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PubMed2006

Determining the ratio of the Gaussian curvature and bending elastic moduli of phospholipids from Q(II) phase unit cell dimensions.

A method is presented for measuring M, the ratio of the Gaussian (saddle splay) elastic modulus to the bending elastic modulus of a lipid monolayer. The ratio M is determined from measurements of the equilibrium bicontinuous inverted cubic (Q(II)) phase unit cell size in excess water as a function of temperature. The analysis includes the effect of a curvature elastic term that is second-order in the Gaussian curvature, K. Preliminary results using data on DOPE-Me validate the method. The fitted value of M is within 8% of the value estimated in an earlier treatment. The method can be used to measure changes in M due to addition of exogenous lipids and peptides to a host lipid system. The Gaussian elastic modulus has a substantial effect on the stability of fusion intermediates (stalks, hemifusion diaphragms, and fusion pores). Studying the effects of peptides and different lipids on M via this method may yield insights into how fusion protein moieties stabilize intermediates in membrane fusion in vivo. The contribution of the K2 curvature elastic term to the free energy of Q(II) phase and fusion pores explains some features of fusion pore stability and dynamics, and some peculiar observations concerning the mechanism of L(alpha)/Q(II) phase transitions.

Animals↗

PubMed1988

[Constrictive and stiffening effects of parasympathetic blockade on the pressure response of the aorta to angiotensin in the conscious dog ].

The elastic response of the thoracic aorta to increasing steps of angiotensin was studied in chronic instrumented conscious dogs with and without parasympathetic blockade by atropine. A pressure microtransducer and two ultrasonic crystals diametrically opposed and fixed in the adventitia enabled to determine the mean and systolic-diastolic changes of pressure (P) and diameter (D). By computing these measurements two representative indexes of dynamic elastic modulus in vivo were calculated; the elastic modulus of Peterson (Ep) Ep = delta P/D.D and the incremental elastic modulus (Ei) Ei = 0.75 EP/gamma, gamma being the ratio of the thickness to the external radius. A positive correlation (p less than 0.01) was obtained between pressure and diameter variations in the presence or absence of atropine but the slope of these relationship were lower with atropine than in controls. The slope of the positive correlations observed between Peterson and incremental elastic modulus and the increase in mean arterial pressure in response to angiotensin (p less than 0.01) was higher in the presence of atropine (p less than 0.05). These observations indicate that in response to angiotensin mediated high blood pressure, the cholinergic blockade of muscarinic receptors with atropine induce a contraction and increasing rigidity of the aorta.

Angiotensin II↗

PubMed1976

Modulus of elasticity and strength properties of dental cements.

The modulus of elasticity of commercial dental cements was determined by an optical strain gauge method. Values of compressive and tensile strengths also were measured. Of the cements of primary consistency tested, a noneugenol zinc oxide cement had the lowest mechanical properties. A zinc phosphate cement had the highest value of compressive strength and modulus, but a zinc polyacrylate cement had the highest tensile strength. A zinc polyacrylate cement base had the highest tensile strength, but a zinc phosphate cement base had the highest compressive strength and modulus of elasticity. A calcium hydroxide liner had higher mechanical properties than an unmodified ZOE liner.

Dental Cements↗

PubMed1999

Stiffness of the aortic wall in hypercholesterolemic children.

