Conference Programme

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K-03: Composite materials
Tuesday, 20/Jun/2017:
10:30am - 12:00pm

Session Chair: Shantanu Shashikant Mulay, Indian Institute of Technology Madras
Session Chair: Kwek Tze Tan, The University of Akron
Location: Rm 311

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10:30am - 11:00am

Modeling Advanced Metacomposites: Unique Control of Stress Wave Propagation

Kwek Tze TAN

The University of Akron, United States

In this talk, we will present the modelling of advanced metacomposites system with the aim to achieve unique control of stress wave propagation. The first part of the talk will introduce the analytical derivation and modeling of metamaterials system with the unique property of negative effective mass density. Mass-in-mass models will be employed to illustrate the concept of negative dynamic mass with the aim to mitigate stress wave propagation. The second part of the talk will provide practical demonstration of stress wave attenuation performance of elastic metacomposites by showing experimental validation of the
mass-in-mass concept. The third part of the talk will show various ways and possibilities of designing metacomposites system. We will utilize numerical finite element models to exhibit impact wave attenuation and blast-wave mitigation capability of advanced metacomposites system. Finally, an interesting area of non-reciprocity will be introduced and demonstrated using the design concept of elastic metacomposites material system.

11:00am - 11:30am

Computational Modelling of Plain Woven Textile Composites

Shantanu Shashikant MULAY, R UDHAYARAMAN

Indian Institute of Technology Madras, India

A detailed study on the micromechanical modelling of plain woven textile composites (PWTC) have been performed in the present work. The primary objective is to compute the equivalent homogenized effective properties of PWTC. A parallel-series model has been formulated to compute the engineering constants in the transverse direction of a unidirectional composite based on the method of subregions. This model is validated against Chamis approach, Mori-Tanaka, and finite element methods for glass-epoxy composites.

Computational homogenization of unidirectional composite representative volume element (RVE) in the transverse direction has been performed considering a plane strain condition and applying prescribed boundary conditions to satisfy the periodicity of the mesostructure. The effective material properties are obtained by numerical homogenization using Hill’s homogeneity conditions.

The RVE of PWTC is approximated as a cross-ply laminate consisting warp and fill plies, each having different global fibre volume fractions. Fibre undulations and the geometry of the yarns are captured using appropriate shape functions. The individual ply properties in the principal material direction are computed by the mechanics of material-based models which are used and formulated in this work for unidirectional composites. The effective material properties are determined for three different undulation categories and the corresponding mathematical formulations, to compute the effective elastic properties of PWTC, are developed by Voight approximation.

The effective engineering constants obtained from the analytical formulations are finally compared with the in-house experimental results and found to be closely matching.

11:30am - 11:45am

Thermo-mechanical Instability Characteristics of Laminated Composite Cylindrical Shells

Manikandan PERIYASAMY1, Sunil Chandrakant JOSHI1, Armando PINTER2

1Nanyang Technological University, Singapore; 2Leonardo Helicopters, Italy

Even with small infinitesimal increase in load, change of equilibrium configuration of completely different character is highly possible for thin shells structures that could make the whole structure unstable. With increasing use of thin fibrous composite structures in flight vehicle structures, a better understanding of its instability characteristics or the buckling behavior is highly desirable.

This article presents investigation on buckling and post-buckling characteristics of tapered laminated composite cylindrical shells subjected to various combinations of a static mechanical load and a thermal load using finite element methods. Buckling mode shapes of special orthotropic, general orthotropic and Quasi isotropic laminates with various tapering angle, fibre orientation angle and stacking sequence were studied in detail. Post-buckling response is simulated using Riks method available in ABAQUS FE code. Buckling mode shapes corresponds to first and second Eigen values were used to introduce artificial imperfections in post buckling analysis. Influence of combined mechanical loads and coupled thermo-mechanical loads on the instability of the shell is presented. The predicted results from finite element analysis compared well with the test data found from literature.

11:45am - 12:00pm

Stress Analysis of Composite Bonded Single-Lap and Strap Joints

Christian DELLA1, Bao-Jun SHI2

1University of Glasgow Singapore, Singapore; 2Shandong Jianzhu University, China

The requirements of strong and lightweight structures in civil, marine, aerospace, automotive, and wind energy industries have attracted the use of adhesive bonded joint technology for composites. However, adhesive bonding technology cannot be fully utilized without validated methods to increase confidence in bonded joint designs. The use of finite element (FE) analysis is essential to further understand the static performance of the bonded joint, which can be also be used to reduce the expensive testing often necessary to certify bonded joints in critical locations.

Single-lap joints have received considerable attention. However, the effect of the thickness of both the adherend and the adhesive need to be further investigated. Whereas, single-strap and double-strap joints have received limited attention in the literature. In the present work, FE models are developed and analysis are conducted to study thin and thick single-lap composite joints and single- and double-strap composite joints. Linear and nonlinear finite elements are used in the models. The stress based criteria to determine the stress acting on the adhesive layer, where the stress criterion is applied at a given distance of the singularity or the stress used in the criterion is averaged along a distance, together with available failure criteria, maximum stress and Tsai-Hill, are used to determine the structural integrity of the bonded composite joints. The results of the FE models are compared with test data to validate the methods used in the present study.

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