Fiber Stiffness Research Articles

Untethered, Dynamic Robotic Fabrics Enabled by Actively‐Rigid Variable Stiffness Fibers

AbstractA robot that uses fabrics as its core body material can be lightweight, compact, and highly flexible. Ideally, the robot's actuation, sensing, and structural support are provided by fiber‐based components, designed to integrate with the fabric's soft and conformable nature while preserving its fiber architecture. Typically, variable stiffness fibers are used for the structural elements, functioning as “bones” that can be turned on and off as needed. However, many variable stiffness fibers are passively‐rigid, only allowing the fabric to become soft when powered, while some require bulky external air or power supplies, making them untenable for untethered robotics. In this work, an electrically‐driven variable stiffness fiber is presented that performs a flat‐to‐curved geometry transition, providing a rigid load‐bearing structure when powered but remaining flexible otherwise. Design principles for pairing the actively‐rigid variable stiffness fiber with a materially compatible fiber‐based actuator are presented, and the actuator performance in different configurations is characterized. The variable stiffness fiber can be arranged into sturdy legs, stable enough for a robotic fabric to lift and hold its own battery pack and onboard electronics. This capability is demonstrated with a first‐of‐its‐kind fully‐untethered locomoting robotic fabric using two different quadruped gaits.

Modeling of periodical shearing flow in a fibrous space with applications in shear-induced brain injury

This paper presents a theoretical model examining the interaction between a fibrous network and viscous fluid flow driven by an oscillating boundary. The aim is to understand how oscillating impacts are transmitted from the skull, through the arachnoid trabeculae network filled with cerebrospinal fluid, as observed in shaken baby syndrome. The model uses an effective medium approach to determine the fluid velocity field while each fiber is treated as a soft string undergoing deformation. Results indicate that the frequency of oscillation, fiber stiffness, and porous structure resistance significantly influence the oscillating shearing flow, as indicated by the Womersley (Wo), Brinkman (α), and Bingham (Bm) numbers. Application of the model to shaken baby syndrome suggests that oscillations in the cerebrospinal fluid and arachnoid trabeculae can significantly surpass those on the skull, leading to intense shear stress penetration to the brain. This model is the first study to integrate the dynamic response of string-like fibrous networks in fluid flows with oscillating boundaries and offers a quantitative framework for predicting the transmission of shearing forces from the skull to the brain matter.

EMG-Constrained and Ultrasound-Informed Muscle-Tendon Parameter Estimation in Post-Stroke Hemiparesis.

Secondary morphological and mechanical property changes in the muscle-tendon unit at the ankle joint are often observed in post-stroke individuals. These changes may alter the force generation capacity and affect daily activities such as locomotion. This work aimed to estimate subject-specific muscle-tendon parameters in individuals after stroke by solving the muscle redundancy problem using direct collocation optimal control methods based on experimental electromyography (EMG) signals and measured muscle fiber length. Subject-specific muscle-tendon parameters of the gastrocnemius, soleus, and tibialis anterior were estimated in seven post-stroke individuals and seven healthy controls. We found that the maximum isometric force, tendon stiffness and optimal fiber length in the post-stroke group were considerably lower than in the control group. We also computed the root mean square error between estimated and experimental values of muscle excitation and fiber length. The musculoskeletal model with estimated subject-specific muscle tendon parameters (from the muscle redundancy solver), yielded better muscle excitation and fiber length estimations than did scaled generic parameters. Our findings also showed that the muscle redundancy solver can estimate muscle-tendon parameters that produce force behavior in better accordance with the experimentally-measured value. These muscle-tendon parameters in the post-stroke individuals were physiologically meaningful and may shed light on treatment and/or rehabilitation planning.

