Fiber Direction Research Articles

Effect of fiber breakage defect and waviness defect on compressive fatigue behavior and damage evolution of 3D multiaxial braided composites

This paper reports the effects of fiber breakage defects and waviness defects on the compressive fatigue behavior and the progressive damage evolution process of 3D Multiaxial Braided Composites (3DMBCs). Combined with finite element compression simulation and ultra-depth microscope, the internal defect content of composites with different braiding angles was determined. The results demonstrate that the weakening effect of waviness and fiber breakage defects is greater than the strengthening effect of the braiding angle. This causes the fatigue resistance of 3DMBCs with the 31° braiding angle being better in both directions of 0° and 90°. The increase of 4° waviness and 10% fiber breakage defect results in the average fatigue life of composites being shortened by 48% and the energy consumption rate increased by 10% at 85% stress level in the 90° compression direction. The alteration in loading direction modifies the included angle corresponding to the stress component. The stress component parallel to the fiber direction under compressive fatigue load leads to interfacial debonding in the composites, whereas the stress component perpendicular to the fiber direction results in pronounced shear failure.

WOODEN MATERIALS USED IN LANDSCAPE APPLICATION IN CRAIOVA CITY

During the history, wood materials have become an indispensable material for human life. (Amati M. 2016). Wood is a material compatible with nature, compatible with other building materials such stone, glasses, offering different texture. (Ahern J. 2007). Wood is one of the materials with best respond to the functions of urban green spaces. First of all, it integrates best, from an aesthetic point of view, alongside stone in urban landscaping projects. (Aybike Ayfer KARADAĞ et al. 2017).Since wood is a natural product, its dimension is limited in that its fibrous structural capacity to bear weight varies according to the fiber direction. Despite its widespread use, it had not been used in multi-storey and wide-span structures to the extent of reinforced concrete and steel structures commonly built after the industrial revolution. (Daniel K, Ternaux E. Materiology. 2009)

Infant skull fractures align with the direction of bone mineralization.

The geometry and mechanical properties of infant skull bones differ significantly from those of adults. Over the past decades, debates surrounding whether fractures in infants come from deliberate abuse or accidents have generated significant impacts in both legal and societal contexts. However, the etiology of infant skull fractures remains unclear, which motivates this study with two main components of work. Firstly, we present and implement a progressive unidirectional fabric composite damage model for infant cranial vaults to represent ductile and anisotropic properties-two typical mechanical characteristics of infant skulls. Secondly, we hypothesize that these intrinsic material properties cause injuries perpendicular to the fiber direction to dominate infant skull fractures, resulting in fracture lines that align with the direction of mineralization in the infant skull. The material model and the finite element (FE) model were verified hierarchically, and this hypothesis was verified by reconstructing two legal cases with known fall heights and implementing the above damage model into CT-based subject-specific infant FE head models. We discovered that the infant skull is more susceptible to injuries within planes perpendicular to the mineralization direction because of the anisotropic mechanical property caused by the direction of mineralization, leading to infant skull fractures aligning with the mineralization direction. Our findings corroborated the several previously reported observations of fractures on cranial vaults, demonstrating that these fractures were closely associated with sutures and oriented along the mineralization direction, and revealed the underlying mechanisms of infant skull fracture pattern. The modeling methods and results of this study will serve as an anchor point for more rigorous investigations of infant skull fractures, ultimately aiming to provide convincing biomechanical evidence to aid forensic diagnoses of abusive head trauma.

