Manufacturing of bio-polyamide 11/basalt thermoplastic laminates by hot compaction: The key-role of matrix rheology

Abstract

The rheology of the polymer matrix plays a crucial role in determining the quality of thermoplastic laminates. To highlight this aspect, we prepared laminates based on polyamide 11 (PA11), a bio-based matrix with tricky rheology, and basalt fiber fabrics. The PA11 viscosity rapidly increases over time due to degradation phenomena. Samples were prepared by two procedures differing in terms of duration and intensity of the hot compaction step. Morphological analyses revealed that the fast procedure ensures a better impregnation of the fabrics, with a substantial reduction of the volume of voids (1%, against 9% of the slow procedure). This reflects in considerable increases of the flexural modulus (ca. + 20%) and strength (ca. + 60%) and a significant reduction the extent of impact damage. This study provides useful guidelines for a correct selection of the processing parameters based on the knowledge of the rheological behavior of the polymer matrix.

Damage detection in bio-polyamide 11/woven basalt fibres composite laminates subjected to dynamic events

“…Such a depth can trigger various damage mechanisms due to a significant participation of the matrix in the energy dissipation process, given also the higher void content of the "slow" specimens. 41 However, in the light of very similar absorbed energy values, the significant difference detected in terms of indentation depth can only be attributed to the occurrence of different damage modes, which will be confirmed through non-destructive tests in the next paragraph.…”

“…In detail, 20 layers of basalt fabric were alternated with PA11 films and compacted according to two moulding procedures on the base of rheological considerations reported elsewhere. 41…”

“…In general, the impact performance of the thermoplastic composite is still under study, due to the complexity of this type of material and the manufacturing procedures. 40,41 In this regard, non destructive evaluation is a handy tool to assess the impact of damage in composite laminates, mainly for new groups of materials, such as green composites, 42,43 additive manufacturing composites 44,45 or high-performance applications. 46–48…”

“…In this work, with the aim of investigating the damage mechanisms triggered in PA11/basalt biocomposites subjected to dynamic stresses, non-destructive investigations were carried out on hot-compacted specimens obtained in two different process conditions. 41…”

Different Production Processes for Thermoplastic Composite Materials: Sustainability versus Mechanical Properties and Processes Parameter

“…Then, misalignment of the reinforcement would act as a manufacturing defect, negatively altering the strength of the laminates. Vitiello et al [ 36 ] implemented two impregnation procedures, in terms of duration and intensity, for the fabrication of basalt fiber-reinforced polyamide 11 (BF-PA) laminates. Regarding “slow” procedure the laminate was compacted at lower pressure (3 MPa) and for longer times (13 min), suffering from the growing viscosity of the matrix.…”