Laravel SQLSTATE[42S22]: Column not found: 1054 Unknown column '0' in 'field list' (SQL: insert into `add_file` (`0`)

I need to submit a form with multiple files to the database in Laravel,each time i fill the form i got this error

SQLSTATE[42S22]: Column not found: 1054 Unknown column '0' in 'field list' (SQL: insert into add_file (0) values ({"name":"Opeyemi Adam","description":"Thanks bro","attach":[["CRITICAL TECHNICAL OBSERVATIONS.doc"]]}))

Below is the Model

class AddFile extends Model{
   protected $table = 'add_file';
   protected $fillable = ['name', 'description', 'attach'];
}

Controller

public function submitform(AddFileFormRequest $request){
    $destinationPath = storage_path('app/attachments/');
    $attach_file =  array();


    $file = $request->file('attach');
    if (!empty($file[0])){
        foreach($file as $key){
            $filename = $key->getClientOriginalName();

            $key->move($destinationPath, $filename);

            $attach_file[] =  array($filename);
        }

    }


    $form_content = new AddFile(array(
        'name'          => $request->get('name'),
        'description'   => $request->get('description'),
        'attach'        => $attach_file
    ));


    var_dump($form_content);
    DB::table('add_file')->insert(array($form_content));


}

Don't know where the field list is coming from

via Chebli Mohamed