Arterial stiffness may be an indicator of early vascular changes signaling the development of vascular disease, while hypercholesterolemia is a well-recognized promoter of atherogenesis. It has been shown that hypercholesterolemic children have a thicker intima-media in the carotid artery than children with normal cholesterol. The aim of this study was to assess the stiffness of the abdominal aorta in children with hypercholesterolemia. Noninvasive imaging evaluation of the aorta was performed in 85 outpatient children (age, 3 to 14 years) with and without high cholesterol levels ((and) 247 mg/dL [6.4 mmol/L], respectively). Ultrasound imaging of the abdominal aorta that allowed diameter measurements was available in 67 children. Using an image-processing workstation, the maximum and minimum internal diameter of the aorta was measured, and the following indices of elastic properties of the abdominal aorta were derived: arterial strain, pressure-strain elastic modulus, and stiffness. No statistical difference for aortic strain, stiffness, and elastic modulus was found in normocholesterolemic compared with hypercholesterolemic children. The effect of age on the elastic modulus was different in the two groups: in normal children, the elastic modulus increased linearly with age (y = -0.020+0.003 x age [months], P<.001), while the high-cholesterol group had a weak increase in this parameter with age (y = 0.118+0.0009 x age, P = .051). The slope of the regression equations (elastic modulus vage) was significantly different in the two groups (t = 2.45, P = .017). The behavior of arterial stiffness with respect to age was similar, y = 0.677+0.018 x age (P = .002) in normocholesterolemic children and y = 2.06+0.00198 x age (P = .66) in hypercholesterolemic children. The slope of the regression equations (stiffness v. age) was significantly different in the two groups (t = 2.37, P = .021). The present study demonstrates an influence of hypercholesterolemia on age-related modification in the elastic properties of the aorta. A remodeling of the aortic wall in hypercholesterolemic children (cholesterolemia >247 mg/dL) could explain the different age-dependent increase in aortic elastic modulus and stiffness.

Adolescent↗

PubMed2006

Elastic modulus-based thrombelastographic quantification of plasma clot fibrinolysis with progressive plasminogen activation.

Thrombelastographic detection of fibrinolysis has been critical in the identification and treatment of coagulopathy in many perioperative settings. However, the fibrinolytic assessments have been at best non-parametric, amplitude-based determinations (e.g. estimated % lysis, clot lysis time or clot lysis rate). Recognizing this limitation, a methodology was developed to measure the onset, speed and extent of clot disintegration by changes in elastic modulus derived from the amplitude. Using this approach, our goal was to characterize the clot disintegration kinetics of progressive plasminogen activation with tissue plasminogen activator (tPA) and to determine the extent of inhibition of fibrinolysis mediated by tPA with aprotinin and activated factor XIII. While the estimated % lysis and clot lysis time were significantly affected by tPA (0-300 U/ml), elastic modulus-based analyses in a more activity-specific fashion demonstrated significantly decreased onset, increased rate and increased extent of fibrinolysis. Furthermore, aprotinin was found to inhibit the onset, rate and extent of fibrinolysis in an activity-dependent fashion, whereas activated factor XIII was noted to enhance the speed of onset of clot growth and delay the onset of fibrinolysis. In summary, our results serve as the rational basis to utilize this elastic modulus-based approach to quantify the extent of fibrinolysis in clinical and laboratory settings, as well as potentially guiding antifibrinolytic therapy.

Analysis of Variance↗

PubMed1999

Influence of age and end-stage renal disease on the stiffness of carotid wall material in hypertension.

BACKGROUND: Incremental elastic modulus, which is the slope of the relationship between stress and strain of arterial vessels, is a marker of wall material stiffness. The radial artery incremental elastic modulus, which is not influenced by age, is normal or reduced in patients with essential hypertension but increased in patients with end-stage renal disease. Authors of studies on hypertension largely ignore the question of whether the incremental elastic modulus, measured in the common carotid artery as typical of a central artery site, differs according to age or to the presence of end-stage renal disease or both. SUBJECTS AND METHODS: The carotid incremental elastic modulus was measured in 208 hypertensive patients divided into four groups according to age (< or = or > 55 years) and the presence or absence of end-stage renal disease. The incremental elastic modulus was calculated from transcutaneous measurements of arterial internal diameter and wall thickness (echo-tracking device) and carotid pulse pressure (tonometry). Because the four groups of subjects had the same mean arterial pressure, the static incremental elastic modulus was calculated both in isobaric conditions and for the same wall stress. RESULTS: In nonuremic subjects, lumen diameter, wall thickness and the incremental elastic modulus were significantly (P < 0.001) increased in older subjects whereas compliance and distensibility were decreased. The mean (+/- SD) elastic modulus was 0.41 +/- 0.14 x 10(3) kPa in younger and 0.71 +/- 0.28 x 10(3) kPa in older subjects. In uremic subjects, the corresponding values were 0.48 +/- 0.30 and 0.90 +/- 0.49 x 10(3) kPa, and therefore higher than in nonuremic subjects, irrespective of age. Multiple regression analysis showed that age, mean arterial pressure and the presence of end-stage renal disease independently influenced carotid diameter, distensibility and the incremental elastic modulus. CONCLUSIONS: In hypertensive patients, the carotid incremental elastic modulus is increased independently in aging men and women and in the presence of uremia. This increase is not dependent on mechanical factors such as the level of mean blood pressure.

