Fabric Composite Laminates Research Articles

In-plane mechanical, thermal and viscoelastic properties of a satin fabric carbon/epoxy composite

The objective of this study was to determine the in-plane mechanical, viscoelastic and thermal properties of a satin fabric composite. This study was performed on a composite laminate material consisting of a satin weave carbon fabric impregnated with an amine cured epoxy resin. The in-plane quasi-static behavior including the failure modes under tension, compression and shear was analyzed and all mechanical properties including elastic moduli and strengths were determined. The viscoelastic properties including the glass transition temperature were determined as well as the coefficients of thermal expansion. These measured properties for the fabric composites were also correlated with their corresponding ones for the unidirectional composite with the same fiber and matrix.

Thermo-flexural analysis of thick laminates of bimodulus composite materials

Here, flexural analysis of laminated composite plates of bimodulus materials subjected to thermal load is carried out. The formulation is based on higher-order theory that accounts for the transverse shear and transverse normal deformations, and incorporates through the thickness approximations of the in-plane displacements. The governing equations obtained using the principle of minimum potential energy are solved through the finite element approach. The results obtained here are compared with those of the theory without thickness stretch/contraction terms and the first-order one. The combined influence of higher-order shear deformation, plate geometry, lay-up and ply-angle on the displacements/stresses and neutral surface locations of bimodulus composite laminate is examined.

Innovative high-pressure laminate insulation for fusion magnets

High-pressure laminate (HPL) composite materials, such as G-10, have been used for many years in both the electrical and magnet industry as insulation for demanding applications. Because of their relative ease of fabrication and ability to be inspected prior to magnet installation, these materials have remained an attractive insulation option for current magnet designers. However, composite insulation for use in many new Next Step Option (NSO) fusion devices must meet an increasingly demanding set of requirements, including cryogenic and elevated temperature performance while withstanding higher radiation levels. The lack of performance in high radiation environments by materials such as G-10 has led Composite Technology Development, Inc. (CTD) to develop a series of new, innovative HPL insulation systems that can meet the new fusion magnet challenges. Material development has focused on highly radiation-resistant resin systems, as well as lower radiation resistant, low cost alternatives. Prototype laminates have been fabricated and evaluated by a leading industrial partner to ensure their suitability for large-scale production. This paper will present several new insulation systems capable of being fabricated in the HPL process, provide processing characteristics, along with mechanical and electrical property data.

Ballistic impact into fabric and compliant composite laminates

The development of tough, high-strength, high-modulus fibers has led to the use of fabrics and compliant composite laminates for a number of impact-related applications, such as turbine blade containment, fuselage protection and body armor. Numerous studies have been conducted to identify material properties and system mechanisms that are important to the performance of these ballistic textiles. The current paper presents a review of the factors that influence ballistic performance; specifically, the material properties of the yarn, fabric structure, projectile geometry and velocity, far field boundary conditions, multiple plies and friction. Each physical mechanism is described in detail, and original references are cited to allow further investigation.

Experimental investigations on the response of stitched/unstitched woven S2-glass/SC15 epoxy composites under single and repeated low velocity impact loading

In the current investigation, damage resistance of stitched/unstitched S2-glass/epoxy composites is studied. Five layer stitched/unstitched plain weave S2-glass woven fabric composite laminates were manufactured using toughened SC15 epoxy resin system. For stitching, two configurations: one with 25.4 mm grid and other with 12.7 mm grid, were used with 6 mm pitch. Damage resistance was evaluated by subjecting 100 × 100 mm samples to low velocity impact loading at energy levels ranging 10–80 J using DYNATUP Model 8210, an instrumented impact test system. Three samples were tested at each energy level. The extent of damage was evaluated using ultrasonic C-scan. Results of the study indicate that stitching confined the damage size. As the damage was low over most of the energy range, the study was further extended to determine the effect of repeated impact loading. Under this study, laminates were subjected to repeated impact loading up to maximum of 40 impacts at energy levels ranging from 10 to 50 J. Results of repeated impact study are reported in terms of peak load, absorbed energy and projected damage area. All the laminates, sustained repeated impact loading up to 30 J. Beyond 30 J, laminates failed to carry repeated loading beyond certain numbers, which depended on the laminate configuration.