Comparative study of toughness and energy evaluation of laminated bamboo composites and toughening mechanism

As toughness becomes an important mechanical property of construction materials, scientific toughness assessment is vital to the development of new materials and helpful for material innovation. For laminated bamboo composites in which the failure modes are relatively uncertain, different methods were applied to evaluate the toughness of bamboo laminate. A comparative study of various toughness evaluation methods was conducted for laminated bamboo. The meaning and error of the toughness expressed by the energy release rate or J-integral determined by different methods were interpreted and analyzed. Based on the calculated toughness, the toughening mechanism of bidirectional laminated bamboo was explored. The results show that the ratio of transverse bamboo strip volume Vf vertical to the initial notch direction has a positive impact on the initial stiffness, maximum load, and energy release rate. Besides that, the layup or arrangement of bamboo strips would also affect the mechanical properties and fracture toughness of laminated bamboo, of which the effect is investigated by dividing the fracture parameters by Vf. It is concluded that the major mechanism for increasing the ductility and the toughness before the maximum load (expressed by D2/D1 and GIcun/Vf or GIc0.8d/Vf) is the crack deflection caused by the hierarchical structure composed of vascular bundles (fiber) and parenchyma tissue (matrix) in a single layer of bamboo laminae. However, the ductility and the toughness after the maximum load (expressed by D3/D2 and GIc0.8d/GIcun) are mainly enhanced by the alternatively arranged bamboo laminae of different fiber directions.

Anisotropic hydrogel sensors with muscle-like structures based on high-absorbent alginate fibers

Hydrogel sensors have attracted much attention as they play a critical role in health monitoring, multifunctional electronic skin, and human-machine interfaces. However, the isotropic structure makes existing hydrogel sensors exhibit isotropic sensing performance. Therefore, it is a challenge to fabricate hydrogels with human tissue-like structures to achieve anisotropic sensing performance. Herein, we proposed a novel method to prepare anisotropic hydrogel sensors using high-absorbent alginate fibers. The anisotropic hydrogel, HAFG@CNTs, was prepared by adsorbing carbon nanotubes on high-absorbent alginate fibers and immobilized using polyacrylamide bonds. The hydrogel had anisotropic mechanical properties and anisotropic ionic conductivity. The modulus and toughness in the parallel fiber direction were 2.31 and 3.75 times higher than those in the perpendicular fiber direction, respectively, and the sensitivity of the parallel fiber direction was higher than that of the vertical direction when strain occurred. In addition, machine learning algorithms were used to predict and classify different action signals obtained from HAFG@CNTs with an accuracy of up to 98.18 %. These advantages offer great potential for applying HAFG@CNTs to wearable devices and medical monitoring.

Abstract 4136863: Diffuse Functional and Structural Abnormalities in Fibrosis: Potential Structural Basis for Sustaining Atrial Fibrillation

Background: Structural remodeling is associated with atrial fibrillation (AF), but detailed structural and functional characteristics is not well defined. Goal: Using a novel transgenic goat model with cardiac-specific overexpression of TGF-β1 leading to increased cardiac fibrosis, we evaluated detailed structural and functional differences between fibrotic and healthy regions of the atria. Methods: Ex-vivo MRI and histology were used to evaluate fibrosis, fiber disarray, and structural anisotropy. Ex-vivo MRI intensity values were scaled to standard deviations around the mean. The functional analysis examined conduction speeds and direction heterogeneity. Conduction anisotropy was measured along the fiber direction obtained with diffusion tensor imaging. Results: The transgenic goats (n=12) had, on average, 21% of the left atria labeled as fibrotic determined from ex-vivo MRI. The histology samples taken from the labeled fibrotic regions had an increase in fibrosis percentage compared to labeled healthy regions (7.78±3.76% vs 2.80±1.86%, p<0.01). The structural anisotropy was lower in fibrotic regions (0.196±0.002 vs 0.244±0.002, p<0.01). Fiber disarray was greater in the fibrotic regions (20.3±0.2° vs 19.2±0.1°, p<0.01). The fibrotic regions had slower conduction speeds (0.78±0.02 m/s vs 1.12±0.02 m/s, p<0.01) and more aligned conduction directions (30.5±0.2° vs 31.6±0.1°, p<0.01), potentially developing unidirectional conduction block. Conduction anisotropy, measured on the fiber directions, was found to be lower in the fibrotic regions (1.86±0.05 vs 2.10±0.02, p=0.04). As scaled MRI intensity increased, the conduction speed, heterogeneity, and anisotropy all decreased. Conclusions: Functional and structural differences exist between fibrotic and healthy regions of the atria. Though statistically significant, the changes are not discrete. The correlation showed gradual functional abnormalities with MRI intensities. Fibrotic regions tended to have increased fiber disarray, slower conduction, and more unidirectional propagation with lower conduction and structural anisotropy. Diffuse functional and structural abnormalities may allow fibrotic regions to serve as a substrate to sustain AF.