Adult↗

PubMed2005

Porcine carotid arterial material property alterations with induced atheroma: an in vivo study.

OBJECTIVE: A novel methodology has been developed to evaluate regional alterations in arterial wall material properties with induced atheroma in an animal model. METHODS: Atheromatous lesions (fatty, fibro-fatty, and fibrous) were induced in the carotid arteries of a Yucatan miniswine model by endothelial cell denudation and high cholesterol diet. The images at base line and 8 weeks after denudation were obtained using intravascular ultrasound (IVUS) imaging along with hemodynamic data. Finite element analysis (FEA) along with optimization was employed to assess regional alterations in elastic modulus in the presence of atheroma confirmed by histology. RESULTS: In animals with 8 weeks of induced atherosclerosis, the elastic modulus increased-(elastic modulus-all values x 10(4) Pa, mean+/-S.D.) normal elements (9.34+/-0.36) compared to abnormal elements (9.52+/-0.36) (p<0.05 versus normal elements). Wall thickness increased with atheroma formation. These data demonstrate stiffening vascular wall elastic modulus with lesion progression. This is different from the behavior of femoral arteries, where the elastic modulus decreases with early stages of atheroma development followed by an increase as lesions progress. CONCLUSIONS: This methodology permits determination of areas with early atheroma development, follow atheroma progression, and potentially evaluate interventions aimed at decreasing atheroma load and normalizing vascular material properties.

Animals↗

PubMed1988

The effect of porosity and mineral content on the Young's modulus of elasticity of compact bone.

The Young's modulus of elasticity, the calcium content and the volume fraction (1-porosity) of 23 tension specimens and 80 bending specimens, taken from compact bone of 18 species of mammal, bird and reptile, were determined. There was a strong positive relationship between Young's modulus and both calcium content and volume fraction. A power law model fits the data better than a linear model. Young's modulus has a roughly cubic relationship with both calcium content and volume fraction. Over 80% of the total variation in Young's modulus in this data set is explained by these two variables.

Animals↗

PubMedDate not supplied

Effect of liners on cusp deflection and gap formation in composite restorations.

This study measured deformation of cusps and gap formation associated with MOD resin composite restorations in maxillary premolars with and without the use of low elastic modulus liners. Low elastic modulus liners may reduce the deformation by absorbing polymerization shrinkage stress. Forty maxillary premolars were mounted in stone and slot MOD cavities were prepared. Teeth were randomized into four groups. In Group A, cavities were etched, Single Bond was applied and the cavities were restored with Z-100 composite. In Group B, the same was done except that a layer of flowable composite (Revolution) was place and cured after the bonding agent. In Group C, the same steps were followed as Group A but a layer of glass ionomer (Vitrebond) was placed and cured before the bonding agent. In Group D, a thin layer of composite was placed (after the bonding agent) as a base and cured and the cavities were filled. The distance between indexed cusp tips was measured before the restorations were finished and five minutes and 24 hours after the restorations were completed. The samples were then sectioned mesiodistally and epoxy resin replicas were made and prepared for SEM evaluation of gap formation. The mean contraction of the cusps in microm at 5 minutes and 24 hours, respectively, for each group was A) 47 and 30, B) 35 and 21, C) 23 and 8 and D) 40 and 28. Groups A and D resulted in the highest deformation, B was intermediate and C was the lowest. There was no statistically significant difference in gap formation between the groups.

