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A phase-shifting shearing interference microscope (PSSIM) is introduced in this paper. It is constructed by placing a Savart shear prism between the objective and sample of a polarizing microscope with a rotatable analyzer as the phase-shifter, and it is capable of determining contour height variation and deformation strain using the principle of shearing interferometry. This paper not only interprets the measurement theory but also presents an experimental setup of the PSSIM. Moreover, this paper exhibits the results from the uses of the setup; the results demonstrate the validity and applicability of the PSSIM.

In this paper the design and recalculation of new type ceiling elements made of carbon reinforced concrete (CRC) is described. With the use of the high-potential composite material carbon reinforced concrete, structures can be, compared to conventional steel reinforced concrete (RC), designed and manufactured slimmer and lighter. Because of this and the increased sustainability of ceiling elements made of CRC a noteworthy amount of concrete can be saved. To show the potential of CRC elements, four different structures for various fields of application are shown. The first ceiling element, which will be introduced, fits perfectly for the use in multi-storey car parks because of the high resistance of the carbon fibers against corrosion. Another CRC structure in this paper was created in a research project as a demonstrator to show the potential of the newly developed concrete mixture for CRC. To prove the ability of this new developed concrete, large-scale CRC I-beams were produced in a precast concrete factory. The third ceiling element was designed and manufactured in form of a shell to combine the high strength composite material with an improved design for ceiling elements. The last introduced CRC element was developed as demonstrator in another research project and was designed in form of a ribbed slab.

The seismic events that struck central Italy in 2016 caused severe damage to a wide range of buildings and infrastructures. Masonry buildings were particularly affected, even for low values of peak ground acceleration. In this paper, the data recorded for three masonry buildings belonging to the Seismic Observatory of Structures (OSS) network are used to detect their seismic damage by means of Spectral Entropy (SE). However, entropy measures are sensitive to the energy inserted in the system, since an input of energy can lead to a more deterministic behavior of the structure and thus to a reduction of the entropy indicator. When non-stationary time series are used to evaluate the presence of damage (e.g. mild seismicity) the entropy of the system could be underestimated, leading to misleading results. For these reasons, in this paper an indicator based on SE is proposed to assess the occurrence of damage also in the presence of mild seismicity.

Discrete Element modelling of concrete requires the precise calibration of model parameters that is a long lasting and computationally expensive task in case of complex models. Present study introduces a method for estimating a model parameter (normal strength of parallel bonds) for concretes with different particle size distribution and aggregate type. The parameter estimation leads to an optimization problem based on physical measurement data. In the present paper, a model and its parameters are proposed to estimate normal strength of parallel bonds based on the density and compressive strength of concrete.

Propagation of shock waves in partially- or fully-confined environments is a complex phenomenon due to the possibility of multiple reflections, diffractions and superposition of waves. In a military context, the study of such phenomena is of extreme relevance to the evaluation of protection systems, such as survival containers, for personnel and equipment. True scale testing of such structures is costly and time consuming but small-scale models in combination with the Hopkinson-Cranz scaling laws are a viable alternative. This paper combines the use of a small-scale model of a compound survival container with finite element analysis (with LS-DYNA) to develop and validate a numerical model of the blast wave propagation. The first part of the study details the experimental set-up, consisting of a small-scale model of a survival container, which is loaded by the detonation of a scaled explosive charge. The pressure-time histories are recorded in several locations of the model. The second part of the study presents the numerical results and a comparison with the experimental data.

The present paper describes a measurement technique for phase-separated velocity profile measurements in the two-phase bubbly flow. The Ultrasonic Velocity Profiler (UVP) method which is nonintrusive measurement, is applied to obtain an instantaneous velocity profile of liquid and bubble separately by using only one resonant frequency. To achieve this target, developed algorithm, which can decompose frequency component of the Doppler signal affected by liquid and bubble, is applied in the UVP system to obtain and separate instantaneous velocity profile of both phases. For confirming the applicability of modified measurement system, the developed UVP was used for the measurement of the velocity profile in bubbly flow on vertical pipe flow apparatus, the measurement accuracy was validated by UVP Original and Particle Image Velocimetry (PIV) method. Finally, the UVP was applied to experiment for observing velocity distribution of both phases in a bubble column.

