Non-crimp 3D Orthogonal Woven Research Articles

X-ray μCT based assessment of thermal cycling induced cracks in non-crimp 3D orthogonal woven composite materials with porosity

This work focuses on X-ray micro-Computed Tomography (μCT) assessment of thermal cycling behavior of a carbon fiber/epoxy matrix composite material reinforced with a non-crimp 3D orthogonal woven preform (3DNCOW) with porosity. Porosity levels and damage mechanisms – i.e. matrix cracking - induced by thermal cycling are characterized by X-ray micro-computed-tomography (μCT). Qualitative and quantitative descriptions of the morphology and the evolution of cracks with thermal cycling are carried out through the analysis of μCT scans of samples at different cycle numbers, with emphasis on the influence of porosity on the damage mechanisms induced by thermal cycling. X-ray μCT image-based Finite Element models are employed to provide rational interpretation to the observed phenomenological scenario.

X-ray micro-computed-tomography characterization of cracks induced by thermal cycling in non-crimp 3D orthogonal woven composite materials with porosity

This paper focuses on an experimental study of the thermal cycling behavior of a carbon fiber/epoxy matrix composite material reinforced with a non-crimp 3D orthogonal woven preform (3DNCOW). The aim is to characterize the damage mechanisms – i.e. matrix cracking – induced by thermal cycling thanks to X-ray micro-computed-tomography (µCT). Qualitative and quantitative descriptions of the morphology and the evolution of cracks with thermal cycling are carried out through the analysis of µCT scans of samples at different cycle numbers. In addition, since the specimens have a certain level of porosity due to the infusion process, a complete description of this defect is carried out, and its influence on the damage mechanisms induced by thermal cycling is analyzed.

Numerical modelling of forming of a non-crimp 3D orthogonal weave E-glass composite reinforcement

A hyperelastic constitutive model is implemented to study the formability on three-dimensional complex shapes of a single layer E-glass non-crimp 3D orthogonal woven reinforcement. Experimental measurements of the main deformation modes have been used to identify the strain energy density function of the constitutive model. The comparison of the finite element simulations and experimental results of tetrahedron and double-dome shaping processes demonstrated the adequacy of the adopted hyperelastic model to describe the deformation mechanisms involved during draping and the efficiency to predict the global behaviour of the non-crimp 3D woven reinforcement during complex shape forming.

Formability of a non-crimp 3D orthogonal weave E-glass composite reinforcement

In this paper, the formability of a single layer E-glass non-crimp 3D orthogonal woven reinforcement (commercialized under trademark 3WEAVE® by 3Tex Inc.) is experimentally investigated. The study involves the forming process of the 3D fabric on two complex moulds, namely tetrahedron and double-dome. The tests are assisted by 3D digital image correlation measurement to have a continuous registration of the fabric local deformation. Moreover, the results of bending tests in warp and weft direction are detailed to enlarge the mechanical properties data set of the 3D reinforcement, necessary for understanding its deformability capacities in forming processes. The elevated bending stiffness of the 3D fabric means that use of a blank-holder during forming is not required. The reinforcement has a good drapability and it is able to form complex shapes without defects (wrinkles and fibre distortions). The collected experimental results represent an important dataset for numerical simulations of any complex shape with the considered 3D fabric composite reinforcement.

Micro-CT analysis of the internal deformed geometry of a non-crimp 3D orthogonal weave E-glass composite reinforcement

An investigation at the unit cell level of the sheared geometry of a single layer E-glass non-crimp 3D orthogonal woven reinforcement (commercialized under trademark 3WEAVE® by 3Tex Inc.) is performed by X-ray micro-computed tomography (micro-CT) observations. The aim is to observe, understand and quantify the effect of in-plane shear deformation on the composite reinforcement geometry, at meso-scale (i.e. unit cell level). It was observed that, increasing the shear deformation, Z-yarns maintain unchanged the distance between the yarns and as consequence the yarn cross-section has a reduced variation of width, mainly in the weft direction.Furthermore, the effect of the shear angle on the textile thickness during compression is measured, this being an important parameter after the forming and molding phases of a composite component production. Compression tests and micro-CT measurements of the thickness show similar values and are in agreement with the prediction obtained assuming the theoretical invariance of the volume in the considered range of shear deformations.