Analysis of Variance↗

PubMed1985

Fatigue of immature baboon cortical bone.

Strain-controlled uniaxial fatigue and monotonic tensile tests were conducted on turned femoral cortical bone specimens obtained from baboons at various ages of maturity. Fatigue loading produced a progressive loss in stiffness and an increase in hysteresis prior to failure, indicating that immature primate cortical bone responds to repeated loading in a fashion similar to that previously observed for adult human cortical bone. Bone fatigue resistance under this strain controlled testing decreased during maturation. Maturation was also associated with an increase in bone dry density, ash fraction and elastic modulus. The higher elastic modulus of more mature bone meant that these specimens were subjected to higher stress levels during testing than more immature bone specimens. Anatomical regions along the femoral shaft exhibited differences in strength and fatigue resistance.

Animals↗

PubMed2004

A two-layered mechanical model of the rat esophagus. Experiment and theory.

BACKGROUND: The function of esophagus is to move food by peristaltic motion which is the result of the interaction of the tissue forces in the esophageal wall and the hydrodynamic forces in the food bolus. The structure of the esophagus is layered. In this paper, the esophagus is treated as a two-layered structure consisting of an inner collagen-rich submucosa layer and an outer muscle layer. We developed a model and experimental setup for determination of elastic moduli in the two layers in circumferential direction and related the measured elastic modulus of the intact esophagus to the elastic modulus computed from the elastic moduli of the two layers. METHODS: Inflation experiments were done at in vivo length and pressure-diameters relations were recorded for the rat esophagus. Furthermore, the zero-stress state was taken into consideration. RESULTS: The radius and the strain increased as function of pressure in the intact as well as in the individual layers of the esophagus. At pressures higher than 1.5 cmH2O the muscle layer had a larger radius and strain than the mucosa-submucosa layer. The strain for the intact esophagus and for the muscle layer was negative at low pressures indicating the presence of residual strains in the tissue. The stress-strain curve for the submucosa-mucosa layer was shifted to the left of the curves for the muscle layer and for the intact esophagus at strains higher than 0.3. The tangent modulus was highest in the submucosa-mucosa layer, indicating that the submucosa-mucosa has the highest stiffness. A good agreement was found between the measured elastic modulus of the intact esophagus and the elastic modulus computed from the elastic moduli of the two separated layers.

Animals↗

PubMed2006

Age-related changes in hardness and modulus of elasticity of dentine.

OBJECTIVES: Little knowledge has been clarified about the relationship between the morphological and physical changes of dentine during aging. The purpose of this study was to clarify the modulus of elasticity and hardness related to the morphological changes of dentine by aging using a transmitted light microscope (TLM) and a nano-hardness tester (NHT). METHODS: Aged human molars and young third molars were used. The dentine morphology was observed under a TLM. The hardness and Young's modulus of elasticity related to the morphologic study were evaluated with an NHT. RESULTS: The thickness of mantle dentine and globular dentine of aged teeth were less than that of young teeth. Transparent dentine was observed only underneath the attrition of young teeth. Reactionary tertiary dentine formed and a "dark zone" was found at the junction between physiologic secondary and reactionary dentine only in aged teeth. At the mantle dentine, hardness and modulus of elasticity of aged dentine were higher than those of young dentine. The reactionary dentine in aged teeth and newly developed secondary dentine in young teeth demonstrated lower modulus of elasticity and hardness than those of other circumpulpal dentine. Relatively low modulus of elasticity and hardness were observed at the zone between secondary and reactionary dentine. CONCLUSIONS: Changes in dentine due to aging resulted in transformation of morphological features causing changes to their hardness and modulus of elasticity at the explicit areas such as the increase of hardness and modulus of elasticity at mantle dentin and the reduction of these properties at the "dark zone" that found in aged teeth.