Simulation of tensile fatigue crack propagation in carbon fiber unidirectional laminates under progressive fatigue damage model

Abstract This paper predicts and analyzes the tensile fatigue crack propagation of carbon fiber reinforced unidirectional laminates at high-stress levels using the carbon fiber stiffness strength degradation formula. The results show that different paving modes significantly affect crack propagation and stress distribution. Under the 45° layup, two cracks appeared. The upper crack expanded along the fiber direction, and the lower crack first appeared as a horizontal crack at the constrained end and then along the fiber direction. Under 0° layering, vertical cracks appear at the prefabricated crack tip, and the crack direction is the same as the loading direction. At a -45° layup, two cracks appeared at the prefabricated crack tip, and then the lower crack extended to the integral separation of the test piece. In addition, the strain characteristic analysis shows that the strain increases and decreases rapidly during crack propagation. This study has a certain reference value for further understanding of fatigue crack propagation characteristics of carbon fiber-reinforced composites.

Micromechanics stiffness upscaling of plant fiber-reinforced composites

Fiber-reinforced green composites made from natural plant fibers are an increasingly popular sustainable alternative to conventional high-performance composite materials. Given the variety of natural fibers themselves, and the even larger variety of possible composites with specific fiber dosage, fiber orientation distribution, fiber length distribution, and fiber–matrix bond characteristics, micromechanics-based modeling is essential for characterizing the macroscopic response of these composites. Herein, an analytical multiscale micromechanics model for elastic homogenization is developed, capable of capturing the variety. The model features (i) a nanoscopic representation of the natural fibers to predict the fiber stiffness from the universal stiffness of the fiber constituents, mainly cellulose, (ii) a spring-interface model to quantify the compliance of the fiber–matrix bond, and (iii) the ability to model any (and any combination of) orientation distribution and aspect ratio distribution. Validation is performed by comparing the predicted stiffness to experimental results for as many as 73 composites available in the literature. Extensive sensitivity analyses quantify the composite stiffening upon increasing fiber volume fraction, fiber alignment, fiber length, and fiber–matrix interface stiffness, respectively.

High stiffness 3D-printed continuous pitch carbon fiber reinforced polymer composites

This study presents a method for 3D printing very high stiffness pitch-based carbon fiber (CF) reinforced polylactic acid (PLA) composites using a modified open-source 3D printer. The fused filament fabrication (FFF) technique was used to fabricate the samples with alternating layers of PLA and PLA-coated pitch CF. The tensile Young’s modulus of the 3D-printed composite samples was measured to characterize the effect of different grades and volume fractions of pitch CF on the behaviour of the printed composites. Three grades of pitch CF which have different Young’s modulus were used with volume fractions ranging from 2.4 to 8.4%. Tensile tests showed that the K1392U CF reinforced composite with a 7.3% volume fraction demonstrated the highest improvement in Young’s modulus of 850% compared to neat 3D-printed PLA. This improvement is notably higher than any previous 3D-printed carbon-based composites at a relatively low volume fraction of CF. Statistical analysis showed increased Young’s modulus in all of 3D-printed composite samples tested. The experimental values were compared to the Halpin-Tsai model and suggest that some degree of fibre breakage occurred during the 3D printing process owing to the relative stiffness of the pitch-based fibers. Future directions and suggestions for process improvements are discussed.

STRAIN MEASUREMENT AND ADHESIVE SELECTION FOR STRAIN GAUGES ON CARBON ROVING IN TEXTILE-REINFORCED CONCRETE STRUCTURES

Textile-reinforced concrete (TRC) is a promising building material that meets modern environmental protection and sustainability requirements. For the widespread use of this innovative building material, empirical models based on material properties determined by laboratory tests are needed. This study investigated the ability to measure the strain of carbon rovings with small strain gauges during standard tensile tests. The measured values were compared and validated using the digital image correlation (DIC) method. Another component of this study is the investigation of a suitable adhesive for the application of the sensors to SBR-coated (styrene-butadiene rubber) carbon roving. Three test series with three different adhesives, cyanoacrylate adhesive, epoxy resin, and polychloroprene, were produced and tested for tensile strength. The validation tests showed that a strain loss occurs in the adhesive joint of the strain gauges. It was found that cyanoacrylate adhesives, such as M-Bond 200, suffered the lowest losses and are recommended for further investigations. The epoxy resin influences the stiffness of the carbon fibers at the contact surface too strongly, while the polychloroprene adhesive could not transfer the actual roving strain due to insufficient stiffness of the bond line.

