Mechanical behaviour of photovoltaic composite structures: Influence of geometric dimensions and material properties on the eigenfrequencies of mechanical vibrations

2017 ◽  
Vol 6 ◽  
pp. 59-62 ◽  
Author(s):  
M. Aßmus ◽  
K. Naumenko ◽  
H. Altenbach
Keyword(s):  
Mechanical Behaviour ◽  
Material Properties ◽  
Composite Structures ◽  
Mechanical Vibrations

Integrally-Stiffened Composite Damage Tolerance Evaluated by Computational Simulation

2001 ◽  
Author(s):  
Christos C. Chamis ◽  
Levon Minnetyan
Keyword(s):  
Material Properties ◽  
Composite Structures ◽  
Failure Modes ◽  
Damage Tolerance ◽  
Epoxy Composite ◽  
Computational Simulation ◽  
Computer Code ◽  
Simulation Design ◽  
Damage Initiation ◽  
Composite Damage

Abstract An integrally stiffened graphite/epoxy composite rotorcraft structure is evaluated via computational simulation. A computer code that scales up constituent micromechanics level material properties to the structure level and accounts for all possible failure modes is used for the simulation of composite degradation under loading. Damage initiation, growth, accumulation, and propagation to fracture are included in the simulation. Design implications with regard to defect and damage tolerance of integrally stiffened composite structures are examined. A procedure is outlined regarding the use of this type of information for setting quality acceptance criteria, design allowables, damage tolerance, and retirement-for-cause criteria.

Maximizing the Fundamental Natural Frequency of Triangular Composite Plates

1996 ◽  
Vol 118 (2) ◽  
pp. 141-146 ◽  
Author(s):  
S. Abrate
Keyword(s):  
Natural Frequency ◽  
Material Properties ◽  
Composite Structures ◽  
Natural Frequencies ◽  
Ritz Method ◽  
Laminated Composite ◽  
Composite Plates ◽  
Mode Shapes ◽  
Fundamental Natural Frequency ◽  
Wide Range

While many advances were made in the analysis of composite structures, it is generally recognized that the design of composite structures must be studied further in order to take full advantage of the mechanical properties of these materials. This study is concerned with maximizing the fundamental natural frequency of triangular, symmetrically laminated composite plates. The natural frequencies and mode shapes of composite plates of general triangular planform are determined using the Rayleigh-Ritz method. The plate constitutive equations are written in terms of stiffness invariants and nondimensional lamination parameters. Point supports are introduced in the formulation using the method of Lagrange multipliers. This formulation allows studying the free vibration of a wide range of triangular composite plates with any support condition along the edges and point supports. The boundary conditions are enforced at a number of points along the boundary. The effects of geometry, material properties and lamination on the natural frequencies of the plate are investigated. With this stiffness invariant formulation, the effects of lamination are described by a finite number of parameters regardless of the number of plies in the laminate. We then determine the lay-up that will maximize the fundamental natural frequency of the plate. It is shown that the optimum design is relatively insensitive to the material properties for the commonly used material systems. Results are presented for several cases.

Review of material test standardization status for the material qualification of laminated thermosetting composite structures

2020 ◽  
pp. 073168442095810
Author(s):  
Sang Yoon Park ◽  
Won Jong Choi
Keyword(s):  
Composite Materials ◽  
Material Properties ◽  
Composite Structures ◽  
Failure Modes ◽  
Laminated Composite ◽  
Test Methods ◽  
Test Method ◽  
Experimental Comparison ◽  
Laminated Composite Materials ◽  
Design Values

This paper presents a review of recent literature related to the static mechanical testing of thermoset-based carbon fiber reinforced composites and introduces a material qualification methodology to generate statistically-based allowable design values for aerospace application. Although most test methods have been found to be effective in determining the specific material properties by incorporating them into the material qualification and quality control provisions, a full validation to clarify the behavior of thermoset-based laminated composite materials is currently lacking, particularly with regard to the characterization of compressive, in-plane, interlaminar shear, and damage tolerance properties. The present study obtains information on the different types of test method that can be employed within the same material properties, and makes an in-depth experimental comparison based on the past literatures. A discussion on the scope of theoretical analysis involves a description of how the proposed test method can be adequate for obtaining more accurate material properties. This discussion is directly applicable to the assessment of material nonlinearity and the geometrical effect of specimens. Finally, the resulting failure modes and the effect of each material property are studied to aid the understanding of the load distribution and behavior of laminated composite materials.

