allow a highly precise digital reconstruction of fractured creep specimens. The digital reconstruction is used to compare and refine conventions for determining one of the ductility candidate values, the uniform elongation, in a consistent, robust and objective way. By utilizing this system, a large amount of long-term creep specimens were re-evaluated including P92 samples with challenging, since macroscopically low ductility values. The results will be discussed in by providing uniform elongation trends and by the use of the Ductility Evaluation of Creep Specimens (DECS) diagram.

Recrystallization and Anisotropy of AZ31 Magnesium Alloy by Asynchronous Rolling

In this study, the microstructure and mechanical properties of AZ31 magnesium alloy were investigated through asynchronous rolling. The results demonstrate that the rolled sample exhibits a refined grain structure with a significant presence of continuous dynamic recrystallization. Notably, as the roll speed ratio increases, the grain refinement becomes more apparent. For the sample with a roll speed ratio of 1.3, the tensile strength in the rolling direction (RD) reaches 273 MPa, while the elongation measures 20.2%. Similarly, in the transverse direction (TD), the tensile strength reaches 282 MPa, accompanied by an elongation of 18.9%. These values indicate a substantial improvement in elongation compared to conventional rolling processes. The enhanced elongation can be attributed to two primary factors. Firstly, recrystallization contributes to a grain refinement recrystallization ratio of 86%, promoting improved mechanical properties. Secondly, the recrystallized grains induce a favorable Schmidt factor, further supporting elongation. Overall, the findings of this research highlight the benefits of asynchronous rolling in refining the microstructure and enhancing the mechanical properties of AZ31 magnesium alloy.

The Effects of the Variable-Pressure Rolling of a Wire Arc Additively Manufactured Inconel625-SS308L Bimetallic Structure

The superior deposition rates of Wire Arc Additive Manufacturing (WAAM) allow for the production of a substantial number of parts while reducing the time and cost associated with machining, and have attracted significant attention. This study focused the microstructural and mechanical properties of a bimetallic thin-wall composed of SS308L and Inconel625, manufactured using variable-pressure rolling WAAM. A detailed analysis of the cross-sectional microstructure of the bi-metallic wall of non-pressure cases revealed a columnar solidification structure. In contrast, the pressured case was dominated by equiaxed structures. The microhardness tests conducted on the bimetallic interface revealed a hardness range of 139–188 HV within the SS308L region, and a 187–222 HV hardness spectrum within the Inconel625 region. The bimetallic interface displayed no unexpected hardness variations. Tensile tests carried out in the vertical direction across the bi-metallic interface resulted in a localized failure at the 308L region. The range of ultimate tensile strength was between 539 and 585 MPa, the yield strength varied from 344 to 377 MPa, and the elongation measurements were found to be within the range of 37 to 44%. All test specimens showed a consistent pattern of ductile rupture upon fractographic inspection, with fracture occurring in the SS308L region.

Synthesis and Physical Characterization of Bioplastics Based on Jicama Starch (Pachyrhizur Erosus) – Chitosan

The development of plastics that can be easily degraded is needed to reduce the impact of plastic use on the environment. This study aimed to utilize the starch present in jicama to be used as the main material for making plastic. In order to overcome the drawback of starch which is less flexible, materials such as chitosan and glycerol were used. The stages of this research consisted of extracting starch from jicama, making bioplastics by mixing yam starch with chitosan and glycerol in varying amounts, as well as analysis and characterization in the form of tensile strength tests, elongation measurements, hydrophobic properties measurements, and degradation tests. The results of the study showed that by varying the amount of glycerol and chitosan, the bioplastic degradation ability obtained could be optimized.

Complete 1D continuum model for a pantographic beam by asymptotic homogenization from discrete elements with shear deformation measure

Starting from a discrete model of a pantographic beam based on beam elements with 6 DOF in 2D space, 2 translational and 1 rotational for each end node, and proposing an energy quadratic in elongation, shear, bending and torsion deformation measures, we find by asymptotic homogenization a model of a complete 1D second gradient continuum. Compared to previous models, the discrete model of the present work includes shear deformation by considering the beam element’s end nodes relative orientation. The resulting continuum model differs in a stiffness coefficient stemming from the shear deformation, but it coincides in the limit of shear stiff elements.