3D digital image correlation measurements during shaping of a non-crimp 3D orthogonal woven E-glass reinforcement

This paper illustrates a methodology for the characterization of textile composite reinforcements during experimental simulation of forming processes. In particular, being the shear deformation considered as the primary deformation mechanism during shaping, the evolution of shear angle distribution on the reinforcement surface is measured by means of 3D digital image correlation analyses. Two different image correlation software programs, i.e. VIC-3D and MatchID3D, are used to study the forming process of a single layer E-glass non-crimp 3D orthogonal woven reinforcement (commercialized under trademark 3WEAVE® by 3Tex Inc.). The comparison of the displacement and shear angle distributions of the reinforcement, shaped on tetrahedral and double-dome moulds, pointed out a good agreement between the results obtained with both software packages.

Wind blade joints based on non-crimp 3D orthogonal woven Pi shaped preforms

Current industrial designs for joining composite wind blade elements allow unstable crack propagation in the thick adhesive layer within the joint. In this work, a novel integral 3D woven Pi-joint element is developed and implemented in an I-beam joint construction that corresponds to a wind blade’s shear web and spar cap. In a series of iterative design–analysis–fabrication–testing cycles, 2.9m long I-beams that used the current practice joint and the novel proposed joint were designed, studied theoretically with the use of a 3D Mosaic analysis tool, then manufactured and loaded to failure in a cantilever flexure loading set up. Experimental data showed significant advantage in the load-bearing capacity of the joint structure with the use of novel Pi-joint element. Excellent agreement was observed between the theoretical predictions and experimental data.

Deformability of a non-crimp 3D orthogonal weave E-glass composite reinforcement

Abstract Deformability of a single-ply E-glass non-crimp 3D orthogonal woven reinforcement (commercialized under trademark 3WEAVE® by 3Tex Inc.) is experimentally investigated. The study is focused on the understanding and measurement of the main deformation modes, tension and in plane shear, which are involved during draping of composite reinforcements by: (i) uniaxial and biaxial tension; (ii) in-plane shear investigation using uniaxial bias extension and picture frame tests; and (iii) measurements of the fabric thickness variation during shear. The test methods common for 2D fabrics are validated for the thick 3D reinforcement. The obtained results represent a data set for the simulation of a forming process with the 3D reinforcement.

Pull-through performance of carbon fibre epoxy composites

An investigation of the through-thickness properties of carbon fibre prepreg laminates, Non-Crimp Fabric laminates and non-crimp 3D orthogonal woven composites by pull-through testing was performed. Influence of matrix system and curing temperature on the performance of the 3D woven composites was investigated.The results showed that the prepreg specimens endured the highest pull-though loads, followed by the 3D woven composites, and the NCFs. It was found however that the prepreg laminates were characterized by the largest extent of damage after the test, whereas only very localized damage was present in the 3D woven composites. The NCF specimens presented overall the worst bolt pull-thought performance. No significant influence of the matrix system and curing temperature on the 3D woven composites’ performance was observed.

Fatigue tensile behavior of carbon/epoxy composite reinforced with non-crimp 3D orthogonal woven fabric

An experimental study of the in-plane tension–tension fatigue behavior of the carbon fiber/epoxy matrix composite reinforced with non-crimp 3D orthogonal woven fabric is presented. The results include pre-fatigue quasi-static test data, fatigue life diagrams, fatigue damage progression, and post-fatigue quasi-static test data for the warp- and fill-directional loading cases. It is revealed that the maximum cycle stress corresponding to at least 3 million cycles of fatigue life without failure, is in the range of 412–450 MPa for both loading directions. This stress range is well above the static damage initiation threshold and significantly above the first static damage threshold (determined by the onset of low energy acoustic emission). The second static damage threshold, determined by the onset of high energy acoustic emission and related to the appearance of local debonds and intensive transverse matrix cracking falls within this range. The established correlation between a 3000,000 cycle fatigue stress limit on one side and the second static damage threshold stress on the other is of a high practical importance, because it will significantly reduce the amount of future fatigue tests required for this class of composites. Surprisingly, for equal maximum cycle stress level, the fatigue life under fill-directional loading appears about three times shorter than that under warp-directional loading. The 100,000 cycle, 500,000 cycle and 1000,000 cycle fatigue loading with 450 MPa maximum cycle stress has resulted in so high variations of post-fatigue static modulus, strength and ultimate strain, that no consistent and statistically meaningful trends could have been established; further extensive experimental studies are required to reliably quantify this effect.

