Residual Stresses Introduced to Composite Structures due to the Cure Regime: Effect of Environment Temperature and Moisture

Table 4

Principal stresses obtained from biaxial tension experiments on EP 280 Prepreg, where is the First-Stress Invariant based on the mechanical stresses [9] and is the First-Stress Invariant based on both the mechanical and residual stresses.

Test number	Mechanical stresses [9]				Residual stresses				% difference
	(MPa)	(MPa)	(MPa)	(MPa)	(MPa)	(MPa)	(MPa)	(MPa)
1	137.65	32.61	4.60	174.86	5.07	4.75	−5.32	179.36	3%
2	95.58	50.92	33.62	180.12	5.07	4.75	−5.32	184.62	2%
3	178.02	28.10	−55.32	150.8	5.07	4.75	−5.32	155.3	3%
4	76.54	44.67	27.80	149.01	5.07	4.75	−5.32	153.51	3%
5	105.26	37.03	31.22	173.51	5.07	4.75	−5.32	178.01	3%
6	70.08	40.51	25.35	135.94	5.07	4.75	−5.32	140.44	3%
7	89.96	29.43	24.34	143.73	5.07	4.75	−5.32	148.23	3%
8	86.80	49.77	31.23	167.8	5.07	4.75	−5.32	172.3	3%
9	101.25	35.61	30.37	167.23	5.07	4.75	−5.32	171.73	3%
10	112.09	41.38	35.04	188.51	5.07	4.75	−5.32	193.01	2%
11	138.47	43.92	31.65	214.04	5.07	4.75	−5.32	218.54	2%
12	162.05	54.18	43.34	259.57	5.07	4.75	−5.32	264.07	2%
13	118.44	31.91	10.68	161.03	5.07	4.75	−5.32	165.53	3%
14	149.68	50.57	41.22	241.47	5.07	4.75	−5.32	245.97	2%
15	89.79	25.78	9.90	125.47	5.07	4.75	−5.32	129.97	4%
16	104.41	44.69	10.80	159.9	5.07	4.75	−5.32	164.4	3%
17	124.87	37.53	23.61	186.01	5.07	4.75	−5.32	190.51	2%
18	79.57	29.42	25.48	134.47	5.07	4.75	−5.32	138.97	3%
19	96.02	36.51	31.16	163.69	5.07	4.75	−5.32	168.19	3%
20	121.95	46.16	39.50	207.61	5.07	4.75	−5.32	212.11	2%
21	137.82	54.91	46.36	239.09	5.07	4.75	−5.32	243.59	2%
22	107.53	55.18	40.24	202.95	5.07	4.75	−5.32	207.45	2%
23	76.43	30.93	27.04	134.4	5.07	4.75	−5.32	138.9	3%
24	115.96	50.59	40.71	207.26	5.07	4.75	−5.32	211.76	2%
25	98.08	39.94	34.69	172.71	5.07	4.75	−5.32	177.21	3%
26	68.60	27.53	24.21	120.34	5.07	4.75	−5.32	124.84	4%