Ball-burst Testing Research Articles

Influence of Epoxidized Natural Rubber of the thermoformability of Poly(Lactic Acid) biopolymer films using elevated temperature ball burst tests

In this paper, we investigated the thermoformability of Epoxidized Natural Rubber (ENR)-filled Poly(Lactic Acid) (PLA) films using elevated temperature tensile and ball burst tests. Three different d-Lactide contents of PLA were used to be able to analyze the effect of crystallization and crystallinity. We observed that the ENR acted as a nucleating agent in PLA when the blend was cooled from melt or cold crystallized, but it retarded the drawing-induced crystallization of PLA at elevated temperature tensile testing since ENR droplets acted as obstacles. The effect of NR on PLA crystallization was also found to be dependent on d-Lactide content. In the ball burst test, different behaviors were observed for PLA with the lowest d-Lactide content, which was caused by the complex stress state that even more induced crystallization of PLA and then a single-axis tensile test.

A reliable and replicable test protocol for the mechanical evaluation of synthetic meshes

Despite the worldwide spread of surgical meshes in abdominal and inguinal surgery repair, the lack of specific standards for mechanical characterization of synthetic meshes, used in hernia repair and urogynecologic surgery, makes performance comparison between prostheses undoubtedly difficult. This consequently leads to the absence of acknowledged specifications about the mechanical requirements that synthetic meshes should achieve in order to avoid patient discomfort or hernia recurrences.The aim of this study is to provide a rigorous test protocol for the mechanical comparison between surgical meshes having the same intended use. The test protocol is composed of three quasi-static test methods: (1) ball burst test, (2) uniaxial tensile test, and (3) suture retention test. For each test, post-processing procedures are proposed to compute relevant mechanical parameters from the raw data. Some of the computed parameters, indeed, could be more suitable for comparison with physiological conditions (e.g., membrane strain and anisotropy), while others (e.g., uniaxial tension at rupture and suture retention strength) are reported as they provide useful mechanical information and could be convenient for comparisons between devices. The proposed test protocol was applied on 14 polypropylene meshes, 3 composite meshes, and 6 urogynecologic devices to verify its universal applicability towards meshes of different types and produced by various manufacturers, and its repeatability in terms of coefficient of variation.The test protocol resulted easily applicable to all the tested surgical meshes with intra-subject variability characterized by coefficient of variations settled around 0.05. Its use within other laboratories could allow the determination of the inter-subject variability assessing its repeatability among users of alternative universal testing machines.

Prophylactic onlay mesh placement techniques for optimal abdominal wall closure: randomized controlled trial in an ex vivo biomechanical model.

Incisional hernias occur after up to 40 per cent of laparotomies. Recent RCTs have demonstrated the role of prophylactic mesh placement in reducing the risk of developing an incisional hernia. An onlay approach is relatively straightforward; however, a variety of techniques have been described for mesh fixation. The biomechanical properties have not been interrogated extensively to date. This ex vivo randomized controlled trial using porcine abdominal wall investigated the biomechanical properties of three techniques for prophylactic onlay mesh placement at laparotomy closure. A classical onlay, anchoring onlay, and novel bifid onlay approach were compared with small-bite primary closure. A biomechanical abdominal wall model and ball burst test were used to assess transverse stretch, bursting force, and loading characteristics. Mesh placement took an additional 7-15 min compared with standard primary closure. All techniques performed similarly, with no clearly superior approach. The minimum burst force was 493 N, and the maximum 1053 N. The classical approach had the highest mean burst force (mean(s.d.) 853(152) N). Failure patterns fell into either suture-line or tissue failures. Classical and anchoring techniques provided a second line of defence in the event of primary suture failure, whereas the bifid method demonstrated a more compliant loading curve. All mesh approaches held up at extreme quasistatic loads. Subtle differences in biomechanical properties highlight the strengths of each closure type and suggest possible uses. The failure mechanisms seen here support the known hypotheses for early fascial dehiscence. The influence of dynamic loading needs to be investigated further in future studies.