Experimental study of joining thick composites reinforced with non-crimp 3D orthogonal woven E-glass fabrics

A comprehensive experimental study was performed to determine the strength of several co-cured and adhesively bonded joints of composite panels reinforced with non-crimp 3D orthogonal woven E-glass fiber fabrics. Various single-lap and double butt-strap joints were fabricated using co-curing and adhesive bonding and tested in uniaxial in-plane tension. The co-cured joints included special stepped 3D woven preforms, stitched and stapled joints. The joint strength appears to have the lowest values for the co-cured single-lap joints, intermediate values for the co-cured double butt-strap joints and the highest values for the adhesively bonded double butt-strap joints. Stitching and stapling dry preforms resulted in significant increase of the co-cured single-lap joint strength. In the range of strap thicknesses studied for the bonded joints, thinner straps provide a higher joint break force than thicker ones. Tapering strap ends to as small angle as possible was found to be the most effective method of increasing break force of double butt-strap bonded joints.

Internal geometry evaluation of non-crimp 3D orthogonal woven carbon fabric composite

Measurements of the internal geometry of a carbon fiber non-crimp 3D orthogonal woven composite are presented, including: waviness of the yarns, cross sections of the yarns, dimensions of the yarn cross sections, and local fiber volume fraction. The measured waviness of warp and fill yarns are well below 0.1%, which shows that the fabric termed here “non-crimp” has nearly straight in-plane fibers as-produced, and this feature is maintained after going through all steps of fabric handling and composite manufacturing. The variability of dimensions of the yarns is in the range of 4–8% for warp and fill directions, while the variability of the yarn spacing is in the range of 3–4%. These variability parameters are lower than respective ranges of variability of the yarn waviness and the cross-sectional dimensions in typical carbon 2D weave and 3D interlock weave composites, which are also illustrated in this work for comparison.

A comparative study of tensile properties of non-crimp 3D orthogonal weave and multi-layer plain weave E-glass composites. Part 2: Comprehensive experimental results

This Part 2 paper presents results of comparative experimental study of progressive damage in 2D and 3D woven glass/epoxy composites under in-plane tensile loading. As Part 1, this Part 2 work is focused on the comparison of in-plane tensile properties of two non-crimp single-ply 3D orthogonal weave E-glass fibre composites on one side and a laminate reinforced with four plies of E-glass plain weave on the other. The damage investigation methodology combines mechanical testing with acoustic emission registration (that provides damage initiation thresholds), progressive cracks observation on transparent samples, full-field surface strain mapping and cracks observation on micrographs, altogether enabling for a thorough characterisation of the local micro- and meso-damage modes of the studied composites. The obtained results demonstrate that the non-crimp 3D orthogonal woven composites have significantly higher in-plane strengths, failure strains and damage initiation thresholds than their 2D woven laminated counterpart. The growth of transverse cracks in the yarns of 3D composites is delayed, and they are less prone to a yarn–matrix interfacial crack formation and propagation. Delaminations developing between the plies of plain weave fabric in the laminate at certain load level never appear in the 3D woven single-ply composites.

A comparative study of tensile properties of non-crimp 3D orthogonal weave and multi-layer plain weave E-glass composites. Part 1: Materials, methods and principal results

Composites fabricated by VARTM technology with the use of single-ply non-crimp 3D orthogonal woven preforms 3WEAVE ® find fast growing research interest and industrial applications. It is now well understood and appreciated that this type of advanced composites provides efficient delamination suppression, enhanced damage tolerance, and superior impact, ballistic and blast performance characteristics over 2D fabric laminates. At the same time, this type of composites, having practically straight in-plane fibers, show significantly better in-plane stiffness and strength properties than respective properties of a “conventional” type 3D interlock weave composites. One primarily important question, which has not been addressed yet, is how the in-plane elastic and strength characteristics of this type of composites compare with respective in-plane properties of “equivalent” laminates made of 2D woven fabrics. This 2-part paper presents a comprehensive experimental study of the comparison of in-plane tensile properties of two single-ply non-crimp 3D orthogonal weave E-glass fiber composites on one side and a laminate reinforced with four plies of plain weave E-glass fabric on the other. Results obtained from mechanical testing are supplemented by acoustic emission data providing damage initiation thresholds, progressive cracks observation, full-field surface strain mapping and cracks observation on micrographs. The obtained results demonstrate that the studied 3D non-crimp orthogonal woven composites have considerably higher in-plane ultimate failure stresses and strains, as well as damage initiation strain thresholds than their 2D woven laminated composite counterpart. Part 1 presents the description of materials used, experimental techniques applied, principal results and their mutual comparisons for the three tested composites. Part 2 describes in detail the experimentally observed effects and trends with the main focus on the progressive damage: detailed results of AE registration, full-field strain measurements and progressive damage observations, highlighting peculiarities of local damage patterns and explaining the succession of local damage events, which leads to the differences in strength values between 2D and 3D composites.