Material and structural behaviour of PMMA from low temperatures to over the glass transition: Quasi-static and dynamic loading

This work aims at characterizing the mechanical behaviour of polymethyl-methacrylate (PMMA) under high velocity impact conditions over a wide range of testing temperatures. To this end, the mechanical response at uniaxial compression is studied for both quasi-static and dynamic conditions covering testing temperatures below, at and above glass transition. A pseudo-brittle to ductile transition in the failure of PMMA is observed at a threshold that depends on testing temperature and strain rate. This analysis allows for the interpretation of the perforation impact tests and to explain the principal deformation and failure mechanisms. To complete the study, the Richeton model to predict yielding is revisited. Finally, we provide a new constitutive model for finite deformations to further identify the deformation mechanisms governing the mechanical behaviour of PMMA and the influence of temperature and strain rate on them.D. Garcia-Gonzalez acknowledges support from the Talent Attraction grant (CM 2018 - 2018-T2/IND-9992) from the Comunidad de Madrid

Perforation Analysis of the Aluminum Alloy Sheets Subjected to High Rate of Loading and Heated Using Thermal Chamber: Experimental and Numerical Approach

The analysis of the mechanical characteristics and dynamic behavior of aluminum alloy sheet due to perforation tests based on the experimental tests coupled with the numerical simulation is presented. The impact problems (penetration and perforation) of the metallic plates have been of interest for a long time. Experimental, analytical as well as numerical studies have been carried out to analyze in details the perforation process. Based on these approaches, the ballistic properties of the material have been studied. The initial and residual velocities laser sensor is used during experiments to obtain the ballistic curve and the ballistic limit. The energy balance is also reported together with the energy absorbed by the aluminum including the ballistic curve and ballistic limit. The high speed camera helps to estimate the failure time and to calculate the impact force. A wide range of initial impact velocities from 40 up to 180 m/s has been covered during the tests. The mass of the conical nose shaped projectile is 28 g, its diameter is 12 mm, and the thickness of the aluminum sheet is equal to 1.0 mm. The ABAQUS/Explicit finite element code has been used to simulate the perforation processes. The comparison of the ballistic curve was obtained numerically and was verified experimentally, and the failure patterns are presented using the optimal mesh densities which provide the stability of the results. A good agreement of the numerical and experimental results is observed

Dynamic behavior of aluminum alloy AW 5005 undergoing interfacial friction and specimen configuration in split hopkinson pressure bar system at high strain rates and temperatures

This article belongs to the Special Issue Behavior, Damage and Fracture of Aluminum Alloy: Experiments and Modeling.In this paper, experimental and numerical results of an aluminum alloy’s mechanical behavior are discussed. Over a wide range of strain rates (10−4 s−1 ≤ έ ≤ 103 s−1) the influence of the loading impact, velocity and temperature on the dynamic response of the material was analyzed. The interface friction effect on the material’s dynamic response is examined using a split Hopkinson pressure bar (SHPB) in a high temperature experiment using finite element analysis (FEA). The effect of different friction conditions between the specimen and the transmitted/incident bars in the SHPB system was examined using cylinder bulk specimens and cylinder plates defined with four-layer configurations. The results of these tests alongside the presented numerical simulations allow a better understanding of the phenomenon and reduces (minimizes) errors during compression tests at high and low strain rates with temperatures ranging from 21 to 300 °C

Perforation Behavior of 304 Stainless Steel Plates at Various Temperatures

The effect of temperature on perforation behavior of 304 austenitic stainless steel plates was investigated experimentally. Perforation tests have been conducted at velocities from 80 to 180 m/s and temperatures between − 163 and 200 °C. Low temperatures were obtained using a specific designed cooling device and the temperature distribution on the specimens was verified to be uniform. Based on the experimental results, the failure mode, the initial-residual velocity curves, the ballistic limit velocities and the energy absorption capacity under different temperatures were analyzed. It was found that petalling was the main failure mode during the perforation process. The average number of petals was three at 20 °C or 200 °C and was increasing continuously to five at − 163 °C. The ballistic limit velocity Vbl was also affected by the initial temperature. It increased slightly from 93 m/s at 200 °C to 103 m/s at − 20 °C and then remained constant at lower temperatures. The material showed better energy absorption capacity at low temperatures and this came not only from the temperature sensitivity of the material but also from the strain-induced martensitic transformation effect. According to martensite measurement by X-ray diffraction technique, the martensite fractions along the fracture surface of petals were 87.1%, 66.2%, 52.8% and 32.4% respectively for initial temperatures of − 163 °C, − 60 °C, − 20 °C and 20 °C