Creep evaluation for fiber-reinforced composites with hybrid fibers: From quantifying fiber anchorage effect to homogenization model

A general micromechanical creep model for fiber-reinforced composites with multi-type hybrid fibers is proposed from quantifying the fiber anchorage effects. An average Eshelby tensor-based homogenization method is employed to calculate the effective creep of composites with realistic-shaped (straight, hooked, and wavy) fibers. A fiber anchorage zone is introduced to depict the anchorage effects of fibers and its parameters are obtained by back analysis. The micromechanical model and fiber anchorage zones are validated by comparing with extensive creep experimental data and finite element simulation. According to the micromechanical model, the effects of fiber shapes, types, direction, anchorage zone, and fiber doping on the creep of composites are systematically explored. The results show fiber shapes and types have obvious effects on composites creep. Fiber deflection angle leads to a monotonous increase in creep. The creep with fiber doping is between the two cases without fiber doping. It indicates that the creep of fiber-reinforced composites can be tailored via proper design for these factors.

Clinical Outcomes and Applicability of Serratus Anterior Muscle Flap With Split Thickness Skin Graft in Thin Resurfacing Reconstructive Surgeries: A Retrospective Analysis.

This retrospective study evaluates the efficacy of the serratus anterior muscle (SAm) free flap combined with a split thickness skin graft (STSG) for thin resurfacing in reconstructive surgery, presenting an alternative to pure skin perforator flaps. It analyzes 14 SAm free flap procedures performed between January 2015 and December 2023. The study cohort comprised 5 women and 9 men, aged 31-80 years, addressing defects caused by infection, malignancy, burn, and trauma, located in various body parts.The study involves harvesting the SAm flap while focusing on anatomical features such as the distinct direction of muscle fibers and the surface location of the vascular pedicle for efficient dissection. It emphasizes the anatomical advantages of the SAm flap, such as robust vascular supply, controlled flap thickness, and preservation of the long thoracic nerve, making it suitable for a range of surgical needs. Complications included STSG loss, partial necrosis, and infection, all managed effectively. Postoperative shoulder function assessment showed no significant impairment.Results demonstrated the successful application of the SAm flap in all cases, with an average flap dimension of 38.21 cm2 and pedicle length of 7.3 cm. The average operation time was 122.1 minutes. The study underscores the SAm flap's adaptability, versatility, and minimal donor site morbidity.It concludes that the SAm flap, in conjunction with STSG, is a viable alternative for thin resurfacing in reconstructive surgery. However, limitations such as the small sample size and procedural variability suggest the need for further research to fully establish the flap's potential in diverse surgical contexts.

Lower limb interosseous membrane in foetuses.