Adolescent↗

PubMed1993

Assessment of smooth muscle contribution to descending thoracic aortic elastic mechanics in conscious dogs.

Early investigators found contradictory evidence that vascular smooth muscle activation reduces the elastic modulus of the arterial wall under isotonic conditions but increases it under isometric conditions, concomitant with increased pulse-wave velocity. We examined the individual contributions of aortic constituents to the elastic modulus of the aortic wall to determine if isobaric analysis produces an accurate assessment of vascular smooth muscle activation. We used a modified Maxwell model assuming an incremental elastic modulus (Einc) composed of the elastic modulus of elastin fibers (EE), the elastic modulus of collagen fibers (EC) affected by the fraction of collagen fibers (fC) recruited to support wall stress, and the elastic modulus of the vascular smooth muscle (ESM) according to the following formula: Einc = EE+EC x fC+ESM.Einc was assessed in eight conscious dogs using descending thoracic aortic pressure (microtransducer) and diameter (sonomicrometry) measurements. Stress-strain relations in the control state and during activation of smooth muscle by continuous administration of phenylephrine (5 micrograms.kg-1 x min-1) were obtained by transient occlusions of the descending aorta and inferior vena cava. Results were as follows: EE was 4.99 +/- 1.58 x 10(6) dynes/cm2 (mean +/- SD), and EC was 965.8 +/- 399.8 x 10(6) dynes/cm2, assessed during the control state. Phenylephrine administration increased the theoretical pulse-wave velocity (Moens-Korteweg equation) from 5.25 +/- 1.03 m/s during the control state to 7.57 +/- 2.53 m/s (P < .005). Active muscle exhibited a unimodal stress-strain curve with a maximum stress of 0.949 +/- 0.57 x 10(6) dynes/cm2 at a corresponding strain value of 1.299 +/- 0.083. The maximum value observed corresponded, on the pressure-diameter curve of the active artery, to a pressure of 234.28 +/- 46.6 mm Hg and a diameter of 17.94 +/- 1.6 mm. The maximum ESM derived from the stress-strain relation of the active muscle was 8.345 +/- 7.56 x 10(6) dynes/cm2 at a strain value of 1.283 +/- 0.079. This point was located at 208.01 +/- 40.8 mm Hg and 17.73 +/- 1.41 mm on the active pressure-diameter curve. During activation of vascular smooth muscle, Einc decreased (P < .05) when plotted against internal pressure but increased (P < .05) when plotted against strain, over the operative range.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed2004

Pipette aspiration technique for the measurement of nonlinear and anisotropic mechanical properties of blood vessel walls under biaxial stretch.

A pipette aspiration technique was proposed for the measurement of nonlinear mechanical properties of arteries under biaxial stretching. A cross-shaped specimen of porcine thoracic aorta whose principal axes corresponded with the axial and circumferential directions of the aortic walls was excised. The intraluminal surface of the specimen was aspirated with a circular cross-sectioned glass pipette while the specimen was stretching in the axial and circumferential directions in 10% increments. The elastic modulus agreed with the incremental elastic modulus obtained through a conventional pressure-diameter test of the same specimen to within an error of 30% at a circumferential stretch ratio below 1.3 and an axial stretch ratio of 1.0, 1.1 or 1.2, which represent lower range of physiological stretch ratios for the porcine aorta. A rectangular cross-sectioned pipette was utilized to measure anisotropic properties of the specimen under biaxial stretching. When aspirated with such a pipette, the specimens' elastic properties along the length of the rectangular pipette cross section can be neglected. The elastic modulus was found to increase rapidly when the specimen was stretched in the direction of the pipette's width. Thus, pipette aspiration should have many advantages such as well measurement of the local nonlinear and anisotropic mechanical properties of blood vessel walls.