Protocol to define material behaviour and failure strain level at low and high strain rates based on a compression test

Compression test is frequently used to define material behaviour. However, this test may be depending on different effects, for example friction, specimen inertia or local stress triaxiality. For this reason, a new design is proposed to analyse the previous effects and to try to minimize it on quantities measured as macroscopic stress and strain. To have a complete understanding, numerical simulations have been performed using finite element method (Abaqus/Standard and Abaqus/Explicit). It allows one to define the macroscopic behaviour and to have an access to the local values not accessible during experiments for a better understanding of the experimental measurements

Multi-scale physico-chemical characterization of CEB/ANS bio-composites

In a vision to identify the non-linear behaviour of the compressed earth blocks (CEB) reinforced by the Argan nut shells particles (ANS) influenced by many parameters like the shape, the distribution and the quantity of the stabilizers, as well as the interactions between both phases: matrix and reinforcement. The use of numerical models seems to be indispensable. Yet, simulations of heterogeneous structures quickly become unaffordable by direct calculations on finite element software. Therefore, a homogenization of the experimental, analytical, and numerical macrostructure is performed. Thus, an overall micro-mesomacro approach to modelling the mechanical behaviour of CEB/CNA bio-composites has been established. It is mainly based on the notion of the representative elementary volume with two different structures (periodic structure and structure with a poisson distribution). The numerical and analytical homogenization results were validated by the Young’s modulus values resulting from the experimental compression test and the corresponding stress-strain curves

The improvement of the physical and mechanical properties of CNTs based composite material

International audienceSince carbon nanotubes and carbon fibers were discovered, the number of research works on these composite materials has exploded, and that's the reason behind using them in this article as reinforcement to improve the mechanical, electrical and thermal behaviors of materials, to enable their use as Nano-sensors in several new applications. This article aims to describe the structure of these materials and their multi-functionality. An analytical estimation of physical properties was presented, using the homogenization technique. Then, a numerical study in Abaqus, to determine thickness and volume fraction effect of CNts on the behavior of composite materials

Experimental and numerical analysis of the aluminum alloy AW5005 behavior subjected to tension and perforation under dynamic loading

The paper describes mechanical behavior of aluminum alloy AW5005 (EN AW5005) under impact loading. The work is focused on tensile tests and the process of perforation of aluminum alloy AW5005 sheets. Experimental, analytical and numerical investigations are carried out to analyse in details the perforation process. Based on these approaches, ballistic properties of the structure impacted by a conical nose shape projectile are studied. Different failure criteria are discussed, coupling numerical and experimental analyses for a wide range of strain rates. Optimization method functions are used to identify the parameters of the failure criteria. Finally, good correlation is obtained between the numerical and experimental results for both tension and perforation tests

Experimental study of brass properties through perforation tests using a thermal chamber for elevated temperatures

International audienceExperimental analysis on standard brass alloy has been carried out using a high pressure gas gun. Perforation tests have been performed for a variety of impact velocities from 40 to 120 m/s in order to study the material behaviour and to define failure modes.The main aim of the study has been to provide results using an innovative thermal chamber that allows to heat specimens before impact. The range of available temperatures is from the room temperature up to 260 ˚C.The experimental study has allowed to discuss the ballistic properties of the structure. The ballistic resistance of sheet plates is strongly dependent on the material behaviour under dynamic loading and changes with temperature. The ballistic properties are also intensely related to interaction between the projectile and thin brass target. The results in terms of the ballistic curve VR (residual velocity) versus V0 (initial velocity) have shown the temperature effect on the residual kinetic energy and thus on the energy absorbed by the plate, revealing a thermal softening of the brass. The ballistic limit corresponding to the maximum impact velocity without complete perforation has decreased by 5-7% for the highest temperature considered.A changing failure pattern is observed. The number of petals varies as a function of impact velocity and temperature. It can be concluded based on experimental observations that thermal softening is a key point on the process of perforation.Preliminary temperature records have been provided using a thermal imaging camera

Experimental and numerical analysis of aluminum alloy AW5005 behavior subjected to tension and perforation under dynamic loading

The paper describes mechanical behavior of aluminum alloy AW5005 (EN AW5005) under impact loading. The work is focused on tensile tests and the process of perforation of aluminum alloy AW5005 sheets. Experimental, analytical and numerical investigations are carried out to analyse in details the perforation process. Based on these approaches, ballistic properties of the structure impacted by a conical nose shape projectile are studied. Different failure criteria are discussed, coupling numerical and experimental analyses for a wide range of strain rates. Optimization method functions are used to identify the parameters of the failure criteria. Finally, good correlation is obtained between the numerical and experimental results for both tension and perforation tests