The leg interosseous membrane (LIM) stabilises the tibia and the fibula. These two bones articulate at the proximal and distal tibiofibular joints. In addition, the LIM is the place of attachment of tibialis anterior muscle, extensor digitorum longus muscle, fibularis tertius muscle (anatomical variant), tibialis posterior muscle and flexor hallucis longus muscle. The specific structure of the collagen fibre network of the LIM provides durability comprising collagenous fibres that are predominately projected longitudinally, obliquely, and often transversely. 222 human foetuses (Male: 120, Female: 102) between 117 and 197 (median 177) days of foetal life were available for the study. The material derived from the foetal collection is stored in the Department of Human Morphology and Embryology, Division of Anatomy of the Medical University of Wroclaw. In this study, we assessed the variability of the foetal LIM using a novel dyeing technique to identify the LIM syndesmotic structure. Overall, the study of the three types of interosseous fibres (transverse, oblique, longitudinal) of the right/left leg revealed that the fibres run in all three directions with frequencies approximating 60-70%. However, there were differences in the frequency of fibre directions and in the size of LIM between sexes. After consideration of the directions and size of fibres of LIM, parts of it can be used for reconstruction of the upper limb interosseous membrane. Sexually dimorphic features of the LIM in the studied material confirm the different dynamics of lower limb growth in each sex.

Characterization of early fatigue damage in CFRP unidirectional laminates based on Micro‐CT

AbstractFatigue damages of Carbon Fiber Reinforced Polymer (CFRP) laminates are not obvious. Obtaining the evolution of the internal fatigue damage in CFRP laminates before visible cracks occur is of vital importance for ensuring structural reliability. Micro X‐ray computed tomography (Micro‐CT) can provide micron scale nondestructive imaging of internal structure of materials. In this paper, a preliminary study was conducted on the early fatigue damage evolution of 0° UD laminates. Axial tension‐tension fatigue tests of [0]16 CFRP laminates were carried out, and the evolutionary behavior of damages was confirmed by fatigue dissipated energy. Then, the internal damages of fatigued specimens were observed and reconstructed using Micro‐CT, and statistical parameters such as damage sphericity, length and angle were calculated. The spatial distribution characteristics of cracks were further acquired by surface porosity and frequency distribution of damage positions in ROI. Early damages from tensile‐tensile fatigue in 0° UD laminates extend along the fiber direction with original defects in the interlayer resin enrichment areas as the nucleus, and tend to concentrate near the width edge of the specimens. Finally, a “sandwich” structural model was developed to analyze the internal stresses of laminates under the influence of interlayer resin enrichment. The FEA results revealed that the internal stresses σy and σz concentrate near the width edges of the specimen, resulting in cracks tend to evolve more in the regions close to edges.Highlights Imaging matrix cracks of specimens by Micro‐CT at 12.91 μm voxel size. Demonstrating evolution patterns of cracks with its morphology statistics. Revealing crack distributions in ROIs with variations of surface porosity. Analyzing internal stress distribution by “sandwich” model created from reality.

Electrospinning Aligned SF/Magnetic Nanoparticles-Blend Nanofiber Scaffolds for Inducing Skeletal Myoblast Alignment and Differentiation.

In the realm of skeletal muscle tissue engineering, anisotropic materials that emulate natural tissues show substantial promise. Electrospun scaffolds, mimicking the fibrillar structure of the extracellular matrix, are commonly employed but often fall short in achieving optimal alignment and mechanical strength. Silk fibroin has emerged as a versatile material in tissue engineering, valued for its biocompatibility, mechanical robustness, and biodegradability. However, conventional electrospinning methods of SF result in randomly oriented fibers, limiting their efficacy. In this work, we developed a straightforward method to fabricate directional tissue scaffolds using silk fibroin. By integrating a magnetic field collecting device and incorporating Fe3O4 nanoparticles into the spinning solution, we successfully produced well-aligned silk nanofiber scaffolds. These aligned fibers not only improved scaffold orientation and mechanical properties but also exhibited magnetic responsiveness. The aligned SF scaffolds effectively guided the adhesion, proliferation, and differentiation of mesenchymal stem cells along the fiber direction. Cultured on these scaffolds, myoblast C2C12 cells demonstrated oriented growth, highlighting the potential of aligned SF fibers in advancing skeletal muscle engineering for biomedical applications.

