Enhanced Interfacial Properties of Carbon Nanomaterial–Coated Glass Fiber–Reinforced Epoxy Composite: A Molecular Dynamics Study

The weak interfacial adhesion has significantly affected the durability, long-term reliability, and performance of glass fiber–reinforced epoxy composites. The coating of graphene and carbon nanotubes on the glass fiber can have a positive effect on the strength, toughness, and thermal insulation performance of glass fiber-reinforced composites. However, the strengthening mechanism of carbon nanomaterial coating on the interfacial adhesion between glass fiber and epoxy has not been fully explored. In this work, the effect of graphene and single-walled carbon nanotubes (SWCNTs) on the interfacial properties of the glass fiber–reinforced epoxy has been investigated at atomistic scale. The graphene and SWCNTs are sandwiched between epoxy and silica to study the debonding behavior of the sandwiched structures. It is found that the interfacial energy is significantly improved with the incorporation of graphene and SWCNTs between epoxy and silica, causing an obvious improvement in adhesion stress for graphene coating and in debonding displacement for SWCNT coating. Compared with the epoxy/silica without coatings where the silica and epoxy detach from the contact surface, the sandwiched structures display different failure modes. The sandwiched structure with graphene coating fails at the epoxy matrix close to the interface, exhibiting a cohesive failure mode because of the relatively stronger interfacial interactions. The structures with SWCNTs fail at the interface between silica and SWCNTs, representing an adhesive failure mode due to the interlocking between SWCNTs and polymer chains. This work provides a theoretical guideline to optimize the interface adhesion of coated glass fiber–reinforced epoxy via structure design and surface modification of coating materials.

PRIORITAS RISIKO PENANGANAN DAN TRANSPORTASI IKAN TUNA DI PELABUHAN PERIKANAN PANTAI (PPP) PONDOKDADAP

Ikan tuna (Thunnus sp) merupakan sumberdaya perikanan dan kelautan di Indonesia yang mempunyai nilai ekonomis tinggi dalam jumlah besar. Salah satu sentra produksi tuna berada di Provinsi Jawa Timur tepatnya di Pelabuhan Perikanan Pantai (PPP) Pondokdadap, Kabupaten Malang. Kualitas ikan tuna di PPP Pondokdadap sebagian besar memiliki kualitas sedang (grade B) dan tidak sedikit pula yang memiliki kualitas C dan D. Hal ini terjadi karena fasilitas penanganan yang kurang memadai dan kurangnya pengetahuan para pelaku usaha bahwa dalam setiap kegiatan penanganan dan transportasi yang kurang baik terdapat risiko yang mengakibatkan terjadinya penurunan mutu sehingga nilai jualnya kurang maksimal. Tujuan penelitian ini yaitu mengidentifikasi dan memetakan risiko prioritas dalam aktivitas penanganan dan transportasi ikan tuna di PPP Pondokdadap dengan pendekatan FMEA. Sehingga didapatkan risiko kritis dan harus segera dilakukan pengembangan mitigasi pada perikanan tuna di PPP Pondokdadap. Penelitian dilaksanakan pada bulan November 2020. Metode pengumpulan data menggunakan metode wawancara dan observasi langsung. Hasil yang diperoleh bahwa penurunan mutu terbesar berada pada spesies tuna albakor dengan berat ≥20kg. Terdapat 4 mode kegagalan (failure mode) yang menjadi risiko prioritas dalam penurunan mutu selama penanganan dan transportasi ikan tuna albakor ≥20kg di PPP Pondokdadap. Mode kegagalan tersebut yaitu pencucian ikan dengan air kotor, ikan dilempar saat penyortiran, ikan diletakkan di lantai tanpa alas dan penggunaan moda transportasi dengan mobil bak terbuka. Kata kunci: Albakor, FMEA, penanganan, pondokdadap, risiko, transportasi

An Empirical Shear Model of Interface Between the Loess and Hipparion Red Clay in a Loess Landslide

