# The Effect of Tin Content on the Strength of a Carbon Fiber/Al-Sn-Matrix Composite Wire

^{1}

^{2}

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Selection of the Matrix Material

## 3. Materials and Methods

#### 3.1. Composite Manufacturing

^{2}, respectively. The volume fraction of the fiber in the composite wire V

_{f}was determined using a standard point counting metallographic method. It varied from 65 to 70%.

#### 3.2. Characterization Methods

^{3}using a piezoelectric transducer. The sound pulse contained five vibrations with a frequency of 5 MHz close to a Gaussian envelope. Two transducers, an exciting sensor and a receiving sensor, were pressed against two mutually parallel opposite faces of the sample. The speed of sound was calculated using the formula c = 2d/∆t, where d is the sample size, and ∆t is the time between two successive pulses on the oscilloscope screen, determined using a digital delay system.

_{0.2}) of the matrix alloy was determined from the compression deformation curve as a stress corresponding to a residual strain of 0.2%. The cylindrical test specimens were 15 mm in diameter and 30 mm in height. The deformation rate was 1.1 × 10

^{−6}. The specimens were made by casting into a graphite chill mold.

_{eff}was calculated as the ratio of the fiber strength σ

_{f}in the composite calculated from the rule of mixtures [4] (Equation (2)) to initial fiber strength (4000 MPa according to the manufacturer’s data).

_{m}was taken to be 60 MPa. The strength of the matrix obviously depends on the tin content. However, to assess the effective strength of the fiber, we neglected the effect of tin on the matrix strength. Because the strength of the fiber exceeds that of the matrix by an order of magnitude, regardless of the tin content, this assumption does not lead to a significant error in the calculations.

## 4. Results

#### 4.1. Microstructure of an Al-Sn Matrix Alloy

#### 4.2. Conditional Yield Stress, Microhardness, Shear Modulus, and Young’s Modulus of the Matrix Alloy

#### 4.3. Fracture Surfaces of A CF/Al-Sn Wire

#### 4.4. Strength of a CF/Al-Sn Wire and Effective Fiber Strength

#### 4.5. Microstructure of a CF/Al-Sn Wire

## 5. Discussion

#### 5.1. Matrix Alloy

#### 5.2. Composite CF/Al-Sn-Wire

_{c}curve denotes the critical stress required for crack propagation in the composite, and the σ* curve denotes the theoretical strength of the composite that takes into account a decrease in the fiber strength with an increase in its critical length according to the Weibull distribution [18]. The intersection of these curves determines τ

_{cr}, which is the value of the boundary shear strength at which the critical stress of crack propagation and the theoretical composite strength are equal. All other conditions being the same, this value is optimal for achieving the greatest strength of the composite material.

_{cr}, which, in turn, is expressed in the form of a monotonic increase in the composite strength (Figure 6a). Thus, the tin content of 50% is not an extreme point of the composite strength, all other conditions being the same.

## 6. Conclusions

- The effect of tin content in the Al-Sn alloy in the range from 0 to 100 at.% on its mechanical properties was studied. An increase in the tin content leads to a monotonic decrease in the microhardness and conditional yield stress of the Al-Sn alloy from 305 to 63 MPa and from 32 to 5 MPa, respectively. In addition, Young’s modulus and the shear modulus of the Al-Sn alloy decrease from 65 to 52 GPa and from 24 to 20 GPa, respectively. The change in these mechanical properties is almost linear, which is most likely due to an almost complete absence of mutual solubility and interaction between aluminum and tin.
- The effect of tin content in the Al-Sn matrix alloy in the range from 0 to 50 at.% on the strength of the CF/Al-Sn composite subjected to three-point bending was also investigated. Increasing tin content up to 50 at.% leads to a linear increase in the composite strength from 1450 to 2365 MPa, which is due to an increase in the effective fiber strength from 65 to 89%.
- The addition of tin up to 50 at.% to the matrix alloy leads to the formation of weak boundaries between the matrix and the fiber. This is most likely due to the suppression of the chemical reaction between aluminum and carbon and the fact that, in the composite structure, tin is predominantly located in the spaces between the fiber and aluminum grains. An increase in the composite strength is accompanied by an increase in the average length of the fibers pulled out at the fracture surface.

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

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**Figure 2.**Microstructure of an Al-Sn matrix alloy with tin content from 5 to 50 at.%: (

**a**) 5% Sn, (

**b**) 10% Sn, (

**c**) 25% Sn, (

**d**) 50% Sn.

**Figure 3.**Dependence of microhardness, conditional yield stress (

**a**) and Young’s modulus and shear modulus (

**b**) of the matrix Al-Sn alloy on the tin content.

**Figure 4.**Fracture surfaces of a CF/Al-Sn composite with tin content from 0 to 50 at.%: (

**a**) 0% Sn, (

**b**) 10% Sn, (

**c**) 25% Sn, (

**d**) 50% Sn.

**Figure 5.**Curves of deformation of a CF/Al-Sn composite with tin content in the matrix of 0 and 50 at.%.

**Figure 6.**Dependence of the strength of a composite CF/Al-Sn wire subjected to three-point bending (

**a**), effective fiber strength and length of the pulled-out part of the fiber at fracture (

**b**) on the tin content.

**Figure 7.**Microstructure of a CF/Al-Sn composite with tin content from 0 to 50 at.%: (

**a**) 0% Sn, (

**b**) 10% Sn, (

**c**) 25% Sn, (

**d**) 50% Sn.

**Figure 8.**Schematic representation of the dependence of the composite strength σ on the shear strength of the interface between the matrix and the fiber τ.

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**MDPI and ACS Style**

Galyshev, S.; Orlov, V.; Atanov, B.; Kolyvanov, E.; Averichev, O.; Akopdzhanyan, T.
The Effect of Tin Content on the Strength of a Carbon Fiber/Al-Sn-Matrix Composite Wire. *Metals* **2021**, *11*, 2057.
https://doi.org/10.3390/met11122057

**AMA Style**

Galyshev S, Orlov V, Atanov B, Kolyvanov E, Averichev O, Akopdzhanyan T.
The Effect of Tin Content on the Strength of a Carbon Fiber/Al-Sn-Matrix Composite Wire. *Metals*. 2021; 11(12):2057.
https://doi.org/10.3390/met11122057

**Chicago/Turabian Style**

Galyshev, Sergei, Valery Orlov, Bulat Atanov, Evgeniy Kolyvanov, Oleg Averichev, and Tigran Akopdzhanyan.
2021. "The Effect of Tin Content on the Strength of a Carbon Fiber/Al-Sn-Matrix Composite Wire" *Metals* 11, no. 12: 2057.
https://doi.org/10.3390/met11122057