Search or add a thesis

Advanced Search (Beta)
Home > Modeling of Damage Growth in Frp Composites With Stress Raisers Such As Holes and Notches

Modeling of Damage Growth in Frp Composites With Stress Raisers Such As Holes and Notches

Thesis Info

Access Option

External Link

Author

Tanveer Ahmad

Program

PhD

Institute

National University of Sciences & Technology

City

Islamabad

Province

Islamabad

Country

Pakistan

Thesis Completing Year

2019

Thesis Completion Status

Completed

Subject

Mechanical Engineering

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/10450/1/Tanveer%20Ahmed_Mech%20Engg_2019_NUST_PRR.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676727791479

Asian Research Index Whatsapp Chanel
Asian Research Index Whatsapp Chanel

Join our Whatsapp Channel to get regular updates.

Similar


Fibre reinforced polymer composite panels are preferred in high performance structural panels because they are strong, stiff and light. Stress raisers such as holes or notches (for accessibility, mechanical joining, and routing of cables etc.) may be present in any engineering structure and composite structures are no exception. Theoretically, a stress raiser is simply a localization of high stress-strain concentrations quantified by the Stress Concentration Factor (SCF). It is well established in literature and engineering practice that stress-strain concentrations due to holes or notches, unless accompanied by local plastic strain hardening, reduce the apparent strength of the panels. Since SCF is a function of elastic properties of the material, so in isotropic materials, the SCF is defined with elastic SCF (entails elastic properties within the elastic range of material) and plastic SCF (entails elastic properties in the plastic range of material). However, literature is scarce of such definition for the case of anisotropic/orthotropic materials, where the SCF is also a function of its elastic properties. Contrary to isotropic homogenous materials, composite panels offer a very complex structure, where fibres are generally regarded as brittle which deform elastically to final failure exhibiting either slight or no linear deformation. Whereas matrices generally experience plastic deformation hence the failure strain in matrics is far higher than the fibres. Additionally, once a composite panel containing a hole is subjected to tensile loading, tangential stress at the periphery of the hole in a perpendicular direction to the load axis attains a magnitude three times the far field stress under plane stress conditions. However, in a composite panel, the location and magnitude of the maximum stress are at the periphery of the hole changes with the fibre orientation and stacking sequence, therefore designers opt for large safety margins. This study has been performed to investigate the pre-damaged SCF and progressive-damaged SCF for anisotropic/orthotropic material analogous to elastic and plastic deformations in isotropic material respectively. The study presents a novel technique of calculating progressive-damaged SCF which evaluates the changing SCF in response to the progressive damage development within the composite panel. Finite Element (FE) representations simulate delamination damage using cohesive elements and in-plane damage using continuum damage mechanics. In the first part of the study, test coupons have been formulated under static conditions to consider important influencing factors on the SCF for the case of the composite panel containing a central circular hole subjected to tensile loading and compared with the already published literature. Later, several xii FE coupons have been formulated to precisely investigate the pre-damaged SCF and progressivedamaged SCF for the composite panel. During the study, the investigations of pre-damaged SCF and progressive-damaged SCF have also been performed using analytical and experimental approaches where applicable. The FE results are found in good agreement with the analytical and experimental results. The study provides a novel systematic FE approach for the estimation of progressive-damaged SCF for a composite panel, which has not been reported in the literature before. Certainly, the study proposes a paradigm shift in design philosophy which at present is limited to no-damage philosophy especially in aerospace, where the weight savings due to less generous safety factors are significant.
Loading...
Loading...

Similar Books

Loading...

Similar Chapters

Loading...

Similar News

Loading...

Similar Articles

Loading...

Similar Article Headings

Loading...

7. Al-A’raf /The Elevated

7. Al-A’raf /The Elevated

I/We begin by the Blessed Name of Allah

The Immensely Merciful to all, The Infinitely Compassionate to everyone.

