Key differences on the compaction response of natural and glass fiber preforms in liquid composite molding

Abstract

In the present work, the effects of fiber structure and fluid absorption on the compaction behavior of jute woven fabrics and sisal mats were analyzed and compared with the response of glass fiber mats. It was found that the fiber content that can be achieved with a certain compaction pressure is lower in the case of natural fiber preforms. In addition, due to the hollow structure of these natural fibers, jute and sisal preforms suffered larger permanent deformation than glass fiber preforms after the compressive loading cycle. In addition, it was found that fluid absorption reduced the compaction pressure in natural reinforcements due to fiber softening. These phenomena were not observed in glass fiber mats.

Processing of plant fiber composites by liquid molding techniques: An overview

“…Authors suggested that plant fiber cell walls collapse and the lumens are closed in an irreversible manner when compressive forces are applied to the preform. These phenomena were found to be more significant when the fiber content (and transverse deformation) was increased . In addition, plastic deformation of plant fibers was confirmed by Poilâne et al during mechanical testing of flax/epoxy composites.…”

“…Another peculiarity of the compaction behavior of plant fiber fabrics is the high permanent deformation that occurs after one or more compressive loading cycles, several times higher than the permanent deformation reported for glass fiber fabrics with similar architecture . This means that the difference between the first and second compaction curves is larger in natural fiber preforms than in the case of glass fiber preforms.…”

“…However, many LCM processes comprise compaction step of dry fibrous preforms. Almost all the authors that have studied the compaction of plant fiber preforms agreed that they are more difficult to compress than preforms made of glass fiber fabrics , in contrast to what could be expected considering that the stiffness of plant fibers is lower than the stiffness of glass fibers. This means that higher clamping forces will be required to achieve a certain fiber volume fraction, or lower fiber content will be achieved with the available clamping force.…”

“…Significant stress relaxation was found to occur in hemp and flax mats by Khoun et al , in jute woven fabrics and sisal mats by Francucci et al and in wood fiber mats manufactured by different techniques by Umer et al . Some reported values for stress relaxation are given in Table .…”

Studies on permeability of sisal fibre mat during thermoset resin filling in vacuum infusion process

“…Francucci et al studied the permeability of jute fibre fabrics. No concrete fibre washing or race tracking problems in the infusion process were observed.…”