Analysis of Water Absorption on the Young’s Modulus and Damping of Sponge Gourd (Luffa cylindrica) Composites

Figures & data

Figure 1. Sonic test set-up: (a) Acoustic sensor model CADPS, (b) IED Automatic impulse device, (c) specimen.

Figure 2. Mass gain (M%) as a function of the square root of time (days 1/2) for the composites with untreated sponge fibers. The nominal fiber volume fraction of the composites is labeled on the curves. (a) Distilled water; (b) Salt water.

Table 1. Diffusion coefficient and mass saturation value for sponge gourd/epoxy composites immersed in distilled water.

Fiber treatment	Fiber volume fraction	M∞	D (10^−6mm^2/s)	Dx (10^−6mm^2/s)	r^2
Untreated	10	19.3	2.90	3.36	0.996
Untreated	20	25.4	3.15	3.65	0.997
Untreated	30	31.8	4.70	5.44	0.997
Mercerization	20	11.8	3.05	3.53	0.990
Mercerization	30	15.9	4.09	4.73	0.995
Hornification	20	12.0	2.10	2.43	0.997
Hornification	30	15.8	2.98	3.45	0.997
Acetylation	20	17.4	2.35	2.72	0.996
Acetylation	30	18.4	2.79	3.23	0.994

Table 2. Diffusion coefficient and mass saturation value for sponge gourd/epoxy composites immersed in salt water.

Fiber treatment	Fiber volume fraction	M∞	D (10^−6mm^2/s)	Dx (10^−6mm^2/s)	r^2
Untreated	10	18.8	1.67	1.93	0.989
Untreated	20	25.4	2.22	2.57	0.995
Untreated	30	35.4	2.27	2.63	0.989
Mercerization	20	10.0	1.20	1.39	0.996
Mercerization	30	16.0	2.94	3.40	0.990
Hornification	20	11.7	1.51	1.75	0.995
Hornification	30	17.5	1.61	1.86	0.993
Acetylation	20	15.1	1.45	1.68	0.990
Acetylation	30	16.3	2.79	1.86	0.986

Figure 3. Mass gain (M%) as a function of the square root of time (days^1/2) for the composites with mercerized sponge fibers. (a) Distilled water; (b) Salt water.

Figure 4. Variation of the Young’s modulus as a function of the immersion time in distilled water. (a) As-received fibers; (b) mercerized; (c) hornified; (d) acetylated.

Figure 5. Composite with 20wt% of acetylated fibers immersed in distilled water. (a) variation of the Young’s modulus; (b) mass gain due to water absorption.

Figure 6. Variation of the elastic modulus before and after immersion in salt water and drying. U stands for untreated, H for hornified, M for mercerized and a for acetylated. The numbers refer to the volume fraction.

Table 3. Average values of the elastic modulus according to the time of immersion in salt water.

Fiber treatment	Fiber volume fraction	Time (h)
		24	48	168	360	1488
Untreated	10	2.95$\pm 0.03$	2.04$\pm$0.08	2.1$0\pm 0.04$	2.12 $\pm 0.03$	2.18$\pm 0.03$
Untreated	20	3.72 $\pm 0.29$	2.78 $\pm$ 0.16	2.66 $\pm 0.20$	2.65 $\pm 0.15$	2.66 $\pm 0.20$
Untreated	30	3.07 $\pm 0.01$	2.12 $\pm 0.04$	2.07 $\pm 0.03$	2.13 $\pm$ 0.01	2.11 $\pm 0.07$
Mercerization	20	3.98 $\pm 0.01$	2.65 $\pm 0.01$	2.66 $\pm 0.01$	2.63 $\pm 0.01$	2.61$\pm 0.01$
Mercerization	30	4.23 $\pm 0.09$	3.62 $\pm 0.33$	3.37 $\pm 0.18$	3.25 $\pm 0.18$	3.10 $\pm 0.13$
Hornification	20	3.75 $\pm 0.02$	2.71 $\pm 0.02$	2.62 $\pm 0.01$	2.61 $\pm$ 0.01	2.59$\pm 0.02$
Hornification	30	4.09 $\pm 0.23$	3.29 $\pm 0.27$	3.12 $\pm 0.27$	3.01 $\pm 0.21$	3.01 $\pm 0.16$
Acetylation	20	3.55 $\pm 0.27$	2.72 $\pm 0.17$	2.59 $\pm 0.18$	2.55 $\pm 0.11$	2.51 $\pm 0.12$
Acetylation	30	3.57 $\pm 0.27$	2.83 $\pm 0.21$	2.56 $\pm 0.33$	2.58 $\pm 0.29$	2.56 $\pm 0.30$

Figure 7. Example of the behavior found for all composites. a) Variation of the damping factor with the immersion time (composites with 20wt% of untreated fibers in distilled water). b) Damping factor values at the end of the saltwater absorption test.