STRAIN MEASUREMENT AND ADHESIVE SELECTION FOR STRAIN GAUGES ON CARBON ROVING IN TEXTILE-REINFORCED CONCRETE STRUCTURES

Textile-reinforced concrete (TRC) is a promising building material that meets modern environmental protection and sustainability requirements. For the widespread use of this innovative building material, empirical models based on material properties determined by laboratory tests are needed. This study investigated the ability to measure the strain of carbon rovings with small strain gauges during standard tensile tests. The measured values were compared and validated using the digital image correlation (DIC) method. Another component of this study is the investigation of a suitable adhesive for the application of the sensors to SBR-coated (styrene-butadiene rubber) carbon roving. Three test series with three different adhesives, cyanoacrylate adhesive, epoxy resin, and polychloroprene, were produced and tested for tensile strength. The validation tests showed that a strain loss occurs in the adhesive joint of the strain gauges. It was found that cyanoacrylate adhesives, such as M-Bond 200, suffered the lowest losses and are recommended for further investigations. The epoxy resin influences the stiffness of the carbon fibers at the contact surface too strongly, while the polychloroprene adhesive could not transfer the actual roving strain due to insufficient stiffness of the bond line.

Fibulin-5 Is Required for Small Artery Development and Function

Introduction: Fibulins are a family of eight extracellular matrix proteins with diverse functions. Fibulin-4 and -5 (FBLN-4 and -5), in particular, have been shown to be important for elastic fiber assembly. Mutations in each of the genes lead to cutis laxa, a syndrome characterized by loose skin with variable organ involvement, particularly in the vasculature, lungs and skeleton. We recently characterized a mouse model carrying a disease-causing mutation in Fbln4 (E57K) and, contrary to conduit arteries that had elastic fiber fragmentation and stiffness, Fbln4E57K resistance arteries were structurally intact. Functionally however, Fbln4E57K mesenteric arteries exhibited endothelial dysfunction secondary to increased shear stress from large artery stiffness. Loss of FBLN5 has been shown to lead to elastic fiber fragmentation in conduit arteries, but the consequences of its loss on resistance arteries are unknown. Therefore, the objectives of this study were to determine the structural and functional consequences of FBLN5 loss on resistance arteries. Methods: We utilized adult Fbln5 knock-out (KO) mice and examined the ultrastructure of renal and mesenteric arteries via transmission electron microscopy. Functionally, using pressure myography, we characterized the myogenic tone and reactivity of Fbln5 KO and littermate control third-order mesenteric arteries to various vasoactive substances including acetylcholine, papaverine, angiotensin II, phenylephrine and potassium chloride. Results: While the internal elastic lamina (IEL) of Fbln5KO mice resistance arteries was largely intact, the external elastic lamina (EEL) was nearly absent. Similar to Fbln4E57K mice, Fbln5KO mesenteric arteries exhibited impaired endothelial-dependent vasorelaxation, likely secondary to proximal large artery stiffness. Unlike Fbln4E57K mesenteric arteries however, Fbln5 KO mesenteric arteries exhibited increased myogenic tone as well as a hypercontractile response to angiotensin II and potassium chloride, but not to phenylephrine. Conclusions: In addition to highlighting differences in the requirements for elastic fiber assembly along the arterial tree, these data emphasize the differential contribution of FBLN4 and FBLN5 to IEL vs. EEL in resistance arteries and suggest pathway-specific changes in smooth muscle cell contractility secondary to FBLN5 deficiency. This work was supported by the Washington University Pediatric Nephrology Research Core Pilot Grant Program to CMH. Funds were also provided by The Department of Pediatrics at Washington University in St. Louis School of Medicine to CMH. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Effects of local incompressibility on the rheology of composite biopolymer networks.

