Table 2.

Elastic and damage constitutive parameters representing mean FPA specimens in each of the six age groups. Data are provided for three constitutive models: the two-fiber-family model with damage in the collagen fibers (2F), the four-fiber-family model also with damage only in the collagen fiber families (4F-CO), and the four-fiber-family model with damage accumulation across all four phenomenological fiber families (4F).

Age group, years		≤30	31–40	41–50	51–60	61–70	71–80
Samples per group		11	9	8	36	32	8
Fits with ERR ≤ 0.05	2F	5	8	7	28	26	7
	4F-CO	9	9	7	26	27	7
	4F	10	8	7	31	30	8
Fits with R2 ≥ 0.9	2F	11	9	8	33	30	8
	4F-CO	11	9	8	35	30	8
	4F	11	8	8	31	31	8
Mean age, years		18.8	35.0	46.0	55.4	65.0	76.3
Elastic Parameters
cgr (kPa)	2F	15.36	9.64	7.14	9.06	3.77	0.77
	4F-CO	9.85	9.79	6.02	6.17	1.25	16.53
	4F	5.25	9.13	7.78	7.05	3.68	10.99
$C_1^{el}$ (kPa)	4F-CO	6.36	3.08	1.50	0.53	6.54	3.72
	4F	3.21	4.93	4.62	13.72	24.81	29.71
$C_2^{el}$	4F-CO	0.38	1.33	2.57	5.15	3.42	5.64
	4F	2.40	2.30	4.82	5.19	9.29	11.43
$C_1^{smc}$ (kPa)	4F-CO	0.67	0.21	1.76	0.62	3.15	5.93
	4F	4.86	9.01	6.33	14.39	27.96	41.72
$C_2^{smc}$	4F-CO	1.11	1.53	1.13	2.15	0.12	3.97
	4F	4.73	10.42	5.13	6.76	10.90	13.37
$C_1^{col}$ (kPa)	2F	2.50	3.59	4.84	7.07	12.91	28.72
	4F-CO	5.62	4.90	9.52	16.58	21.59	33.51
	4F	11.93	3.93	5.33	3.52	1.66	10.74
$C_2^{col}$	2F	2.70	3.39	4.56	7.01	11.47	10.20
	4F-CO	2.49	4.78	6.28	6.78	12.47	13.03
	4F	0.21	4.41	4.28	7.33	9.19	10.83
φ (°)	2F	48.38	41.58	41.75	39.07	45.48	42.89
	4F-CO	51.60	50.30	46.49	41.44	50.60	42.12
	4F	35.40	49.53	49.05	33.44	43.74	34.20
Damage Parameters
γ∞ (kPa)	2F	25.85	25.32	24.38	21.66	15.08	15.31
	4F-CO	22.21	18.61	18.06	19.41	14.11	14.06
${\gamma }_{\infty }^{col}$ (kPa)	4F	99.61	19.84	23.63	22.09	21.35	8.77
${\gamma }_{\infty }^{el}$ (kPa)		25.43	40.92	24.13	23.09	15.85	16.97
${\gamma }_{\infty }^{smc}$ (kPa)		19.35	11.40	20.10	18.76	13.09	13.25
βs	2F	35.15	39.26	32.75	19.15	14.30	17.91
	4F-C0	46.51	43.61	28.30	21.12	14.96	18.23
${\beta }_s^{col}$	4F	4.27	48.06	34.53	27.23	43.41	48.45
${\beta }_s^{el}$		39.25	0.88	42.53	22.64	14.98	16.45
${\beta }_s^{smc}$		14.89	1.69	25.61	15.75	18.04	15.41