(Nano)structure, skin/core and tension behaviour of polyamide fibres

Abstract

International audienceThe micro/nanostructural evolution of ultrahigh-performance and textile (containing a dispersion of TiO2 powder) polyamide 66 fibres during tensile loading and failure initiation was studied using Raman spectroscopy low-wavenumber collective modes (100 cm-1) as a mechanical probe representative of the crystalline domains. The analysis of the wavenumber distribution revealed the skin/core heterogeneity. A compressive residual stress in the skin was evaluated at about 200 MPa from calibration plots. The homogeneity of the TiO2 grain dispersion was mapped on fibre sections and scanned along their lengths. In situ analysis at different strain levels shows that the amorphous region accommodates the stress up to ca 350 MPa, from which point elastic behaviour is observed. Particular attention was devoted to analysing crack formatio

Micro-Raman study of the fatigue and fracture behaviour of single PA66 fibres: Comparison with single PET and PP fibres

“…Raman vibrational analysis was performed on single fibres extracted from the yarn as described in refs [10,11]. These previous studies demonstrated that the size applied to the fibre surface during manufacture does not contribute to the Raman spectra in the analysed wavenumber ranges.…”

“…number of chemical bond per volume unit). The rather large strains obtained with some of these fibres under imposed strain conditions has required the use of a Universal Fibre Tester described in refs [10][11][12] with a fixed grip and a mobile grip (Fig. 2a).…”

“…stabilisation of stress versus time, Raman spectra were recorded from t acq=0 to t end according to the procedure described in ref. [10]. The recording time ranged between ~600 (PET) and 3000 s (PA).…”

“…This is obvious from the comparison of polarized spectra (Figs 3 and refs. [10,11]): the modes at about 80-100 cm -1 assigned to a lattice mode involving the translational/librational movement (T') of the chains of the unit-cell exhibit the stronger degree of polarization. Roughly speaking, this mode can be described as a translation of the whole chain with respect to adjacent ones.…”

“…The present study examines and compares the behaviour of PA 66 (previously published in detail [9][10][11]) and PET fibres under fatigue loading until fracture and the correlation between the fibre (nano)structure and structural heterogeneity, with fatigue lifetimes. Comparison will be extend to two very different fibres, PP (poly(propylene)) a viscoelastic material and PBO (poly(p-phenylenebenzobisoxazole), an elastic high modulus material [7].…”