Comparison of low velocity impact behaviour of thermoplastic composites reinforced with glass and basalt woven fabrics

The effects of interface strength on the quasi-static and low velocity impact behaviour of woven basalt and woven glass/polypropylene (PP) laminates have been investigated and the performances of the resulting composites compared. The fibre/matrix interface strength has been managed by modifying the matrix with a coupling agent (maleated PP) acting as a compatibilizer. Quasi-static flexural tests showed that the compatibilizer improves both flexural modulus and strength, as well as the strain at yield in glass fibre based laminates. On the contrary, for systems reinforced with basalt woven fabrics, probably owing to a specific surface pre-treatment, only limited gains in flexural properties were detected after compatibilizer addition to the matrix. This consideration is reflected in different effects on the impact strength. An improved interface strength, such that of glass fibre/compatibilized PP samples, lowered the perforation threshold because crack propagation cannot be blocked and matrix or fibre breakage become the main dissipative mechanisms. The reduction of the interface strength allows further dissipative mechanisms (fibre splitting, larger fibre and matrix deformations, frictions) and improves the perforation threshold. In particular, PP/basalt fabric composites showed the highest perforation threshold among all prepared laminates (perforation occurring above 60 J), due to the very weak interface strength and the higher ultimate properties of basalt fibres with respect to glass ones.