Strain Rate Effect on Progressive Failure and Tensile Behaviour of Kevlar Epoxy Composites

2020 ◽  
Vol 12 (4) ◽  
Author(s):  
C. Ganesan ◽  
P.S. Joanna ◽  
Dalbir Singh
Keyword(s):  
Mechanical Properties ◽  
Progressive Failure ◽  
Axial Loading ◽  
Experimental Tests ◽  
Strain Rate Effect ◽  
Matrix Cracking ◽  
Epoxy Composites ◽  
Tensile Behaviour ◽  
Strain Rates ◽  
The Difference

This study investigates about the effect of different strain rates on the tensile behaviour of kevlar epoxy composites and progressive failure of kevlar epoxy composites under displacement controlled axial loading. A series of experimental tests were conducted under different strain rates to find out the tensile behaviour of kevlar epoxy composites. Two different strain rates 0.5mm/ min and 1.5mm/ min were applied to the kevlar epoxy specimen in order to understand the difference in mechanical properties and progressive failures of composites. Tensile strength increases with an increase in strain rates. Failure in kevlar epoxy composites is analysed under different stages for both 0.5mm/min and 1.5 mm/min. For all the tests, failure starts with matrix cracking followed by delamination and ends with fracture.

scholarly journals Static Mechanical Properties of Expanded Polypropylene Crushable Foam

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 249
Author(s):  
Przemysław Rumianek ◽  
Tomasz Dobosz ◽  
Radosław Nowak ◽  
Piotr Dziewit ◽  
Andrzej Aromiński
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Strain Rate ◽  
Energy Absorption ◽  
Experimental Tests ◽  
Absorption Capacity ◽  
Strain Rates ◽  
Foam Density ◽  
Energy Absorption Capacity ◽  
Closed Cell

Closed-cell expanded polypropylene (EPP) foam is commonly used in car bumpers for the purpose of absorbing energy impacts. Characterization of the foam’s mechanical properties at varying strain rates is essential for selecting the proper material used as a protective structure in dynamic loading application. The aim of the study was to investigate the influence of loading strain rate, material density, and microstructure on compressive strength and energy absorption capacity for closed-cell polymeric foams. We performed quasi-static compressive strength tests with strain rates in the range of 0.2 to 25 mm/s, using a hydraulically controlled material testing system (MTS) for different foam densities in the range 20 g/dm3 to 220 g/dm3. The above tests were carried out as numerical simulation using ABAQUS software. The verification of the properties was carried out on the basis of experimental tests and simulations performed using the finite element method. The method of modelling the structure of the tested sample has an impact on the stress values. Experimental tests were performed for various loads and at various initial temperatures of the tested sample. We found that increasing both the strain rate of loading and foam density raised the compressive strength and energy absorption capacity. Increasing the ambient and tested sample temperature caused a decrease in compressive strength and energy absorption capacity. For the same foam density, differences in foam microstructures were causing differences in strength and energy absorption capacity when testing at the same loading strain rate. To sum up, tuning the microstructure of foams could be used to acquire desired global materials properties. Precise material description extends the possibility of using EPP foams in various applications.

scholarly journals Effect of Fibre Types on the Tensile Behaviour of Engineered Cementitious Composites

2021 ◽  
Vol 8 ◽  
Author(s):  
Mingzhang Lan ◽  
Jian Zhou ◽  
Mingfeng Xu
Keyword(s):  
Mechanical Properties ◽  
Experimental Result ◽  
Tensile Behaviour ◽  
Cementitious Composites ◽  
Matrix Interface ◽  
Cementitious Composite ◽  
Engineered Cementitious Composite ◽  
Fibre Bridging ◽  
The Difference ◽  
Fibre Matrix

Engineered cementitious composite (ECC) is a group of ultra-ductile fibre-reinforced cementitious composites, characterised by high ductility and moderate content of short discontinuous fibre. The unique tensile strain-hardening behaviour of ECC results from a deliberate design based on the understanding of micromechanics between fibre, matrix, and fibre–matrix interface. To investigate the effect of fibre properties on the tensile behaviour of ECCs is, therefore, the key to understanding the composite mechanical behaviour of ECCs. This paper presents a study on the fibre-bridging behaviour and composite mechanical properties of ECCs with three types of fibres, including oil-coated polyvinyl alcohol (PVA) fibre, untreated PVA fibre, and polypropylene (PP) fibre. The experimental result reveals that various fibres with different properties result in difference in the fibre-bridging behaviour and composite mechanical properties of ECCs. The difference in the composite mechanical properties of ECCs with different fibres was interpreted by analysing the fibre-bridging behaviour.

scholarly journals Generation and homogenization of foamed polymer RVEs: microstructure-mechanical properties relationship