07:01
Alif. Lam. Mim. Sad.
07:02
This Book - The Qur’an - is being sent down on to you O The Prophet.
So let there be no distress in your heart due to this.
While you are to warn the disbelieving audience through it,
this is a Reminder to the believers.
07:03
O The People!
Follow what is being sent down on to you by your Rabb - The Lord, and
do not follow the whims of others or take others for worship apart from HIM.
Yet little you understand and follow.
07:04
And how many of habitations have WE destroyed before!
So it happened that OUR Punishment came upon them suddenly - either by the night or
while they were in the midst of their noon-nap.
07:05
And when OUR Punishment finally overtook them, they had nothing to say, except crying out:
‘We have indeed been unfair’ to ourselves by sinning!
07:06
It will be during the Time of the Final Judgment that WE will certainly question those to whom WE had assigned OUR Messengers if they followed their teachings, and
WE will also question the Messengers if they had conveyed OUR Message and how did the people respond to it.
07:07
WE will definitely recount their deeds and dealings to them with knowledge and accuracy,
for WE were never absent from their midst!
07:08
And at The Time of the Final Judgment, the weighing of their deeds and dealings will be
fair and just.

Then whose deeds of righteousness will be heavier than their bad deeds on the scales,
those –...

Constitutional Provisions for the Rights of Non-Muslim Minorities in Pakistan

Pakistan is a Muslim country and got freedom from British Government, on August 14, 1947. It was separated from India on the basis of Islamic ideology. Though majority of population was Muslims but there was sufficient number (5%) of non Muslims, such as Hindus, Christians, Sikhs, Calashes’, Baha’is, Zikaria’s, and Parsis etc.  The presence of non Muslims in Pakistan was a great challenge to safe guard their rights in the constitution of Pakistan to maintain the communal harmony in the country. This paper focuses on the provisions of non-Muslim rights in the constitution of Pakistan. It discusses the constitutional provision for the rights of non Muslims. Such as personal law, freedom to religion, safe guard against special taxes, non discrimination in respect of access to public places, discrimination in services, preservation of language script and culture, promotion of social justice and predication of social evils, right to vote,   reservation of seats in National assembly and to run and manage their religious institutions. This paper also suggests some recommendations for the solution of contemporary non Muslim minorities, problems in Pakistan and also achievement of Ministry of non Muslim Minorities Affairs, 2008 to 2010 in Pakistan.

Measurement of the Performance of Islamic Financial Institutions: An Evaluation and Analysis

Performance of banking sector is critical for the functioning of the financial system of a country as it ultimately casts impacts on economic stability and growth. Islamic banking has become substantial component of financial structure of many Muslim and non‐Muslim countries. Islamic banking in Pakistan has won remarkable market share in just a few years. While failure of conventional banks in western world has caused economic crisis in those economies, Islamic banks have proved to be robust due to their profit and loss sharing mechanism. This study is an attempt to analyze performance of Islamic banks in comparison of their conventional counterparts. This study does not apply a single performance evaluation method. It rather addresses several dimensions of performance using multiple methods like Ratio Analysis, DEA, Malmquist Index and Regression. Performance of Islamic and conventional banks is compared using parametric and non‐parametric statistical tests of significance. This study conceptualizes performance as combination of efficiency and effectiveness. Total Factor Productivity change is further decomposed into subcomponents. Tobit regression is applied to estimate determinants of change in efficiency, effectiveness and performance. This study analyzes 2004 to 2009 financial data of all the Islamic and conventional banks working in Pakistan. However, to find out determinants of profitability this study analyzes the quarterly data of Meezan Bank, which is the pioneer full‐fledged Islamic bank of Pakistan. Islamic banks outperformed conventional banks in terms of financial ratios of capital adequacy, asset quality, liquidity, asset turn over and risk. However, performance of conventional banks has been higher in terms of DEA scores of efficiency and effectiveness. Although both the types experienced decline in TFP Malmquist index, yet no significant difference in performance pointed out. Bank specific factors cause variation in efficiency whereas market specific and macroeconomic indicators affect effectiveness significantly. Liabilities, capital, overhead expenses and earning assets have positive impact on profitability. Deposits, service income and financing are inversely related with profitability of Islamic banks.