Animals↗

PubMed2003

Effect of MTAD on flexural strength and modulus of elasticity of dentin.

The purpose of this study was to evaluate the effect of MTAD on the flexural strength and modulus of elasticity of dentin. Dentin bars were randomly assigned to eight groups treated with various concentrations of NaOCl (5.25%, 2.65%, 1.31%, 0.66%), 17% EDTA, MTAD, saline, or according to a clinical protocol with 1.3% NaOCl and then 5 min of MTAD. Specimens were subjected to flexural strength and modulus of elasticity tests. Two-sample t test (alpha = 0.05) showed no statistically significant differences between various groups except for a reduction in flexural strength for the 2-h MTAD group (p = 0.002) and the EDTA group (p = 0.002). A significant reduction of modulus of elasticity for the 2-h MTAD group (p < 0.001), EDTA group (p < 0.001), and 0.6% NaOCl (p < 0.002) also was noted. There was no significant difference in flexural strength and modulus of elasticity between the dentin bars exposed to saline or MTAD when applied according to the clinical protocol (p > 0.05). These results indicate that MTAD can be used as prescribed for clinical use without affecting the physical properties of the dentin.

Analysis of Variance↗

PubMed2006

Biomechanical properties of different segments of human umbilical cord vein and its value for clinical application.

No satisfactory effects have been obtained with the use of synthetic blood vessels (diameter <6 mm) as substitutes for human small arteries or veins for the purpose of clinical vascular reconstruction. Therefore, blood vessels of human origin, for example, umbilical cord blood vessels, with their wide availability, still should be considered. However, little information on biomechanical properties of human umbilical cord blood vessels is available. The objective was to provide a theoretical basis for the clinical application of umbilical cord veins as optional material for small-caliber grafts. This was a nonrandomized, noncontrolled in vitro study. The experiment was conducted in the Laboratory of Medical Biomechanics, Yunyang Medical College. Umbilical cord veins of 20 normal fetuses of spontaneous labor were collected by the Department of Obstetrics and Gynecology, Taihe Hospital in Shiyan City, Hubei Province. The fetuses aged 37-40 weeks, and the parturients were 20-30 years old. Umbilical cord veins of the 20 fetuses were used and the placental ends were treated as proximal ends while the fetal ends as distal ends. The fetal ends were divided into three segments: proximal, middle, and distal segments. The relationship between pressure of umbilical cord veins segments and the diameters was measured on the biomechanical experiment stand for soft tissues, and then the elastic modulus was calculated. The materials were transversely extracted, refrigerated, and sliced up before HE staining. The geometrical morphology indexes were measured by a computer image analysis system (Leica-Q500IW). The main outcome measures were: incremental elastic modulus (E(inc)), pressure-strain elastic modulus (E(p)), volume elastic modulus (E(v)), diameter, and wall thickness of the veins. E(inc), E(p), and E(v) of umbilical cord veins of proximal, middle, and distal segments increased with the pressure elevated. The three kinds of elastic modulus of proximal segments (E(inc): 26.98 +/- 3.21, E(p): 16.58 +/- 2.12, E(v): 8.31 +/- 2.35) were all lower than those of distal segments (E(inc): 33.20 +/- 4.21, E(p): 119.45 +/- 2.87, E(v): 9.71 +/- 1.32) (F = 95.74-126.52, p < 0.05), and a tendency to increase was shown from proximal segments to distal segments. Media thickness [(0.30 +/- 0.05)] mm, (0.24 +/- 0.03) mm] and the diameters [(3.07 +/- 0.12) mm, (2.30 +/- 0.13) mm] decreased gradually from proximal to distal segments (F = 12.76, p < 0.01). It is feasible to use umbilical cord veins as substitutes for the transplantation of small-caliber arteries in terms of basic biomechanical properties. On vascular grafting, different segments of umbilical cord veins should be chosen cautiously so that the biomechanical characteristics of umbilical cord vein grafts could be in accordance with those of host to increase the long-term patency rate of transplanted blood vessels.