Cog Threads for Transvaginal Prolapse Repair: Ex-Vivo Studies of a Novel Concept

The diagnosis and treatment of pelvic organ prolapse (POP) remain a relevant and scientifically challenging topic. The number of cases of genital prolapse increases each year, one in ten women need at least one surgical procedure and one in four women in midlife have asymptomatic prolapse. Using mesh implants to correct POP presents unsatisfactory clinical outcomes, requiring hospital readmission and further surgery. We hypothesize using an alternative surgical intervention technique, applying injectable biodegradable cog threads, currently used for face lifting procedures, to reinforce and correct vaginal wall defects. The threads used in this investigation are commercially available 360° 4D barb threads (PCL-19G-100), made of polycaprolactone (PCL), supplied in sterile packs (Yastrid, Shanghai, China). Eleven sows’ vaginal walls were used to analyze the immediate reinforcement effect of the threads. Uniaxial tensile testing and scanning electron microscopy (SEM) was performed for the initial characterization of the threads. Threads were inserted into the vaginal wall (control n = 5, cog n = 5) and were characterized by ball burst testing; a pull-out test was performed (n = 6). With SEM images, dimensions, such as thread diameter (≈630 µm), cut angle (≈135°), cut depth (≈200 µm) and cog distance (≈1600 µm) were measured. The mechanical behavior during uniaxial tensile testing was nonlinear. Threads could sustain 17–18 N at 18–22% of deformation. During the ball burst test, vaginal tissue reinforced with threads could support 68 N more load than normal tissue (p < 0.05), indicating its strengthening effect. Comfort and stress zones were significantly stiffer in the tissues reinforced with threads (p < 0.05; p < 0.05). Both groups showed identical deformation (elongation); no significant differences in the comfort zone length were observed, showing that threads do not affect tissue compliance. The pull-out test showed that the threads could sustain 3.827 ± 0.1891 N force when the first cog slip occurs, at 11.93 ± 0.8291 mm. This preliminary research on using PCL cog threads for POP treatment showed promising results in increased vaginal wall resistance to pressure load and, at the same time, not affecting its compliance. Nevertheless, to obtain long term host response in vivo, further investigation will be carried out.

Cardioprotective effect of silicon-built restraint device (ASD), for left ventricular remodeling in rat heart failure model

This study aims to evaluate the feasibility and cardio-protective effects of biocompatible silicon-built restraint device (ASD) in the rat’s heart failure (HF) model. The performance and compliance characteristics of the ASD device were assessed in vitro by adopting a pneumatic drive and ball burst test. Sprague-Dawley (SD) rats were divided into four groups (n = 6); control, HF, HF + CSD, and HF + ASD groups, respectively. Heart failure was developed by left anterior descending (LAD) coronary artery ligation in all groups except the control group. The ASD and CSD devices were implanted in the heart of HF + ASD and HF + CSD groups, respectively. The ASD’s functional and expansion ability was found to be safe and suitable for attenuating ventricular remodeling. ASD-treated rats showed normal heart rhythm, demonstrated by smooth -ST and asymmetrical T-wave. At the same time, hemodynamic parameters of the HF + ASD group improved systolic and diastolic functions, reducing ventricular wall stress, which indicated reverse remodeling. The BNP values were reduced in the HF + ASD group, which confirmed ASD feasibility and reversed remodeling at a molecular level. Furthermore, the HF + ASD group with no fibrosis suggests that ASD has significant curative effects on the heart muscles. In conclusion, ASD was found to be a promising restraint therapy than the previously standard restraint therapies.Stepwise ASD fabrication process (a) 3D computer model of ASD was generated by using Rhinoceros 5.0 software (b) 3D blue wax model of ASD (c) Silicon was prepared by mixing the solutions (as per manufacturer instruction) (d) Blue wax model of ASD was immersed into liquid Silicon (e) ASD model was put into the oven for 3 hours at 50 °C. (f) Blue wax started melting from the ASD model (g) ASD model was built from pure silicon (h) Two access lines were linked to the ASD device, which was connected with an implantable catheter (Port-a-cath), scale bar 100 µm. (Nikon Ldx 2.0).

