Compressive crack resistance analysis of unidirectional thermoplastic composites

Abstract

Thermoset composite materials are nowadays a well-consolidated reality in the aerospace industry. However, the aeronautical sector is struggling to find more sustainable and damage tolerant options to produce safer and lighter structures. Thanks to the new consolidation processes with reduced production cost, fibre-reinforced thermoplastic (FRTP) materials stand out now as an appealing alternative. Among the others, PEKK-based composites have recently attracted the interest of several companies thanks to their remarkable mechanical properties and a lower processing temperature. This work stands out as one of the first attempts to characterize the compressive longitudinal intra- laminar fracture toughness of a carbon fibre PEKK composite (AS4/PEKK). Geometrically scaled Double Edge Notched Compression (DENC) specimens were tested in accordance with the size-effect methodology. Two different specimen configurations were considered for this study: 1) edge- loaded DENC with a specimen length-to-width ratio of 1.5, 2) alternative slender coupons (length- to-width ratio >4) tested with the support of a Combined Loading Compression fixture (DENCLC)