Fibre Surface and Morphology Testing

Fibre surface and morphology testing characterises fibre surface topography, chemical composition, wettability, and crystalline structure using electron microscopy, X-ray diffraction, XPS, contact angle measurement, and atomic force microscopy — analytical techniques essential for surface treatment verification, finishing development, and fibre-matrix interface optimisation in composites. Scanning electron microscopy (SEM, JEOL JSM-7600F, Zeiss Sigma, 1–15 kV accelerating voltage, gold or carbon sputter coating 5–10 nm for non-conducting fibres): resolves surface features at 10 nm resolution — wool scale geometry (scale height 300–500 nm, scale overlap length 2–5 µm), cotton surface wax and cuticle (convolution morphology at 200×, wax layer 0.1–0.3 µm), carbon fibre surface treatment grooves (200–500 nm width from oxidative surface treatment), corona discharge treatment etching on PP (surface pit density 5–20 pits/µm²). X-ray diffraction (WAXD — wide-angle X-ray diffraction, CuKα radiation λ = 0.154 nm, 2θ = 5–50°): cotton crystallinity index CI by Segal method (I₂₀₀ − Iam)/I₂₀₀ × 100 where I₂₀₀ = peak at 22.8° (crystalline), Iam = 18.0° (amorphous) — mercerised cotton CI 65–70%, native cotton CI 70–80%; PET crystal d-spacing at 2θ = 17.5° and 25.6° (triclinic unit cell) — heat setting increases PET crystal size from 3.5 to 6.0 nm. XPS (X-ray photoelectron spectroscopy, monochromatic AlKα, binding energy survey 0–1,400 eV, surface depth 5–10 nm): carbon fibre surface chemistry — O/C ratio 0.05 (unsized, untreated) → 0.15 (oxidative surface treatment) → 0.12 (epoxy-sized) — O/C ratio directly predicts ILSS interlaminar shear strength (R² = 0.88).