Damage analysis and fracture toughness evaluation in a thin woven composite laminate under static tension using infrared thermography

This work deals with the issue of damage growth in thin woven composite laminates subjected to tensile loading. The conducted tensile tests were monitored on-line with an infrared camera, and tested specimens were analysed using Scanning Electron Microscopy (SEM). Combined with SEM micrographs, observation of heat source fields enabled us to assess the damage sequence. Transverse weft cracking was confirmed to be the main damage mode and fiber breakage was the final damage leading to failure. For cracks which induce little variation of specimen stiffness, the classic “Compliance method” could not be used to compute energy release rate. Hence, we present here a new procedure based on the estimation of heat source fields to calculate the energy release rate associated with transverse weft cracking. The results are then compared to those computed with a simple 3D inverse model of the heat diffusion problem and those presented in the literature

Hierarchical scaling law for the strength of composite fibre bundles

This paper presents an analytical model for size effects on the longitudinal tensile strength of composite fibre bundles. The strength of individual fibres is modelled by a Weibull distribution, while the matrix (or fibre–matrix interface) is represented through a perfectly–plastic shear–lag model. A probabilistic analysis of the failure process in hierarchical bundles (bundles of bundles) is performed, so that a scaling law relating the strength distributions and characteristic lengths of consecutive bundle levels is derived. An efficient numerical scheme (based on asymptotic limits) is proposed, hence coupon– sized bundle strength distributions are obtained almost instantaneously. Parametric studies show that both fibre and matrix properties are critical for bundle strength; model predictions at different scales are validated against experimental results available in the literature

Making sense of missense variants in TTN-related congenital myopathies.

Mutations in the sarcomeric protein titin, encoded by TTN, are emerging as a common cause of myopathies. The diagnosis of a TTN-related myopathy is, however, often not straightforward due to clinico-pathological overlap with other myopathies and the prevalence of TTN variants in control populations. Here, we present a combined clinico-pathological, genetic and biophysical approach to the diagnosis of TTN-related myopathies and the pathogenicity ascertainment of TTN missense variants. We identified 30 patients with a primary TTN-related congenital myopathy (CM) and two truncating variants, or one truncating and one missense TTN variant, or homozygous for one TTN missense variant. We found that TTN-related myopathies show considerable overlap with other myopathies but are strongly suggested by a combination of certain clinico-pathological features. Presentation was typically at birth with the clinical course characterized by variable progression of weakness, contractures, scoliosis and respiratory symptoms but sparing of extraocular muscles. Cardiac involvement depended on the variant position. Our biophysical analyses demonstrated that missense mutations associated with CMs are strongly destabilizing and exert their effect when expressed on a truncating background or in homozygosity. We hypothesise that destabilizing TTN missense mutations phenocopy truncating variants and are a key pathogenic feature of recessive titinopathies that might be amenable to therapeutic intervention

フクゴウ ザイリョウ ニ オケル トランスバース ハカイ ハッセイ ノ ビシテキ ケンキュウ : ガクサイテキ マルチスケール カイセキ

京都大学0048新制・課程博士博士(工学)甲第11881号工博第2574号新制||工||1360(附属図書館)23661UT51-2005-N715京都大学大学院工学研究科機械工学専攻(主査)教授 北條 正樹, 教授 落合 庄治郎, 教授 宮﨑 則幸学位規則第4条第1項該当Doctor of EngineeringKyoto UniversityDA

Effect of fiber array irregularities on microscopic interfacial normal stress states of transversely loaded UD-CFRP from viewpoint of failure initiation

A detailed investigation has been carried out to determine the effect of local fiber array irregularities and controlling fiber distribution parameters on microscopic interfacial normal stress states for transversely-loaded unidirectional carbon fiber (CF)/epoxy composites. Linear elastic finite element analyses were carried out for two-dimensional image-based models composed of about 70 fibers. The relationship between the geometrical distribution of two adjacent fibers and the interfacial normal stresses (INSs) is investigated for all fibers in different image-based models. Three boundary conditions for loading were selected: Case A involved cooling from the curing temperature (the difference in temperature was -155 K); Case B involved transverse loading of 75 MPa chosen as an example of macroscopic transverse fracture strength; and Case C involved both cooling from the curing temperature and transverse loading of 75 MPa. High compressive INSs due to the difference in the coefficients of thermal expansion are observed at the location of the shortest interfiber distance for Case A (cooling). High tensile INSs are observed at the location of the shortest interfiber distance and where the fiber alignment angle to the loading direction is small for Case B (loading). For Case C (cooling and loading), the high thermal residual compressive INSs and the high mechanical tensile INSs compensate each other, and the INSs at a short interfiber distance are much lower than those for Case B. These results clearly indicate the importance of the contribution of the thermal residual stresses to the transverse tensile failure initiation of CF/epoxy laminates

The Effects of Variable Ratio Schedules of Reinforcement on Extinction in a Slot Machine

The present study examines the effects from a variable ratio (VR) schedule of reinforcement in conjunction with the reinforcement schedule, on extinction. Seventeen college students participated in a within participants design by playing a computerized slot machine program displaying two slot machines concurrently, in which under one condition, the machine has a VR schedule of 10 and the other has a VR 20 schedule of reinforcement but get twice as many points as the participants in condition one. This study will examine how the different schedules of reinforcement impact extinction by recording machine preference and the amount of credits bet by the participant during each trial