**4. Conclusions**

*Aerospace Engineering*

**Table 7.**

**Table 8.**

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

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

**46**

**Figure 23.**

glass fibers) [4, 16–18, 38, 52, 53].

*plot and (c) Young's modulus-strain rate plot.*

Results indicate that the material is strain rate dependent presenting an increase in the properties when strain rate applied increases, which is evidenced more accurately with DIC strain measurement and comparing it with the quasi-static results. The mechanical behavior observed on this material coincides with data reported for other similar materials in open literature (thermoplastic matrixes reinforced with

*PPSCFC properties as function of the strain rate: (a) strength-strain rate plot, (b) ultimate strain-strain rate* 

The mechanical behavior of the materials is linear elastic at all tested strain rates. Mechanical properties remain constant with respect to the strain rate applied for each regime. Results obtained for PPSCFC indicate compressive strength of 532.603 MPa, failure strain of 1.284%, and Young's modulus of 43.859 GPa for quasi-static regime and 534.93 MPa for compressive strength, 1.345% for failure strain, and 53.014 GPa for Young's modulus at high strain rates. PPSGFC results give compressive strength of 358.295 MPa, failure strain of 1.676%, and Young's modulus of 21.999 GPa for quasi-static regime and for the dynamic regime 496.758 MPa for compressive strength, 2.034% for strain failure, and 27.168 GPa for Young's modulus.

Comparing the obtained values for the mechanical properties calculated under the quasi-static and dynamic regimes, it is found that the PPSCFC exhibits a strain rate insensitive mechanical behavior with respect to the strain rates applied, while the PPSGFC is strain rate dependent, which means enhancement on mechanical properties when the strain rate increased. Compressive strength increases by 38%, failure strain increases by 21%, and Young's modulus increases by 23%.

According to the strain spectrum obtained from the strain measurement by DIC, the strain measurement by the SHPB system shows the highest strain value in the specimen; however, due to the strain behavior at dynamic tests, it is better to perform strain localized measurement, in order to compare mechanical properties calculated in both regimes.

The behavior for the PPSCFC reported herein is not in accordance with data and similar material reports elsewhere. This can be attributed to the fact that the resin used for this material (PPS) is semicrystalline and presents a reaction with the carbon fibers at the crystallization moment during the cooling, generating transcrystallinity on the fiber-resin interphase which affects the mechanical properties. Further studies must be performed to establish if this is why the material behavior is affected.

The behavior obtained for the PPSGFC is what is expected according to data and similar material reports published in the literature; the strain rate dependency of the mechanical properties is attributed to the viscoelasticity of the resin.

The failure mode observed for the materials, in general terms, is mixed. Delamination and shear mode are identified, and it is observed that the failure aspects are not significantly affected by strain rates, which in tum leads to conclude that the failure mechanism is not strain rate dependent. The failure mechanisms are governed by the material configuration and the fiber-resin interphase more than the strain rate applied, which explain that typical fractographic characteristics for composite materials submitted to uniaxial compression were developed.

Bigger efforts must be made to understand the generation and dissipation of heat during the material strain process for high strain rates to understand better their effect on the fractographic aspects of the material ("melted" surfaces).