With the non-periodicity and discrete nature, and unnecessary of phase unwrapping process, digital speckle correlation method shows its significant advantages in three-dimensional (3D) shape measurement. Combining with the spatial correlation and temporal correlation method in the digital speckle correlation, a spatio-temporal digital speckle correlation was developed in this paper, which can improve the accuracy of 3D shape measurement and effectively reduce the number of the recorded speckle images for restoring the corresponding 3D shape at the same time. In the experiment, only 5 frames of the required speckle images was needed to reconstruct the 3D shape of a complex object with spatio-temporal digital speckle correlation method, and its accuracy was same as the result when 20 frames speckle images were used in temporal correlation method.

This paper proposes a method for obtaining surface normal orientation and 3-D shape of plano-convex lens using refraction stereo. We show that two viewpoints are sufficient to solve this problem under the condition that the refractive index of the object is known. What we need to know is that (1) an accurate function that maps each pixel to the refraction point caused by the refraction of the object. (2) light is refracted only once. In the simulation, the actual measurement process is simplified: light is refracted only once; and the accurate one-to-one correspondence between incident ray and refractive ray is realized by known object points. The deformed grating caused by refraction point is also constructed in the process of simulation. A plano-convex lens with a focal length of 242.8571 mm is used for stereo data acquisition, normal direction acquisition, and the judgment of normal direction consistency. Finally, restoring the three-dimensional information of the plano-convex lens by computer simulation. Simulation results suggest that our method is feasibility. In the actual experiment, considering the case of light is refracted more than once, combining the calibration data acquisition based on phase measurement, phase-shifting and temporal phase-unwrapping techniques to complete (1) calibrating the corresponding position relationship between the monitor and the camera (2) matching incident ray and refractive ray.

The monitoring of stress changes in structural components under various kinds of dynamical loading is crucial for the assessment of their integrity and lifetime. In addition to many methodologies available, such as strain gauges, optical fiber sensors, X-Ray diffraction and digital image correlation, we introduce a novel non-contact method to visualize stress distributions based on mechanoluminescence (ML). ML is a phenomenon occurring in some materials that emit light upon an applied stress level. In this paper, we develop the ML material (Ca0.4Sr0.6)Al2Si2O8:1%Eu2+,1%Ho3+, a glow-in-the-dark material, to visualize stress distribution in a disc, as well as the stress field of an ultrasonic transducer. The properties of defects in the ML phosphors, which are responsible for ML in this material, are vital for stress visualization.

Studying the deformation and microstructure evolution for Ni-based single crystal alloys at high temperature has important effects on the design of turbine blades and disks. However, in-situ high temperature tests under scanning environment pose an important challenge for the current experimental conditions. In this paper, the resistance heating system was introduced into the high temperature fatigue experimental apparatus. The in-situ tensile test of 900 °C was successfully carried out. The experimental results showed that the crack initiation was mainly caused by inclusion debonding. The fracture mode was mainly characterized by the connection of micro holes.

In this paper, dynamic fracture process and strain rate effect of a porous SiC ceramic were investigated. The failure process under dynamic loading conditions was monitored by a high-speed camera. Digital image correlation (DIC) method was further utilized to calculate the surface strain field. The high-speed images show that crack initiates in the center of the specimen and then propagates to the entire specimen under dynamic loading. In addition, DIC result showed that cracks occur on the surface of the specimen formed a band. And the band finally caused the collapse of the specimen. The test results showed that compressive strength of the porous SiC ceramic is rate sensitive. Under quasi-static conditions, the compressive strength is about 120 MPa, while in dynamic conditions strength increased to 247 MPa. Energy absorption during the deformation process is much larger under dynamic loading.

Fire-testing of Textile Reinforced Concrete (TRC) is an interesting field in which quite limited research has been conducted so far. In this paper some preliminary tests are presented, where mortars used as binders are heated to 850 °C and their residual strength is tested, while the Ultrasonic Pulse Velocity (UPV) is also measured, before and after heating, and compared. Additionally, TRC specimens are subjected to flame exposure with a simple set-up and the residual strength is also tested by flexural tests. It is concluded that even with simple set-ups, interesting results can be obtained regarding the structural degradation of the material.

Through the life cycle of civil infrastructures, quality assessments shall be implemented when construction, in-service, before/after repair and so forth; however, there are no decisive techniques to evaluate inside of structures non-destructively. The authors have developed an advanced measurement method using tomographic approaches. With these advanced technologies, internal damage or defects can be visualized as a distribution of elastic wave parameters such as velocities so that damage identification consisting of locations and damage degree would be possible. In the paper, fracture processes of concrete decks are visualized by the acoustic approaches. Specifically, RC slabs with/without water supply subject to wheel loads are cyclically damaged with monitoring acoustic approaches. As a result, depending on the water condition, different pattern of fracture progress can be confirmed.

