Wyniki wyszukiwania - Biblioteka Nauki

1

Analysis of fatigue behavior of composite structures with circular internal delamination

100%

Składanowska K. , Sanetra I. , Muc A.

Composites Theory and Practice

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2017

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tom R. 17, nr 3

121--125

EN

The aim of the paper is to demonstrate and describe the fatigue failure mechanisms of eight-layer glass-epoxy composites with a central circular delamination, numerical description of the delamination problems and a possible optimal design. There are a few variables (tension and compression forces, number of cycles, construction of the tested plates) which can be changed during the experiment that will very likely provide different results. The problem is to find the link among all those variables to fully describe their influence on the physical behavior of the epoxy plate which is the subject of the experiment. The results are illustrated with the use of the numerical analysis method. Thanks to that, it is possible to describe how the number of cycles, tension force and stress variations affect the whole fatigue process.

PL

Celem pracy jest zademonstrowanie i opisanie mechanizmów uszkodzenia zmęczeniowego ośmiowarstwowych kompozytów szkło/żywica epoksydowa z kołową delaminacją. Opierano się na numerycznym opisie problemów z rozwarstwieniem. Brane są pod uwagę różne zmienne (siły rozciągające i ściskające, liczba cykli), którymi można operować podczas eksperymentu, co wpływa na wyniki. Problem polega na znalezieniu powiązania wszystkich tych zmiennych, aby w pełni opisać ich wpływ na fizyczne właściwości płyty, która jest przedmiotem badania. Wyniki są ilustrowane za pomocą metody analizy numerycznej. Dzięki temu możliwe jest opisanie, jak liczba cykli, siła i zmiany naprężeń wpływają na cały proces zmęczeniowy.

2

Effective elastic constants of unidirectional fiber-reinforced composites with the concept of interphase

100%

Rucevskis S. , Chate A. , Reichhold J. , Bledzki A. K.

International Journal of Applied Mechanics and Engineering

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2003

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tom Vol. 8, no spec.

109-115

EN

In this paper we discuss the effect of an interphase on the elastic constants of unidirectional fiber-reinforced composites. The interphase has its own set of elastic properties. The Young's modulus of the interphase is described with the help of a mathematical model. The results of the experiment and the model are compared, and the Young's modulus of the interphase is identified.

3

Analysis of discontinuities effect in relation to attenuation level in glass fibre reinforced polymer composites

84%

Bieniaś J. , Ostapiuk M. , Surowska B. , Beer K.

Kompozyty

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2011

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tom R. 11, nr 1

70-74

EN

In recent years, composite structures have become very popular for different applications, predominantly in the aerospace industry. Their mechanical properties provide very useful materials in aviation as a primary structure. It is well known that glass/epoxy polymer composite is characterised by its lightweight and corrosion resistance in comparison to traditional materials. The main aim is to guarantee durability and safety during the manufacturing process in the case of the possible appearance of structural defects. Porosity and delamination detection is a very important factor in solving the problem of quality. One of the basic non-destructive testing methods of detecting discontinuities in structures used in aviation is ultrasonic inspection with C-scan images. Their objective is to analyse the composite structures particularly for quality inspection in aviation. This paper presents research about the relationship between the attenuation level of an NDT technique (C-scan) and void content in glass/epoxy composites. An analysis of the microstructure and characteristics of discontinuities are presented and discussed. The observations have given the results of three distinguished types of microstructures depending on the attenuation level in ultrasonic testing. The level of void content for this specific type of composite was determined from 2% to 5% and this can be classified as a medium quality composite structure. A linear dependence was found between the attenuation level in ultrasonic inspection and the percentage of voids content in a glass fiber reinforced polymer composite. The correlation between ultrasonic inspection and the analysis of microstructure is a useful method in composite structures engineering.