Investigation of the thermoformability of various D‐Lactide content poly(lactic acid) films by ball burst test

AbstractIn this article, we investigated the thermoformability of poly(lactic acid) (PLA) films with various D‐Lactide contents and therefore different crystallization properties, performing tensile and ball burst tests at various temperatures and testing rates. We found that the behavior of the PLA films tested above the glass transition temperature significantly differs due to the difference in D‐Lactide content, and thus crystallinity. During tensile testing, elevated temperatures and mechanical stress caused the crystallization temperature to decrease and thus highly induced crystallization. At the same time, as testing speed was increased, the ability of the polymer to crystallize decreased. In ball burst tests, the PLA films crystallized more than during tensile testing. We described the differences found between tensile testing and ball burst testing, which latter better represents the conditions of thermoforming through inducing biaxial deformation.

Extracellular matrix regenerative graft attenuates the negative impact of polypropylene prolapse mesh on vagina in rhesus macaque

The use of wide pore lightweight polypropylene mesh to improve anatomical outcomes in the surgical repair of prolapse has been hampered by mesh complications. One of the prototype prolapse meshes has been found to negatively impact the vagina by inducing a decrease in smooth muscle volume and contractility and the degradation of key structural proteins (collagen and elastin), resulting in vaginal degeneration. Recently, bioscaffolds derived from extracellular matrix have been used to mediate tissue regeneration and have been widely adopted in tissue engineering applications. Here we aimed to: (1) define whether augmentation of a polypropylene prolapse mesh with an extracellular matrix regenerative graft in a primate sacrocolpopexy model could mitigate the degenerative changes; and (2) determine the impact of the extracellular matrix graft on vagina when implanted alone. A polypropylene-extracellular matrix composite graft (n= 9) and a 6-layered extracellular matrix graft alone (n= 8) were implanted in 17 middle-aged parous rhesus macaques via sacrocolpopexy and compared to historical data obtained from sham (n= 12) and the polypropylene mesh (n= 12) implanted by the same method. Vaginal function was measured in passive (ball-burst test) and active (smooth muscle contractility) mechanical tests. Vaginal histomorphologic/biochemical assessments included hematoxylin-eosin and trichrome staining, immunofluorescent labeling of α-smooth muscle actin and apoptotic cells, measurement of total collagen, collagen subtypes (ratio III/I), mature elastin, and sulfated glycosaminoglycans. Statistical analyses included 1-way analysis of variance, Kruskal-Wallis, and appropriate post-hoc tests. The host inflammatory response in the composite mesh-implanted vagina was reduced compared to that following implantation with the polypropylene mesh alone. The increase in apoptotic cells observed with the polypropylene mesh was blunted in the composite (overall P < .001). Passive mechanical testing showed inferior parameters for both polypropylene mesh alone and the composite compared to sham whereas the contractility and thickness of smooth muscle layer in the composite were improved with a value similar to sham, which was distinct from the decreases observed with polypropylene mesh alone. Biochemically, the composite had similar mature elastin content, sulfated glycosaminoglycan content, and collagen subtype III/I ratio but lower total collagen content when compared to sham (P= .011). Multilayered extracellular matrix graft alone showed overall comparable values to sham in aspects of the biomechanical, histomorphologic, or biochemical endpoints of the vagina. The increased collagen subtype ratio III/I with the extracellular matrix graft alone (P= .033 compared to sham) is consistent with an ongoing active remodeling response. Mesh augmentation with a regenerative extracellular matrix graft attenuated the negative impact of polypropylene mesh on the vagina. Application of the extracellular matrix graft alone had no measurable negative effects suggesting that the benefits of this extracellular matrix graft occur when used without a permanent material. Future studies will focus on understanding mechanisms.