A wide range of bulk materials with different physical properties are nowadays handled in the packaging industry using different material conveying techniques. Nevertheless, experimental methodologies to characterise flowability of granular materials in actual handling conditions are still under development. This paper presents a new fully instrumented device for flowability assessment by granular column collapse of bulk materials. The generated granular flow is monitored by load cells that register the flow heights and by a high-speed video camera that captures the bulk flow kinematics through particle image velocimetry analysis. The 3D surface morphology of the final condition is determined with a 2D laser profile scanner. Results show the effect of varying the initial column aspect ratio on flow response.

This paper discusses a method for eliminating geometric optics errors that can occur when combining three-dimensional thermal images using hybrid digital holography. We obtained reconstructed digital holography using phase detection autofocus technique and arbitrary tilt plane correction.

In an aircraft engine, some pieces are describing a rotating movement. These parts are in contact with rotating and non-rotating parts through the bearings and gears. The different contact patches are lubricated with oil. During the lifetime of the engine, mechanical wear is produced between the contacts. This wear of the bearings and gears will produce some debris in the oil circuit of the engine. To ensure the effective operation of the aircraft engines, the debris monitoring sensors play a significant role. They detect and collect the debris in the oil. The analysis of the debris can give an indication of the overall health of the engine. The aim of the paper is to develop, design and model an oil test bench to simulate the oil lubrication circuit of an aircraft engine to test two different debris monitoring sensors. The methodology consists of studying the oil lubrication system of the aircraft engine. The first step is to build the oil test bench. Once the oil test bench is functional, tests are performed on the two debris monitoring sensors. A test plan is followed, three sizes of debris, like the type and sizes of debris found in the aircraft engine oil, are injected in the oil. The test parameters are the oil temperature, the oil flow rate and the mass of debris injected. Each time debris is injected, it is detected and caught by the two sensors. The test results given by the two sensors are similar to the mass debris injected into the oil circuit. The two sensors never detect the total mass of debris injected in the oil. On average, 55%–60% of the mass injected is detected and caught by the two sensors. The sensors are very efficient at detecting debris whose size corresponds to the design range parameters of the sensors, but the efficiency falls when detecting debris whose size lies outside this range.

It’s difficult to directly measure the pressure on the surface of the material in the impact process. PVDF (Polyvinylidene Fluoride) gauges may help to solve this problem. In this paper, some split Hopkinson pressure bar (SHPB) experiments were carried out with the PVDF gauges as specimens, with the strain gauges pasted on the bars being used as the measurement method. By comparing the results of the strain gauges and the PVDF gauges, it is proved that there is a stress concentration when the PVDF gauges were sandwiched directly in the solid interface. Then, two methods to eliminate the stress concentration are verified by experiments. The first method is adding a cushion, such as electrical tape. The second method is using 502 glue, which is evenly coated on the interface.

In this paper, the specificity and/or the common features of materials coming from such new additive manufacturing processes will be compared to more classical one, like casting process. Fatigue properties of Ti-6Al-4V specimens built by EBM and SLM are first compared depending on several process parameters. Then, at the microstructure scale, it is shown that surface defects and unmelted zones seem to be the dominant features. It will be shown that similarities can then be drawn with casting processes where shrinkage and pores are also associated to damage mechanisms.

In this paper, a device with high accuracy capacitive sensor (with the error of 0.1 micrometer) is constructed to measure the axial thermal expansion coefficent of the twisted carbon fibers and yarns of Kevlar. A theoretical model based on the thermal elasticity and the geometrical features of the twisted structure is also presented to predict the axial expansion coefficient. It is found that the twist angle, diameter and pitch have remarkable influences on the axial thermal expansion coefficients of the twisted carbon fibers and Kevlar strands, and the calculated results are in good agreement with experimental data. We found that, with the increase of the twist angle, the absolute value of the axial thermal expansion coefficient increases. For the Kevlar samples, the expansion coefficient will grow by about 46% when the twist angle increases from 0 to 25 degrees, while the carbon fiber samples will grow by about 72% when the twist angle increases from 0 to 35 degrees. The experimental measurements and the model calculations reveal important properties of the thermal expansion in the twisted structures. Most notably, the expansion of the strand during heating or cooling can be zero when the twist angle is around β = arcsin(αL/αT)^1/2, where β denotes twist angle of the strand and αL, αT are the longitute and the transverse thermal expansion coefficient of the strand, respectively. According to the present experiments and analyses, a method to control the axial thermal expansion coefficient of this new kind of twisted structure is proposed. Moreover, the mechanism of this tunable thermal expansion is discussed. Based on the model, a method that can be used to rectify the thermal expansion properties of the twist structures is established. This may be a new way of fabricating zero expansion composite materials in the future.

