Assessment of ageing effect on the mechanical and damping characteristics of thin quasi-isotropic hybrid carbon-Kevlar/epoxy intraply composites

Figures & data

Figure 1. (a) Intraply fabric and (b) Representation of intraply weaving design.

Table 1. Details of the fabric used

Type of fibre	Fabric type	Style	Weight	Thickness	Yarn Count	Balance	Manufacturer
Carbon Kevlar Hybrid	Woven intraply Fabric	Plain weave	188 GSM	0.3 mm	3K	Unbalanced	Dupont

Table 2. Details of the matrix used

Epoxy Resin	Viscosity at 25° C	Density at 25° C	Hardener	Viscosity at 25° C	Density at 25° C
Araldite® LY 5052	1000–1500 mPa s	1.17 g/cm^3	Aradur® 5052 CH	40–60 mPas	0.94 g/cm^3

Figure 2. Fibre orientation and stacking arrangement of the fabricated laminate (1 and 8 represent the top and bottom layers).

Figure 3. (a) Compression molding machine (b) Cured laminate.

Figure 4. (a) Tensile test setup (b) Test specimen.

Figure 5. Flexural test setup.

Figure 6. (a) Impact hammer test setup (b) Test specimen.

Table 3. Specimen coding and test details

Specimen Coding	Ageing condition	Tests carried out for each ageing condition	No. of samples tested for each ageing condition
Quasi-isotropic carbon-Kevlar/epoxy composite	Pristine	Tensile	5
	Ambient	Flexural	5
	Sub-zero	Short beam shear (SBS)	5
	Humid	Impact hammer	5

Figure 7. Moisture absorption behaviour of the laminate for different ageing conditions.

Table 4. Moisture diffusion parameters

Ageing Condition	Saturation moisture uptake (%)	Ageing time	Diffusion Coefficient DZ (mm^2/s)
Ambient	4.167	180 days	8.944 × 10^−8
Sub zero	2.762	180 days	8.177 × 10^−8
Humid	1.162	180 days	7.897 × 10^−8

Table 5. Tensile properties of the specimens

Type of Ageing	Ultimate strength (MPa)	Tensile modulus (GPa)	Tensile failure strain (mm/mm)
Pristine	270.03 ± 9.22	7.00 ± 0.57	0.050 ± 0.0025
Ambient	223.29 ± 6.93	5.86 ± 0.43	0.045 ± 0.0026
Sub-zero	247.93 ± 8.21	6.48 ± 0.58	0.048 ± 0.0025
Humid	231.56 ± 10.24	6.25 ± 0.62	0.047 ± 0.0026

Figure 8. Stress vs strain graphs of pristine and aged specimens.

Figure 9. Ultimate tensile strength and modulus of the specimens.

Figure 10. Strength retention after tensile testing.

Figure 11. SEM micrographs of fractured (a) Pristine (b) Ambient (c) Sub-zero and (d) Humid aged tensile test specimens.

Figure 12. Flexural strength and modulus of pristine and aged specimens.

Figure 13. (a) Post flexural test samples (b) Enlarged view of the fractured area.

Figure 14. SBS strength and SBS strength retention of pristine and aged samples.

Figure 15. Light microscope pictures of fractured (a) Pristine (b) Ambient (c) sub-zero and (d) humid aged SBS test specimens.

Table 6. Damping properties of pristine and aged specimens

Ageing condition	logarithmic decay (δ)	Damping coefficient (ζ)	Natural frequency(fn)	Storage modulus, Es (GPa)
Pristine	0.22	0.036	21.47	23.37
Ambient	0.119	0.019	16.51	13.83
Sub-zero	0.20	0.030	19.81	19.91
Humid	0.155	0.024	18.16	16.73

Figure 16. Damping characteristics of pristine specimens (a) Acceleration amplitude vs frequency (b) Acceleration amplitude vs time.

Figure 17. Damping characteristics of ambient aged specimens (a) Acceleration amplitude vs frequency (b) Acceleration amplitude vs time.

Figure 18. Damping characteristics of sub-zero aged specimens (a) Acceleration amplitude vs frequency (b) Acceleration amplitude vs time.

Figure 19. Damping characteristics of humid aged specimens (a) Acceleration amplitude vs frequency (b) Acceleration amplitude vs time.