Mechanical properties of metal and polymeric viscoelastic materials and their applications

Nowadays, With the wide application of metals and polymeric materials, how to describe the property of Viscoelastic material and how to apply them in engineering has become more and more critical. Due to the lack of insight into the mechanical properties of viscoelastic materials, many scholars have done a lot of experiments in studying the behavior of viscoelastic materials. Axial tensile tests were conducted on specimens to derive different mechanical behaviors of metals, polymers, and other materials at different temperatures and loading rates. Metal can generally be divided into elastic and plastic parts, while polymeric materials have the phases of the linear elastic region, drawing region, and oriented molecular strength region. This paper also shows a test conducted by Argon, Ali S., and M. I. Bessonov of four different kinds of polymers at different circumstances of temperature. After that, the paper shows the application of viscoelastic materials as CLD in damping and some engineering problems caused by the mechanical properties of viscoelastic materials. Currently, research on viscoelasticity should mainly focus on the application of Finite Element Methods and the acquisition of more experimental data to establish a complete theoretical system.

Innovative and Sustainable Materials in Architectural Engineering

The advantages of fiber-reinforced polymer (FRP) composite material have attracted architectural engineers as alternative construction materials. FRP materials are noncorrosive, lightweight, exhibit high tensile strength, and stiffness, are easily fabricated and constructed. For architectural applications, FRP materials are fabricated using a polymer matrix, such as epoxy, vinyl ester, or polyester, and reinforced with various grades of carbon, glass, and/or aramid fibers. In this study, FRP coupons have been tested under axial tensile load to evaluate the strength of these materials for architectural application. Coupon specimens were cut from two different types of glass-FRP (GFRP) tubes namely: Type I and II, the two types had constant internal diameter equal to 152 mm. The GFRP tubes Type I consist of six layers with (±60°) fibers angles oriented mainly in the hoop direction with respect to the longitudinal axis of the tubes, the total thickness is 2.65 mm. While GFRP tubes I consist of fourteen layers with different fibers angles (±65, ±45, ±65) and the total thickness are 6.4 mm. The test results were presented and discussed. The strength of the coupon showed an acceptable level to be used for architectural application. Some of the FRP composites successful applications are briefly presented and discussed to provide the appropriate background for the application of FRP composites in architectural engineering. The promising results presented for the GFRP materials represent a further step toward architectural application.

Fused filament fabrication of continuous optic fiber reinforced polylactic acid composites

Purpose The limited strength of polylactic acid (PLA) hinders its extensive engineering applications. This paper aims to enhance its strength and realize diverse applications. Design/methodology/approach Here, the continuous fiber reinforced PLA composites are fabricated by a customized fused filament fabrication three-dimensional printer. Uniaxial tensile and three-point flexural tests have been conducted to analyze the reinforcement effect of the proposed composites. To unveil the adhering mechanism of optic fiber (OF) and PLA, post failure analysis including the micro imaging and morphology have been performed. The underlying mechanism is that the axial tensile strength of the OF and the interfacial adhesion between PLA and OF compete to enhance the mechanical properties of the composite. Findings It is found that 10%–20% enhancement of strength, ductility and toughness due to the incorporation of the continuous OF. Originality/value The continuous OFs are put into PLA first time to improve the strength. The fabrication method and process reported here are potentially applied in such engineering applications as aerospace, defense, auto, medicine, etc.

Centrifuge study of seismic response of soil-nailed walls supporting a footing on the ground surface

Seismic design of soil-nailed walls requires demonstrations of tolerable ranges of wall movements, especially when a surcharge load exists near the wall. In this study, the effect of surcharge location on seismically induced wall movements was investigated using four centrifuge tests. The axial tensile forces, developed along the soil nails during the seismic loadings, were also measured during the tests. At 50g centrifugal acceleration, model tests represented a 12-m-high prototype wall reinforced with five rows of soil nails. To apply a surcharge stress of 30 kPa at the specified location relative to the wall for each model test, a rigid footing was placed on the soil surface. The model soil-nailed walls were subjected to three successive earthquake motions. Surprisingly, it was found that the model wall with the footing located behind the soil-nailed region experienced the largest seismic movements, even more than when the footing was directly behind the wall. Further, the tests showed that the lower soil nails played a key role in the wall stability during earthquake shaking, acting as a pivot for the pre-collapse cases tested, whereas the upper soil nails needed to be sufficiently extended to properly contribute to the seismic stability of the wall.