This paper presents the experimental results obtained with a post-peak loading device of hydraulic fracture controlled by setting circumferential deformation of a specimen to be a closed-loop feedback signal during servo-water-driven and monitored with the optical technique of speckle-shearing interferometry (SSI). The macro-scale complete loading curve obtained by the post-peak loading system indicate the stiffness, peak strength and post-peak behavior of quasi-brittle material subjected to borehole water pressure. The micro-scale out-of-plane displacement (OPD) obtained by SSI corresponding to complete loading curve was exhibited where the internal crack tip was located. The complete hydrofracture evolution from displacement continuity to displacement discontinuity was investigated. The test results provide a better understanding of the hydraulic fracture mechanism which is helpful for the development of theoretical and numerical solutions related to hydraulic fractures.

The first-generation of autonomously healed concrete elements is under construction: beams (SIM-SECEMIN project, Flanders Belgium), one-way flat slabs (MeMC, VUB, Belgium) and wall panels (Materials4Life project, UK) are designed with the embedment of encapsulated repair agent. In the presence of cracks, capsules rupture releasing the agent that fills the crack void. The released agent seals and mechanically restores the crack discontinuity. This automatic process can be repeatable using vascular networks that carry the agent and release it at different locations into concrete. The innovative design is built up following several series of laboratory-scale beam tests configured over the last decade. This paper discusses the application of numerous experimental techniques that assess the mechanical performance of autonomously healed concrete: Acoustic Emission, Ultrasound Pulse Velocity, Optical Microscopy, Digital Image Correlation, Capillary Water Absorption, Computed Tomography. The study focuses on the performance and efficiency of each method on laboratory and real-scale tests. The techniques with the most promising output are selected and combined in order to design a sensing tool that evaluates healing on real applications.

This proceedings paper presents the investigation of different cruciform specimen designs for the characterization of Sheet Molding Compounds under biaxial loading. Biaxial tensile tests allow the investigation of damage evolution under multiaxial stress states, which is particularly interesting due to the different damage phenomena in composite materials. A key challenge is to find a suitable specimen shape, because typical cruciform specimens fail in the arms before damage occurs in the area of interest which is the area of the biaxial stress state in the center region of the specimen. For all of the introduced designs the stiffness degradation is analyzed more in detail and compared to that of a uniaxial bone specimen. For the best performing specimen which is reinforced by unidirectional reinforced tapes on the arms, the strain field is analyzed by finite element simulations, taking into account the mechanical properties of the different layers of the specimen. Especially in the center area and at critical points, strain concentrations and non-symmetrical strain distributions are analyzed and evaluated.

Clinch joining or clinching is a mechanical joining technique for sheet material. In this paper, the mechanical behaviour of multiple clinched joints under mixed-mode loads (peel, shear and pull-out) is investigated using a modified Arcan test. The experimental results are compared with a proposed equivalent model for clinched joints to validate if the model can reproduce the deformation behaviour up to maximum force. The theoretical maximum resistance force of the configurations are then compared to the experimental maximum resistances to investigate the influence of interaction effects on the maximum strength of the configuration. This study is part of a global design strategy for clinched joints in large structures.

This paper presents an inverse analysis method for estimating the temperature and thermal residual stress distributions in the pipe from the temperature history measured on the outer surface. A regularization method was introduced. It is found from numerical simulations that the proposed inverse analysis method with regularization is useful for obtaining a reasonable estimate of the inner surface temperature and thermal stress.

In this paper the potential application of experimental modal testing of railway bridges by application of the forced vibration excitation method is proposed to identify reliable and reproduceable values of the natural frequencies and damping coefficients. It will be shown, that the damping values that are determined by in-situ experimental modal testing are in most cases significant higher than the values given in EN 1991-2 and that the normative damping values are quite conservative. The measuring results of a framed concrete bridge with 16.1 m span length are presented and the dependence of dynamic parameters to seasonable temperature changes and to the size of bridge vibration amplitude will be discussed in detail.