일방향-평직 복합재 혼합 적층판의 체결부 강도 연구

일방향-평직 복합재 혼합 적층판의 체결부 파손하중 및 파손모우드를 결정하기 위한 실험과 유한요소해석을 수행하였다. 체결부 실험은 끝단거리 대 원공직경의 비 및 시편 폭과 원공직경의 비가 다른 총 9가지의 모델에 대하여 편하중을 가하여 수행하였다. 체결부 파손해석을 위한 방법의 검토를 위해, MSC/NASTRAN을 사용하여 핀과 모재의 접촉 및 마찰을 고려한 비선형 해석을 수행하였다. 파손여부는 특성곡선 상에서 Tsai-Wu 방법과 Yamada-Sun 방법을 사용하여 평가하였다. 적층판의 체결부 파손하중 및 파손모우드는 원공 중심에서 끝단까지의 거리가 작거나, 시편의 폭이 작을 경우 파손하중에 큰 영향을 미치지만, 일정값 이상이 되면 파손하중과 파손모우드의 변화는 거의 없는 것으로 밝혀졌다. 특성길이 방법에 의한 유한요소해석은 대체로 파손하중과 파손모우드를 비교적 잘 예측하는 것을 볼 수 있었다. The failure load and mode of the unidirectional and fabric hybrid composite laminate joints are studied by test and finite element analysis. Test is conducted for the specimens with nine various geometries under pin loading. Finite element analysis is performed considering the contact and friction effects between the pin and laminate by MSC/NASTRAN. Failure is estimated by Tsai-Wu and Yamada-Sun criteria on the characteristic curve. While the failure of the specimens with the small width and edge length are much affected by the joint geometry, the geometry effects are negligible in the specimens with large width and edge length. Finite element analysis based on the characteristic length method reasonably predicts the failure load and mode of the joints.

The Numerical Simulation of the Mechanical Behavior of CFCC with Matrix Anisotropic Damage by Homogenization Method

The purpose of the present paper is to establish a damage constitutive model for predicting the elastic-brittle mechanical behavior of continuous fiber reinforced ceramic matrix composites (CFCC). In this paper, the anisotropic damage is applied to describe the matrix phase damage which reflects all types of damage that the matrix material undergoes such as matrix cracking and transverse cracking. The asymptotic expansion homogenization method is used to obtain the effective mechanical properties of the composites, and to derive homogenized damage elastic concentration factor of unidirectional and cross-ply laminate composite materials. Internal variables are introduced to describe the evolution of the damage state under uniaxial loading and as a subsequence the degradation of the material stiffness. Results obtained from the numerical simulations include damage evolution prediction and non-linear stress-strain analyses of macro-microstructure, and they are compared well with existing experimental data.

Modeling inelastic and strength properties of textile laminates: a unified approach

A unified approach based on bridging micromechanics model to the simulation of inelastic and strength properties of textile (woven, braided, and knitted) fabric reinforced composite laminates is reviewed and summarized in this paper. The approach is performed ply by ply. While classical lamination theory is employed to determine the load shared by a lamina ply, the individual ply analysis essentially consists of three steps. In the first step, a representative volume element (RVE) of the lamina is isolated and the geometry of the textile preform in the RVE is identified. According to this geometrical description, the RVE is divided into a series of unidirectional (UD) composites whose orientations have all been known. Thus, the second step is concerned with the analysis of all the UD composites, which is accomplished by using the bridging model. The three fundamental quantities, i.e. the stress increments in the fiber, the stress increments in the matrix, and the overall compliance matrix of the composite, are explicitly obtained at each load level. The last step deals with an assemblage of all the UD composites to obtain the mechanical response characteristics of the considered ply. The ply failure is assumed if the internal stress state in any constituent attains its ultimate value, and a progressive failure process of the laminate results. Otherwise, the ply instantaneous compliance matrix is adapted to define the overall instantaneous stiffness matrix of the laminate for additional analysis. Ultimate failure strengths of different textile composite laminates subjected to in-plane, fatigue, as well as out-of plane bending loads have been obtained, which compare favorably with our experimental data.