Clinically relevant mechanical testing of hernia graft constructs

BackgroundTo understand the mechanical behavior of grafts in the context of hernia repair, there is a need to develop and adopt methods for mechanical testing of grafts in a clinically-relevant manner with clinically-relevant outcomes. Materials and methodsBall-burst and planar-biaxial methods were used to test three commercially-available hernia grafts (DermaMatrix, Biodesign, VitaMesh Blue). Both load-to-failure and cyclic fatigue tests were performed (n=6–11/group/test). Grafts were tested as sutured constructs in patch geometry. Dilatational strain analysis was performed considering the construct (both test methods) or the graft (planar-biaxial only) as the area of interest. ResultsDermaMatrix, Biodesign, and VitaMesh grafts showed differences in mechanical properties at the point of construct failure (load, in-plane load-per-suture and membrane tension) in ball-burst tests and differences in sub-failure properties (stiffness, dilatational strain at 16N/cm and cyclic mechanical properties) in planar-biaxial tests. In both load-to-failure and cyclic fatigue tests, each graft construct tended to be stiffer in planar-biaxial than ball-burst testing. In biaxial testing, the strain analysis method influenced the mechanical properties with the construct being more compliant than the graft. ConclusionsThis study demonstrates that graft-fixation method, test mode and analysis method are important considerations for mechanical characterization of hernia grafts. Ball-burst tests can only estimate construct or material properties, whereas planar-biaxial tests capture anisotropy and can estimate construct, graft and material properties of the same test specimen. When the clinical performance of a graft in the context of hernia repair is of interest, testing a sutured construct and performing construct strain analysis arguably provides the most clinically-relevant assessment method.

Development of a Novel Sheep Model of Human Implant-Based Breast Reconstruction

INTRODUCTION: This study was conducted to (i) develop a full-scale animal model (FAM) in sheep that emulates the mechanical and biological environment of 2-stage breast reconstruction, and (ii) evaluate the clinical, mechanical and biological performance of the SBS over 12 months in situ. METHODS: Twelve sheep underwent bilateral implantation of tissue expanders (TE) under the latissimus dorsi muscle with partial muscle coverage. The SBS was sutured between the latissimus dorsi and the chest wall creating an infra-mammary fold (IMF) and defining a soft tissue lower pole. Animals were evaluated 1, 3, 6 and 12 months post-surgery; those designated for the 6 and 12 month endpoints had TE/breast implant exchange at 3 months. Implant sites were assessed through clinical observation and imaged at 6 and 12 months using CT and MRI. At necropsy, lower pole samples were assessed for thickness and drapability, and biomechanical strength was determined using a standard ball-burst test. Early model development involved (i) drain optimization and (ii) the evaluation of a non-SBS sham group. RESULTS: There was 1 incident of surgical site infection (which resolved without requiring implant removal), 1 incident of TE rotation, and no incidents of implant migration or bottoming-out. SBS features were not palpable at any time point; SBS-suture line edges were minimally discernable up to 4 months. SBS position was visualized by MRI at 6 months. SBS was fully ingrown from 1 month onward with SBS-tissue thickness increasing initially and then maintained (0.9±0 mm at time=0 to 1.9±1.3 mm at 1 month to 2.2±1.0 mm at 12 months). All tissue explants were drapable (Figures 1 and 2). The tissue burst strength was consistent (p>0.05) over all time points (and stronger than sheep fascia) while the strength of the SBS alone, following complete extraction of ingrown tissue, steadily declined with complete strength loss by 12 months.Figure 1: Figure 1.Figure 2: Figure 2.CONCLUSION: The FAM in sheep is a satisfactory means of evaluating implant based breast reconstruction. Results indicated a progressive transfer and maintenance of load-bearing responsibility from SBS to newly generated functional tissue capable of supporting the breast pocket through expansion and long-term implant reconstruction. DISCLOSURES: The study was sponsored by Allergan, Inc. The author disclosures are listed below. John E. Gross: Consultant (Allergan Medical, Serica Inc, Tissue Regeneration Inc, Stryker Craniofacial), Medical Director (Skin Deep Laser Medspa), Co-Founder and Medical Officer (Alford and Hoff Luxury Men's Skincare) Rebecca L. Horan: Employee (Allergan), Shareholder (Allergan) José M. García-López: No Disclosures Matthew Gaylord: Employee (Allergan) Raymond E. Olsen: Research Support Recepient (IMDS) Gregory H. Altman: Employee (Allergan), Shareholder (Allergan)