This paper studies a novel geometry for the in-plane shear test performed with an axial electromechanical testing machine. In order to investigate the influence of the triaxiality rate on the mechanical behavior, different tests will be performed on the studied material: simple tensile tests, large tensile tests and shear tests. For the whole campaign, a common equipment should be employed to minimize the impact of the testing device. As a consequence, for the shear tests, the geometry of the specimen must be carefully designed in order to adapt the force value and make it comparable to the one obtained for the tensile tests. Like most of the existing shear-included tensile test specimens, the axial loading is converted to shear loading at a particular region through the effect of geometry. A symmetric shape is generally preferred, since it can restrict the in-plane rotation of the shear section, keep shear increasing in a more monotonic path and double the force level thanks to the two shear zones. Due to the specific experimental conditions, such as dimensions of the furnace and the clamping system, the position of the extensometer or the restriction of sheet thickness (related to the further studies of size effect at mesoscale and hot temperature), several geometries were brought up and evaluated in an iterative procedure via finite element simulations. Both the numerical and experimental results reveal that the final geometry ensures some advantages. For instance, a relatively low triaxiality in the shear zone, limited in-plane rotation and no necking are observed. Moreover, it also prevents any out-of-plane displacement of the specimen which seems to be highly sensitive to the geometry, and presents a very limited influence of the material and the thickness.

The main aim of this paper was to computationally simulate the cardiac ischemia employing Finite Element Method (FEM) and detect its presence and localization using data mining approach. A simplified heart-torso model was created based on computed tomography (CT) images, with performed segmentation of the heart (17 zones). Ischemic and non-ischemic cardiac beats were simulated in different zones with aim to create a virtual database which was used for data mining. Using the virtual database, we trained several classifiers and tested them for the purpose of ischemic beat detection based on the body surface potentials map (BSPM). If the ECG is classified as ischemic by the first stage classifier, potentials were processed by the second stage data mining model, which predicted the location of the ischemic area. The use of the second stage classifier, which located the ischemia in one of the heart’s segments created in the FEM model, goes beyond the current state of the art. Thus, the proposed approach is improved solution which can instantly allow clinicians to implement an adequate treatment strategy in future.

Textile reinforced cements (TRC), combining a cementitious matrix with fibre textiles, are a well-researched subject in literature. The material offers several advantages such as the design of low-weight, slender structures. However, one of the main drawbacks of this composite material is the time consuming manufacturing process using two dimensional fibre textiles. Three dimensional fibre textile architectures offer a solution to this problem, while retaining the TRC advantages. Most 3D fibre textiles use distance holders to bridge two, or more textile layers at a certain distance from each other. The influence of this distance holder on the mechanical properties of the whole TRC remains relatively unstudied in literature and will be the research topic of this paper. This research will present the results of three point bending experiments, performed on short TRC beams with a length to thickness ratio of approximately 4 to 1. A comparison is drawn between 3D TRC with fully operational 3D fibre textiles and 2D TRC with the same textile geometry and orientation, but without distance holders. A positive influence on the flexural response is witnessed for the 3D fibre textile, with an increased flexural stiffness up to 35%.

Pathein suspension bridge situated in Pathein City in the south of Myanmar has shown various symptoms of damage, and the safety of the bridge is questionable. The authorities concerned reported that the bridge has undergone severe deterioration since its construction, involving the towers’ inclination, excessive deflections, bearing failure, heavy corrosion of main cables and hangers, hangers’ inclination, and slippage of clamps. The deformed shape of the stiffening girder was found to be unusual, with maximum deflection nearer to the towers; however, in a single span bridge, such as Pathein Bridge, the maximum deflection is expected to be at mid-span. This paper will explain the possible reasons for the unusual excessive deformations in the stiffening girder and bearing failure. The tension force of hangers was estimated based on vibration measurements, and the distribution of hangers’ tension force along the bridge’s span was found to be non-uniform with low-tension force in hangers closer to the towers. The non-uniform distribution of the hangers’ tension force is possibly due to shortcomings of the design of the cable system. The towers’ inclination has caused the road level to drop down; however, the unusual deformations in stiffening girder are attributed to the non-uniform distribution of the tension force in the hangers. Low-tension force in the hangers near the towers caused the bearing to carry excessive force, which eventually caused the bearing to fail; the bearing was rehabilitated by adding steel rollers.

Finite Element Model Updating (FEMU) is an intuitive inverse technique enabling to efficiently characterize plastic material behavior. Although, conclusive proof of concept for this method can be found in literature, a thorough understanding of the key FEMU-ingredients and their impact on the identification of plastic anisotropy is currently missing. In this paper, we aim at minimizing the experimental work associated with yield locus identification of sheet metal via homogeneous biaxial tensile tests. To this end, a biaxial tension apparatus with link mechanism is used to generate a heterogeneous deformation field within a perforated cruciform specimen. The experimentally measured force and displacement field are used in the FEMU procedure to identify an anisotropic yield criterion. The FEMU approach is assessed by comparing the results with experimental data acquired from state-of-the-art stress-controlled biaxial tensile test in the first quadrant of stress-space.

