# Effect of the Test Procedure and Thermoplastic Composite Resin Type on the Curved Beam Strength

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Experiment

#### 2.1. Material

_{g}) and melt temperature (T

_{m}) that are significantly lower than the two remaining matrices. These have almost identical T

_{g}, but PEEK has a T

_{m}38 °C higher than the PAEK matrix. When comparing the fibre-reinforced laminate with PPS, PEEK and PAEK, we find that most properties differ at the minimum. The greatest differences are in the strength properties in the 90° direction and in-plane shear strength; see Table 2.

**Figure 3.**Compared thermal properties of the PPS, PEEK and PAEK matrices [29].

Property | PPS | PEEK | PAEK |
---|---|---|---|

Specific gravity (g/cm^{3}) | 1.35 | 1.3 | 1.4 |

T_{g} (°C) | 90 | 143 | 147 |

Melt temperature T_{m} (°C) | 280 | 343 | 305 |

Moisture absorption (%) | 0.02 | 0.2 | 0.2 |

Tensile strength (MPa) | 90.3 | 97.2 | 95 |

Tensile modulus (GPa) | 3.8 | 3.59 | 3.7 |

Elongation at yield (%) | 3 | 3 | 4.5 |

Compression strength (MPa) | 148 | 120 | 117 |

Compression modulus (GPa) | 3.0 | - | - |

Flexural strength (MPa) | 125 | 138 | 141 |

Flexural modulus (GPa) | 3.7 | 4.1 | 4.2 |

Processing temperature (°C) | 320–350 | 370–400 | 325–350 |

Property | PPS | PEEK | PAEK |
---|---|---|---|

Tensile strength 0° (MPa) | 757 | 776 | 805 |

Tensile modulus 0° (GPa) | 55.8 | 56.1 | 58 |

Tensile strength 90° (MPa) | 754 | 827 | 739 |

Tensile modulus 90° (GPa) | 53.8 | 55.6 | 59 |

Compressive strength 0° (MPa) | 643 | 585 | 628 |

Compressive modulus 0° (GPa) | 51.7 | 51.6 | 52 |

Compressive strength 90° (MPa) | 637 | 595 | 676 |

Compressive modulus 90° (GPa) | 51.7 | 49.7 | 53 |

In Plane Shear Strength (MPa) | 119 | 155 | 147 |

In Plane Shear Modulus (GPa) | 4.4 | 4.5 | 4.1 |

Flexural strength 0° (MPa) | 1027 | - | 1040 |

Flexural modulus 0° (GPa) | 60 | - | 60 |

Flexural strength 90° (MPa) | 831 | 859 | 879 |

Flexural modulus 90° (GPa) | 44.8 | 46.3 | 48 |

#### 2.2. Material Structure Analysis

#### 2.3. Test Method

_{t}and l

_{b}).

_{t}= 75 mm and l

_{b}= 100 mm); the second configuration used a modified ASTM (ASTM mod) span (l

_{t}= 45 mm and l

_{b}= 75 mm); and the third was per the AITM standard. In this method, the spans are calculated based on the sample geometry in Equations (1)–(4). Based on these calculations, l

_{t}= 26.4 mm and l

_{b}= 40.6 mm were set.

_{t}denotes the span of the top fixture, l

_{b}is the span of the bottom fixture, R

_{i}is the inner radius, t is the thickness of the sample, D is the roller diameter and φ is the angle from the horizontal of the sample legs.

#### 2.4. Statistical Analysis

_{g}represents a grand mean term common to all observations, α

_{i}is the effect of the ith level of A, β

_{j}is the effect of the jth level of B, and (αβ)

_{ij}is the interaction effect of level i of A and level j of B combined. Also, a test for normality of residuals ε needs to be done.

## 3. Results and Discussion

#### 3.1. Test Method Evaluation

#### 3.2. Thermoplastic Type and Temperature Evaluation

## 4. Conclusions

## Author Contributions

## Funding

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 6.**Measured interlaminar strength, σ

_{r}(MPa): the test method comparison using statistic evaluation showed a significant difference of the AITM method.

**Figure 8.**Graphical comparison of the interlaminar strength results: temperature and thermoplastic-type influence.

**Figure 9.**Examples of a typical failure mode for set PPS-CT: the set with the highest coefficient of variation, with the values given in the figure being strengths in MPa.

**Figure 10.**Examples of a typical failure mode for set PAEK-CT: the set with the lowest coefficient of variation, with the values given in the figure being strengths in MPa.

