scholarly journals Physical modelling of failure in composites

2016 ◽  
Vol 374 (2071) ◽  
pp. 20150280 ◽  
Author(s):  
Ramesh Talreja
Keyword(s):  
Composite Materials ◽  
Failure Modes ◽  
Structural Integrity ◽  
Failure Mechanisms ◽  
Local Stress ◽  
Physical Modelling ◽  
Stress Fields ◽  
Systematic Analysis ◽  
Composite Failure ◽  
Failure Theories

Structural integrity of composite materials is governed by failure mechanisms that initiate at the scale of the microstructure. The local stress fields evolve with the progression of the failure mechanisms. Within the full span from initiation to criticality of the failure mechanisms, the governing length scales in a fibre-reinforced composite change from the fibre size to the characteristic fibre-architecture sizes, and eventually to a structural size, depending on the composite configuration and structural geometry as well as the imposed loading environment. Thus, a physical modelling of failure in composites must necessarily be of multi-scale nature, although not always with the same hierarchy for each failure mode. With this background, the paper examines the currently available main composite failure theories to assess their ability to capture the essential features of failure. A case is made for an alternative in the form of physical modelling and its skeleton is constructed based on physical observations and systematic analysis of the basic failure modes and associated stress fields and energy balances. This article is part of the themed issue ‘Multiscale modelling of the structural integrity of composite materials’.

A Review of Damage Tolerant Design, Certification and Repair in Metals Compared to Composite Materials

2014 ◽  
Vol 891-892 ◽  
pp. 1597-1602 ◽  
Author(s):  
Nabil Chowdhury ◽  
Wing Kong Chiu ◽  
John Wang
Keyword(s):  
Composite Materials ◽  
Composite Structures ◽  
Failure Modes ◽  
Structural Integrity ◽  
Fiber Reinforced Polymers ◽  
Carbon Fiber Reinforced Polymers ◽  
Reinforced Polymers ◽  
Repair Efficiency ◽  
Mechanically Fastened ◽  
Damage Tolerant

A review of some of the various fatigue models introduced over the years for both metallic materials, in particular aluminium alloys followed by fatigue and durability concerns associated with composite materials. The move towards light weight and high stiffness structures that have good fatigue durability and corrosion resistance has led to the rapid move from metal structures to composite structures. With this brings the added concern of certifying new components as the damage mechanisms and failure modes in metals differ significantly than composite materials such as carbon fiber reinforced polymers (CFRP). The certification philosophy for composites must meet the same structural integrity, safety and durability requirements as that of metals. Hence this is where the challenge now lies. Substantial work has been conducted in the reparability of composite structures through bonding using various adherend thicknesses and joint types and has been shown to have higher durability than mechanically fastened repairs for thin adherends however these are currently unacceptable repair methods as they cannot be certified. Repairs are designed on the basis that the repair efficiency can be predicted and should be designed conservatively with respect to the various failure modes and include the surrounding structure.

scholarly journals Effects of local stress fields around broken fibres on the longitudinal failure of composite materials

2019 ◽  
Vol 156-157 ◽  
pp. 294-305 ◽  
Author(s):  
Rodrigo P. Tavares ◽  
Jose M. Guerrero ◽  
Fermin Otero ◽  
Albert Turon ◽  
Joan A. Mayugo ◽  
...  
Keyword(s):  
Composite Materials ◽  
Local Stress ◽  
Stress Fields

Damage Mechanisms in Loaded Aramid Composites by Means of Embedded PVDF Acoustic Emission Sensors

2006 ◽  
Vol 13-14 ◽  
pp. 337-342 ◽  
Author(s):  
Claudio Caneva ◽  
I.M. De Rosa ◽  
F. Sarasini
Keyword(s):  
Acoustic Emission ◽  
Composite Materials ◽  
Polyvinylidene Fluoride ◽  
Structural Integrity ◽  
Fibrous Composite ◽  
Failure Mechanisms ◽  
In Situ Monitoring ◽  
Epoxy Composites ◽  
Pvdf Film ◽  
Emission Data

Cost-effective and reliable damage detection is critical for the utilization of composite materials due to the relatively localised nature of damage formation and the resultant reduction in structural integrity. Of the methods available, Acoustic Emission (AE) is considered as one potential technology for on-line and in situ monitoring of structural degradation of composite materials. Purpose of this work was to study the interaction between embedded PVDF (polyvinylidene fluoride) transducers and composite samples as well as detect and characterize the failure mechanisms in aramid/epoxy flexural test specimens using acoustic emission data obtained by embedded PVDF film sensors. Furthermore, it has been realized a comparison with surface mounted PVDF data. Results of our previous works (Caneva et al., 2005) dealing with monitoring tensile and flexural behaviour of glass/epoxy composites enabled to extend this methodology to aramid/epoxy composites. The use of Acoustic Emission and Scanning Electron Microscopy (SEM) observations enabled to identify and understand the failure mechanisms of the composites tested. Furthermore, satisfactory results of this work highlighted that the application of PVDF shows promise as a suitable acoustic emission transducer for fibrous composite materials.

