PSI - Issue 77

Sunny O. Uguzo et al. / Procedia Structural Integrity 77 (2026) 521–528

525

[±65 2 /±75 2 ] laminate TCP loses 20.4% strength as T i ranges from 4

o C – 120 o C, while [±55

2 /±30 2 ] and [±75 2 /±30 2 ] loses

18.8% and 15.6% respectively. Overall [30] 4 laminate TCP gives the highest baseline stability but [±75 2 /±30 2 ] laminate TCP best balances baseline strength and minimal thermal decay, whilst all high layup laminate TCP [±65 2 /±75 2 ] and [±55] 4 are the least attractive when subjected to the described thermomechanical load concurrently.

Fig. 3. Variation of P cr vs. T i

Overall TCP buckling strength is highly sensitive to laminate architecture as through thickness thermal gradient. However, maximizing P cr should be weighed against other requirements such as material limit, load variations, manufacturability etc. Thus, optimal TCP laminate lay ups are application specific, balancing axial stability with broader operational needs. 3.2. Effect of laminate architecture material failure and failure mode Furthermore, failure analysis was conducted by reapplying the respectively obtained P cr values detailed in Table 3 using the Hashin and von-Mises failure criteria to analyse the TCP laminate and liners respectively.

Table 4: TCP controlling failure load and mode vs laminate architecture at varying T i .

Laminate T i – 4

o C

T

i – 30

o C

T

i – 60

o C

T

i – 90

o C

T

i – 120

o C

[±30] 4 [±55] 4

2230 kN (MT) 1680 kN (B)

1930 kN (MT) 1593 kN (B)

1450 kN (MT) 1495 kN (B)

1000 kN (MT+PY) 100 kN (PY)

1100 kN (PY)

590 kN (PY)

[±55 2 /±30 2 ] 3098 kN (MC+FC) 2935 kN (MC+FC) 1200 kN (PY) [±75 2 /±30 2 ] 3100 kN (MC+FC) 2980 kN (FT+MC+FC) 2850 kN (FT+MC+FC) 2700 kN (MC+FC) 1670 kN (PY) [±65 2 /±75 2 ] 1445 kN (B) 1385 kN (B) 1322 kN (B) 1215 kN (PY) 745 kN (PY) Note: B-Buckling, MT-Matrix tension, MC-Matrix compression, FT-Fibre tension, FC-Fibre compression, PY-Liner plastic yielding o C, material failure loads clustered around 1810-3100kN, dropping to 100-1750kN at the highest T i , reflecting APC-2 PEEK matrix softening and liner yield. For instance, [±30] 4 laminate TCP’s material failure load declined from 2230kN (4 o C) to 100kN (120 o C). Additionally, hybrid ply laminate TCPs mixing high and low angles exhibited much better material strength across T i . The [±75 2 /±30 2 ] and [±55 2 /±30 2 ] laminate TCPs produced higher material failure loads of 3100kN and 3098kN respectively, while the [±30] 4 , [±65 2 /±75 2 ]and [±55] 4 laminate TCPs exhibited much lower values of 2230kN, 1940kN and 1810kN respectively. Material failure indicated higher sensitivity to thermal gradient and increasing T i than buckling. From the results in Table 4, most TCP configurations were limited by material failure. However, at T i ≤ 60 o C, [±55] 4 and [±65 2 /±75 2 ] laminate TCPs buckled without material damage. Above T i = 60 o C, all configurations became limited by material failure. For instance, [±55] 4 transitioned from buckling to liner yielding. At T i = 120 o C, inner liner 2755 kN (FT+MC+FC) 2180 kN (PY) Material strength declined rapidly with rising T i . AtT i =4