Compaction of textile reinforcements for composites manufacturing. III: Reorganization of the fiber network

Abstract

The objectives of this series of papers are to describe the mechanical behavior of textile reinforcements under normal load and to quantify the effects of diverse processing parameters on that behavior. In the first and second papers of the series, experimental compaction and relaxation results were reported; general trends were identified and the effects of changes in the processing parameters were analyzed. In this paper, the results of sequences of successive compaction cycles applied to dry textiles and to textiles saturated in distilled H2O and silicone oil are presented. The reinforcements investigated are produced by assembling tows or rovings following different patterns; it is shown that the resulting heterogeneity, or regular variation of the local fiber volume fraction, can be associated to some particular elements of the mechanical behavior of the reinforcements. The reorganization of the fiber network and the effect of friction at the fiber contacts are demonstrated. Different stages in the reorganization process are identified; each stage is controlled by different parameters and corresponds to a precise behavior. Successive compaction cycles applied to a preform can reduce the void content of the final part.

A methodology for determining preform compaction in bladder-assisted resin transfer molding with elastomeric bladders for tubular composite parts

“…(15) and (16). Similar to saturation experiments presented in a previous paper of the authors [8], a constant bladder and injection pressure of 4.0 and 1.5 bar, respectively, is used while the injection is performed at atmospheric pressure (p f =0).…”

“…This is widely reported in literature for woven and braided fabrics assuming that preform compaction is not time dependent [5,14,15,21,[27][28][29]:…”

“…The latter one only occurs in multi-layer preforms and depends on various textile parameters such as the binding pattern, degree of shear and number of layers [11][12][13]. Moreover, it was shown that preform compaction is time dependent, non-elastic and influenced by the presence of a saturating fluid causing lubrication effects that facilitate reorganization of the fiber network [14][15][16]. Although some authors have made considerable efforts in compaction modelling of textile preforms based on force, energy or finite element approaches, preform compliance is still widely characterized by means of experimental compression tests and analytically described using empirical compaction models [10,11,17,18].…”

Compressibility and relaxation models for fibrous reinforcements in Liquid Composites Moulding

“…For the experimental part, several authors were interested in the study of the compressibility of the reinforcements. An abundant literature exists on this aspect in particular the study of the effect of the type of reinforcement, the rate of compression, the number of plies or the impregnation [8][9][10]. The experimental studies highlight at the same time the phase of compression and the phase of relaxation which are represented on the same figures [11].…”

“…Several authors underlined the large dispersion of the results obtained for these two parameters and some modifications of this model has been proposed [2,3] in order to better fit the experimental results. Chen et al [4] proposed a model using physical parameters.…”