Simulation Analysis of Limit Operating Specifications for Onshore Spoolable Reinforced Thermoplastic Pipes

Spoolable reinforced plastic line pipes (RTPs), exhibiting a series of advantages such as good flexibility, few joints, long single length, light weight, easy installation, etc., have been widely used in the onshore oil and gas industry such as oil and gas gathering and transportation, high pressure alcohol injection, water injection, sewage treatment, and other fields. However, due to the lack of clear standard specificationof the limit operating properties for RTPs, three typical failure modes, i.e., tensile, flexure, and torsion, frequently occur in terrain changes,construction operation, and subsequent application, which seriously affects the promotion and use of RTPs. In this paper, the stress distribution of a non-bonded polyester fiber reinforced high-density polyethylene (HDPE) pipe (DN 150, PN 2.5 MPa) was systematically studied by the finite element method (FEM),and then the limit operating values under the axial tensile, coiled bending, and torsion load were determined.The corresponding experiments were conducted to validate the reliability and accuracy of the FEM model. The FEM results showed that the critical strain for axial tensile was 3%, the minimum respooling bend radius was 1016.286 mm, and the limit torsion angle of this RTP was 58.77°, which are very close to the experimental results. These limit values will be useful to establish normative guidelines for field construction and failure prevention of onshore RTP.

A Standardised Approach to the Biomechanical Evaluation of Tracheal Grafts

The ideal tracheal substitute must have biomechanical properties comparable to the native trachea, but currently there is no standardised approach to evaluating these properties. Here we propose a novel method for evaluating and comparing the properties of tracheal substitutes, thus systematising both measurement and data curation. This system was tested by comparing native rabbit tracheas to frozen and decellularised specimens and determining the histological characteristics of those specimens. We performed radial compression tests on the anteroposterior tracheal axis and longitudinal axial tensile tests with the specimens anastomosed to the jaw connected to a measuring system. All calculations and results were adjusted according to tracheal size, always using variables relative to the tracheal dimensions, thus permitting comparison of different sized organs. The biomechanical properties of the decellularised specimens were only slightly reduced compared to controls and significant in regard to the maximum stress withstood in the longitudinal axis (−0.246 MPa CI [−0.248, −0.145] MPa) and the energy stored per volume unit (−0.124 mJ·mm−3 CI [−0.195, −0.055] mJ·mm−3). The proposed method is suitable for the systematic characterisation of the biomechanical properties of different tracheal substitutes, regardless of the size or nature of the substitute, thus allowing for direct comparisons.

Numerical investigations of the clinching process and the failure prediction of clinched joints for dissimilar sheets

The clinching process is more and more used in automotive design and manufacturing. Traditional quality inspection of joints needs a lot of destructive tests, which is time-consuming and material-consuming. In this paper, the clinching process and joints failure of dissimilar materials, 6061 aluminium alloy and HC340/590DP dual-phase steel, are studied. A two-dimensional finite element model is established. Experiments were carried out to verify the numerical model. Through the axial tensile test, the quality of clinched joints for upper steel-lower aluminium alloy and upper aluminium alloy-lower steel were measured, respectively, and the strength and safety of the joints met the requirements of design indexes. The conventional prediction model of maximum tensile force and its modified model was researched. Combined with numerical simulation results, the fracture load, the separation load, and the failure mode of two clinched joints were predicted, respectively. Furthermore, the results are in good agreement with the experimental results. The results show that the modified prediction model of maximum tensile force has a good prediction result, and the error rate is less than 10%. The modified prediction model of maximum tensile force can effectively predict the tensile failure test results, which provides a basis for the quality evaluation and strength prediction optimization of dissimilar materials clinched joints.

Mechanical performance of aluminum reinforced wood plastic composites under axial tension: an experimental and numerical investigation

Wood plastic composites (WPCs) are low-cost biomass composite materials with good mechanical stability and good weather resistance that are mainly used in the areas with low stress levels. Aimed at improving the mechanical properties of WPCs, this paper proposes a new WPC reinforced with aluminum. The WPC and aluminum were hot pressed to form an aluminum reinforced wood plastic composites (A-WPC). The axial tensile properties, stress–strain relationship, and failure mechanism of the composite were studied experimentally. The results show that the ultimate stress and strain, elastic modulus, and other mechanical parameters of A-WPCs are much higher than those of WPCs. The elongation at break is 10.13 times that of WPCs, which greatly improves the ductility. Based on the equivalent stiffness theory, two calculation models were proposed to predict the tensile stress–strain relationship of A-WPCs. The tensile rebound process of A-WPCs was analyzed in depth, and then the calculation formula of the residual curvature was deduced to compare with the test results. The experimental results are in good agreement with the calculation results.