Rotating AdS3× S3 and dyonic strings from 3-dimensions

We make a general Killing spinor analysis of a particular D = 3, N = 4 gauged supergravity that comes from a consistent S3 reduction of D = 6, N = (1, 0) supergravity coupled to a single chiral tensor multiplet. We then focus on its supersymmetric solutions with a null Killing vector and find three new ones. Two of these, namely the null warped AdS3 (also known as the Schrödinger spacetime) and the charged domain wall solutions, admit non-trivial gauge fields which give rise to rotating solutions in 6-dimensions. The uplift of the first one produces an interesting AdS3 × S3 background with a non-trivial rotation in the U(1) fiber direction of the S3 which retains the Schrödinger scale invariance that the seed solution has. The second one leads to the well-known rotating dyonic string solution. Finally, the uplift of the third one, which is a domain wall solution with no gauge fields, results in a distribution of dyonic strings.

An anisotropic eigenfracture approach accounting for mixed fracture modes in wooden structures by the Representative Crack Element framework

Finite Element analysis of anisotropic fracture phenomena in wood is a challenging task, particularly when dealing with intricate loading scenarios and mode-specific behavior. The appeal of energetically motivated approaches, such as the eigenfracture method, is that they enable simulation of fracture without prior knowledge of the crack path. The promising eigenfracture method has shown good numerical performance for isotropic materials, and this contribution showcases its application to anisotropic materials. Wood is one such anisotropic material and in this manuscript, the directional dependence of both elasticity and fracture evolution are incorporated into the eigenfracture approach. Further, the eigenfracture approach is used in conjunction with Representative Crack Elements (RCE), which permit accurate modeling of physical crack deformations. The governing equations are systematically derived and implemented into the Finite Element framework. By representative numerical examples, some advantages over the alternative phase-field method are demonstrated. Another highlight of this work is that it is possible to provide a realistic ratio of the energy release rates parallel to and perpendicular to the fiber direction in order to achieve physically accurate crack patterns. Additionally, the calculation effort is reduced, because the unknowns required to determine the crack kinematics can be solved analytically at the material level, a feature that also enables parallelization.

Optimizing tensile strength and failure prediction in hemp fiber composites: Coupling effects of microfibril angle and fiber orientation under off-axis loading

In response to environmental concerns associated with synthetic fiber-reinforced materials, plant fiber-reinforced composites are increasingly recognized as a more sustainable alternative. However, predicting the mechanical properties of these composites remains challenging due to the unique microstructure of plant fibers. This study proposes an optimized Tsai-Hill failure criterion that incorporates the microfibril angle (MFA) and fiber orientation to enhance failure predictions. The MFA of hemp fibers was measured using X-ray diffraction (XRD), and the failure mechanisms of unidirectional hemp fiber composites under off-axis tensile stresses were thoroughly analyzed. Experimental results reveal a 10.69 % increase in tensile strength at a 5° off-axis angle compared to the fiber direction. As the off-axis angle increases, the failure mode transitions from fiber fracture and pull-out to matrix tearing and interlayer shear failure. For angles above 10°, the failure stress aligns with both the maximum stress and Tsai-Hill criteria. For angles below 10°, integrating MFA into the Tsai-Hill criterion significantly improves prediction accuracy. These findings offer critical insights for optimizing the tensile performance of hemp fiber composites and predicting their behavior under off-axis loading conditions. Consequently, this study can support the use of hemp fiber composites in a broader range of applications.

A homogenized constitutive model for 2D woven composites under finite deformation: Considering fiber reorientation

Two-dimensional (2D) woven composites exhibit excellent mechanical properties along the fiber directions. The mechanical behaviors demonstrate nonlinearity in specific applications. Although plasticity methods can be applied to predict complex behaviors, however, fiber reorientation has been observed during finite deformation, indicating that the fiber directions are no longer along orthotropic material axes when the angle between fibers changes. The angular bisectors of two fiber directions can serve as the orthotropic material axes due to the rotational symmetries even in finite deformation scenarios. This study reports a homogenized nonlinear constitutive model based on the rotational symmetry axes, incorporating plasticity and fiber reorientation phenomena. The plasticity model contains a two-parameter flow potential and power function. Plastic deformations are computed using an explicit method. Fiber reorientation angles are computed both theoretically and numerically. The relationship between mechanical properties and fiber reorientation angles is studied using finite element method (FEM). Due to introduce of a novel approach to determining the strain and stress of 2D woven composites undergoing finite deformation, the proposed model should have potential in engineering predictions.