Direct polymer additive tooling – effect of additive manufactured polymer tools on part material properties for injection moulding

2019 ◽  
Vol 25 (10) ◽  
pp. 1575-1584 ◽  
Author(s):  
Achim Kampker ◽  
Johannes Triebs ◽  
Sebastian Kawollek ◽  
Peter Ayvaz ◽  
Tom Beyer
Keyword(s):  
Mechanical Properties ◽  
Surface Roughness ◽  
Mechanical Behaviour ◽  
Material Properties ◽  
Tensile Elongation ◽  
Morphological Structure ◽  
Mould Insert ◽  
Content Type ◽  
3D Print ◽  
Standard Specimens

Purpose This study aims to investigate the influence of additive manufactured polymer injection moulds on the mechanical properties of moulded parts. Therefore, polymer moulds are used to inject standard specimens to compare material properties to specimens produced using a conventional aluminium tool. Design/methodology/approach PolyJet technology is used to three-dimensional (3D)-print a mould insert in Digital ABS and selective laser sintering (SLS) technology is used to 3D-print a mould insert in polyamide (PA) 3200 GF. A conventionally aluminium milled tool serves as reference. Standard specimens are produced to compare resulting mechanical properties, shrinkage behaviour and morphology. Findings The determined material characteristics of the manufactured prototypes from the additive manufactured tools show differences in terms of mechanical behaviour to those from the aluminium reference tool. The most significant differences are an up to 25 per cent lower tensile elongation and an up to 63 per cent lower elongation at break resulting in an embrittlement of the specimens produced. These differences seem to be mainly due to the different morphological structure caused by the lower thermal conductivity and greater surface roughness of the polymer tools. Research limitations/implications The determined differences in mechanical behaviour can partly be assigned to differences in surface roughness and morphological structure of the resulting parts. The exact extend of either cause, however, cannot be clearly determined. Originality/value This study provides a comparison between the part material properties from conventionally milled aluminium tools and polymer inserts manufactured via additive tooling.

scholarly journals Tissue material properties and computational modelling of the human knee: A critical review

2017 ◽  
Author(s):  
Abby E Peters ◽  
Riaz Akhtar ◽  
Eithne J Comerford ◽  
Karl T Bates
Keyword(s):  
Systematic Review ◽  
Finite Element ◽  
Knee Joint ◽  
Mechanical Behaviour ◽  
Material Properties ◽  
Computational Modelling ◽  
Biological Tissues ◽  
Finite Element Models ◽  
Human Knee ◽  
Tissue Material