Fibrous networks such as collagen are common in biological systems. Recent theoretical and experimental efforts have shed light on the mechanics of single component networks. Most real biopolymer networks, however, are composites made of elements with different rigidity. For instance, the extracellular matrix in mammalian tissues consists of stiff collagen fibers in a background matrix of flexible polymers such as hyaluronic acid (HA). The interplay between different biopolymer components in such composite networks remains unclear. In this work, we use 2D coarse-grained models to study the nonlinear strain-stiffening behavior of composites. We introduce a local volume constraint to model the incompressibility of HA. We also perform rheology experiments on composites of collagen with HA. Theoretically and experimentally, we demonstrate that the linear shear modulus of composite networks can be increased by approximately an order of magnitude above the corresponding moduli of the pure components. Our model shows that this synergistic effect can be understood in terms of the local incompressibility of HA, which acts to suppress density fluctuations of the collagen matrix with which it is entangled.

Fabrication and Characterization of PDMS Waveguides for Flexible Optrodes.

With the growth of optogenetic research, the demand for optical probes tailored to specific applications is ever rising. Specifically, for applications like the coiled cochlea of the inner ear, where planar, stiff, and nonconformable probes can hardly be used, transitioning from commonly used stiff glass fibers to flexible probes is required, especially for long-term use. Following this demand, polydimethylsiloxane (PDMS) with its lower Young's modulus compared to glass fibers can serve as material of choice. Hence, the long-term usability of PDMS as a waveguide material with respect to variations in transmission and refractive index over time is investigated. Different manufacturing methods for PDMS-based flexible waveguides are established and compared with the aim to minimize optical losses and thus maximize optical output power. Finally, the waveguides with lowest optical losses (-4.8dB cm-1 ± 1.3dB cm-1 at 472nm) are successfully inserted into the optogenetically modified cochlea of a Mongolian gerbil (Meriones unguiculatus), where optical stimuli delivered by the waveguides evoked robust neuronal responses in the auditory pathway.

Controlled Stiffness of Direct-Write, Near-Field Electrospun Gelatin Fibers Generates Differences in Tenocyte Morphology and Gene Expression.

Tendinopathy is a leading cause of mobility issues. Currently, the cell-matrix interactions involved in the development of tendinopathy are not fully understood. In vitro tendon models provide a unique tool for addressing this knowledge gap as they permit fine control over biochemical, micromechanical, and structural aspects of the local environment to explore cell-matrix interactions. In this study, direct-write, near-field electrospinning of gelatin solution was implemented to fabricate micron-scale fibrous scaffolds that mimic native collagen fiber size and orientation. The stiffness of these fibrous scaffolds was found to be controllable between 1 MPa and 8 MPa using different crosslinking methods (EDC, DHT, DHT+EDC) or through altering the duration of crosslinking with EDC (1 h to 24 h). EDC crosslinking provided the greatest fiber stability, surviving up to 3 weeks in vitro. Differences in stiffness resulted in phenotypic changes for equine tenocytes with low stiffness fibers (∼1 MPa) promoting an elongated nuclear aspect ratio while those on high stiffness fibers (∼8 MPa) were rounded. High stiffness fibers resulted in the upregulation of matrix metalloproteinase (MMPs) and proteoglycans (possible indicators for tendinopathy) relative to low stiffness fibers. These results demonstrate the feasibility of direct-written gelatin scaffolds as tendon in vitro models and provide evidence that matrix mechanical properties may be crucial factors in cell-matrix interactions during tendinopathy formation.