Spherical indentation of free-standing acellular extracellular matrix membranes

Numerous scaffold materials have been developed for tissue engineering and regenerative medicine applications to replace or repair damaged tissues and organs. Naturally occurring scaffold materials derived from acellular xenogeneic and autologous extracellular matrix (ECM) are currently in clinical use. These biological scaffold materials possess inherent variations in mechanical properties. Spherical indentation or ball burst testing has commonly been used to evaluate ECM and harvested tissue due to its ease of use and simulation of physiological biaxial loading, but has been limited by complex material deformation profiles. An analytical methodology has been developed and applied to experimental load–deflection data of a model hyperelastic material and lyophilized ECM scaffolds. An optimum rehydration protocol was developed based on water absorption, hydration relaxation and dynamic mechanical analysis. The analytical methodology was compared with finite element simulations of the tests and excellent correlation was seen between the computed biaxial stress resultants and geometry deformations. A minimum rehydration period of 5min at 37°C was sufficient for the evaluated multilaminated ECM materials. The proposed approach may be implemented for convenient comparative analysis of ECM materials and source tissues, process optimization or during lot release testing.

Biomechanical evaluation of potential damage to hernia repair materials due to fixation with helical titanium tacks

This study aimed to determine whether the strength and extensibility of hernia repair materials are negatively influenced by the application of helical titanium tacks. This study evaluated 14 meshes including bare polypropylene, macroporous polytetrafluoroethylene, absorbable barrier, partially absorbable mesh, and expanded polytetrafluoroethylene materials. Each mesh provided 15 specimens, which were prepared in 7.5 × 7.5-cm squares. Of these, 5 "undamaged" specimens were subjected to ball-burst testing to determine their biomechanical properties before application of helical titanium tacks (ProTack). To 10 "damaged" specimens 7 tacks were applied 1 cm apart in a 3.5-cm-diameter circle using a tacking force of 25 to 28 N. The tacks were removed from five of the specimens before ball-burst testing and left intact in the remaining five specimens. The application of tacks had no effect on the tensile strength of Dualmesh, ProLite Ultra, Infinit, Ultrapro, C-QUR Lite (<6 in.), Prolene Soft, or Physiomesh, but the tensile strengths were reduced for Bard Mesh, C-QUR, ProLite, and C-QUR Lite (>6 in.). Most of the meshes did not exhibit significantly different tensile strengths between removal of tacks and tacks left intact. Exceptions included C-QUR, Prolene, Ultrapro, and Bard Soft Mesh, which were weaker with removal of tacks than with tacks left intact during the test. Damage due to the application of helical titanium tacks also caused increased strain at a stress of 16 N/cm for all the meshes except C-QUR Lite (>6 in.) and Physiomesh. Many of the meshes evaluated in this study exhibited damage in the form of reduced tensile strength and increased extensibility after the application of tacks compared with the corresponding "undamaged" meshes. Meshes with smaller interstices and larger filaments were influenced negatively by the application of helical titanium tacks, whereas mesh designs with larger interstices and smaller filaments tended to maintain their baseline mechanical properties.

Effect of Repetitive Loading on the Mechanical Properties of Synthetic Hernia Repair Materials

Hernia repair materials undergo repeated loading while in the body, and the impact on mechanical properties is unknown. It was hypothesized that exposure to repetitive loading would lead to decreased tensile strength and increased strain, and that these differences would become more pronounced with greater loading and unloading sequences. Polypropylene, expanded polytetrafluoroethylene, composite barrier, and partially absorbable meshes were evaluated. Twenty specimens (7.5 × 7.5 cm) were prepared from each material. Five specimens were subjected to ball burst testing to determine baseline biomechanical properties. Cycles of 10, 100, and 1,000 loading sequences were also performed (n = 5 each). BardMesh (CR Bard/Davol), Dualmesh (WL Gore), and Prolene (Ethicon) exhibited significantly reduced tensile strength; BardMesh, Proceed (Ethicon), Prolene, ProLite (Atrium Medical), ProLite Ultra (Atrium Medical), and Ultrapro (Ethicon) exhibited significantly increased strain after exposure to 1,000 cycles compared with their baseline properties. BardMesh and Prolene demonstrated both reduced tensile strength and increased strain values after 1,000 cycles, suggesting that repetitive loading has the greatest effects on these materials. In addition, BardMesh and Prolene exhibited progressively worsening effects as the number of cycles was increased. Deterioration of the tensile strength of the mesh or an increase in the ability of the mesh material to stretch (ie, increased strain values) could potentially lead to hernia recurrence or a poor functional result. However, the results of this study should not be interpreted to mean that hernia repair materials will fail in the body after only 10, 100, or 1,000 cycles. The conditions used in this study were more extreme than most physiologic scenarios and were intended as a pilot investigation into how the mechanical properties of hernia repair materials are affected by in vitro cyclic testing.

