Table 9.

Stiffness reduction for both SW and DW samples with flute rotated by 15 degrees for three cases of perforation.

Stiffness Reduction	SW-26-F-15 (%)	SW-44-F-15 (%)	SW-62-F-15 (%)	DW-26-F-15 (%)	DW-44-F-15 (%)	DW-62-F-15 (%)
$1-A_{11}$ $/A_{11}^{*}$	0.523	2.121	3.519	0.508	1.903	3.364
$1-A_{22}$ $/A_{22}^{*}$	8.133	27.66	49.46	7.852	27.77	50.98
$1-A_{33}$ $/A_{33}^{*}$	2.480	13.01	25.04	2.735	12.66	24.50
$1-D_{11}$ $/D_{11}^{*}$	0.449	1.769	3.187	0.467	1.786	3.247
$1-D_{22}$ $/D_{22}^{*}$	5.110	23.03	48.40	6.377	25.41	49.18
$1-D_{33}$ $/D_{33}^{*}$	1.677	8.598	18.81	2.171	10.25	20.88
$1-R_{44}$ $/R_{44}^{*}$	0.435	1.545	1.273	−0.349	1.032	1.177
$1-R_{55}$ $/R_{55}^{*}$	4.851	25.41	33.84	4.060	18.48	30.95

* denotes the reference value of non-perforated specimen (i.e., SW-0-F-15).