Review on Fundamental Considerations During Lignocellulosic Fiber Characterization in Light Micromechanical Analysis of Their Composites

Lignocellulose fibers (Cellulosic fibers) are among the major agricultural resources from plant whose potentials are not exploited in some cases and/or underexploited in many cases. If their potentials for industrial application could be exploited, selling the fibers for manufacturing uses would be a win-win situation for both the industries and the farmers, and provide the latter with a much needed source of additional income since composite material reinforced with lignocellulose fibers can be used for diverse application including the production of parts in automotive industry. For this to be successful, it is mandatory to make fiber level characterization. In this process, there are various determinants that affects the characteristics of lignocellulose fiber including agro-ecological zone, plant age from which the fiber is extracted, lignocellulose structure, fiber extraction method and subsequent treatment to enhance properties. This review, therefore, presents the basics of lignocellulose fiber potential and insight into selected deliberation related to fiber level characterization in light of micromechanical analysis for new biocomposite under development. Included in this review, there are considerations to be potted during characterization at fiber level. For fiber diameter measurement and estimation, the following considerations are reported in this paper: measurement method validation, proper cross-section and fiber geometry assumption, lignocellulose structure and internal holes; enough sample consideration, incorporation of analytical method for cross checking. Likewise consideration during estimating fiber density, single fiber tensile strength and stiffness are review and discussed in this review.

Anisotropic power-law viscoelasticity of living cells is dominated by cytoskeletal network structure

During physiological and pathological processes, cells experience significant morphological alterations with the re-arrangement of cytoskeletal filaments, resulting in anisotropic viscoelasticity. Here, a structure-based cell model is proposed to study the anisotropic viscoelastic mechanical behaviors of living cells. We investigate how cell shape affects its creep responses in longitudinal and perpendicular directions. It is shown that cells exhibit power-law rheological behavior in both longitudinal and perpendicular directions under step stress, with a more solid-like behavior along the longitudinal direction. We reveal that the cell volume and cytoskeletal filament orientation, which have been neglected in most existing models, play a critical role in regulating cellular anisotropic viscoelasticity. The stiffness of the cell in both directions increases linearly with increasing its aspect ratio, due to the decrease of cell volume. Moreover, the increase in the cell's aspect ratio produces the aggregation of cytoskeletal filaments along the longitudinal direction, resulting in higher stiffness in this direction. It is also shown that the increase in cell's aspect ratio corresponds to a process of cellular ordering, which can be quantitatively characterized by the orientational entropy of cytoskeletal filaments. In addition, we present a simple yet robust method to establish the relationship between cell's aspect ratio and cell volume, thus providing a theoretical framework to capture the anisotropic viscoelastic behavior of cells. This study suggests that the structure-based cell models may be further developed to investigate cellular rheological responses to external mechanical stimuli and may be extended to the tissue scale. Statement of significanceThe viscoelastic behaviors of cells hold significant importance in comprehending the roles of mechanical forces in embryo development, invasion, and metastasis of cancer cells. Here, a structure-based cell model is proposed to study the anisotropic viscoelastic mechanical behaviors of living cells. Our study highlights the crucial role of previously neglected factors, such as cell volume and cytoskeletal filament orientation, in regulating cellular anisotropic viscoelasticity. We further propose an orientational entropy of cytoskeletal filaments to quantitatively characterize the ordering process of cells with increasing aspect ratios. Moreover, we derived the analytical interrelationships between cell aspect ratio, cell stiffness, cell volume, and cytoskeletal fiber orientation. This study provides a theoretical framework to describe the anisotropic viscoelastic mechanical behavior of cells.

Stiffness modeling of thermoset polymer fibers

AbstractRecent progress in creating micro and nano‐scale thermoset polymer fibers through extensional flow reveals remarkable mechanical properties. For instance, epoxy microfibers display a notable increase in stiffness, strength, and toughness as their diameter decreases. This size‐dependent behavior, well‐explored and explained in thermoplastic polymers, is far from being understood in thermoset polymers, as their densely cross‐linked network structure seems to restrain preferential directionality. Our theoretical analysis proposes that, during the pre‐gel curing phase, when the thermoset polymer begins clustering but remains in a liquid state, substantial cluster elongation is induced by the extensional flow. This elongated formation persists to some extent after curing completion, resulting in enhanced mechanical properties along the fiber's primary axis. Concurrently, the high extension reduces fiber diameter, leading to a power‐law diameter dependence of fiber stiffness. The model agrees well with experimental data from tensile tests on epoxy microfibers, highlighting the potential to fine‐tune mechanical properties by controlling the curing process, and laying the groundwork for future improvements.

