# Calculation and engineering structure an airplane made of laminated polymeric composite materials taking into account the effects interlaminar

### Аuthors

Grischenko S. V.

Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia

e-mail: grischenko1911@gmail.com

### Abstract

The article is devoted to the actual problem of layered polymer composites considering vozmozhnoyh interlaminar negative effects that lead to delamination — mean the destruction of the composite, which is the worst predicted today. This problem is particularly relevant for areas of variable structure laying laminate composite, in other words — the transition zones. Due to changes in the structure of the load is distributed between the layers, which leads to the entry in the work space of the interlayer shear and tearing.

The question is based on the design strength and is considered mainly in relation to the transitional zone. Solutions are based on the assumption that the interlayer tension in the layered composite material similar to stresses in the adhesive joint. It is also the most logical, since by itself layered composite is a set of layers glued together.

Since the flexural rigidity of its own composite layer is relatively small, and they are rigidly connected to each other with the minimum eccentricity to determine the interlayer stresses as the base model will use a model of Volkersen with more altered boundary conditions.

The concepts of strong and weak layers: a strong layer — a layer that gives the load in the redistribution, weak layer — a layer that takes the pressure off during redistribution.

The highest values of shear and normal stresses occur interlaminar on the free edge of the weak layer, so from the point of view of the load-bearing capacity, we are interested mainly by their highest values. The shear stresses between the layers occur due to the difference of the glued layers. Normal stresses arise due to the occurrence of local points, which causes separation plate.

In practice, before determining the amount of stress between the layers, it is necessary to analyze the structure of the transition zone, highlight the strong and weak layers, define their characteristics of elasticity and thickness.

After identifying the strengths and weaknesses of layers to them, respectively, are assigned to the indices 1 and 2. Then, you must adhere to the following sequence:

1. Determine the hardness of strong and weak layers;

2. If necessary (in case of continuous layers), recalculate the load on a strong layer;

3. To determine the coefficient of mutual stiffness layers;

4. Calculate excessive force;

5. Determine the stresses in the interlayer space.

This technique not only allows speculative and constructive choose the design parameters of the transition zone, but also to evaluate the strength. Also, a technique gives an idea of the physics of structure work of the transition zone under load, provides requirements and recommendations that will effectively reduce the range of possible values of matching options, and generally reduce the complexity of the design. The dependences obtained open additional possibilities for parametric design optimization of constructive transition zones.

### Keywords:

composite material, mode of deformation, stress-strain state, interlaminar stresses, interlayer shear, adhesive bonding

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