2021 ◽  
Author(s):  
Jean-Luc Bouvard ◽  
Shaoheng Feng ◽  
Florent Alexis ◽  
Marc Bernacki ◽  
Daniel Pino-Munoz ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Experimental Testing ◽  
Experimental Tests ◽  
Image Correlation ◽  
Strain Rates ◽  
Polypropylene Foam ◽  
Tension And Compression ◽  
The Relationship ◽  
Level Set Framework ◽  
Good Agreement

The main purpose of this study is to better understand the relationship between the microstructure of foamed polymer and mechanical properties. X-Ray tomography was performed on polypropylene foam specimens machined from injected plates. These plates were obtained for different thicknesses and exhibit different microstructure morphologies. The tomography scans were first digitalized and meshed. Then, numerical simulations were performed on representative volume elements (RVEs) to get homogeneous mechanical property of the material using a parallel C++ library Cimlib developed at CEMEF. Numerical methods described in this study focused on immerged or body-fitted strategy (FE context - level set framework - meshing adaptation) for exact and statistical RVEs generation. The numerical results were compared to experimental testing performed under tension and compression at different strain rates using image correlation. Good agreement was observed between simulations performed at the mesoscale and experimental tests carried out at the macroscale for both real and statistical RVEs. This methodology opens a way for the development of digital materials designed for specific mechanical properties.

Interfacial Residual Stress Measurement of SiC/Epoxy Composites by Microphotoelastic Method

2006 ◽  
Vol 326-328 ◽  
pp. 273-276
Author(s):  
Xin Wei Yang ◽  
Xin Hua Ji ◽  
Yong Ming Xing ◽  
Yu Wen Qin
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Residual Stresses ◽  
Stress Measurement ◽  
Fem Analysis ◽  
Epoxy Composites ◽  
Residual Stress Field ◽  
Finite Element Software ◽  
Novel Technique ◽  
The Difference

Interfacial residual stresses play an important role in the mechanical properties. In this paper, the interfacial residual stresses of SCI/Epoxy composites were determined using a novel technique-microphotoelastic method. The thermal residual stress field was also numerically simulated using a finite element software MSC.MARC. The difference and the similarities between the experimental results and the simulation of FEM analysis were discussed and the availability of the method was preliminarily certified.

A novel model to predict the stiffness and strength of unidirectional glass/epoxy composites at different strain rates

2020 ◽  
Vol 54 (21) ◽  
pp. 2853-2871
Author(s):  
Alireza Khademi ◽  
Mahmood M Shokrieh ◽  
Shahram Etemad Haghighi
Keyword(s):  
Experimental Data ◽  
Mechanical Properties ◽  
Strain Rate ◽  
Present Model ◽  
Glass Fibers ◽  
Micromechanical Model ◽  
Epoxy Composites ◽  
Strain Rates ◽  
Rate Dependent ◽  
Unidirectional Glass

In the present research, a novel rate-dependent micromechanical model was presented to predict the stiffness and strength of unidirectional glass/epoxy composites. To predict the strain-rate dependent stress–strain behavior of glass fibers, using the Maxwell model with the aid of semi-empirical relations, a new viscoelastic constitutive model was proposed. Moreover, to predict the strain-rate dependent ultimate strength of brittle glass fibers, the elasto-plastic strain-rate dependent Cowper-Symonds material model was simplified by deleting the plastic terms. The strain-rate dependent mechanical properties of the polymer were also investigated by using the modified Goldberg model. Then, by modifying the Mori-Tanaka micromechanical model, a rate dependent micromechanical model was developed to predict the effective elastic properties (stiffness and strength) of unidirectional fibrous composites at arbitrary strain rates. The present model was called the strain-rate dependent Mori-Tanaka micromechanical model. As inputs, the present model just needs the viscoelastic and viscoplastic properties of fibers and polymer. Therefore, the present model reduces the necessary experimental data to predict the rate-dependent mechanical properties of unidirectional composites. For verification of the present model, the results were compared with experimental data and very good consistency in predicting the rate-dependent behavior of unidirectional composites was observed.

scholarly journals Effect of CNT-Based Resin Modification on the Mechanical Properties of Polymer Composites

2021 ◽  
Vol 7 ◽  
Author(s):  
Suhas Yeshwant Nayak ◽  
Satish Shenoy ◽  
Mohamed Thariq Hameed Sultan ◽  
Chandrakant R. Kini ◽  
Aashna Seth ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Impact Strength ◽  
Mechanical Tests ◽  
Matrix Cracking ◽  
Epoxy Composites ◽  
Low Velocity Impact ◽  
Material System ◽  
Limited Information ◽  
Pull Out ◽  
Modes Of Failure