Quaternary loess is widely distributed over the tertiary Hipparion red clay on the Loess Plateau of China. Large-scale loess landslides often occur along the weak contact interface between these two sediment materials. To investigate the failure mode and shear strength characteristics of the loess–Hipparion red clay contact interface, a series of shearing experiments were performed on interface specimens using purpose-built shear equipment. In this article, the relationship between shear strength and interface morphology is discussed, and an empirical shear model of the interface is proposed based on the experimental results and theoretical work. The results indicate that discontinuities between the loess and the Hipparion red clay reduce the shear strength of specimens significantly. The contribution of the contact interface to shear performance including failure mode, shear deformation, and shear strength varies with the interface morphology and the applied normal stress. With low interface roughness or normal stress, sliding failure is likely to occur. With increasing interface roughness and normal stress, the peak strength increases rapidly. With further increase in the interface roughness and normal stress, the increment of peak strength decreases gradually as the failure mode transitions from sliding mode to cutoff mode. A staged shear model that takes the failure mode into consideration is developed to express the non-linear change in the interface shear strength. The shear model’s capability is validated by comparing model estimates with experimental data. This work improves our understanding of shear mechanisms and the importance of considering the effects of interfacial properties in the mechanical behavior of contact interfaces.

Dynamic mechanical properties of hybrid fiber reinforced concrete

In this study, the dynamic mechanical properties of hybrid fiber reinforced concrete (HFRC) are analyzed with respect to failure mode, dynamic increase factor (DIF), and peak strain by means of a SHPB testing apparatus. The factors that influence the dynamic mechanical properties include fiber type and fiber content. It is concluded that the best dynamic mechanical properties of fibers are CS-PHFRC at medium and low strain rates and AS-PHFRC at a high strain rate. Within a certain range, the higher the fiber content is, the larger the DIF of the corresponding HFRC and the more obvious the increase in dynamic compressive strength. AS-CSHFRC improves the dynamic compressive deformability of the HFRC. The polypropylene fiber causes plasticity, as shown in the failure mode of concrete. The Ottosen nonlinear elastic model, modified by introducing the damage factor, can better describe the dynamic mechanical properties of HFRC.

ANALISIS RISIKO KECELAKAAN KERJA PADA PROYEK PEMBANGUNAN DENGAN METODE FMEA DAN HAZOP

Risiko kecelakaan kerja pada proyek konstruksi merupakan risiko yang tinggi, namun terkadang faktor-faktor yang dapat mengurangi kecelakaan kerja masih kurang mendapatkan perhatian. Menurut Peraturan Menteri Pekerjaan Umum Nomor : 05/PRT/M/2014 pada Bab 1 Pasal 1 Sitem Manajemen Keselamatan dan Kesehatan Kerja Konstruksi adalah bagian dari sistem manajemen organisasi pelaksanaan pekerjaan konstruksi dalam rangka pengendalian risiko K3. Penelitian ini menjelaskan tentang perbandingan risiko kecelakaan pelaksanaan suatu proses pembangunan menggunakan dua metode yaitu metode FMEA (Failure Mode and Effect Analysis) dan HAZOP (Hazard Analysis and Operability Study), penerapan penelitian secara kuantitatif penelitian ini adalah dengan melakukan pengamatan langsung di proyek pembangunan lalu menganalisis risiko kecelakaan sesuai dengan data K3 (Keselamatan dan Kesehatan Kerja) dan sesuai dengan hasil pengamatan yang telah dilakukan di Proyek Pembangunan Pasar Johar Selatan, Semarang. Dari hasil analisis dengan metode FMEA diperoleh nilai RPN (Risk Priority Number) 15,39 terdapat pada, pekerjaan pembesian, yaitu pekerja yang tertusuk kawat. Risiko yang terjadi berdasarkan metode HAZOP memiliki Risk Level 7,18 terdapat pada pekerjaan pembesian. Tindakan mitigasi yang dilakukan sesuai dengan metode FMEA dan HAZOP yaitu dengan sering melakukan arahan kepada para pekerja untuk rajin menggunakan APD sesuai standar K3, memberikan penyuluhan tentang pentingnya APD, dan Penataan kepada para pekerja untuk keselamatan kerja.Kata Kunci: FMEA, HAZOP, Risiko Kecelakaan, K3