The study seeks to investigate a failure of laminated composite structure subjected to a thermomechanical loading. Failure analysis of composite structures is an important design requirement. The stacking sequence of the structure investigated is restricted to ten thin layers. The fiber orientation, stacking sequence and material properties influence the response from the composite structure. Formulas are presented which are used to estimate the response of multi-layered composite structure to thermomechanical loads. A failure analysis is performed based on some known failure criteria. The values of the engineering properties for multi-layered composite structure and the results of the stress and strain distributions subjected to the forces and bending moments are presented. The numerical results were computed by using MATLAB script. Selected results of the numerical analysis have been presented.

The Local Defect Resonance (LDR) approach is a technique which is used to detect and localize defects in structural components in a non-invasive way. In this contribution, we will assess whether the local resonance frequencies changes by altering a set of experimental testing conditions (i.e. imposed boundary condition, number of excitation points and excitation location). The specimen is made of a carbon fiber reinforced polymer and contains multiple flat bottom holes. However, here, we will focus on three detectable defects. The measured response analyzed through a parametric data-processing approach confirms that the local resonance frequencies are independent of the proposed changes.

Three reinforced concrete (RC) slab-panels are repaired by using the crack injection method. This is because web-shaped crack networks are observed after 46 years in service. In the present research, an attempt is made to confirm the effectiveness of the repair by comparing the velocity distribution of elastic waves obtained from Acoustic Emission (AE) tomography analysis, before and after the repair. Thus, the velocity recoveries due to injection are found in all of the slab panels, and it is confirmed that the elastic wave velocities obtained using this technique can serve as an indicator for examining the state of crack and void filling with injected material. Further, a good correlation is found between the low-velocity region before repair and the amount of injection. These results show the potential of the AE tomography technique to be used as a method for estimating the effect of injection repair.

In this paper digital image correlation (DIC) has been applied to study the deformation process of cementitious material at very early age. After mixing of cement-based materials, the cement hydration process begins. Consequently, the ongoing chemical reactions result in a 3D deformation process (shrinkage). The mechanism affecting the very early age hydration as well as specifically the deformation behavior of cementitious materials is a challenging topic. In view of that, it is essential to determine the significant effect of concrete hardening process on the deformation progression at different stages. The technique of DIC is highly sensitive and allows for the first time in literature an accurate and non-contact optical monitoring of the shrinkage of fresh cementitious material. The displacement of the surface is measured by correlating the different digital images taken at different ages after mixing of the material. The system enables a 3D observation that allows a deeper understanding of the deformation progression. The surface displacement determined by DIC-software is compared to the displacement measured by LVDT sensors for calibration purposes. DIC system realizes a more precise method avoiding the effect of self-weight of the traditional sensor. The purpose of this work is to check the sensitivity as well as the effectiveness of DIC technique, to characterize and better understand the 3D deformation process of fresh cementitious materials.

Friction which happens between plants and soil particles with the agricultural machine parts leads to substantial losses due to wear these parts. Nowadays, polymer matrix composites are playing a great role as a replacement of some critical fast-wearing steel due to their high properties, and this replacement leads to increase the machine reliability besides better corrosion resistance and lighter construction. Five types of composite materials were suggested to replace these steel parts. We chose ESD PA6 G, HD1000, PA6E, PA6G and PA66GF30 as test materials. And two kinds of testing methods were done to test these materials. First one is a pin-on-plate test with sliding abrasive clothes, the second one is a sand slurry test which uses standard abrasive particles. In the pin-on-plate abrasive wear system, we found that PA6G was the best choice of the used polymers because it had the lowest wear rate.

In this study, a single-pulse laser technique was examined as an advanced repair process as an alternative to existing processes. This repair process involves using a single-pulse laser to irradiate the area ahead of the crack tip to reduce the fatigue crack propagation rate and/or deflect the crack path. Specifically, fatigue tests were conducted on specimens with a hole at the center and an induced fatigue crack at the edge of the hole. A single-pulse laser irradiation was applied ahead of this natural crack tip, and the delaying effect of laser irradiation was then evaluated by a detailed examination of the fatigue crack propagation behavior. Finally, it was confirmed that a single-pulse laser is a viable technique to repair cracked components.

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 has remarkable influences on the axial thermal expansion coefficients of the twisted carbon fibers and Kevlar strands, and the calculated results take good agreements with the experimental data. We can 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 for the carbon fiber samples, which 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(α_L/α_T)^1/2. Where β denotes twist angle of the strand, α_L, α_T is 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 which 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.

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.

Using large lightweight prefabricated sandwich panels offers great possibilities for the renovation of existing dwellings. By facilitating the installation process it reduces the total renovation time to a couple of days. During their life-time, these panels will be subjected to wind loading, equivalent to a repeated loading. The effect of this loading condition on the structural behavior of the sandwich panels was verified experimentally. Four-point bending tests were conducted, both static and cyclic. Results showed that the subjection to different loading-unloading cycles resulted in a residual deformation and a decreased stiffness. After being subjected to a repeated loading, the residual ultimate capacity was lowered with 30%.

The Milan Cathedral, built between 1386 and 1813, is one of the largest masonry monuments ever built. After a brief description of the Cathedral, the paper presents the conceptual design of the monitoring system aimed at assisting the condition-based structural maintenance of the historic building. To the authors’ knowledge, the presented monitoring system is the largest ever implemented in a Cultural Heritage monument; in addition, appropriate strategies of Structural Health Monitoring have been developed for the continuous interrogation of sensors installed in the structure and the extraction from measured data of features which are representative of the current state of structural health.