Effect of ultraviolet-protective 2-ethylhexyl salicylate incorporation on the mechanical properties of different maxillofacial silicone elastomers

Statement of problemWhether the incorporation of ultraviolet-protective 2-ethylhexyl salicylate (UV-ES) affects the mechanical properties of different maxillofacial silicone elastomers, limiting the service life of facial prostheses, is unclear. PurposeThe purpose of this in vitro study was to examine the mechanical properties of different maxillofacial silicone elastomers incorporating different ratios of UV-ES. Material and methodsThree different ratios of UV-ES were incorporated into 3 different types of maxillofacial silicones (M511, TechSil-25, and A-2000), and the mechanical properties of the silicones were investigated. Silicone pigments were added to each silicone type to mimic skin color. Dumbbell-shaped specimens were fabricated for tensile strength, percentage elongation, and hardness measurements, and trouser-shaped specimens for tear strength measurement. A total of 240 specimens were prepared. UV-ES in 3 different ratios (1%, 2%, and 5%) and a control group of each silicone type were generated (n=10). The effects of maxillofacial silicone type and ultraviolet protective ratios on hardness, tensile strength, percentage elongation, and tear strength were examined by factorial ANOVA (α=.05). ResultsThe Shore-A hardness in the control and UV-ES added groups was not significantly different in M511 material (P>.05), and a statistically significant decrease was observed in all ratios in TechSil S-25 and A-2000 silicones (P<.05). After adding 1%, 2%, and 5% UV protective into the silicones, the tensile strength and elongation of TechSil S-25 silicone material decreased significantly (P<.05), while these mechanical properties of M511 and A-2000 were not affected by UV-ES addition (P>.05). Tensile and tear strength values of the silicone elastomers were highest for TechSil S-25. ConclusionsThe mechanical properties of M511 and A-2000 silicone elastomers were not adversely affected by the addition of 1%, 2%, or 5% UV-ES.

Validation of a method to elute viruses from different types of face masks

Due to the SARS-CoV-2 pandemic, it is crucial to study the efficiency of face masks in retaining viruses for the upcoming years. The first objective of this study was to validate a method to elute viruses from polyester and cotton face masks. We observed that deionized water followed by 3% beef glycine (pH 9.5 or pH 7.2) was significantly more efficient (p &lt; 0.05) in eluting the bacteriophage phiX174 virus from polyester (4.73% ± 0.25% to 28.67% ± 1.89%), polyester/cotton (3% ± 0.33%), and cotton (1.7% ± 0.21%) face masks than 3% beef glycine only (pH 9.5 or pH 7.2) as a single eluent (3.4% ± 0.16% to 21.33% ± 0.94% for polyester, 1.91% ± 0.08% for polyester/cotton, and 1.47% ± 0.12% for cotton face masks). Also, deionized water was significantly less efficient as a single eluent for eluting bacteriophage phiX174 from all the studied face mask types. The polyethylene glycol (PEG) precipitation method was substantially more efficient (p &lt; 0.05) as a second step concentration method for the viruses in the eluates than the organic flocculation (OF) method. Higher viral loads were eluted from polyester face masks than cotton ones. We also found varying viral loads in the eluate solutions from different commercial polyester face masks, with the highest percentage seen for the N95 face mask. The second objective was to apply the validated method to study the effect of autoclaving on the different face mask materials. Results of the study did not show any significant differences in the viral loads eluted from the studied face masks before and after one and five autoclaving cycles. Moreover, a scanning electron microscope (SEM) analysis revealed no changes in the yarns, elongation, tensile strength, and contact angle measurements of the polyester or cotton materials after one or five autoclaving cycles.

Evaluation of the measurement uncertainty during the tensile tests of high-strength bolts

A developed methodology for evaluating measurement uncertainty during the tensile tests of metals and alloys is presented. In this connection, the various sources of uncertainty are considered. The object of studies included high-strength bolts made of 40Kh “Selekt” steel, which were subjected to tensile tests according to the GOST 1497-85 State Standard using a UMM-100 universal tensile testing machine. The basic sources of uncertainty in the measurement of relative elongation and reduction were shown to include repeated measurements of relative elongation; errors of measuring the finite length by a vernier calliper and marking the initial length of a calculated section, as well as the measurement error of the tensile testing machine. These also include operator reading error, repeated relative reduction measurements, as well as the error of measuring the sample diameter by a micrometer before and after the tests. During the measurements, temperature deviation was demonstrated to constitute an additional source of uncertainty when the ambient temperature is different from the standard temperature value ((20±5)°C). Assumptions underlying laws describing the distribution of input values were assigned. Tensile tests are shown to be characterised by two components of uncertainty evaluated as types A and B. A mathematical model constructed for measuring relative elongation and relative reduction during tensile tests is presented. The standard uncertainties of input values are evaluated based on the assumed laws of their distribution. A correlation between the final length of the calculated section, the diameter of the sample following the test, and the applied force, is revealed. Expressions for the calculation of sensitivity coefficients, which characterize variations in the output value (relative elongation) depending on variations of input values, were obtained. The total and extended measurement uncertainties were evaluated. Based on the performed studies, a procedure for evaluating measurement uncertainty when carrying out tensile tests of high-strength bolts was described. The evaluation of measurement uncertainty during the product testing was shown to be a rather labourconsuming work. In this regard, the authors propose the development of procedures for evaluating the measurement uncertainty during the tests with their inclusion into regulatory documents for control methods.