In-plane properties of an in-situ consolidated automated fiber placement thermoplastic composite

Automated fiber placement (AFP) has been employed to manufacture aerospace structures for decades, with a recent focus on thermoplastic composites (TPCs). The in-situ consolidation AFP of TPCs is pursued as an energy-efficient additive manufacturing (AM) approach for fabricating composite structures. This work compares the in-plane mechanical properties of in-situ consolidated coupons with those of compression molded counterparts to provide new insights into their failure mechanics and processing-structure relationships. Tensile and compressive properties along the fiber and transverse directions, in-plane shear properties, and short beam strength were measured for all samples. Failure modes and mechanics in tested coupons were related to AFP defects and processing, i.e., resultant crystallinities, fiber misalignment, matrix mechanical properties, porosity, and fiber–matrix interfacial strength. The findings of this study can be used to guide the manufacturing of future TPC structures and potentially open new avenues for applications where post-processing is not feasible or reduced mechanical performance is acceptable.

Effectiveness of Retraction 30 over Gross Stretch For Relieving Pectoralis Minor Tightness Among College Students

Background: The Pectoralis minor muscle originates from different 3 ribs and converges into one attachment point. Pectoralis minor shortening can contribute to many syndromes and impairments, especially at the shoulder. Some of them are impingement of the soft tissues, adhesive capsulitis etc. The prevalence of pectoralis minor tightness is very high in college-going students. The gross stretch is the stretching procedure that increases the length of the pectoralis minor muscle. This shoulder position produces tension in the muscle insertion in a posterior direction in conjunction with the scapular motion that is performed at flexion and elevation in the scapular plane, thereby lengthening the muscle. Retraction 30 is stretching with scapular retraction at 30 degrees of shoulder flexion; the flexion angle at 30 degrees can lengthen the muscle along the muscle fiber direction in the coronal plane. 30 degrees of flexion is considered to be more comfortable than a higher angle of flexion, as well as the angle is closest to the line of force Objectives of the study: To compare the effectiveness of gross stretch and retraction 30 in relieving pectoralis minor muscle tightness which can be co-operated in further treatment protocols. Study Design: Comparative Study Methodology: Two group pre–test–post–test design was used with purposive sampling. Selected subjects were allocated to two groups. Fourty subjects (20 males and 20 females) who fulfilled inclusion and exclusion criteria were recruited for the study. The independent variables are gross stretch and retraction 30 whereas the dependent variables were PMI (pectoralis minor index), pectoralis minor length test and Cervical Curvature. Result: This study results imply that retraction 30 is better when compared to gross stretch for correcting pectoralis minor tightness. Hence should be included as an inevitable part of stretching treatment. Practicing clinicians should continue to use evidence-based decisions when treating pectoralis minor tightness.

