High-temperature fracture behavior of carbon fiber reinforced PEEK composites fabricated via fused filament fabrication

Abstract

This study investigates the influence of temperature on the mechanical and fracture properties of carbon fiber reinforced (CF) polyetheretherketone (PEEK) composites, with a specific focus on different layer heights used in the additive manufacturing process. Tensile and compact tension fracture tests were conducted at varying temperatures to evaluate the orthotropic mechanical properties and crack growth resistance curves, respectively. The key findings underscore the pronounced orthotropic mechanical behavior in additively manufactured CF-PEEK composites, showing substantial variations of up to 50% in Young's modulus and yield strength across orientations. Additionally, as test temperatures increase, crack initiation becomes easier, indicating reduced crack resistance at elevated temperatures. Notably, the effect of layer height on initiation toughness is relatively minor compared to temperature. Moreover, the study reveals that fracture energy for crack growth is less temperature-sensitive but depends on layer height, with larger defects in taller layers resulting in decreased damage resistance. These findings stress the importance of considering the distinct sensitivities of initiation and steady-state fracture energies to temperature, emphasizing the critical role of effective fracture toughness in evaluating material resistance to high-temperature fractures. These observations contribute to our understanding of the mechanical and fracture behavior of CF-PEEK composites under high operating temperatures. This understanding facilitates the optimization of their manufacturing processes and their application in various industries such as aerospace.