Micro-Computed Tomography with 3D Image Analysis to Reveal Firing Temperature Effects on Pore Systems in Archaeological and Ethnographic Ceramics

Understanding the firing regimes of archaeological ceramics reveals clues about the history of technological developments, but current methods for determining firing history have limitations. We experimented with non-destructive micro-CT combined with 3D image analysis to collect data on 42 pore variables, hypothesizing that pore systems are affected by ceramic firing temperatures. Analysis of variance showed that 26 of the variables are significantly related to firing temperature. Total volume porosity (open and closed pores) goes down with increased firing temperature, as does the fraction of pores accessible to a surface. Maximum pore volume, maximum and standard deviation of pore surface area, and pore elongation measures all decrease with higher firing temperatures while shape factors indicating greater sphericity increase. Pore connectivity measures decrease with higher firing temperatures, and variation in pore and connection lengths increases. The highest fired ceramics have low connection tortuosity. Three-dimensional image analysis of micro-CT data can augment existing methods of archaeothermometry, and since many pore characteristics impact the functional properties of ceramics (density, durability, mechanical strength, thermal conductivity, permeability, and diffusion), firing temperature studies of pore systems can inform wider archaeological ceramics research.

The biomechanics of ultra-stretchable nerves

When digging in the ground during egg laying the female locust extends her abdomen to 2-3 times of its original length. How the abdominal nervous system accommodates such extreme elongation remains unknown. We characterized and quantified the system's biomechanical response using controlled exvivo elongation and force measurements. The microstructure of the nerves was studied using histology and high-resolution confocal microscopy. Although the nervous system of sexually mature females demonstrated fully reversible hyper-extensibility of up to 275%, the elongation observed in premature females and males was much more limited. The unique extension dynamics of the different groups were captured by their very different force-displacement curves. Confocal microscopy suggested that elongation is not owing to undulations of the nervous system structure. Thus, the exceptional resistance to deformation and rupture presents the female locust abdominal nervous system as a valuable model for understanding the functionality and pathology related to nerve extension and reversible elongation.

Effect of sediment form and form distribution on porosity: a simulation study based on the discrete element method

Porosity is one of the key properties of dense particle packings like sediment deposits and is influenced by a multitude of grain characteristics such as their size distribution and shape. In the present work, we focus on the form, a specific aspect of the overall shape, of sedimentary grains in order to investigate and quantify its effect on porosity, ultimately deriving novel porosity-prediction models. To this end, we develop a robust and accurate simulation tool based on the discrete element method which we validate against laboratory experiments. Utilizing digital representations of actual sediment from the Rhine river, we first study packings that are composed of particles with a single form. There, porosity is found to be mainly determined by the inverse equancy, i.e., the ratio of the longest to the smallest form-defining axis. Only for small ratios, additional shape-related properties become relevant, as revealed by a direct comparison to packings of form-equivalent but smooth ellipsoids. Since sediment naturally features form mixtures, we extend our simulation tool to study sediment packings with normally-distributed forms. In agreement with our single form studies, porosity is found to depend primarily on the inverse of the mean equancy. By supplying additional information about a second form factor and the standard deviations, we derive an accurate model for porosity prediction. Due to its simplicity, it can be readily applied to sediment packings for which some measurements of flatness and elongation, the two most common form factors, are available.Graphical abstract

Fiber Optic Hydrophones for towed array applications

In this paper, we report the design and development of a fiber optic hydrophone for underwater applications. The sensing configuration is based on a Michelson interferometer where a fiber coil is wrapped around a compliant mandrel acting as a sensitive element. The acoustic wave leads to a deformation of the mandrel that is transferred into strain in the optical fiber. Two Fiber Bragg gratings are used at the terminal ends of the fiber coil to enable the fiber elongation measurement. A similar “dummy” hydrophone is used as reference. The sensor was designed to be sensitive to sea state zero. The fabricated hydrophones were characterized in an instrumented tank. An acoustic source was used to generate acoustic tones in the frequency range 3 ÷ 25 kHz. A reference piezoelectric hydrophone was used to record the underwater acoustic waves in the tank. The hydrophone exhibited a responsivity of about 19 nm/Pa in the frequency range 3 ÷ 10 kHz allowing a resolution of 0.3 mPa/Hz1/2. The linearity and directivity of the sensors were carefully investigated. The fiber optic hydrophone was used as a basic building block to conceive and fabricated a towed array with five elements. The multiplexed hydrophones in the towed array were simultaneously interrogated and the responsivity of the hydrophones were retrieved. Beyond the good repeatability in terms of hydrophone responsivity, the tests in the tank confirm the capability of the fiber optic technology to offer technological solutions for underwater operation with potential advantages in terms of lightness and small-size for use in unmanned underwater vehicles.