Adult↗

PubMed2002

Determination of the modulus of elasticity of bone material by an acoustical approach at the forearm distinguishes women with and without vertebral fractures independent of bone mineral density.

The modulus of elasticity is a parameter characterizing fracture stability of bone independent of bone mineral density. Measurement of acoustical properties of the forearm by determination of the resonant frequency of the ulna in longitudinal direction as a function of sound transmission velocity after adjustment of the measuring result by ulna length yields information about the modulus of elasticity. It was the aim of this study to investigate whether this parameter may distinguish between subjects with and without vertebral fractures independent of bone mineral density. Fifty females (61.1 +/- 9.1 years) were enrolled into the study, 25 with, and 25 age-matched without prevalent osteoporotic vertebral fracture(s). Especially low bone mineral density was not considered an exclusion criteria for enrollment into the control group. Resonant frequency of the ulna multiplied by ulna length was significantly lower in the group with prevalent fractures (53.6 +/- 6.8 m/s versus 56.8 +/- 5.2 m/s) after adjustment for age and after additional adjustment for forearm bone mineral density. Linear regression analysis showed complete independence of the acoustical parameter from bone mineral density. This study demonstrates that the modulus of elasticity of bone material is an independent risk factor for osteoporotic fractures. Acoustical measurement at the forearm by analyzing the resonant frequency of the ulna and correcting it by ulna length as geometrical parameter is capable of determining the modulus of elasticity in vivo.

Acoustics↗

PubMed2005

Effect of cross-sectional design on the modulus of elasticity and toughness of fiber-reinforced composite materials.

STATEMENT OF PROBLEM: Many current fabrication protocols for dental fiber-reinforced composites use hand lay-up techniques and technician design input. Little information exists regarding how the manipulation of the cross-sectional design of a prosthesis might affect the modulus of elasticity and toughness. PURPOSE: The aim of this study was to determine the effect of simple and complex cross-sectional designs on the modulus of elasticity and toughness of fiber-reinforced composite used for dental prostheses. MATERIAL AND METHODS: Two particulate composites (BelleGlass HP and Targis) were reinforced with ultra-high-molecular-weight polyethylene fiber ribbon (Connect), woven E-glass fibers (Vectris Frame), or unidirectional R-glass fibers (Vectris Pontic). A range of fiber positions, orientations, or geometries were incorporated into the rhombic specimens (2 x 2 x 25 mm(3)) to achieve simple and complex experimental cross-sectional designs. The control specimen did not contain fiber reinforcement. Specimens (n=6) were stored 1 week in distilled water at 37 degrees C prior to 3-point load testing to determine the modulus of elasticity (GPa) and toughness (MPa). The data within each main fiber group were subjected to 1-way analysis of variance and a Tukey post hoc test (alpha=.05). Cross-sections of randomly selected test specimens (n=2) were made for scanning electron microscope (SEM) analysis of the fiber distribution. RESULTS: The mean modulus of elasticity varied from 8.7 +/- 2.0 GPa (Targis control) to 21.6 +/- 1.4 GPa (2 unidirectional glass fiber reinforcements, 1 each at the tension side and the compression side). Mean toughness varied from 0.07 +/- 0.02 MPa (unidirectional glass fiber positioned at the compression side) as the lowest mean, to 4.53 +/- 0.89 MPa (unidirectional glass fiber positioned at the tension side) as the highest. Significant differences were identified between specimen groups in each main category (all groups P<.001, except modulus of elasticity of the woven E-glass groups, where P=.003). SEM micrographs showed fiber distribution in the cross section of test specimens to correspond with the intended fiber geometry. CONCLUSION: The modulus of elasticity of the composite specimens increased when 1 or more glass fiber groups were located at the compression side of the specimen. Toughness was most effectively increased when 1 or more fiber groups were located at the tension side of the specimen.

Analysis of Variance↗