In this study an attempt was made to explore the possibility of substituting 3D E-glass fabric with eco-friendly basalt fabric along with the modification of resin using MWCNTs, a material system about which very limited information exists. The study involved comparing the mechanical properties of two sets of composites. The first set was comprised of 3D orthogonally woven E-glass-reinforced epoxy composites, basalt-reinforced epoxy composites, and hybrid 3D E-glass orthogonally woven/basalt-reinforced epoxy composites while the second set of composites was the same as the first but prepared with resin modified with Multi Walled Carbon Nanotubes (MWCNTs). All the composites were fabricated by hand lay-up and compression molding techniques. To modify the resin for the second set of composites, MWCNTs were dispersed into the epoxy resin with acetone as a surfactant by magnetic stirring and ultra-sonification. Mechanical tests included tensile, flexural, and low velocity impact strength which were evaluated as per standards. Scanning electron microscopy (SEM) was employed to study the fractured surfaces. Results showed that resin modification did not yield any positive results on the mechanical properties of the composites. The highest tensile (364.4 MPa) and flexural strength (345.3 MPa) was obtained for 3D E-glass composites followed by basalt composites and hybrid 3D E-glass/basalt composites while the highest impact strength of 198.42 kJ/m2 was exhibited by the hybrid 3D E-glass/basalt composites. SEM micrographs showed de-bonding between the modified matrix and fiber which was seen as one of the primary causes for relatively poor performance of the composites prepared with modified resin. Fiber breakage, matrix cracking, fiber pull-out, and delamination were the other modes of failure. Results suggest that hybridization with basalt fibers is a much safer, more cost effective, and eco-friendly option over resin modification.

Study on the Mechanical Properties of Soft Rock under Dynamic Uniaxial Compression

2004 ◽  
Vol 261-263 ◽  
pp. 277-282 ◽  
Author(s):  
Hai Bo Li ◽  
Jun Ru Li ◽  
Qing Chun Zhou ◽  
Yong Qiang Liu ◽  
X. Xia
Keyword(s):  
Mechanical Properties ◽  
Experimental Study ◽  
Compressive Strength ◽  
Strain Rate ◽  
Uniaxial Compression ◽  
Hard Rock ◽  
Soft Rock ◽  
Strain Rate Effect ◽  
Strain Rates ◽  
Young’S Moduli

The present paper introduces the experimental study on soft rock (analogized with mortar)under dynamic uniaxial compression at the strain rates from 10-5 to 101s-1. It is indicated that thecompressive strength of the soft rock increase with the increasing strain rate and the rising rates are higher than that of hard rock. The Young's moduli and Poisson's ratio of the soft rock increase with the increasing strain rate, but the rising rates are less than that of compressive strength. In addition, the mechanism of the strain rate effect of the soft rock is primarily analyzed based on the SEM results.

Influence of Fiber Surface Energy on Mechanical Properties of Sisal Fiber - Bio Based Epoxy Composites

2019 ◽  
Vol 35 (4) ◽  
pp. 485-496
Author(s):  
S. RAJKUMAR ◽  
◽  
R. JOSEPH BENSINGH ◽  
M. ABDUL KADER ◽  
SANJAY K NAYAK ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Surface Energy ◽  
Fiber Surface ◽  
Epoxy Composites ◽  
Sisal Fiber

Effect of silver nitrate on some mechanical properties of heat polymerizing acrylic resins

2019 ◽  
Vol 14 (1) ◽  
pp. 110
Author(s):  
Assiss. Prof. Dr. Sabiha Mahdi Mahdi ◽  
Dr. Firas Abd K. Abd K.
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Silver Nitrate ◽  
Surface Hardness ◽  
Mechanical Tests ◽  
Hardness Tester ◽  
Acrylic Resins ◽  
The Difference

Aim: The aimed study was to evaluate the influence of silver nitrate on surfacehardness and tensile strength of acrylic resins.Materials and methods: A total of 60 specimens were made from heat polymerizingresins. Two mechanical tests were utilized (surface hardness and tensile strength)and 4 experimental groups according to the concentration of silver nitrate used.The specimens without the use of silver nitrate were considered as control. Fortensile strength, all specimens were subjected to force till fracture. For surfacehardness, the specimens were tested via a durometer hardness tester. Allspecimens data were analyzed via ANOVA and Tukey tests.Results: The addition of silver nitrate to acrylic resins reduced significantly thetensile strength. Statistically, highly significant differences were found among allgroups (P≤0.001). Also, the difference between control and experimental groupswas highly significant (P≤0.001). For surface hardness, the silver nitrate improvedthe surface hardness of acrylics. Highly significant differences were statisticallyobserved between control and 900 ppm group (P≤0.001); and among all groups(P≤0.001)with exception that no significant differences between control and150ppm; and between 150ppm and 900ppm groups(P>0.05).Conclusion: The addition of silver nitrate to acrylics reduced significantly the tensilestrength and improved slightly the surface hardness.

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