Pneumatic Characterization of Composite Materials

The dimensional change of some composite materials induced by ambient air pressure change was discovered and dubbed pneumatic strain in 2000. This pneumatic behavior closely resembles hygric behavior, and pneumatic strain is proportional to the ambient air pressure change by the coefficients of the pneumatic expansion. A method termed the suspension method was employed in this work to characterize the pneumatic behavior of unidirectional T700 carbon/epoxy composite laminate and other materials, such as Kevlar 49 fiber, aluminum plate, aluminum foil, paper, celluloid sheet and pure epoxy plate. Longitudinal and transverse pneumatic strains of T700 carbon/epoxy composite lamina induced by 1 atm air pressure change were measured. The results also indicated that Kevlar 49 fiber and aluminum have no pneumatic behavior, while paper, celluloid film and epoxy plate do have pneumatic behavior. Two major contributions of this work are verifying the effectiveness of suspension method for the pneumatic characterizing and discovering more materials having pneumatic behavior.

The antisymmetry bending theory of generalized equivalent of functionally gradient materials structure

FGM structure is defined as a kind of generalized equivalent structure according to the structure and properties of materials. This paper uses the mature plate theory and the composite material laminate theory in the analysis of FGM structure and thus puts forward a kind of new concept and a new idea. A brand-new theory, the generalized equivalent antisymmetry bending theory, which can be used to analyze the structure and properties of FGM, is formed. In addition, the correctness, reliability and foresightedness of the theory are testified through concrete analysis and calculation of the applicable FGM structure by utilizing the generalized double Fourier series solution on one hand; on the other hand, it is compared with the existing theories and experiments.

Dynamic fracture toughness measurements in composites by instrumented Charpy testing: influence of aging

The dynamic behavior of three different fiber fabric composite laminates was studied by testing notched specimens in an instrumented Charpy machine. The registered impact force and displacement at the specimen hammer contact point were used to evaluate Mode-I fracture energy and dynamic fracture toughness. The changes in fracture toughness due to impact velocity, crack size and stacking sequence of the specimen were investigated with different degrees of aging conditions. Aging was found to significantly affect the dynamic fracture toughness, but had less effect on the static fracture toughness.

Strengthening of BWR Mark III reinforced concrete containment with fibre composite laminate material

Zusammenfassung Numerical analyses are carried out by using the abaqus finite element program to predict the ultimate pressure capacity and the failure mode of the BWR Mark III reinforced concrete containment strengthened by composite materials or steel plates at various positions. Material non-linear behaviour for concrete, steel, and fibre composite laminate material are all simulated with proper constitutive models. It has been shown that the use of [±θ/90/0]5S composite materials with 50≤θ≤90° to strengthen the containment at the upper cylinder and the dome achieves the most satisfactory strengthening results. (The fibre angle of the lamina is measured counter-clockwise through the outward normal direction from the meridian of the containment shell structure.)

Progressive Failure Analysis of Laminated Knitted Fabric Composites Under 3-Point Bending

The bending behavior of laminated beams reinforced with differently arranged plain-weft knitted fabrics has been investigated in this paper. Experiments were carried out to measure the bending stiffness and strength of six layers knitted fabric rein-forced epoxy composite laminates under 3-point bending. The laminate lay-ups of [0/0/0/0/0/0], [90/90/90/90/90/90] and [0/-45/45/45/-45/0] have been taken into account, where 0 denotes that the fabric wale direction is arranged along the beam axial direction. A simulation procedure is presented to analyze the bending property of the laminated beams based on the bridging micromechanics model and the classical lamination theory. It has been found that the use of a stress failure criterion only is no longer enough for estimating the ultimate bending strength of the laminate. An additional critical deflection condition is also required. By using only the constituent properties, which were measured using bulk material specimens independently, and the fabric knitting and lay-up parameters, the predicted stiffness and strength agree favorably with the experimental data.

Drilling of composite structures

Structural parts made of composites have frequently to be drilled in the aircraft industry. However, little is know about the interacting conditions between the drilling tool and the material, which may be multi-type and multi-size. This study proposes a model which links the axial penetration of the drill bit to the conditions of delamination (crack opening mode I) of the last few plies. Several types of tool/material contact conditions were analyzed and were compared with experimental measurements, and with a model taken from the literature. Our study shows a close correlation between experiment and calculation when the thrust force of the drill is modeled by taking into account the geometrical nature of the contact between the tool and a laminate composite material.