Physicomechanical Evaluation of Polypropylene, Polyester, and Polytetrafluoroethylene Meshes for Inguinal Hernia Repair

For meshes to be used effectively for hernia repair, it is imperative that engineers and surgeons standardize the terminology and techniques related to physicomechanical evaluation of these materials. The objectives of this study were to propose standard techniques, perform physicomechanical testing, and classify materials commonly used for inguinal hernia repair. Nine meshes were evaluated: 4 polypropylene, 1 polyester, 1 polytetrafluoroethylene, and 3 partially absorbable. Physical properties were determined through image analysis, laser micrometry, and density measurements. Biomechanical properties were determined through suture retention, tear resistance, uniaxial, and ball burst testing with specimens tested in 2 different orientations. A 1-way ANOVA with Tukey's post-test or a t-test were performed, with p < 0.05. Significant differences were observed due to both mesh type and orientation. Areas of interstices ranged from 0.33 ± 0.01 mm² for ProLite (Atrium Medical Corp) and C-QUR Lite (Atrium Medical Corp) Large to 4.10 ± 0.06 mm² for ULTRAPRO (Ethicon), and filament diameters ranged from 99.00 ±8.1 μm for ProLite Ultra (Atrium Medical Corp) and C-QUR Lite Small to 338.8 ± 3.7 μm for Parietex Flat Sheet TEC (Covidien). These structural characteristics influenced biomechanical properties such as tear resistance and tensile strength. ProLite Ultra, C-QUR Lite Small, ULTRAPRO and INFINIT (WL Gore & Associates) did not resist tearing as effectively as the others. All meshes exhibited supraphysiologic burst strengths except INFINIT and ULTRAPRO. Significant differences exist between the physicomechanical properties of polypropylene, polyester, polytetrafluoroethylene, and partially absorbable mesh prostheses commonly used for inguinal hernia repair. Orientation of the mesh was also shown to be critical for the success of meshes, particularly those demonstrating anisotropy.

Physicomechanical evaluation of absorbable and nonabsorbable barrier composite meshes for laparoscopic ventral hernia repair

This study aimed to compare the physicomechanical properties of composite prostheses for laparoscopic ventral hernia repair (LVHR) through standard testing and a proposed classification system. Seven prostheses (four with absorbable barriers and 3 with nonabsorbable barriers) were evaluated. The barrier layer was removed, after which the area of the interstices and the diameter of the filaments were determined. The barrier layer was left intact during thickness, density, suture retention strength, tear resistance, uniaxial tensile, and ball-burst testing. Specimens were oriented parallel or perpendicular to their longest dimension during testing. One-way analysis of variance (ANOVA) with Tukey's posttest or an unpaired, two-tailed t-test was performed to determine whether differences existed due to mesh or orientation, and a p value<0.05 was considered significant. Significant differences were observed between mesh types and due to the orientation of the mesh during testing. Of the absorbable barrier meshes, Bard Sepramesh IP Composite demonstrated the greatest suture retention and tear strengths, followed by C-QUR mesh. Of the permanent barrier meshes, DUALMESH demonstrated the greatest suture retention strength in the perpendicular direction, followed by Bard Composix E/X. DUALMESH and Bard Composix E/X demonstrated equivalent suture retention strength in the parallel direction and equivalent tear resistance in both testing directions. All meshes demonstrated tensile strengths greater than the physiologically relevant range of 16-32 N/cm. This study provided a basic understanding of how the structural aspects of each mesh design influence functionality. Differences between composite barrier prostheses commonly used for LVHR were observed due to barrier type, mesh type, and orientation. A set of standard testing techniques and a classification system also were presented to define fully the properties of these materials.

