Effect of non‐woven flax mat manufacturing parameters and consolidation pressure on properties of composites manufactured using vacuum‐assisted resin transfer molding

Abstract

AbstractComposite parts, used in transportation industries, are manufactured using vacuum‐assisted resin transfer molding (VARTM) and non‐woven glass fiber mats that are optimized for impregnation, fiber volume fraction (Vf), and composite properties. However, such optimized hemp and flax mats are not available. Extending the research on hemp mats manufactured using air‐laying, the effect of needle depth (2 or 8 mm) and punch density (0–72 punches/cm2) used to bind the fibers in the mat together, as well as consolidation pressure (101–560 kPa) applied during manufacturing, on mat permeability and composite properties were studied. Non‐woven flax mats exhibited heterogeneity in spatial distribution of areal density (GSM) and fiber distribution. This, together with the distribution in flax fiber diameter and properties, resulted in large scatter in the measured composite properties. The out‐of‐plane permeability and the consolidation of the mat decreased with increase in punch density and depth. This, together with the variation of Vf in the starting mat, resulted in complex variation in the Vf in the composite. 30‐P mat, with tightly bound fibers, resulted in optimal composite properties at VARTM (101 kPa) pressure while 0‐P and 72‐P mats, with loosely bound fibers, resulted in optimal properties at 560 kPa.