Evaluation of steel drilling tool with sinter-bonded graded cemented carbide coating

This paper presents the micromechanical three-dimensional finite element models of the 2/2 twill weave T300 carbon/epoxy woven fabric composite laminates with drilled circular holes of different sizes. A fiber breakage failure criterion for predicting the ultimate tensile notched strength of fiber dominated composites is also proposed. It is found that the location of failure initiation for laminates with large hole size is different from those for laminates with smaller holes while the stress concentration may not occur at the notch roots for the fiber dominated laminates. Based on the uniaxial, shear and von Mises stress distributions in the yarn and matrix, the influence of hole-size on the stress distributions and stress concentration is discussed. Standard tensile tests with modifications are performed for this particular type of woven fabric composites. The apparent strain concentration factors and notched strengths determined by experiments are presented and the finite element models are verified by satisfactory correlation between prediction and experiment.

3D finite element analysis of tensile notched strength of 2/2 twill weave fabric composites with drilled circular hole

This paper presents the micromechanical three-dimensional finite element models of the 2/2 twill weave T300 carbon/epoxy woven fabric composite laminates with drilled circular holes of different sizes. A fiber breakage failure criterion for predicting the ultimate tensile notched strength of fiber dominated composites is also proposed. It is found that the location of failure initiation for laminates with large hole size is different from those for laminates with smaller holes while the stress concentration may not occur at the notch roots for the fiber dominated laminates. Based on the uniaxial, shear and von Mises stress distributions in the yarn and matrix, the influence of hole-size on the stress distributions and stress concentration is discussed. Standard tensile tests with modifications are performed for this particular type of woven fabric composites. The apparent strain concentration factors and notched strengths determined by experiments are presented and the finite element models are verified by satisfactory correlation between prediction and experiment.

Orientation-dependent properties of silicon nitride with aligned reinforcing grains

Silicon nitride with the aligned reinforcing grains was prepared by tape casting with addition of the silicon nitride whiskers and gas-pressure sintering at 2148 K. The microstructure and the mechanical properties of the sintered sample, including the fracture toughness and the three-point flexural strength, were highly anisotropic. Both the fracture toughness and the flexural strength were the highest when the crack-propagation direction was normal to the alignment direction. This result was interpreted from the laminate composite materials’ point of view. Although the large elongated grains were as long as 44.4 ± 12 μm and as wide as 5.1 ± 0.67 μm, they were not the fracture origins.

Methods for fabricating and characterizing a new generation of biomimetic materials

Bringing together current ideas in the fields of biomineralization and composite laminate materials, we have attempted to fabricate model materials that mimic abalone nacre through the rapid assembly of inorganic tablets, such as talc. Several physical methods were tested to aid the orientation of the talc tablets in fluid suspensions with a low percentage, 10% by dry weight, of organic binding material. The orientation of talc tablets in the synthesized composites was characterized by X-ray diffraction and scanning electron microscopy. The modulus of rupture of the materials was measured in a three-point bending test. We demonstrate that the alignment of tablets increases by the use of physical methods and from chemical surface treatment. Important factors to consider in making materials that mimic abalone nacre are discussed. Important factors to consider in making materials that mimic abalone nacre are discussed.

Analysis of bending fracture propagation of laminar composite materials using quasi-molecular dynamics

Recently, quasimolecular dynamics has been successfully used to simulate the deformation characteristics of actual size solid materials. In quasimolecular dynamics, which is an attempt to bridge the gap between atomistic and continuum simulations, molecules are aggregated into large units, called quasimolecules, to evaluate large scale material behavior. In this paper, a 2-dimensional numerical simulation using quasimolecular dynamics has been performed to investigate laminar composite material fracture and crack propagation behavior in the uniform bending of laminar composite materials. We verified that laminar composite materials deform quite differently from the case of homogeneous materials under bending deformation.

Comparison of in situ damage assessment in unbalanced fabric composite and model laminate of planar (one-directional) crimping

In order to develop a basic understanding of damage and failure mechanisms in fabric (woven) composites, a comparative study has been undertaken of in situ damage development in two composite systems. The two composite systems, an unbalanced (6:1) five-harness satin (5HS) fabric composite and a model laminate with planar (one-directional) fiber crimping, were tested in tension. The in situ damage observations were made by means of a portable load frame placed on an optical microscope stage. The damage in the unbalanced fabric initiated in the form of yarn interface cracks and then developed further as intra-yarn delamination before failure. In the case of the model laminate, the damage first appeared as cracks in transverse laminae and then further developed as lamina interface cracks. The fiber breakage that was observed in the wavy region of the model laminate appeared to be limited to the free-edge region of the specimens. Stress analyses of the two composite systems need to be performed in order to understand the damage development modes. The damage in the model laminate is expected to serve as a basis for understanding damage development mechanisms in woven composites.