Issue 68

V. O. Alexenko et alii, Frattura ed Integrità Strutturale, 68 (2024) 390-409; DOI: 10.3221/IGF-ESIS.68.26

joints, especially with the low PEI contents in the prepregs (Fig. 3, a and b). However, local discontinuities (such as interlayer cracks) were formed in the prepregs at the USW duration of 600 ms (especially with the high PEI contents), according to Fig. 3, h and i.

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(m) (o) Figure 3: The optical images of the structure on the cross-sections of the USW joints for different combinations of the USW durations and the PEI/CF-fabric ratios in the prepregs; PEI/CF-fabric ratio of 23/77 (a,d,g,j,m); 30/70 (b,e,h,k,n); 43/57 (c,f,i,l,o); t = 400 ms (a,b,c) ; t = 500 ms (d,e,f) ; t = 600 ms (g,h,i); t = 800 ms (j,k,l); t = 800 ms (m,n,o). (n)

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