Set (Resin) | Fabric | Lay-Up | Ø Width (mm) | Ø Thickness (mm) | Ø α (Deg) | Number of Samples | |
---|---|---|---|---|---|---|---|

RT | CT | ||||||

PEEK | T300JB 3K, 5HS, 280 gsm FAW, 42% RC (50% BV) | [(0,90)/(±45)]_{4}/(0,90) | 25.31 | 2.78 | 91.0 | 6 | 5 |

PPS | T300 3K, 5HS, 280 gsm FAW, 43% RC (50% BV) | [[(0,90)/(±45)]_{4}] | 25.14 | 4.95 | 89.5 | 5 | 5 |

PAEK | T300JB 3K, 5HS, 277 gsm FAW, 42% RC (50% BV) | [[(0,90)/(±45)]_{4}] | 25.24 | 4.65 | 90.7 | 5 | 5 |

σ_{r} (MPa) | PPS | ||
---|---|---|---|

ASTM | ASTM Mod | AITM | |

Mean | 71.3 | 75.1 | 81.4 |

S.D. | 4.09 | 6.36 | 3.33 |

C.V. | 5.73 | 8.47 | 4.09 |

Min. | 65.4 | 68.9 | 84.7 |

Max. | 78.8 | 85.6 | 77.4 |

- | Interlaminar Strength (MPa) | |||||

RT | CT | |||||

PPS | PEEK | PAEK | PPS | PEEK | PAEK | |

83.6 | 79.8 | 91.8 | 89.8 | 87.3 | 99.5 | |

84.7 | 86.4 | 88.3 | 89.5 | 78.2 | 95.0 | |

80.0 | 73.3 | 92.0 | 95.3 | 78.1 | 99.7 | |

63.5 | 78.6 | 96.0 | 73.1 | 87.0 | 94.6 | |

77.4 | 82.3 | 92.7 | 77.8 | 98.2 | 100.1 | |

- | 77.0 | - | - | - | - | |

Mean | 77.9 | 79.6 | 92.2 | 85.1 | 85.8 | 97.8 |

S.D. | 8.52 | 4.49 | 2.73 | 9.26 | 8.29 | 2.75 |

C.V. | 10.95 | 5.65 | 2.97 | 10.89 | 9.66 | 2.81 |

Min. | 63.5 | 73.3 | 88.3 | 73.1 | 78.1 | 94.6 |

Max. | 84.7 | 86.4 | 96.0 | 95.3 | 98.2 | 100.1 |

Source of Variation | Degrees of Freedom | Sum of Squares (Partial) | Mean Squares (Partial) | F Ratio | p-Value |
---|---|---|---|---|---|

Model | 5 | 1468.419 | 293.6838 | 6.8664 | 0.0004 |

A: thermoplastic type | 2 | 1128.575 | 564.2875 | 13.1932 | 0.0001 |

B: Temperature | 1 | 312.3451 | 312.3451 | 7.3027 | 0.0122 |

AB | 2 | 3.4559 | 1.7279 | 0.0404 | 0.9605 |

Residual | 25 | 1069.2783 | 42.7711 | ||

Pure Error | 25 | 1069.2783 | 42.7711 | ||

Total | 30 | 2537.6973 |

**Table 7.**Statistical comparison of individual files using t-tests. D, files are different; ND, files are not different.

- | RT | CT | |||||
---|---|---|---|---|---|---|---|

PPS | PEEK | PAEK | PPS | PEEK | PAEK | ||

RT | PPS | - | ND | D | ND | ND | D |

PEEK | ND | - | D | ND | ND | D | |

PAEK | D | D | - | ND | ND | D | |

CT | PPS | ND | ND | ND | - | ND | D |

PEEK | ND | ND | ND | ND | - | D | |

PAEK | D | D | D | D | D | - |

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**MDPI and ACS Style**

Hron, R.; Kadlec, M.; Růžek, R. Effect of the Test Procedure and Thermoplastic Composite Resin Type on the Curved Beam Strength. *Materials* **2021**, *14*, 352.
https://doi.org/10.3390/ma14020352

**AMA Style**

Hron R, Kadlec M, Růžek R. Effect of the Test Procedure and Thermoplastic Composite Resin Type on the Curved Beam Strength. *Materials*. 2021; 14(2):352.
https://doi.org/10.3390/ma14020352

**Chicago/Turabian Style**

Hron, Robin, Martin Kadlec, and Roman Růžek. 2021. "Effect of the Test Procedure and Thermoplastic Composite Resin Type on the Curved Beam Strength" *Materials* 14, no. 2: 352.
https://doi.org/10.3390/ma14020352