Modelling and design of fiber optic Fabry-Pérot accelerometer with high figure merit

The Fabry-Pérot (F-P) accelerometer model with a high figure of merit is proposed, and the corresponding accelerometer is designed and experimentally researched. Theoretical analysis shows that this accelerometer is independent of the encapsulated optical fiber stiffness and its sensitivity can be enormously improved. Meanwhile, the method of wavelength demodulation is adopted and the figure of merit is introduced to evaluate the comprehensive Characteristic of the accelerometer. The results of the experiment showed that the accelerometer has a good response, its flat range is 10 Hz to 280 Hz, the corresponding sensitivity is 22.57 nm/G to 35.55 nm/G, and the cross sensitivity is less than 3.16 dB. The figure of merit is up to 10918.77 nm·Hz/G, the comprehensive response characteristics indicate that the sensor has good technical indexes. It not only has ultra-high sensitivity, but also has miniaturization potential.

Regional shear wave speeds track regional axial stress in nonuniformly loaded fibrous soft tissues

Ligaments and tendons undergo nonuniform deformation during movement. While deformations can be imaged, it remains challenging to use such information to infer regional tissue loading. Shear wave tensiometry is a promising noninvasive technique to gauge axial stress and is premised on a tensioned beam model. However, it is unknown whether tensiometry can predict regional stress in a nonuniformly loaded structure. The objectives of this study were to (1) determine whether regional shear wave speed tracks regional axial stress in nonuniformly loaded fibrous soft tissues, and (2) determine the sensitivity of regional axial stress and shear wave speed to nonuniform load distribution and fiber alignment. We created a representative set of 12,000 dynamic finite element models of a fibrous soft tissue with probabilistic variations in fiber alignment, stiffness, and aspect ratio. In each model, we applied a randomly selected nonuniform load distribution, and then excited a shear wave and tracked its regional propagation. We found that regional shear wave speed was an excellent predictor of the regional axial stress (RMSE = 0.57 MPa) and that the nature of the regional shear wave speed-stress relationship was consistent with a tensioned beam model (R2 = 0.99). Variations in nonuniform load distribution and fiber alignment did not substantially alter the wave speed-stress relationship, particularly at higher loads. Thus, these findings suggests that shear wave tensiometry could provide a quantitative estimate of regional tissue stress in ligaments and tendons.

Modified plastic damage model for steel fiber reinforced concrete

AbstractSteel fiber reinforced concrete (SFRC) structures have been widely adopted and attracted great research attention due to their excellent performance in resisting tension and flexure bending. However, the existing analytical and numerical analyses of SFRC structures rely mainly on the experimental data of material tests, thereby being suitable for a case‐by‐case basis. This is due to the lack of a general and reliable constitutive material model for SFRC, which analytically considers the fiber‐dependent parameters such as fiber geometry, fiber stiffness, and interface properties of fibers and concrete matrix. This study presents an approach to modify the concrete plastic damage model to represent the SFRC material constitutive relations for simulating the structural behavior of SFRC. In this approach, the general procedure to integrate the bridging effect of fibers through the pull‐out mechanism into the constitutive relation of SFRC was proposed. The comparison between the numerical and experimental results was conducted to verify the reliability of the proposed model. The results demonstrated the proposed model could well represent the material performance of SFRC and the numerical simulations could capture reasonably the effect of the volume fraction, geometry, and properties of fibers on the structural response of SFRC.