Proteomic Evidence for Amyloidogenic Cross-Seeding in Fibrinaloid Microclots

In classical amyloidoses, amyloid fibres form through the nucleation and accretion of protein monomers, with protofibrils and fibrils exhibiting a cross-β motif of parallel or antiparallel β-sheets oriented perpendicular to the fibre direction. These protofibrils and fibrils can intertwine to form mature amyloid fibres. Similar phenomena can occur in blood from individuals with circulating inflammatory molecules (and also some originating from viruses and bacteria). Such pathological clotting can result in an anomalous amyloid form termed fibrinaloid microclots. Previous proteomic analyses of these microclots have shown the presence of non-fibrin(ogen) proteins, suggesting a more complex mechanism than simple entrapment. We thus provide evidence against such a simple entrapment model, noting that clot pores are too large and centrifugation would have removed weakly bound proteins. Instead, we explore whether co-aggregation into amyloid fibres may involve axial (multiple proteins within the same fibril), lateral (single-protein fibrils contributing to a fibre), or both types of integration. Our analysis of proteomic data from fibrinaloid microclots in different diseases shows no significant quantitative overlap with the normal plasma proteome and no correlation between plasma protein abundance and their presence in fibrinaloid microclots. Notably, abundant plasma proteins like α-2-macroglobulin, fibronectin, and transthyretin are absent from microclots, while less abundant proteins such as adiponectin, periostin, and von Willebrand factor are well represented. Using bioinformatic tools, including AmyloGram and AnuPP, we found that proteins entrapped in fibrinaloid microclots exhibit high amyloidogenic tendencies, suggesting their integration as cross-β elements into amyloid structures. This integration likely contributes to the microclots’ resistance to proteolysis. Our findings underscore the role of cross-seeding in fibrinaloid microclot formation and highlight the need for further investigation into their structural properties and implications in thrombotic and amyloid diseases. These insights provide a foundation for developing novel diagnostic and therapeutic strategies targeting amyloidogenic cross-seeding in blood clotting disorders.

Laser-assisted automated tape laying: Effects of placement rate and heated tooling on layer bonding and tensile properties

This paper investigates the processing parameters placement rate and tooling temperature of laser-assisted automated tape laying (ATL). Plates with carbon fiber-reinforced polyether ether ketone (CF/PEEK) were produced at 6 m/min, 9 m/min and 18 m/min, and 23°C and 250°C tooling temperature, respectively. Correlations of processing conditions with micrographs, void content, thickness, the degree of crystallinity and the shear strength of the compression shear test, including a fractographic analysis, were derived. Processing conditions that increase the degree of crystallinity were only found to improve the compression shear strength at 6 m/min placement rates, primarily due to a void content below 3.4 % and degree of crystallinity above 26 %. The fractographic analysis derived from the compression shear test revealed a strong correlation between the degree of crystallinity and the size of ductile drawings. In contrast, the transverse tensile test showed no influences on the ATL processing conditions, whereas the tensile strength in fiber direction decreased by 11 % from a placement rate of 6 m/min to 18 m/min. ATL with a 250°C tooling temperature increased the strengths by 14 % compared to those at room temperature. A further tensile strength improvement of 0° and 90° to 1754 MPa and 75 MPa was obtained by a subsequent out-of-autoclave consolidation using vacuum bagging.

Static in-situ curing characteristics of CFRP based on near infrared laser

Study on static in-situ curing characteristics of CFRP based on near infrared laserThe quick curing method of carbon fibre reinforced plastics (CFRP) is one of the hotspots in current research. A static in-situ curing method for CFRP prepreg based on near-infrared laser was put forward in this study. The in-situ curing structural characteristics and the mechanism of CFRP were investigated through real-time surface temperature measurement, COMSOL temperature field simulation, 3D measurement of curing morphology and resin curing degree test. The thermal conductivity of the CFRP along the fiber direction is considerably higher than that along the perpendicular fiber direction. As a result, the temperature profile in the plane takes on an elliptical shape. During the transfer, the temperature field gradually decreases, resulting in an ellipsoidal 3D high-temperature distribution. The different shrinkage phenomena in the different curing regions between the layers lead to an irregular ellipsoidal solidification morphology of the unidirectional CFRP. The temperature in the center of the heat affected zone increases as a power exponential function with time. The area and depth of the heat-affected zone increases with the laser power, and the curing area is positively correlated with the degree of curing. As a result, curing temperature governing equations based on laser power and layer thickness have been proposed, while relationship equations based on laser power, curing depth and curing morphology have been developed. In addition, prediction equations based on curing morphology have been developed for curing degree, in order to achieve precise curing of CFRP.