The inflammation and lipid accumulation in the arterial wall represents a progressive disease known as atherosclerosis. In this study, a numerical model of atherosclerosis progression was developed. The wall shear stress (WSS) and blood analysis data have a big influence on the development of this disease. The real geometry of patients, and the blood analysis data (cholesterol, HDL, LDL, and triglycerides), used in this paper, was obtained within the H2020 SMARTool project. Fluid domain (blood) was modeled using Navier-Stokes equations in conjunction with continuity equation, while the solid domain (arterial wall) was modeled using Darcy’s law. For the purpose of modeling low-density lipoprotein (LDL) and oxygen transport, convection-diffusion equations were used. Kedem-Katchalsky equations were used for coupling fluid and solid dynamics.

Imaging systems for measuring surface displacement and strain fields such as stereoscopic Digital Image Correlation (DIC) are increasingly used in industry to validate model simulations. Recently, CEN has published a guideline for validation that is based on image decomposition to compare predicted and measured data fields. The CEN guideline was evaluated in an inter-laboratory study that demonstrated its usefulness in laboratory environments. This paper addresses the incorporation of the CEN methodology into an industrial environment and reports progress of the H2020 Clean Sky 2 project MOTIVATE. First, while DIC is a well-established technique, the estimation of its measurement uncertainty in an industrial environment is still being discussed, as the current approach to rely on the calibration uncertainty is insufficient. Second, in view of the push towards virtual testing it is important to harvest existing data in the course of the V&V activities before requesting a dedicated validation experiment, specifically at higher levels of the test pyramid. Finally, it is of uttermost importance to ensure compatibility and comparability of the simulation and measurement data so as to optimize the test matrix for maximum reliability and credibility of the simulations and a quantification of the model quality.

Up until today, mode-I fatigue delamination testing has not been standardized, because no consensus exists on best practices to reduce the observed scatter in data, and on the proper parameter describing similitude. A dominant contributor to the scatter seems the fibre bridging observed in the tests. This paper proposes a straightforward experimental and analysis approach to derive zero-bridging delamination resistance curves from each tested specimen without requiring a theoretical model.

In this paper, the MLMM modal parameter estimation method (Maximum Likelihood estimation of a Modal Model) and its new variant will be introduced. The MLMM method tackles some of the remaining challenges in modal analysis (e.g., modal analysis of highly-damped cases where a large amount of excitation locations is needed such as the modal analysis of a trimmed car body). Another big advantage of the MLMM method is its capability to fully integrate, within the estimated modal model, some important physical constraints, which are required for the intended applications, e.g., realness of the mode shape and FRFs reciprocity. More classical modal parameter estimation methods have rarely the possibility to fully integrate these constraints and the obtained modal parameters are typically altered in a subsequent step to satisfy the desired constraints. It is obvious that this may lead to sub-optimal results. The MLMM method uses the Levenberg-Marquardt optimization scheme to directly fit the modal model to the measured FRFs. The applicability of MLMM to estimate an accurate constrained modal model will be demonstrated using two challenging industrial applications.

For the prediction of long term behavior several methods are known. This paper focuses on creep in dynamic mechanical analysis (DMA) and in a tensile setup. The investigated material was Polyamide 6 (PA6). As a pre-study for the DMA, Polypropylene (PP) was tested considering five different factors. To determine the significant influences, the results were interpreted statistically.

The use of composite materials, like glass- and carbon- fiber reinforced polymers, is expected to increase exponentially in the coming years. Consequently, in order to monitor the structural health of these materials, the development of new sensing devices is rapidly accelerating. For this purpose, our research groups have recently developed new ultra-thin polymer waveguide sensors which can be exploited to measure both uniaxial and multiaxial strains occurring in composite components. These sensing foils are manufactured by creating Bragg gratings in waveguides realized in flat polymeric substrates, which makes their placement and alignment easier compared to traditional fiber optic sensors. Moreover, using a non-straight waveguide it is possible to spatially multiplex the sensing gratings in such a way that an optical strain rosette can be created. This paper investigates the suitability of the proposed polymer waveguide sensors for the estimation of the modal parameters of composite components.