*3.1.3 Mechanical property comparison for PPSCFC*

**Tables 3** and **4** present that the mechanical properties are not significantly affected by the strain rate effect while strain rate increases. Peak stress variation is less than 3.5% when results of specimens tested at quasi-static and dynamic regimes are compared, which indicate that strength is not strain rate dependent for this material. Strain at peak stress measured by the SHPB system presents higher variation than the strain measured by DIC (29.23–17.977%, respectively) compared with quasi-static results; however, the failure mechanism has not presented any difference which is why both can be considered negligible and the difference is attributed to the measurement method. The variation observed on the modulus is given by the obtained strain data; higher values for strain at peak stress obtained by SHPB gauges give modulus' lower values for dynamic tests and lower variation between quasistatic and dynamic regime compared with results with strain data measured by DIC; however, modulus is taking as constant, too, that is, it is not strain rate dependent.

Strain rate insensitivity is also observed in **Figure 14**, where peak stress-strain rate relation (a), strain at peak stress-strain rate relation (b), and Young's modulusstrain rate relation (c) are shown. Quasi-static (QS) and dynamic (D) average data is plotted for each property, differentiating SHPB strain data and DIC strain data.

It can be concluded that the material is not strain rate dependent and the measurement of dynamic strain by DIC allows a more accurate comparison with respect to the measurement of the quasi-static strain by the video strain gauge system. PPSCFC mechanical behavior discussed does not coincide with the behavior

**39**

**Figure 13.**

**Table 3.**

*SEM images for PPSCFC tested at 832.3 s<sup>−</sup><sup>1</sup>*

*High Strain Rate Characterization of Thermoplastic Fiber-Reinforced Composites…*

observed on similar materials (thermoplastic matrixes reinforced with carbon fiber) [11, 16, 19, 23, 27, 38]. This can be explained by the effect of carbon fiber on the resin (PPS) crystallization reported in open literature, where it has been found that transcrystallinity on the fiber-resin interphase affects the mechanical proper-

*Average mechanical properties for PPSCFC with strain measured by SHPB system.*

*(b) "unmelted" surface at 100×, (c) Z1 marked in (b) at 1000×, and (d) Z2 marked in (b) at 1000×.*

Failure mode is not strain rate dependent, either. The material presents mixed failure aspects (delamination and shear), which is characteristic for a laminate fabric submitted to compression according to Greenhalgh [40]. The material tested under the highest strain rate presents separation on multiple parts indicating severe damage due to the high-speed load application and insufficient dissipation of the heat generated in the deformation process. It is also worth to mention that it is observed that the delamination becomes more predominant at highest strain rate, which coincides with what Greenhalgh [40] reports for laminates submitted to

*. (a) "Melted" surface at 500× with 2500× zoom of the marked zone,* 

ties of the composite [32, 38, 47–49].

high-speed impact loading.

*DOI: http://dx.doi.org/10.5772/intechopen.82215*

**Figure 12.** *Images sequence taken by HSIS for PPSCFC tested at 832.2 s<sup>−</sup><sup>1</sup> .*

*High Strain Rate Characterization of Thermoplastic Fiber-Reinforced Composites… DOI: http://dx.doi.org/10.5772/intechopen.82215*

#### **Figure 13.**

*Aerospace Engineering*

to compression [40, 44–46].

*3.1.3 Mechanical property comparison for PPSCFC*

while the zone Z2 (**Figure 13d**) presents riverlines (yellow arrows) and feather marks (red circles). This fractographic aspects are typical of a composite submitted

**Tables 3** and **4** present that the mechanical properties are not significantly affected by the strain rate effect while strain rate increases. Peak stress variation is less than 3.5% when results of specimens tested at quasi-static and dynamic regimes are compared, which indicate that strength is not strain rate dependent for this material. Strain at peak stress measured by the SHPB system presents higher variation than the strain measured by DIC (29.23–17.977%, respectively) compared with quasi-static results; however, the failure mechanism has not presented any difference which is why both can be considered negligible and the difference is attributed to the measurement method. The variation observed on the modulus is given by the obtained strain data; higher values for strain at peak stress obtained by SHPB gauges give modulus' lower values for dynamic tests and lower variation between quasistatic and dynamic regime compared with results with strain data measured by DIC; however, modulus is taking as constant, too, that is, it is not strain rate dependent. Strain rate insensitivity is also observed in **Figure 14**, where peak stress-strain rate relation (a), strain at peak stress-strain rate relation (b), and Young's modulusstrain rate relation (c) are shown. Quasi-static (QS) and dynamic (D) average data is plotted for each property, differentiating SHPB strain data and DIC strain data. It can be concluded that the material is not strain rate dependent and the measurement of dynamic strain by DIC allows a more accurate comparison with respect to the measurement of the quasi-static strain by the video strain gauge system. PPSCFC mechanical behavior discussed does not coincide with the behavior

**38**

**Figure 12.**

*Images sequence taken by HSIS for PPSCFC tested at 832.2 s<sup>−</sup><sup>1</sup>*

*.*

*SEM images for PPSCFC tested at 832.3 s<sup>−</sup><sup>1</sup> . (a) "Melted" surface at 500× with 2500× zoom of the marked zone, (b) "unmelted" surface at 100×, (c) Z1 marked in (b) at 1000×, and (d) Z2 marked in (b) at 1000×.*


#### **Table 3.**

*Average mechanical properties for PPSCFC with strain measured by SHPB system.*

observed on similar materials (thermoplastic matrixes reinforced with carbon fiber) [11, 16, 19, 23, 27, 38]. This can be explained by the effect of carbon fiber on the resin (PPS) crystallization reported in open literature, where it has been found that transcrystallinity on the fiber-resin interphase affects the mechanical properties of the composite [32, 38, 47–49].

Failure mode is not strain rate dependent, either. The material presents mixed failure aspects (delamination and shear), which is characteristic for a laminate fabric submitted to compression according to Greenhalgh [40]. The material tested under the highest strain rate presents separation on multiple parts indicating severe damage due to the high-speed load application and insufficient dissipation of the heat generated in the deformation process. It is also worth to mention that it is observed that the delamination becomes more predominant at highest strain rate, which coincides with what Greenhalgh [40] reports for laminates submitted to high-speed impact loading.


#### **Table 4.**

*Average mechanical properties for PPSCFC with strain measured by DIC.*