Abstract 782: Correlation between collagen peptides and physical features of fibrosis in breast tissue from women at increased risk of cancer

Abstract Breast cancer risk increases significantly in women who maintain higher radiologically dense breast tissue as they age. However, the mechanisms that underlie this association remain poorly understood, especially in postmenopausal women. A predominant contributor to dense breasts and differences between women is the relative amount of fibrillar collagens. Experimental models suggest that changes in collagen properties such as fiber alignment and stiffness promote local stromal fibrosis, which we hypothesize may contribute to the relationship between breast density, aging, and tumorigenesis. Normal breast biopsy samples from the contralateral, healthy breast of 32 postmenopausal breast cancer patients participating in a clinical trial for drug effect on breast density were examined and scored for areas of fibrosis and analyzed using second harmonic generation microscopy (SHG) and mass spectrometry proteomics. Our aim was to identify areas of fibrosis and relate the severity of focal fibrosis to the physical properties and peptide composition of collagen fibers. Using GraphPad Prism, we conducted one-way ANOVA and Kruskal-Wallis tests and post-hoc multiple comparison tests. H&E-stained breast tissue samples were scored according to percent fibrosis. The minimum and maximum percent fibrosis were 5% and 100%, respectively, with a median of 60% (95% CI: 97.06%). Out of 31 people, 16 had a higher fibrosis score than the median. Consistent with pathologic scoring of the presence and extent of fibrosis, fiber counts were significantly lower in tissue with lower fibrosis scores than samples with more highly scored fibrosis (p-value <0.001). Distance to the nearest fiber was greater in samples with < 20% fibrosis, whereas greater alignment to the nearest fiber was observed in higher fibrosis percentages. At the molecular level, 22 peptides demonstrated a strong correlation with percent fibrosis (spearman r ≥ 60), of which 13 peptides were statistically significant (p-value <0.0001). The putatively identified peptides belong to type I, III, IV and VI collagens. Fiber length and straightness, but not fiber width, were higher in tissues with greater percent fibrosis. Significant correlations were identified between collagen physical features and peptides: two distinct peptides correlated with collagen fiber length and straightness while 20 peptides correlated with fiber width. These putative peptides belong to types I, III, IV and V collagens with ~70% of the peptides containing at least one hydroxyproline modification. This study is the first to explore the link between focal fibrosis and collagen-associated peptides in healthy breast tissue of high-risk postmenopausal women. These findings provide novel insights on stromal collagens associated with fibrotic changes in normal at-risk breast tissue that may act in tissue susceptibility to tumor formation. Citation Format: Denys Rujchanarong, Alison T. Stopeck, Christina Preece, Ren Sun, Pavani Chalasani, Sean Brown, Ji D. Bai, Heather Jensen Smith, Sungyong You, Peggi M. Angel, Patricia Thompson. Correlation between collagen peptides and physical features of fibrosis in breast tissue from women at increased risk of cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 782.

On the Micro-Stress Fields in Fibre-Hybrid Polymer Composite Laminae with Periodic Microstructure Under Transverse Tension and Transverse Shear Loading

AbstractThis paper investigates the effect of intra-laminar fibre hybridisation, i.e., primary and secondary fibres within a matrix, on the homogenised properties and micro-stress fields in uni-directional polymer composite laminae. The study is focused on S-glass/epoxy laminae which are hybridised with secondary fibres (e.g., polypropylene). Two-dimensional repeating unit cells (2D RUCs) with periodic microstructures are developed to conduct the micro-mechanical analyses under transverse tensile and transverse shear loading conditions. Uni-directional fibre-hybrid S-glass/epoxy laminae with different secondary fibres are studied by varying (a) the periodic microstructure and (b) the material properties of the constituent fibres to assess the effect of such geometric and material variations on the homogenised elastic lamina properties and intra-lamina micro-stress fields. The results show that intra-laminar fibre hybridisation significantly affects the elastic lamina properties and micro-stress fields. Notably, the presence of the secondary fibres significantly increases or reduces the stress fields in the matrix and at the fibre-matrix interfaces (i.e. normal and shears stress components)–depending on the microstructure and the stiffness of the secondary fibres–which could be explored to manipulate the damage modes and thus energy dissipation mechanisms.