# Hybrid Prepreg Tapes for Composite Manufacturing: A Case Study

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## Abstract

**:**

## 1. Introduction

## 2. Experimental

#### 2.1. Materials Used

#### 2.2. Preparation of Tapes

#### 2.3. Characterization and Test Methods

## 3. Spreading Process

^{2}− 3l + 1 filaments. The number of layers l

_{n}in a close honeycomb structure is related to the total number of filaments n [27].

_{n}is the same area as the area circumscribed to the close honeycomb structure composed from filaments with diameter d [27].

_{T}= T/t. If n

_{T}= n, the tow can ideally follow a full-close honeycomb structure. The fineness of roving T is the product of the cross-section area of filaments S and glass density ρ. The diameter D

_{T}[mm] of ideal circular roving is then expressed in the form:

_{lim}= 0.907 and for real filaments is µ about 0.7. For tow with fineness 1200 tex and glass density ρ = 2580, kg m

^{−3}is then for a compact honeycomb D

_{T}= 0.808 mm and for real multifilaments D

_{T}= 0.9198 mm. During flattening the most optimal arrangement according to the compact honeycomb structure is maintained (see Figure 6).

- A.
- Assumption of the constant area during spreading in combination with Kemp racetrack cross-section of tape leads to the relation [28]:

- B.
- Assumption of constant perimeter during spreading in combination with Kemp racetrack cross-section of tape leads to the relation [29]:

_{T}= 0.808 mm and for real multifilaments it is D

_{T}= 0.9198 mm. For filament fineness of 0.505 tex, the corresponding diameter is 0.0159 mm. The spread tow (SLT) has the same shape characteristics as tow SL. The corresponding relative width and thickness for both packing densities are given in Table 3.

_{c}from Equation (4) for different packing densities through D

_{T}. It is visible that for µ = 0.7, the values of α and α

_{c}are closer (see also points in Figure 7).

## 4. Results and Discussion

#### 4.1. Hybrid Tape Geometry

#### 4.2. Fiber Strength Distribution

#### 4.3. Roving Strength Distribution

_{r}defined by relations

#### 4.4. Hybrid Tapes Strength Distribution

_{m}is the matrix modulus, v

_{f}is the volume fractions of the fiber, and ε

_{B}is the breaking strain of the fiber bundle, which is related to the bundle strength σ

_{B}= E

_{f}ε

_{B}, where the tensile modulus of the bundle is identical to that of the fiber.

_{T}is the sum of contribution of the fibrous phase σ

_{Tf}and the matrix phase σ

_{TM,}given as:

_{f}= 0.642) and matrix phases to the hybrid tape strength calculated from the simple rule of mixture are given in Table 7.

_{B}, the tape strength is σ

_{T,}as well as being approximately normally distributed, and for mean tape strength ${\overline{\sigma}}_{T}$ it is valid [16].

_{T}has the form:

_{B}are the mean fiber bundle strength and its standard deviation. These relations are showing the prediction of tape strength basic statistical characteristics from characteristics of roving and matrix. Table 8 shows the calculated mean tape strength and corresponding standard deviations from parameters of roving and filament strengths (calculated from Equations (15) and (16)).

_{c}[30]

_{f}is the fiber radius and ${\tau}_{y}$ is the yielding shear strength of the matrix adjacent to the interface or that of the fiber–matrix interface, whichever is less. This modification is crucial so that the effect of fiber–matrix interaction can be included. The mean ${\overline{\sigma}}_{T}$ and standard deviation S

_{T}of tape strength can be, therefore, simply calculated by replacing bundle strength and standard deviation by ${\overline{\sigma}}_{B}\left({l}_{c}\right)$ and ${S}_{B}\left({l}_{c}\right),$ i.e., by modification of parameter B due to different lengths (replacing l

_{f}by the critical length l

_{c}) [31,32].

## 5. Conclusions

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 4.**Semi-operating device for preparing a prepreg (© Global Science Press) [20].

**Figure 5.**Honeycomb structure [27]. (

**a**) 1 + 6+12 + 18 + …m (i). (

**b**) Close honeycomb. (

**c**) Open honeycomb. Limit packing density $\mathsf{\mu}$

_{hm}$=0.907$.