Analytically derived material properties of multilaminated extracellular matrix devices using the ball-burst test

Xenogeneic extracellular matrices (ECMs) have been shown to be effective as naturally occurring scaffolds for soft-tissue repair. As acellular tissue substitutes at the time of surgical implantation, ECMs are subjected to the mechanical forces and micro-environmental conditions representative of the anatomical location in which they are placed. Ideally such natural scaffolds would possess mechanical properties that allow for normal tissue function in and around the implant site. The ball-burst test was used to simulate biaxial forces and to determine the strength of the ECM scaffold under a relevant physiological loading condition. The ball-burst test, in itself, does not quantify intrinsic mechanical properties and therefore a methodology was developed to determine the maximum stress resultant tangent modulus (MSRTM) or the maximum stress tangent modulus (MSTM), stress to failure ( σ f ) , failure stress resultant ( N f ) , ball-burst pressure ( P ) , and maximum elongation ( λ max ) from the raw ball-burst data obtained at a constant-rate of transverse. The analytical methodology was compared to finite element simulations and showed good correlation with the analytical solution presented. The proposed approximations were used to compute biaxial failure properties for a variety of multilaminate ECM devices with varying number of layers, disinfection and sterilization, and organ origin.

Determination of Structural Characteristics of Stitched and Knitted Fabric

The mechanical properties of stitched-bonded fabrics are investigated in the paper. The main structural characteristics of stitch-and-knitted nonwovens ric in two different density made on automatic warp knitting machine with compound needles and with one laying bar were calculated. Breaking strength of the fabric is determined by means of tensile tester with a constant speed of specimen deformation and at the ball burst test. The tensile test showed a 100% bigger breaking force in warp related to weft direction, while the breaking elongation is 50% greater in welt direction for both of samples. Results of this measurements were showed in diagram.

Multilaminate resorbable biomedical device under biaxial loading

The design and test of a multilaminate sheet developed for a hernia repair application is presented. As biomaterial applications become more complex, characterization of uniaxial properties becomes insufficient and biaxial testing becomes necessary. A measure of the in-plane biaxial strength of the device is inferred from a ball burst test. The results of this test for different thicknesses of the device are correlated with the uniaxial strength of the material. A biaxial test such as the ball burst test is more indicative of the properties of a planar material than would be a uniaxial test. The interactions in the biaxial mode of failure are of value and can be related back to a classical uniaxial tensile test from the ball burst test. The material used in this study to fabricate the device was a resorbable biomaterial called small intestinal submucosa (SIS). The effects of rehydration on the stiffness and associated ball burst properties of the SIS device were also measured. It is shown that at a rehydration time of 5 min from a reference dry state, steady-state mechanical properties are reached. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 43: 277–281, 1998

Characterization of path effects on the properties of balloon films

The effect of stress and temperature path on the mechanical properties of a balloon film material (Astrofilm E2) have been studied using two techniques. The first technique is based on uniaxial tensile measurements of prestrained strips of the film as a function of temperature. Data are analyzed in terms of two temperature coefficients, defined here as a stiffness coefficient and a strength coefficient; and by comparing the areas under the stress-strain curves. The second technique investigated the effect of stress and temperature path on inflated cylinders of the same material. The changes in the mechanical properties due to preconditioning in the biaxial stress state were evaluated using the ball burst test. Preliminary findings indicate that the material is stress and temperature path dependent. Changes in stiffness coefficient, draw strength and toughness were measured and discussed. The above techniques may be suitable to document path dependent changes, and to discriminate among films of different manufacture.

An Analysis of the Mechanical Behavior of Triaxial Fabrics and the Equivalency of Conventional Fabrics

The results are presented of an earlier analysis of a triaxial fabric by extension of the classical results of Peirce and Grosberg. Using the geometrical model of this earlier work, a theoretical analysis is presented in which the work necessary to deform the fabric is approximated by the change in strain energy in the constituent threads. The relationship between triaxial and conventional fabrics is discussed in the context of equivalency. The relationships among triaxial, plain, and leno fabrics are discussed. Using a specially constructed biaxial test fixture, fabric moduli predicted in earlier work are experimentally verified. In addition, equivalent weight conventional fabrics, both plain and leno, are compared with a triaxial fabric through ball burst and tear testing. The study shows that, although both conventional fabrics can be thought of as equivalent to the triaxial fabric, in reality no conventional equivalent exists.