Impact Response of Composites

2010 ◽  
pp. 193-210
Keyword(s):  
Composite Materials ◽  
Matrix Composite ◽  
Failure Mechanisms ◽  
Dispersed Phase ◽  
Brittle Matrix ◽  
Composite Failure ◽  
Foreign Objects ◽  
Thermoplastic Matrix ◽  
Brittle Matrix Composite ◽  
Rubber Toughened

Abstract As fiber-reinforced polymeric composites continue to be used in more damage-prone environments, it is necessary to understand the response of these materials when subjected to impact from foreign objects. This chapter provides an overview of the analysis methods for impact-damaged composites. It discusses the causes and effects of various failure mechanisms in composite materials. The failure mechanisms covered are brittle-matrix composite failure, tough-matrix composite failure, thermoplastic-matrix composite failure mechanisms, untoughened thermoset-matrix composite failure mechanisms, toughened thermoset-matrix composite failure mechanisms, particle interlayer-toughened composite failure mechanisms, and dispersed-phase, rubber-toughened thermoset-matrix composite failure mechanisms.

Study on Failure Mechanisms of Composite Materials Based on HHT

2013 ◽  
Vol 477-478 ◽  
pp. 30-33
Author(s):  
Wen Qin Han ◽  
Jin Yu Zhou
Keyword(s):  
Composite Materials ◽  
Failure Mechanisms ◽  
Acoustic Emissions ◽  
Deep Understanding ◽  
Intrinsic Mode Functions ◽  
Hilbert Huang Transform ◽  
Composite Failure ◽  
Mode Decomposition ◽  
Materials Failure ◽  
Twill Weave

In order to get a deep understanding of composite failure mechanisms, the new advanced signal processing methodologies are established for the analysis of acoustic emission (AE) data obtained from the quasi-static tension test of composite materials. Tensile test were carried out on twill-weave composite specimens, and acoustic emissions were recorded from these tests. AE signals were decomposed into a set of Intrinsic Mode Functions (IMF) components by means of Empirical Mode Decomposition (EMD) , the Hilbert-Huang Transform (HHT) of each IMF component was performed, it was shown that the frequency distribution of IMF component in time-scale could be directly related to composite materials failure mechanisms.

Methodology for Analysis of Schottky Diode Failures

2010 ◽  
Author(s):  
Bhanu P. Sood ◽  
Michael Pecht ◽  
John Miker ◽  
Tom Wanek
Keyword(s):  
Failure Mode ◽  
Schottky Diode ◽  
Failure Modes ◽  
Schottky Diodes ◽  
Failure Mechanisms ◽  
Forward Voltage ◽  
Fast Switching ◽  
Voltage Drops ◽  
The Common

Abstract Schottky diodes are semiconductor switching devices with low forward voltage drops and very fast switching speeds. This paper provides an overview of the common failure modes in Schottky diodes and corresponding failure mechanisms associated with each failure mode. Results of material level evaluation on diodes and packages as well as manufacturing and assembly processes are analyzed to identify a set of possible failure sites with associated failure modes, mechanisms, and causes. A case study is then presented to illustrate the application of a systematic FMMEA methodology to the analysis of a specific failure in a Schottky diode package.

Analysis of the Relationship Between Rail Seat Load Distribution and Rail Seat Deterioration in Concrete Crossties

2014 ◽  
Author(s):  
Matthew Greve ◽  
Marcus S. Dersch ◽  
J. Riley Edwards ◽  
Christopher P. L. Barkan ◽  
Jose Mediavilla ◽  
...  
Keyword(s):  
Load Distribution ◽  
Failure Modes ◽  
Failure Mechanisms ◽  
Past Research ◽  
Concrete Surface ◽  
Hydraulic Pressure ◽  
Valuable Insight ◽  
Increased Risk ◽  
Abrasive Erosion ◽  
Field Experimentation

One of the most common failure modes of concrete crossties in North America is the degradation of the concrete surface at the crosstie rail seat, also known as rail seat deterioration (RSD). Loss of material beneath the rail can lead to wide gauge, rail cant deficiency, and an increased risk of rail rollover. Previous research conducted at the University of Illinois at Urbana-Champaign (UIUC) has identified five primary failure mechanisms: abrasion, crushing, freeze-thaw damage, hydro-abrasive erosion, and hydraulic pressure cracking. The magnitude and distribution of load applied to the rail seat affects four of these five mechanisms; therefore, it is important to understand the characteristics of the rail seat load distribution to effectively address RSD. As part of a larger study funded by the Federal Railroad Administration (FRA) aimed at improving concrete crossties and fastening systems, researchers at UIUC are attempting to characterize the loading environment at the rail seat using matrix-based tactile surface sensors (MBTSS). This instrumentation technology has been implemented in both laboratory and field experimentation, and has provided valuable insight into the distribution of a single load over consecutive crossties. A review of past research into RSD characteristics and failure mechanisms has been conducted to integrate data from field experimentation with existing knowledge, to further explore the role of the rail seat load distribution on RSD. The knowledge gained from this experimentation will be integrated with associated research conducted at UIUC to form the framework for a mechanistic design approach for concrete crossties and fastening systems.

Stress Field of Semi-Infinite Interface Crack Tip of Double Dissimilar Orthotropic Composite Materials

2010 ◽  
Vol 97-101 ◽  
pp. 1223-1226
Author(s):  
Jun Lin Li ◽  
Shao Qin Zhang
Keyword(s):  
Composite Material ◽  
Composite Materials ◽  
Interface Crack ◽  
Interfacial Crack ◽  
Crack Tip ◽  
Stress Fields ◽  
Displacement Fields ◽  
Orthotropic Composite ◽  
Stress Functions ◽  
Secular Equations

The problem of orthotropic composite materials semi-infinite interfacial crack was studied, by constructing new stress functions and employing the method of composite material complex. In the case that the secular equations’ discriminates the and theoretical solutions to the stress fields and the displacement fields near semi-infinite interface crack tip without oscillation and inter-embedding between the interfaces of the crack are obtained, a comparison with finite element example was done to verify the correction of theoretical solution.

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