**Figure 6.**Idealized spreading process (

**a**) a = 4d, b = 3d (

**b**) a = 6d, b = 2d (

**c**) a = 10d, b = d [27].

**Figure 8.**Material SL and SLT (

**a**) glass filaments cross-section, (

**b**) prepreg tape cross-section, (

**c**) longitudinal view of roving, (

**d**) longitudinal view of prepreg tape.

**Figure 9.**Histogram characterized by experimental distribution of filament strength (red curve is the probability density of normal distribution).

**Figure 10.**Q-Q graphs for data normality verification (red line is the ideal shape for normal distribution).

**Figure 11.**Experimental distribution of roving strength (red curve is the probability density of normal distribution).

**Figure 12.**Q-Q graph for data normality verification (red line is an ideal shape for normal distribution).

**Figure 13.**Experimental distribution of tape strength (red curve is the probability density of normal distribution).

**Figure 14.**Q-Q graph for data normality verification (red line is the ideal shape for normal distribution).

Properties | Unit | Value |
---|---|---|

Fineness | Tex | 1200 |

Filament diameter | µm | 16 |

Tensile strength | N | 450 |

Material | Standard | Resin | Manufacturer | Acronym |
---|---|---|---|---|

Roving | ASTM D 1505 | - | Slovakia | SL |

Hybrid tape | ASTM C 338 | CHS-EPOXY 200 V 55 | Czech Republic–TUL and Večerník | SLT |

Material | Width ‘a’ [mm] | Thickness ‘b’ [mm] | D_{T}[mm] | α | β | α_{c} |
---|---|---|---|---|---|---|

SLT µ = 0.9 | 5.122 | 0.158 | 0.81 | 6.34 | 0.196 | 4.05 |

SLT µ = 0.7 | 5.122 | 0.158 | 0.92 | 5.57 | 0.172 | 4.603 |

Material | Mean Value [GPa] | Standard Deviation [GPa] | Coefficient of Variation [%] |
---|---|---|---|

Fibers from SL | 1.93 | 0.43 | 22.37 |

Material | Mean Value [GPa] | Standard Deviation [GPa] | Threshold A [GPa] | Weibull Form C [-] | Weibull Scale B [GPa] |
---|---|---|---|---|---|

SL | 0.88 | 0.11 | 0.57 | 3.10 | 0.35 |

Material | Mean Value [GPa] | Standard Deviation [GPa] | Threshold A [GPa] | Weibull Form C [-] | Weibull Scale B [GPa] |
---|---|---|---|---|---|

SLT | 1.06 | 0.18 | 0.36 | 4.49 | 0.77 |

Material | Tape ${\overline{\mathit{\sigma}}}_{\mathit{T}}$ [GPa] | Fiber ${\overline{\mathit{\sigma}}}_{\mathit{T}}$ [GPa] | Matrix ${\overline{\mathit{\sigma}}}_{\mathit{T}}$ [GPa] | ${\mathit{E}}_{\mathit{m}}/{\mathit{E}}_{\mathit{f}}$ |
---|---|---|---|---|

SLT | 1.064 | 0.568 | 0.496 | 0.178 |

Material | Mean Pred. [GPa] | Standard Deviation Pred. [GPa] |
---|---|---|

SLT | 1.1835 | 0.0117 |

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**MDPI and ACS Style**

Venkataraman, M.; Militký, J.; Samková, A.; Karthik, D.; Křemenáková, D.; Petru, M.
Hybrid Prepreg Tapes for Composite Manufacturing: A Case Study. *Materials* **2022**, *15*, 619.
https://doi.org/10.3390/ma15020619

**AMA Style**

Venkataraman M, Militký J, Samková A, Karthik D, Křemenáková D, Petru M.
Hybrid Prepreg Tapes for Composite Manufacturing: A Case Study. *Materials*. 2022; 15(2):619.
https://doi.org/10.3390/ma15020619

**Chicago/Turabian Style**

Venkataraman, Mohanapriya, Jiří Militký, Alžbeta Samková, Daniel Karthik, Dana Křemenáková, and Michal Petru.
2022. "Hybrid Prepreg Tapes for Composite Manufacturing: A Case Study" *Materials* 15, no. 2: 619.
https://doi.org/10.3390/ma15020619