Nonwoven polyester interleaving for toughness enhancement in composites

Abstract

Various researchers have developed techniques to control delamination in laminated structures. One of these techniques is “interleaving,” adding high toughness material to key interfaces in a laminate. This paper studies using polyester veil as a low-cost interleaf alternative to other materials and focuses on a nonwoven, polyester spunbond material. Two different interleaf thicknesses, 0.18 mm and 0.74 mm, are primarily used. In addition, fine 4 g/m2 polyester was also compared. Carbon/epoxy composites are manufactured using 2 × 2 Twill 24″–12k carbon fibers embedded in an epoxy resin, with polyester interleaves at key interfaces. Specimens are fabricated using wet hand layup and cured at room temperature in a vacuum bag. Mode I fracture toughness is measured using the double cantilever beam test and Mode II fracture toughness is examined using the end-notched flexure test. Further evaluation is made using static indentation and full penetration impact testing. Toughness is compared, and the resulting fracture surfaces are investigated. Significant improvement is seen in Mode I testing. Up to a factor of 4 increase in propagation energy per unit area resulted from the inclusion of the interleaf material. Smaller improvements were observed in Mode II, with the best cases showing an increase in propagation energy to maximum load by about a factor of 2 compared with control cases. The polyester interleaf significantly influences the fracture morphology observed in static indentation and full penetration tests.

Enhanced interlaminar shear and impact performance of woven carbon/epoxy composites interleaved with needle punched high performance polyethylene fiber nonwoven

“…41 Similarly, nylon 6,6 nonwoven fabric has been reported to increase the Mode-I initiation and propagation fracture toughness of carbon fiber epoxy composites by 34% and 156%, respectively. 28 Interleaves made of high toughness materials can contribute to enhance interlaminar toughness of the composite laminates, 37 therefore, selection of the interleaves made of appropriate material is important. 41 Ultra-High Molecular Weight Polyethylene (UHMWPE) or high-performance polyethylene (HPPE) fibers possess attractive properties, such as, high specific strength and modulus, low density, high elongation and energy absorption characteristics.…”

“…However, the tensile strength of the composites containing aramid interleaves was lower than that of control samples due to reduced volume fraction of the carbon fibers. Gheryani et al 37 investigated the effect of polyester nonwoven interleaves on fracture toughness of woven carbon fabric epoxy composites and found that Mode‐I and Mode‐II fracture toughness was increased. The increase in Mode‐I fracture toughness was significant compared with Mode‐II fracture toughness.…”

Analysis of the Fiber Laydown Quality in Spunbond Processes with Simulation Experiments Evaluated by Blocked Neural Networks

“…in [5] results of experimental studies are presented, where the porosity of the spunbonded fabrics in composites is analyzed. The authors of [6] deal also with spunbonded nonwovens in composites, but focuses on their application as interleaves and the enhanced resulting toughness of the composite. In the application of spubonded nonwovens for filter media, the bicomponent nonwovens in particular play an important role.…”

“…Effect of the input material parameters on the fiber laydown characteristics: the effect of E modulus (first row, left figure) and the effect the density (first row, right figure) are on the same order of magnitude, while the effect of the line density is approximately 10 times bigger than the effect of E modulus and density (see second row, center figure).TA B L E 1 Average elasticity measures (dimensionless quantities) computed due to equation(6) …”

“…Hence, we introduced in section 4 a scalar measure -the so-called average elasticity measure -in order to quickly rank the effect of the input parameters on the fiber laydown. We compute the average elasticity measures due to equation (6). Table 1 shows the average elasticity values for each of the five input parameters with respect to the three different output parameters.…”