An experimental study of glass fibre roving sizings and yarn finishes in high-performance GF-PA6 and GF-PPS composite laminates

In the present study a range of glass fibre (GF) coatings (roving sizings and yarn finishes) were investigated for the manufacture of high-performance composite laminates based on Polyamide 6 (PA6) and Polyphenylene Sulfide (PPS) matrices. Matrix compatibility and resulting composite performance of press-consolidated laminates was evaluated by macro-mechanical testing on the basis of 3-point flexural and short-beam-shear tests. Among the tested yarn finishes, γ-aminopropyltriethoxysilane (A-1100 aminosilane yarn finish) and chromium(III)methacrylate (Volan®A chromium yarn finish) stood out as highly efficient adhesion promoters for both PA6 and PPS. Flexural strength properties of laminates prepared from finished yarn fabrics (up to 770 MPa) surpassed industrial grade laminates. A GF-epoxy laminate yielded lower flexural strength (570 MPa) compared to the GF-PPS laminates at an identical fibre volume fraction of 56%. These findings exemplified that neat PA6 and PPS matrices require no further chemical modification, i.e. adhesion and resulting composite strength can be tailored most efficiently by fibre coating adaptation. SEM imaging further verified that PA6 and PPS polymers adhere strongly to specific glass fibre coatings. In contrast, laminates made from desized (uncoated) fabrics exhibited interfacial debonding, and hence the lowest laminate performance throughout. Additional compression, and compression after impact tests (50 J impact) revealed that laminates made from sized or finished fabrics boast superior impact attenuation when compared to their desized fabric counterparts.