PL

Struktury kompozytowe w ostatnich latach stanowią bardzo popularne rozwiązania w odniesieniu do różnych zastosowań, w szczególności w lotnictwie. Dobre właściwości mechaniczne predysponują te materiały na odpowiedzialne części struktur. Kompozyty polimerowe wzmacniane włóknem szklanym charakteryzują się niską gęstością i odpornością korozyjną w porównaniu do tradycyjnych materiałów. Głównym zadaniem podczas ich wytwarzania jest zagwarantowanie trwałości i bezpieczeństwa w procesie produkcji ze względu na możliwość wystąpienia defektów w strukturze. Wykrywanie porowatości i delaminacji stanowi istotny czynnik w rozwiązywaniu problemu jakości. Defektoskopia ultradźwiękowa jest jedną z podstawowych metod nieniszczących do wykrywania nieciągłości, szczególnie w strukturach stosowanych w lotnictwie. W artykule przedstawiono badania wpływu poziomu nieciągłości na poziom tłumienia metodą obrazowania C-scan w kompozytach polimerowych wzmacnianych włóknem szklanym. Zaprezentowano analizę mikrostruktury oraz charakterystykę nieciągłości. Wyróżnione zostały trzy typy mikrostruktury w zależności od poziomu tłumienia. Poziom porowatości dla badanej struktury kompozytowej został określony w zakresie od 2% do 5%, klasyfikując tę strukturę jako średniej jakości. Wykazano liniową zależność pomiędzy poziomem porowatości a procentowym udziałem porowatości w kompozycie polimerowym wzmacnianym włóknem szklanym. Korelacja pomiędzy badaniami ultradźwiękowymi i analizą mikrostruktury stanowi pomocną metodę w inżynierii struktur kompozytowych.

4

Nieniszcząca metoda oceny udziału wzmocnienia w kompozytach epoksydowo-szklanych

84%

Wróbel G. , Pawlak S.

Zeszyty Naukowe. Chemia i Technologia Chemiczna / Akademia Techniczno-Rolnicza w Bydgoszczy

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2006

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tom z. 11

165-168

PL

W artykule poddano ocenie możliwość budowy relacji diagnostycznej, będącej podstawą wyznaczania zawartości włókien szklanych w kompozycie epoksydowo- -szklanym metodą ultradźwiękową.

5

A comparison study of the pulse-echo and through-transmission ultrasonics in glass/epoxy composites

84%

Wróbel G. , Pawlak S.

Journal of Achievements in Materials and Manufacturing Engineering

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2007

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tom Vol. 22, nr 2

51-54

EN

Purpose: The aim of the present study was to assess the limits and compare abilities of the pulse-echo and through-transmission ultrasonics to evaluate a chosen property of composite materials. Design/methodology/approach: Two different ultrasonic non-destructive techniques were employed to measure the mechanical wave velocity in glass/epoxy composites. The study was performed on various specimens with different glass content at the range from 30 to 65%. The exact glass content in examined materials was determined using the standard destructive analysis. Findings: A comparison showed that the results obtained for the wave velocity from pulse-echo and through-transmission are in good agreement, indicating that both techniques can be considered as a quantitative non-destructives tools of local fiber content evaluation. The results are presented in the form of linear relationships of wave velocity versus fiber content in the composite materials. Research limitations/implications: In order to obtain lower dispersion of data, there are many factors to be considered such as void content in composite materials and/or transducer frequency of ultrasonic device, which were out of the scope of the present study. Practical implications: The considered ultrasonic techniques can be applied to the industrial quality control of composite products, but for any different composite structures, distinct relationships should be determined. Originality/value: The results presented would be of interest to the industrial quality procedures, especially in the case of products with high failure-free requirements.

6

Ultrasonic evaluation of the fibre content in glass/epoxy composites

67%

Wróbel G. , Pawlak S.

Journal of Achievements in Materials and Manufacturing Engineering

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2006

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tom Vol. 18, nr 1-2

187--190

EN

Purpose: The aim of the work was to find relationships between the selected parameter of an ultrasonic wave and the local fibre content in a glass/epoxy composite. Design/methodology/approach: The experiments have been performed in two distinct phases. During the first phase, typical glass/epoxy composite materials with different fibre content were examined by means of through-transmission and pulse-echo ultrasonics. In the second phase, the standard destructive method was applied to determine the actual glass content in investigated composite materials Findings: The experimental results showed relationships between ultrasonic wave velocity and the local fibre content in investigated composite materials. This study has also assessed the ability of pulse-echo technique to carry out such a testing. Research limitations/implications: Relationships found may be useful to local fibre content examination, but for each composite material different relationships are required to be determined, as was done in the present study. Practical implications: The described method can be applied to the post-production quality control of a finished composite product, but in the case of composites made of different components it is necessary to determine distinct relationships for each material. Originality/value: A new approach to the problem of fibre content examination has been demonstrated by means of pulse-echo technique. The method developed should be of interest to the industrial quality control procedures and has great importance for products with a high failure-free requirements.