Determination of strength criteria on conditions  of visual testability of impact damage in composite aircraft constructions

One of the principal criteria of aircraft composite design strength on the conditions of damage tolerance is the minimum defect size of accidental impact damage that is sure to be located during regular maintenance checks. Construction strength with similar (BVID – Barely Visible Impact Damage) and smaller damages must be ensured under design load. The analysis of operational factors affecting the criterion value is conducted in the paper. The effects of personnel qualification, surface color, level of contamination, distance to the object as well as defect size variations during the time due to relaxation of inner strains in the damaged construction were studied.Research was carried out using 90 carbon fiber three stinger panels of different color and contamination levels which were subject to impact damages by a 25 mm spherical striker. Totally 80 blows were struck when applying energy within the range of 3–107 J. In the visual damage detectability test under different conditions 42 experts were participated including 25 airlines inspectors. For the statistical analysis of empirical data and determination of dependence for the damage detection probability on its size, the Weibull function was utilized. Determination of BVID size using "90/95" criterion was performed by means of the bootstrap method (95% of inspectors must detect not less than 90% of defects with the size not smaller than BVID). The results obtained in this study enabled to access the degree of various operational factors impact on reliability of damage detectability during the visual inspection and determine BVID values depending on the combination of the given factors. In particular, it was demonstrated that from all the viewing distances the defects in polymer composite materials are more detectable on the blue surface than on the gray and red ones. Conducted research demonstrated a significant effect of relaxation (the reduction effect of the surface defect sizes in the composite panel affected by different factors during time span) on the probability of defect detectability during operation. Also water saturation of the construction under excessive temperatures has the critical compared with other factors impact on relaxation of damages in polymer composite materials. The obtained results accord with the data in foreign publications making them more supplement and specific. On the basis of conducted research the entire range of recommendations for aircraft designers and operators utilizing composite constructions is formulated.

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Barely visible impact damage vid detectability comparison of execution results of nondestructive ultrasonic control and optical sureace profilometry of polymer composite materials-samples

Composite Materials Constructions ◽

10.52190/2073-2562_2021_4_43 ◽

2021 ◽

pp. 43-50

Author(s):

S. A. SMOTROVA ◽

A. V. SMOTROV ◽

V. I. IVANOV

Keyword(s):

Composite Materials ◽

Polymer Composite ◽

Impact Damage ◽

Polymer Composite Materials ◽

Ultrasonic Control

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Sorption and diffusion of moisture in polymer composite materials with drop-weight impact damage

Mechanics of Composite Materials ◽

10.1007/s11029-016-9547-6 ◽

2016 ◽

Vol 51 (6) ◽

pp. 761-770 ◽

Cited By ~ 2

Author(s):

V. O. Startsev ◽

S. V. Panin ◽

O. V. Startsev

Keyword(s):

Composite Materials ◽

Polymer Composite ◽

Impact Damage ◽

Polymer Composite Materials ◽

Drop Weight ◽

Weight Impact ◽

And Diffusion

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Study on metal powder-polymer composite materials. I. Determination of oxides on the surface of copper powders by an acid dissolution method.

NIPPON KAGAKU KAISHI ◽

10.1246/nikkashi.1988.149 ◽

1988 ◽

pp. 149-152 ◽

Cited By ~ 1

Author(s):

Kunio MORI ◽

Yoshihiro OKAI ◽

Akira WATANABE ◽

Yoshiro NAKAMURA

Keyword(s):

Composite Materials ◽

Metal Powder ◽

Polymer Composite ◽

Polymer Composite Materials ◽

Acid Dissolution ◽

Dissolution Method ◽

Copper Powders

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Determination of the composition and density of polymer composite materials in details and constructions by nondestructive methods

Polymer Science Series D ◽

10.1134/s1995421216020155 ◽

2016 ◽

Vol 9 (2) ◽

pp. 176-180 ◽

Cited By ~ 3

Author(s):

K. S. Mishurov ◽

V. V. Murashov

Keyword(s):

Composite Materials ◽

Polymer Composite ◽

Polymer Composite Materials ◽

Nondestructive Methods

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MODELLING OF CRACK DEVELOPMENT PROCESSES IN COMPOSITE ELEMENTS BASED ON VIRTUAL CRACK CLOSURE TECHNIQUE AND COHESIVE ZONE MODEL

Periódico Tchê Química ◽

10.52571/ptq.v17.n35.2020.50_li_pgs_591_599.pdf ◽

2020 ◽

Vol 17 (35) ◽

pp. 591-599

Author(s):

Yulong; ; LI ◽

Vasiliy N. DOBRYANSKIY ◽

Alexander A. OREKHOV

Keyword(s):

Composite Materials ◽

Polymer Composite ◽

Cohesive Zone ◽

Cohesive Zone Model ◽

Fiber Composites ◽

Polymer Composite Materials ◽

Zone Model ◽

Virtual Crack Closure Technique ◽

Closure Technique

Fiber composites based on polymer matrices are promising structural materials that meet high requirements for strength, reliability, durability, and hardness. Therefore, composite materials are widely used as structural materials for aerospace products. The problems associated with the destruction of fiber composites were relevant at all stages of technology development. A variety of reinforcing fibers and polymer binders, as well as reinforcement schemes, allow directional control of strength, stiffness, level of working temperatures and other properties of polymer composite materials. This article discusses a methodology for experimental determination of the mechanical properties of carbon-based fiber-reinforced polymer composite materials, including the determination of the interlayer fracture toughness under loading under separation conditions using the doublecantilever beam method (DCB) and the fracture toughness under transverse shear conditions using the ENF (End-Notched Flexure) method and interlayer strength. The test results of samples of polymer composite materials with a carbon reinforcing filler with different surface densities are presented. The experimental data were used to identify the parameters of the VCCT (Virtual Crack Closure Technique) and CZM (Cohesive Zone Model) closure models used to describe the development of cracks in the composites under consideration. It was found that the parameters determining the strength of layered composites are such characteristics as interlayer strength and crack resistance. It was found that the decrease in the strength of individual layers of the composite does not always affect the current stress state of the entire structure, which is often difficult to detect experimentally, but can significantly affect the further behavior of the object under study provided that the crack develops further.

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Study of the samples of polymer composite materials with an uneven surface using hydrostatic weighing

Industrial laboratory Diagnostics of materials ◽

10.26896/1028-6861-2018-84-8-32-35 ◽

2018 ◽

Vol 84 (8) ◽

pp. 32-35

Author(s):

M. I. Dushin ◽

K. I. Donetski ◽

R. Yu. Karavaev ◽

A. A. Platonov

Keyword(s):

Composite Materials ◽

Polymer Composite ◽

Physical And Mechanical Properties ◽

Binder Content ◽

Polymer Composite Materials ◽

Uneven Surface ◽

Carbon Plastics ◽

New Energy ◽

Hydrostatic Weighing

An increase in the size and the number of the elements of the aircraft structures made of polymer composite materials (PCM) required the search for new energy-saving and less expensive non-autoclave technologies. The use of one of them, vacuum infusion, inevitably leads to formation of an uneven surface, thus inhibiting determination of the true thickness by standard methods, and, in turn, affects determination of the physical and mechanical properties of the material. The results of measuring density of carbon plastics by hydrostatic weighing are presented to calculate the true thickness of materials, volume content of binder and porosity. The developed method is also suitable for PCMs based on combustible reinforcing materials like organic plastics, hybrid and other materials that cannot be subjected to burning-off to determine the binder content.

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