Understanding how structural and functional alterations of individual tissues impact on whole-joint function is challenging, particularly in humans where direct invasive experimentation is difficult. Finite element computational models produce quantitative predictions of the mechanical and physiological behaviour of multiple tissues simultaneously, thereby providing a means to study changes that occur through healthy ageing and disease such as osteoarthritis. As a result significant research investment has been placed in developing such models of the human knee. Previous work has highlighted that model predictions are highly sensitive to the various inputs used to build them, particularly the mathematical definition of material properties of biological tissues. The goal of this systematic review is two-fold. First, we provide a comprehensive summation and evaluation of existing material property data for human knee joint tissues, tabulating numerical values as a reference resource for future studies. Second, we review efforts to model whole-knee joint mechanical behaviour through finite element modelling with particular focus on how studies have sourced tissue material properties. The last decade has seen a renaissance in material testing fueled by development of a variety of new engineering techniques that allow the mechanical behaviour of both soft and hard tissues to be characterised at a spectrum of scales from nano- to bulk tissue level. As a result there now exists an extremely broad range of published values for human knee tissues. However, our systematic review highlights gaps and ambiguities that mean quantitative understanding of how tissue material properties alter with age and osteoarthritis is limited. It is therefore currently challenging to construct finite element models of the knee that are truly representative of a specific age or disease-state. Consequently, recent whole-joint finite element models have been highly generic in terms of material properties even relying on non-human data from multiple species. We highlight this by critically evaluating current ability to quantitatively compare and model 1) young and old and 2) healthy and osteoarthritis human knee joints. We suggest that future research into both healthy and diseased knee function will benefit greatly from a subject- or cohort-specific approach in which finite element models are constructed using material properties, medical imagery and loading data from cohorts with consistent demographics and/or disease states.

scholarly journals Analytic analysis of auxetic metamaterials through analogy with rigid link systems

2018 ◽  
Vol 474 (2210) ◽  
pp. 20170753 ◽  
Author(s):  
Daniel Rayneau-Kirkhope ◽  
Chengzhao Zhang ◽  
Louis Theran ◽  
Marcelo A. Dias
Keyword(s):  
Finite Element ◽  
Mechanical Behaviour ◽  
Material Properties ◽  
Threshold Value ◽  
Finite Element Simulations ◽  
Elastic Instability ◽  
Lattice Systems ◽  
Rigid Link ◽  
Post Buckling ◽  
Insight Into

In recent years, many structural motifs have been designed with the aim of creating auxetic metamaterials. One area of particular interest in this subject is the creation of auxetic material properties through elastic instability. Such metamaterials switch from conventional behaviour to an auxetic response for loads greater than some threshold value. This paper develops a novel methodology in the analysis of auxetic metamaterials which exhibit elastic instability through analogy with rigid link lattice systems. The results of our analytic approach are confirmed by finite-element simulations for both the onset of elastic instability and post-buckling behaviour including Poisson’s ratio. The method gives insight into the relationships between mechanisms within lattices and their mechanical behaviour; as such, it has the potential to allow existing knowledge of rigid link lattices with auxetic paths to be used in the design of future buckling-induced auxetic metamaterials.

A Numerical Approach for the Investigation of Guided-Waves Propagation Mechanisms in Reinforced Polymers through a DoE Analysis

2019 ◽  
Vol 957 ◽  
pp. 329-339
Author(s):  
A. de Luca ◽  
Donato Perfetto ◽  
Francesco Caputo
Keyword(s):  
Material Properties ◽  
Composite Structures ◽  
Guided Waves ◽  
Lamb Waves ◽  
Numerical Models ◽  
Detection Sensitivity ◽  
Fe Model ◽  
Structural Health ◽  
Waves Propagation ◽  
Local Material Properties

Thanks to their high damage detection sensitivity and low requested power consumption, guided-waves (Lamb waves) have been increasingly used in the last years to monitor the structural integrity in primary and secondary composite structures. The monitoring of the structural health through the propagation of Lamb waves in composite structures is notoriously complex and, for this reason, the development of a prediction model can be a helpful tool for the improvement of Structural Health Monitoring (SHM) systems. Finite Element Method (FE) appears to be the best candidate for such type of simulation. However, since Lamb waves propagation depends strictly on the local material properties of the medium they propagate through, their numerical characterization is a thorny phase. Real composite components are usually affected by the presence of a large number of voids and defects, which cannot be reproduced in numerical models; this leads to a variability of the mechanical properties of materials, with particular reference to elastic moduli and density. These aspects get really ambitious the development of a well-established FE model. In this paper, a design of experiment (DOE) has been carried out to numerically investigate on the effects of the material properties variability on guided-waves time of flight.

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